volume 10 | issue one winter 2014 acoustics today · 2014. 10. 26. · regarding the magazine....

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AcousticsToday

A publication of the Acoustical Society of America

This Issue :

Acoustical Horizontal Array Coherence Lengths and the Carey Number

How Does Wind Turbine Noise Affect People?

Exploring Our Sonic Environment Through Soundscape Research & Theory

Volume 10 | Issue One Winter 2014

2 | Acoustics Today | Winter 2014

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T A b L E O f C O N T E N T S

6 from the Editor

8 Letters to the Editor

featured Articles

10 Acoustical Horizontal Array Coherence Lengths and the “Carey Number” James F. Lynch, Timothy F. Duda and John A. Colosi

The late Bill Carey came up with the rule of thumb that the horizontal array coherence length in shallow water is, on the average, 30 wave-lengths.

20 How Does Wind Turbine Noise Affect People? Alec N. Salt and Jeffrey T. Lichtenhan

The many ways by which unheard infrasound and low-frequency sound from wind turbines could distress people living nearby are described.

30 Exploring Our Sonic Environment Through Soundscape Research and Theory Bennett M. Brooks, Brigitte Schulte-Fortkamp, Kay S. Voigt and Alex U. Case

“How can we know what people think of their sonic environment? - Well, we ask them!”

Departments

41 | Book Reviews – Philip L. MarstonA Dictionary of Hearing by Maryanne Maltby, Ultrasonic and Electromagnetic NDE for Structure and Material Characterization by Tribikram Kundu (editor), Computa-tional Aeroacoustics: A wave number approach by Chris-topher K. W. Tam, and Unsteady Combustor Physics by Tim C. Lieuwen.

50 | Passings Tributes to Kim C. Benjamin, Stephen H. Crandall and William C. Cummings.

55 | ASA News – Allan D. PierceBarbara Shinn-Cunningham receives mentoring award, Smartphone APP Student Competition, James A. Sim-mons receives Gerritt S. Miller Award, Editorial Manager to replace PXP, POMA submission requirements may change.

58 | ASA Announcements Allan D. Pierce and Arthur N. PopperAcoustical Society Foundation, Acoustics Today Update and Acoustics Today Interns

62 Classif ieds

63 business Directory

64 Advertisers Index

About the Cover

Volume 10 | Issue 1 | Winter 2014

The top panel shows a time series of the vertical displacement of the water column, with nonlin-ear internal wave trains very evident. The second panel shows the angle at which the transmitted signal hits the array, which is stable at ~28 degrees, except when the internal wave trains pass through, which pushes the energy out of plane (a 3D effect). The third panel shows the “Carey Number” (Lcoh / λ) measurement. In the fourth panel is shown coherence length versus steering angle, the the source of second and third panel results.

A publication of the Acoustical Society of America

AcousticsToday

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Acoustical Society of AmericaThe Acoustical Society of America was founded in 1929 “to increase and diffuse the knowledge of acoustics and to promote its practical applications.” Information about the Society can be found on the Internet site www.acousticalsociety.org.

The Society has approximately 7,000 members, distributed worldwide, with over 30% living outside the United States. Membership includes a variety of benefits, a list of which can be found at the website www.acousticalsociety.org/membership/membership_and_benefits.

All members receive online access to the entire contents of the Journal of the Acoustical Society of America from 1929 to the present. New members are welcome, and several grades of membership, including low rates for students and for persons living in develop-ing countries, are possible. Instructions for applying can be found at the Internet site above.

future IssuesPlans for the Spring issue are not complete. We are looking for new articles and so anyone interested in writing for Acoustics Today is encour-aged to send an e-mail giving some particulars to [email protected]. And, please see “From the Editor” to learn more about his thoughts regarding the magazine.

ACOUSTICS TODAY (ISSN 1557-0215, coden ATCODK) January 2014, volume 10, issue 1, is published quarterly by the Acoustical Society of America, Suite 1NO1, 2 Hun-

tington Quadrangle, Melville, NY 11747-4502. Periodicals Postage rates are paid at Huntington Station, NY, and additional mailing offices. POSTMASTER: Send address changes

to Acoustics Today, Acoustical Society of America, Suite 1NO1, 2 Huntington Quadrangle, Melville, NY 11747-4502. Copyright ©2014, Acoustical Society of America. All rights

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website: www.copyright.com/, or contact them at (978)-750-8400. Persons desiring to photocopy materials for classroom use should contact the CCC Academic Permissions Service. Au-

thorization does not extend to systematic or multiple reproduction, to copying for promotional purposes, to electronic storage or distribution, or to republication in any form. In all such

cases, specific written permission from the Acoustical Society of America must be obtained. Permission is granted to quote from Acoustics Today with the customary acknowledgment of

the source. To reprint a figure, table, or other excerpt requires the consent of one of the authors and notification to ASA. Address requests to AIPP Office of Rights and Permissions, Suite

1NO1, 2 Huntington Quadrangle, Melville NY 11747-4502; Fax (516) 576-2450; Telephone (516) 576-2268; E-mail: [email protected]. An electronic version of Acoustics Today is

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may not be modified. Articles may not be reprinted or translated into another language and reprinted without prior approval from the Acoustical Society of America as indicated above.

Editor Arthur N. Popper | [email protected]

book Review EditorPhilip L. Marston

Advisory CommitteeBrenda L. Lonsbury-Martin, ChairTessa Bent Geoffrey F. EdelmannMatthew V. Golden Veerle M. Keppens Thomas R. Moore Peter H. RogersMatthew D. Shaw Andrea M. Simmons

ASA Publications Staf fMary Guillemette: [email protected] Wall Murray: [email protected]

ASA Editor-In- ChiefAllan D. Pierce

Acoustical Society of AmericaJames H. Miller, PresidentPeter H. Dahl, Vice PresidentDavid Feit, TreasurerPaul D. Schomer, Standards DirectorSusan E. Fox, Executive Director

AddressAcoustical Society of AmericaPublications OfficePO Box 2741170 Main StreetWest Barnstable, MA 02668




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from the Editor | Ar thur N. Popper

I am honored to have been selected as the new editor of Acoustics Today. This is a daunting responsibility since Dick Stern founded and de-veloped a truly fine magazine. And so “filling his shoes” is not an easy task, nor is it one that I take lightly. Indeed, I

see my role as taking a magazine that we are all very proud of and making it even better, and perhaps moving it in a few new directions that will increase its value to ASA and the broader acoustics community.

I want to make it clear, though, that while I have a number of ideas for the future of the Acoustics Today “enterprise,” I am firm in my conviction that the heart of what we do is the print magazine sent to all ASA members. It is my belief that even in these days when most of what we read is on a screen, there is a significant value to have something one can carry around, read on a plane or subway, and browse cover-to-cover. And for some of us, there still is nothing like print for reading and learning!

I want to take this column to share with you some of my thinking about where I would like us to take Acoustics Today. At the same time, I am also very much open to other ideas and suggestions, and I want to encourage ASA members who have thoughts about my plans, or about Acoustics Today, to drop me a note ([email protected]) and share your thinking.

My primary goal for Acoustics Today is to ensure that it has a broad set of articles that are of wide interest to all ASA members, and that these articles are all understandable, and readable, by every member of the ASA, whatever their spe-cialization may be. Thus, I want to ensure, especially starting in future issues, that every article is not only understood and appreciated by members from the same specific discipline as the authors, but also that the articles will be read and under-stood by members from all of the numerous disciplines within ASA. I do appreciate that writing articles for a more general acoustics audience is a greater challenge than writing for one’s peers, but the feedback I have already gotten from prospective authors and other ASA members is that moving in this more “general” direction is highly desirable and appreciated.

Over time, I also want to ensure that each year we publish articles from the broadest possible range of disciplines within ASA. I realize this won’t always be feasible, and it may be impossible for my first few issues since I am still early learning the job and working to get articles, but I see this as a long-term goal. That said, as we say in other places in this issue we are looking for interesting articles and I encourage potential authors to drop me a note to discuss ideas.

We are also, even with this issue of Acoustics Today, making a few interesting changes. First, we are instituting a “Letters to the Editor” department. This will be an opportunity for members to (in up to 150 words) comment on past articles, raise issues of interest to our community, and share observa-tions. We will review all letters (send them to me please, in Word format) and retain the right to select which we use. But, assuming we don’t get inundated by letters, we will certainly try and use as many letters as we can within our space con-straints.

Another development is to initiate book reviews. In the past, Acoustics Today has had book announcements. While these have been useful, their presence depended on the authors


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sending material to Dick, and so not every new book was included. Our new policy is to have actual reviews, and we have invited the JASA book review editor, Philip Marston, to also be the Acoustics Today book review editor. In fact, we have decided to generally have the same book reviews in both ven-ues. The rationale here is that with JASA being on line, many readers never really see book reviews. By including reviews in Acoustics Today we very much expand the opportunity for ASA members to see reviews and learn about new books, and for ASA reviewers to get a wider audience.

I anticipate other changes in the magazine in the future, and am open to new ideas, but let me assure you again that I only intend to build on the excellent magazine that is Dick Stern’s legacy, and make it even better.

Allow me to share a few other ideas that we are working on for the Acoustics Today “enterprise.” Most importantly, we are already working on developing AcousticsToday.org, a new web site that will contain, ultimately in searchable form, all current and past articles from the print magazine. Thanks to the very effective leadership of ASA Editor-in-Chief Allan Pierce, all Acoustics Today articles starting with the very first issue are now open access. This is a really important change since it means that articles can be read by ASA members and non-members alike – and our goal is to make the articles from Acoustics Today accessible to, and used by, courses, regulators, and anyone else who has an interest in acoustics. This means that Acoustics Today has the potential to be a real leader in acoustics and help ASA increase its value to the community well beyond our membership. A related goal is to have Acous-ticsToday.org the center for that information. Please watch this space for an announcement of our web site – we hope to have it up no later than May 1.

I will only briefly mention two other initiatives that we will be working on over the next months. One is to initiate what we are calling “Acoustics Today Interns.” These interns will be ASA graduate students and postdocs selected to work for the magazine for perhaps a year (with an expected work load of no more than a few hours a week, so as not to detract from their education) to do specific tasks that will enhance Acoustics Today. This would provide young acousticians with an oppor-tunity to learn about journals and publishing and contribute skills that we would not otherwise have. Interns might be involved in getting Acoustics Today (and perhaps ASA) more involved with social media, helping develop AcousticsToday.org, and perhaps working with news and other sections of the magazine. More details about Acoustics Today interns and how to apply to be part of the first intern group can be found under Announcements in this issue.

The other project is to develop a reader survey to find out how the magazine is used by members, their views on content, and perhaps solicit articles. This will help us learn how the magazine can best serve ASA members and our community, and we would hope that once this is launched you will fill out the survey.

In summary, my approach to Acoustics Today is to make it an even more valuable part of our community. I intend to work with the Acoustics Today Advisory Committee to develop ideas, but I also look forward to hearing from readers about their thoughts about the magazine.

Finally, I want to thank Allan Pierce for his exceptional job as acting editor for Acoustics Today and for being an invaluable and willing mentor as I learn my new job. And, for any ASA member who wants to find out a bit about me, please don’t hesitate to check my website at www.popperlab.umd.edu.

Arthur Popper

http://www.popperlab.umd.edu


Letters to the Editor

Dear Editor,

Paul Schomer’s comments (Schomer 2013) on my paper (Leventhall 2013a) contain errors, whilst employing two typical methods of false criticism: 1. Create flawed opinions, which were not in the original, and cen-

sure these whilst side-stepping the main issue (Straw Man). 2. Undermine credibility by frequent use of “assertion.”Some of the Straw Man examples are: “ Professor Leventhall goes on to assert with absolute certainty that

no problems are generated by low frequency sound whatsoever.” “ The assertion that every single person world-wide is being affected

only by non-acoustic factors is totally unfounded.” “ He categorically rules out research in the infrasonic region; that

research is unacceptable to him.”

These, and other statements, are not in my paper and are not my opinion, but are Paul’s creation. Toward the end of his comments, Paul goes off topic, referring to unrelated matters, such as his dis-pute with Duke Energy.

One of Paul’s errors concerns the round window as a shunt which was taken into account in deducing that the levels in the vestibule from heartbeat and breathing are considerably greater than levels from wind turbine noise at similar frequencies.

Geoff Leventhall [email protected]

Leventhall, G (2013a) “Concerns about infrasound from wind turbines.” Acoustics Today 9(3): 30-38

Leventhall, G (2013b) “Infrasound and the ear.” Proc 5th International Meeting on Wind Turbine Noise, Denver, Colorado August 2013

Schomer, P (2013) “Comments on recently published article “Concerns about

infrasound from wind turbines”.” Acoustics Today 9(4): 7-9.

Persons wishing to submit “Letters to the Editor” are wel-come to do so. Letters can be on any topic related to acous-tics, and may be comments on material in recent issues. Letters will be published on a space-available basis. Submitters should feel free to express their opinions, but are expected to follow the normal rules of polite writing. Letters should be free of commercialization. Submission implies giving the Editor and the Publications Office Staff the authority to make minor editing changes to improve the quality of writing and clarity. Inclusion of any letter is at the discretion of the edi-tor. Letters should be no more than 150 words (no figures or mathematical equations) and may include up to two citations in the form of footnotes (citations are not included in the word count). Citations should include full title, all authors, and source.

- Want to Contribute to

Acoustics Today?

To suggest ideas for articlesor inquire about authoring one,

contact Arthur Popper at:[email protected]



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Introduction Though the genesis of this paper is of a somewhat sad origin (the passing of close friend and colleague Bill Carey of Boston University last year) the outcome is repre-sentative of what occurred when people interacted with Bill – he made them think about interesting problems. In organizing and participating in some memorial sessions for Bill (at both the Underwater Acoustics meeting in Corfu, Greece and the upcom-ing Providence ASA meeting), we looked at one of Bill’s signature research areas, horizontal array coherence, and decided to focus on that. It is an area that all of the authors have worked in, and so we thought we could nicely elucidate the physics of one of Bill’s coherence results, specifically that the horizontal array coherence length in shallow water is measured to be ~20-40λ (average 30λ) at frequencies around 400 Hz (Carey, 1998). However, the physical origin of that number, and even the measure-ments of it, were not as simple to summarize as we thought, and so in digging back into Bill’s research, we again were given something to think further about.

Array signal coherence is of interest because it (in part) determines the overall array gain, the amount an array “amplifies” a signal against the noise. Specifically, it determines the signal re-lated part of the array gain. For an N element array, array gain (AG), quoting Urick (1983) “is by definition the ratio, in decibel units, of the signal to noise of the array to the signal to noise of a single element, so that

The gain of the array therefore depends on the sum of the cross-correlation coefficients between all pairs of elements of the array, for both noise and signal.” The array signal gain (ASG), which is the quantity that Carey concentrated on in his work, is the numerator of the above AG expression. The noise effect which appears in the denominator, is also a very interesting and complicated entity, but it is not the focus of what we want to look at here. Regarding the array gain for a simple case, if the signal is coherent, the ASG against white noise goes as N 2 whereas if the signal is incoherent, it goes as N. The difference between an N and an N 2 dependence can be many dB of gain, so understanding the ASG is of great practical value.

James F. Lynch and Timothy F. Duda

Woods Hole Oceanographic InstitutionWoods Hole, MA 02543

John A. ColosiNaval Postgraduate School

Monterey, CA 93943

Acoustical Horizontal Array Coherence Lengths and the “Carey Number”The late Bill Carey came up with the rule of thumb that the horizontal array coherence length in shallow water is, on the average, 30 wavelengths.

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beam-formers and DecoherenceBefore getting to details of how the decorrelation/decoherence of a signal causes loss of array signal gain, it would be good to quickly review how basic array beam-formers work. There are two types that are of interest to us: plane wave beam-formers (for sources “at infinity”) and focused beam-formers (for sources in the near-field, i.e. where wave-front curvature effects are important.) In Figure 1a, we show a simple (discretely sampled) plane wave beam-former. The additional distance ∆rn that the plane wave travels to each ad-ditional element along the array is simply given by ∆rn = n∆lsin0. If we compensate the extra distance by a time delay, we get ∆tn = ∆rn/c, which we can also express as a frequency (ϖ) dependent phase shift, ∆ϕn= w∆tn. For focused arrays, we also work to cancel the additional path, which is now (in continuous form) ∆r = (∆l)²/2R₀. Again, we can use ∆r = ∆t for the time delay and ∆ϕ= w∆t for the equivalent phase shift. Note that we concentrate on phase variation here. To first order, the amplitude varies smoothly for an individual multipath, since it is subject to cylindrical spreading and medium attenuation, which vary slowly.

If we had perfect plane wave or spherical wave arrivals, we would be done here, and the ASG would go as N 2. But a variety of things dis-tort the acoustic wave-fronts and, unless you know them perfectly and can compensate for them in the beam-forming, they make the array signal gain less than the theoretical maximum. Let’s look at

what they are. The ocean and seabed effects that distort the wave-fronts are: fronts (shelf-break and tidal mixing fronts are the larger ones), internal waves (nonlinear and linear), internal tides (large in-ternal waves at tidal frequencies), eddies, spice (density compensated temperature structure in the ocean), surface waves, bottom geo-acoustic properties (how the bottom reflects and absorbs sound), and bathymetric roughness (assuming the larger scale bathymetry is known). We could also consider unaccounted for array deforma-tions in the list of things that effectively decohere the signal, but as this is a (supposedly) correctable instrumental effect, we will ignore it in our list for now. As mentioned, noise enters into the overall array gain as well, but not into the signal gain, so we will also ignore it here. But even without looking at noise and array deformation, this is a formidable shopping list of sound refractors and scatterers to deal with. (Katznelson et al, 2012).

Before leaving this section, we will also note that we are doing some-thing a bit different philosophically from the AG definition above. Specifically, we are looking at the deterministic change of phase across an array due to specific ocean features, which we represent by suitably simplified feature models. We can look at averages and sta-tistics of our deterministic results later, and so reconcile our results to Urick’s definition. But our work here will really be an instanta-neous look at how an ocean process affects phase across an array, and thus the instantaneous beam-forming power output.

Methods for Obtaining LcohGiven that we are dealing with an impressively complex environ-ment for acoustic propagation and scattering, how do we deal with getting some concrete numbers for the array signal gain? There are, at the present time, four alternatives for obtaining coherence length estimates: 1) large numerical models (oceanographic plus 3D acoustics), 2) wave propagation in a random medium calculations (WPRM), 3) “simple forms” for scattering (to be discussed later), and 4) direct measurement. However, when Bill Carey first did his work in the early 1980’s, the first three alternatives weren’t really available. Numerical modeling of the ocean and 3D acoustic propa-gation were still in their infancy, WPRM methods were just being

“ The outcome is representative of what occurred

when people interacted with bill – he made them

think about interesting problems.”

Figure 1a: A steered plane wave (far-field) beam-former, using discrete array elements with constant spacing.

Figure 1b: A focused curved wave-front (near-field) beam-former with continuous element spacing.

Figure 1a Figure 1b

c


developed for deep water (with shallow water being largely ignored), and the “simple model” approach to looking at scattering from the above list of ocean and seabed objects didn’t have enough knowledge of the ocean and seabed available as input to make it feasible. The Navy wanted operational numbers for array performance as quickly as possible, and so only one real option was available – direct mea-surement. As money for at-sea work was more plentiful then than today, that was in fact an attractive option. Thus Bill Carey took to sea and made his direct measurements.

In doing at-sea measurements of the horizontal array coherence, there are a number of issues which have to be dealt with carefully. The first concern is geometry. A geometry where the array is broad-side to the source is preferred, as this obviates the problem of the ambiguity of the horizontal beam steering angle versus the vertical multipath angle. In a broadside geometry, all the multi-paths arrive on the same zero degree steered beam. The next concern is signal to noise ratio (SNR). Ambient noise from continuous sources in shallow water “Kuperman-Ingenito noise,”(Kuperman and In-genito, 1980) produces very short (fraction of a 400 Hz wavelength) horizontal correlation scales, and so one needs to be well above this noise level to see longer scales experimentally. Noise from large, discrete sources (e.g. ships) mimics the multi-paths from the experimental source, and can give spurious results (larger correlation lengths, if the noise source is on the experimental source-to-receiver line and smaller lengths if off it). Source or receiver motion (or both) is yet another concern. This motion quickly produces a large number of realizations of the environment, and even can affect the statistics of the measurement if the environment one passes through is non-stationary. Using a fixed source and receiver geometry cures this, in that one has a bathymetrically stationary system and an oceanographically more slowly varying environment to deal with. Another experimental issue is broadband versus narrowband signals. Generally, the longer integration time needed to get good SNR with narrowband signals is a disadvantage, but given a fixed geometry, longer times (up to several minutes) are often available. A final experimental consideration is adequate measurement of the ocean and seabed condition, so that one can correlate the coherence length

measured to the regional and seasonal ocean condition. Carey’s mea-surements provided this “general context” of where, when, and in what ocean condition the data were taken, but they did not have the detail to comment on all the individual acoustic scattering mecha-nisms that were discussed above. That level of experimental detail of the environment would have to wait for the “Shallow Water 2006” (SW06) experiment performed two decades after Carey’s experi-ments (Tang et al, 2007).

Measurements of LcohAt this point, it is appropriate to show both Carey’s measurements and the later SW06 measurements, to see the experimental story. In Figure 2, we show a synopsis of his data, along with some calculated points from our “simple theory”, which we will discuss soon. Carey’s 400 Hz data, at first glance, shows a 20-40λ spread of Lcoh, with an average of about 30λ. One also might suspect that the coherence length is increasing with source-to-receiver range, which could be due to higher mode stripping by differential attenuation of (seabed-interacting sound) or other effects.

Figure 2 : A synopsis of Bill Carey’s coherence measurements, along with two theory points based on “simple” calculations of shelf-break front effects. Four of the experiments had multiple source/receiver ranges.

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In Figure 3, we show similar data (at 200 Hz) from SW06, where a 465m horizontal array was deployed on the bottom, and listened to fixed sources. This was not a broadside geometry, due to deployment issues; however, each multipath was filtered and compensated for that in the processing (Duda, Collis et al, 2012). Of interest in this figure is that the spread from 20-40λ is apparent at first in panel 3, but then it drastically decreases when a nonlinear internal wave train passes through. This decrease was in fact predicted by Oba and Finette (2002) using numerical models, and Katznelson and Pereselkov (1997) long before the SW06 experiment was performed, and initially observed by Badiey et al. (2002). After the waves pass by, Lcoh returns to the 20-40λ range. The SW06 data shown are at only one range, due to the source being moored. They are also shown for one only fre-quency, as that is the only one that has been extensively processed, and we hope the other frequencies transmitted (100, 400, 800 Hz) might be looked at in the future for Lcoh. The SW06 data set is useful in that: 1) it corroborates Carey’s basic numbers, 2) it actually represents a time series, which augments Carey’s single snap-shots at multiple ranges, and 3) it has an enormous amount of support-ing environmental measurements, which will allow us to dissect the scattering processes that contribute to the measured Lcoh. (As we have already seen from Figure 3 nonlinear internal waves are one process that strongly affects the measured number.)

Before leaving this data, we should note that there is a bit of variety in the literature in how Lcoh is defined, and due to this there can be a factor of two or more between what various authors report or

calculate. We will not attempt to reconcile all the defini-tions in this rather descriptive article, but would note that when one finally gets down to detailed inter-comparisons, these definitions need to be considered.

Theory for Lcoh Having looked at the data, let us now look at attempts to theoretically describe where the number comes from in shallow water. Let us start with ocean numerical models. A rather seminal early nu-merical study was conducted by Finette and Oba (op cit) in which they combined the shallow water oceanography

of a weak linear internal wave field with that of a stronger, nonlinear internal wave field (a dnoidal soliton wave packet), and showed that the effect on the coherence length at 400 Hz (a popular frequency, as it is close to “optimal” for long range, shallow water propaga-tion) was strongly dependent on the angle of the acoustic track to the soliton packet; indeed Lcoh became very small when the soliton wavecrest direction was close to the acoustic track direction. This is exactly what the SW06 data discussed above shows, and their paper also included a very nice calculational prediction of the 3D acoustic ducting by solitons, which was observed and published in the same year (Badiey et al., 2002). Their computer prediction of the coher-ence length for the case of the acoustic track being perpendicular to the soliton wave crests was very large (order 600m, or 150λ), which is consistent with our simple model, and also would seem to indicate that, for this across-crest geometry, the nonlinear (plus linear) internal waves do not dictate Lcoh , which is the smaller 30λ number (Duda et al.,2012).

Figure 3 : The top panel shows a time series of the vertical displacement of the water column, with nonlinear internal wave trains very evident.The second panel shows the angle at which the transmitted signal hits the array, which is stable at ~28 degrees, except when the internal wave trains pass through, which pushes the energy out of plane (a 3D effect). The third panel is the most important to us, as it is the “Carey Number” (L-coh / λ ) measurement. The fourth panel shows coherence length versus steering angle, and is the source of second and third panel results.


More recently, work is being conducted under an ONR program called “IODA” (Integrated Ocean Dynamics and Acoustics), which ties in very modern coastal oceanography models, with virtually all of the physical oceanography described above incorporated into it, with fully 3D acoustics models. This is a very ambitious extension for both the acoustics and oceanography, as it attempts to reach down to sampling scales of meters and seconds, as opposed to the hours and kilometer scales that are the usual state of the art. Acous-tics is sensitive to small-scale ocean phenomena with large hori-zontal temperature and sound-speed gradients, so in order to fully model the acoustic field, we need to reach such spatial and temporal resolutions. In weighing whether or not to use such models, one notes that the model generates full 3D acoustics realizations of the pressure field, from which one can generate Lcoh and much more. Moreover, one can generate space-time series and statistics from such a model, and use these instead of running the model for each case. However, the price you pay is that you have to know how to run (and have the input for) state of the art ocean and acoustics models. These models also have some hefty computer requirements associ-ated with them, and they are not easy-to-use, general public tools.

Another theoretical approach is the “wave propagation in a random medium” approach, which is well known to the public due to its famous application to astronomy (star twinkle). In this approach, as applied to ocean acoustics, one goes from the statistics of the medi-um (e.g. sound-speed) fluctuation to the statistics of the fluctuations in the acoustic amplitude or phase. Calculations in WPRM (Flatte, 1979 and Colosi, 2013) tend to be a bit mathematically involved, but a simple example of what type of form one obtains (from Carey et al, 2002) shows that the phase variance between two receivers goes as a double integral over the paths to the two receivers (includ-ing vertical ocean structure), with the “kernels” of the integrals containing known background quantities and the correlation func-tion containing our statistical knowledge of the ocean. The strength of this approach is that it only asks for basic statistics of the ocean variability as input. However, this is not as easy a thing to provide as it sounds, as the ocean has (as discussed above) numerous processes

going on in shallow water with a variety of scales, and moreover they are spatially and temporally inhomogeneous and anisotropic. However, one can often get adequate answers with even an ap-proximate correlation function, which can be based on either ocean dynamics and scales or direct measurements. Such an approximate correlation function, based on shallow water oceanography mea-sured in the 1996 PRIMER experiment off New England, produced a 30λ average horizontal correlation length, in agreement with the SW06 data above (Lynch et al., 2003). Both PRIMER and SW06 were conducted in the Mid Atlantic Bight region, and close to the shelf-break and its associated front, so the agreement between these two results is less surprising than it would be for two very distantly separated sites. These two measurements also make one begin to think that the shelf-break oceanography (perhaps the front) is a large contributor to the 30 wavelength result.

The question now arises – how do we separate the effects of the various pieces of oceanography and the seabed from one another? We can turn various pieces of oceanography “on and off” in the large numerical models, and even do so (using individual process dynamic models) in the correlation functions. But while this tactic may produce answers, it produces comparatively little insight into the physics, and one has to run models over large, multidimensional parameter spaces to get a complete set of answers. So where do we go?

“Simple” feature Models and LcohA recent, and ongoing, attempt to answer that question has been to employ simple “feature models” of the ocean and seabed. In this approach, which has been successful in both oceanography and acoustics (A. Robinson and D. Lee (eds.), 1994 and Lynch et al., 2010), one reduces the ocean features to simple geometric forms (e.g. eddies become circles, fronts become straight linearly sloping (in depth) features, nonlinear internal waves become square shaped instead of hyperbolic cosecant squared shaped, etc.). The feature’s internal structure (i.e. the ocean interior sound-speed profile) also can be simplified, so that the vertical and horizontal temperature/sounds-speed profiles of the ocean features become very convenient to deal with geometrically. Indeed, this allows one to use simple

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Euclidean geometry in the horizontal direction and equally simple first order perturbation theory forms for the features when includ-ing their vertical structure. Beginning work on this using depth averaged ocean features was discussed in the Bill Carey memorial session of the UA in Corfu (Lynch et al, 2013), and showed the ba-sic equations for Lcoh for a number of the ocean features we listed, as well as numerical results for a shelf-break front (based on the SW06 region parameters). In this paper, we are extending that work to show numbers for the effects of nonlinear internal waves, so that we can cross compare two of the “major players” in creating acoustic field spatial decoherence. We will, given the limited space, stick to the simplest “depth averaged ocean” and “resolved modes” cases, and hope to eventually include the whole feature model story (interfer-ing modes and rays, and the many other ocean/seabed effects) in a future article.

A simple 2-D depth averaged model of a nonlinear internal wave train propagating across an acoustic track is shown in Figure 4. In this figure, θ is the angle between the acoustic track and the direc-tion of propagation of the internal wave train, L is the width of each internal soliton (kept constant here for simplicity), and Rperp is the distance from the source to the center of the broadside array. D is the distance between the individual solitons (again, kept constant), but it is not D we need so much in this case, as the phase integral used to get Lcoh does not care about the soliton spacing.

We also need to consider the acoustic frequency ϖ, the average water column sound-speed co, and the depth averaged sound-speed co perturbation due to the internal waves, ∆cpert. When we do so, and after a very small amount of geometric manipulation, we get the simple form:

This form is very clean in terms of containing the basic ingredients of the system: the acoustic frequency and source receiver separation, the sound-speed perturbation due to the waves, their size and their number, and the angle between the acoustic track and the orienta-tion of the oceanography of interest. The answer depends strongly

on this relative orientation angle, as one would expect. There are two interesting features to this expression, one obvious, and one not as obvious. The obvious feature is that the expression becomes infinite at θ = 0. This is actually not unexpected for a straight line internal wave interacting with something that is nearly a plane acoustic wave. The subtler problem for this equation is that it breaks down for acoustic propagation along and in between the internal wave crests. In this case, one physically sees 3D ducting of sound between the internal waves, and our simple equation above becomes inadequate.

The answer we get from Equation 2 is qualitatively similar to what one sees in Finette and Oba, i.e. a very large Lcoh at small θ, and small Lcoh for θ large. If we put in numbers typical of Carey’s experiments, i.e. f= 400 Hz, Rperp = 10 km, N=10, L=200m, and ∆cpert.=40*(10/100) m/s, we get that the 30λ point is at about 77°, which corresponds to “close to along-shelf ” propagation. Carey did his experiments primarily near shelf-breaks and at constant isobaths, so this is not an inconsistent result. However, other experiments, e.g. SW06 above, show the 20-40λ result for smaller cases as well, and it is not amiss to think that other ocean processes (e.g. fronts, see Lynch et al, 2013) drive the coherence length down from the large number that both our simple theory and other models predict in that angular regime due to just nonlinear internal waves.

Even in the context of a very simple depth averaged model, there are some things that we have omitted that one could point to, and ask about their importance. These include: the true “sech squared” na-ture of the individual solitons, their rank ordering (decreasing soli-ton amplitude as one goes further into the wave train), the curvature of the solitons in the x-y plane, the horizontal refraction of sound by the soliton waves, and mode coupling. Preliminary calculations show these to be of second order importance to Lcoh, but a more careful study needs to be (and is being) done.

One thing that can be done very easily with our “simple forms” is an error analysis. Error in the environmental parameters (N, Δc, L and λ) is translated directly into Lcoh via the displayed Lcoh equa-tion. Given an error tolerance in Lcoh that a user specifies, one can immediately see just how good the environmental input has to be

Figure 4 : Plan-view schematic of a train of (two) nonlinear internal waves, with an acoustic propagation track crossing them at an angle Θ.


from a numerical model or data. In terms of our soliton work, this is particularly useful, as solitons are a nonlinear phenomenon, and even the best model/data will show substantial enough changes in N, Δc, L and λ due to this effect. This is in addition to the normal fluctuation in the internal waves due to changing density stratifica-tion and currents. Seeing how big such fluctuations are, and how they affect useful acoustic quantities such as Lcoh is part of our ongoing research.

In the depth averaged approach to estimating Lcoh, simplifica-tion was achieved by just considering the vertical average of the sound-speed perturbation. However, we can also use the simple perturbation theory forms to look at the detailed vertical sound-speed structure. This is most easily done in the acoustic normal mode picture, which happily is also a very good descriptor of low frequency, shallow water acoustics. The results obtained will now be on a mode-by-mode basis, i.e.; Lcoh Lcoh(n) each mode now has its own coherence length. The perturbed phase accumulation over each modal path to the broadside array, ∆ϕ = ∫∆ Lcoh LCr can be expressed using a simple background waveguide (e.g. the “hard bot-tom” waveguide, with analytic eigenvalues)

which is perturbed by a mixed layer and internal waves below the mixed layer. In a simple “square wave soliton” approximation (Lynch et al., 2010), we can write the perturbed wavenumber as

In the above, all the parameters that comprise the wavenumbers are very simple environmental quantities, so that the physical depen-dence on the environment is very clear. Specifically, H1W is the internal wave peak depth, D is the mixed layer depth, H is the water

column depth, and n is an integer (the mode number). If we inte-grate the ∆k1W along the path, we get a very similar result to what we had in the depth-averaged case, i.e.

The modal form is just as simple as the depth averaged form, and now has the added richness of including the water column vertical structure in the ∆k1W term. This form can also include bottom prop-erty variability, and be used to compare bottom versus water column effects. We would note that in experiments where one can filter the modes in time (e.g. SW06), the coherence along a horizontal array on a mode by mode basis shows clearly, as shown by Figure 5. The left three panels visually show coherence when no strong internal wave train is present. Ignoring the top panel, the second panel down shows the first four mode arrivals on a vertical line array, and the bottom panel shows the arriving modal wave-fronts on a 465m horizontal line array lying on the seabed. The right three panels, again ignoring the top, show the arrivals during a period of strong internal wave activity – it is obvious that the coherence length drops as the nonlinear internal waves pass through the acoustic track, and the numbers for Lcoh have been presented in Figure 3, panel 3. We have not pursued the coherence versus mode number in detail, but we do see the qualitative decrease versus increasing mode number we predict above in the SW06 data.

As a last note on the modal picture (See figure 5), we can also look at groups of interfering (unresolved) multipaths, if we wish. This pushes us to looking at the complex pressure, and makes a little more mess, but can be treated largely similarly to what we have shown above. The coherence length then will be some amplitude-weighted average of the coherence lengths of the individual modes.

n

n

n

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future DirectionsWe have concentrated here on the internal wave field as one of the “major players” in determining Lcoh in shallow water, but as we said at the beginning, it is only one of a number of shallow water oceanography processes that affect the overall coherence length. We still have a number left to treat: internal tides, eddies, linear internal waves, spice, bottom geo-acoustic properties and bathymetric scattering. These will be treated similarly to what we have done with nonlinear internal waves here, and so this paper hopefully gives a good representation of our work. An interesting question that will need to be answered when we get through the list is: what are the dominant effects? The overall coher-ence length measured (whether modal or otherwise) will be some sort of weighted average of all these effects, with the smallest (limit-ing) length of a strong process probably determining the result the most. We can’t linearly superpose Lcoh results, so some reasonable scheme for weighting will need to be devised.

Another useful direction for this work is to look at source/receiver motion through the ocean (feature model) medium. For sources and receivers that move quickly compared to the ocean features (gener-ally true, with the exception of surface waves), the ocean can be taken as “frozen” and useful results obtained quickly from the forms we have been considering.

Yet another major direction for the work is to look at other impor-tant acoustic quantities with this simple feature model approach. Of first order interest will be: the transmission loss (TL), the scintil-lation index (SI), and the mode coupling matrix (Cmn.) All of these, based on some preliminary work, should be amenable to this approach, and we look forward to completing these extensions in the future.

We will conclude with our thanks to a departed, but never-to-be-forgotten col-league, Bill Carey, for provid-ing us with yet another set of puzzles to solve. We hope he would be pleased by these few pieces we have been able to place together so far.

AcknowledgementsWe thank ONR for their support of this work throughout the years. We also thank Allan Pierce for his critical reading of our paper. Thanks too to Art Newhall for his help with the figures. And again, we thank Bill Carey for his inspiration.

biosketches

Dr. James Lynch obtained his B.S. in Physics from Stevens Institute of Technology in 1972 and his Ph.D. in Physics from the University of Texas at Austin in 1978. He then worked for three years at the Applied Research Labo-ratories of the University of Texas at Austin (ARL/UT) from 1978 to 1981, after which

he joined the scientific staff at the Woods Hole Oceanographic Institution (WHOI). He has worked at WHOI since then, and cur-rently holds the position of Senior Scientist. His research specialty areas are ocean acoustics and acoustical oceanography. He also greatly enjoys occasional forays into physical oceanography, marine geology, and marine biology. Dr. Lynch is a Fellow of the Acoustical Society of America, a Fellow of IEEE, a former Editor-in-Chief of the IEEE Journal of Oceanic Engineering, and current Editor-in-Chief of the Journal of the Acoustical Society of America Express Letters. His hobbies include amateur astronomy and computer gaming.

Figure 5 : Visual look at the mode-by-mode coherence of the first four modes in SW06. Intensity on the L-array is plotted.

Figure 5


Timothy F. Duda (M’05–SM’09) received the B.A. degree in physics from Pomona College, Claremont, CA, in 1979 and the Ph.D. degree in oceanography from the Scripps Institution of Oceanography, University of California, San Diego, in 1986. He worked at the University of California, Santa Cruz, from 1986 to 1991. He has been a Scientist at the Woods Hole Oceano-

graphic Institution, Woods Hole, MA, since 1991. His three pri-mary fields of study are ocean acoustic propagation, ocean internal gravity waves, and ocean mixing processes. His research into these has included theoretical and observational physical process studies, development of new measurement tools, and computational acoustic modeling. Dr. Duda is a member of the IEEE Oceanic Engineering Society. He is also a member of the American Meteorological Soci-ety, the American Geophysical Union, and the Acoustical Society of America (Fellow).

John A. Colosi received his B.A. degree in Physics from the Uni-versity of California, San Diego in 1988, and a PhD in Physics from the University of California, Santa Cruz in 1993. He is presently a Professor of Oceanography at the

Naval Postgraduate School (NPS) in Monterey California. Before his arrival at NPS in 2005 he was a tenured Associate scientist at the Woods Hole Oceanographic Institution (WHOI) in the department of Applied Ocean Physics and Engineering (AOPE), and he was an active faculty member in the Massachusetts Institute of Technology (MIT)/WHOI Joint Program. He has authored/co-authored over 50 refereed publications on the topic of ocean acoustics and physical oceanography. He was the recipient of the 2001 A.B Wood Medal, and the 2011 Medwin Prize in Acoustical Oceanography, and he was recently elected Fellow of the Acoustical Society of America. His scientific interests are in wave propagation through random media, acoustical remote sensing, and internal waves and tides.

Badiey M., Lynch J. F., Tang X., Apel J., and the SWARM group (2002). “Azimuthal and temporal dependence of sound propagation due to shallow water internal waves.” IEEE J. Oceanic Eng’g. 27(1), pp. 117-129.

Carey, W. M., (1998). “The determination of signal coherence length based on signal coherence and gain measurements in deep and shallow water.” J. Acoust. Soc. Am. 104, 831-837.

Carey W. M., Cable P., Siegmann W., Lynch J. F, and Rozenfeld I. (2002). “Measurement of sound transmission and signal gain in the Strait of Korea.” IEEE J. Oceanic Eng., 27(4), pp. 841-852.

Colosi, J.A. (2013). “On horizontal coherence estimates from path integral theory for sound propagation through random ocean sound-speed perturbations”, J. Acoust. Soc. Am., 134 (4), pp3116-3118.

Duda, T. F., (2006). “Temporal and cross-range coherence of sound traveling through shallow-water nonlinear internal wave packets,” J. Acoust. Soc. Am. 119, 3717-3725.

Duda, T. F., Collis J. M., Lin Y. T., Newhall A. E., Lynch J. F., and DeFerrari H. A. (2012). “Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity,” J. Acoust. Soc. Am, 131, 1782-1797.

Finette, S., and Oba, R. (2003). “Horizontal array beam-forming in an azimuthally anisotropic internal wave field,” J. Acoust. Soc. Am. 114, 131–144.

Flatte S., (Editor) (1979). “Sound transmission through a fluctuat-ing ocean”, Cambridge University Press, New York, New York.

Katznelson B. G., Petnikov V., and Lynch J. F. (2012). “Fundamen-tals of shallow water acoustics”, ONR series book, Springer Verlag, 520 pages.

References

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- Katznelson B. G., Pereselkov S. A. (1997). Sound field intensity in a shallow-water waveguide in the presence of internal waves Acoust. Phys 43(5), pp.564-570.

Kuperman W. A., and Ingenito F. (1980). “Spatial correlation of surface generated noise in a stratified ocean”, J. Acoust. Soc. Am. 67, 1988.

Lynch J. F., Duda T. F., Siegmann W., Holmes J., and Newhall A. (2013). “The Carey number in shallow water acoustics.” in Proceed-ings of the 1st International Conference and Exhibition on Underwater Acoustics, June 23-28, Corfu, Greece.

Lynch J. F., Newhall A., Sperry B., Gawarkiewicz G., Tyack P., Ab-bot P. and Chiu C.S., (2003). “Spatial and temporal variations in acoustic propagation characteristics at the New England shelf-break front.” IEEE J. Oceanic Eng’g. 28(1), pp. 129-150.

Lynch J. F., Lin Y. T, Duda T. F., and Newhall A.E., (2010).“Acous-tic ducting, reflection, refraction, and dispersion by curved nonlin-ear internal waves in shallow water”, IEEE J. Oceanic Eng. 35(1), pp. 12-27.

Oba R. and Finette S. (2002). “Acoustic propagation through aniso-tropic internal wave fields: Transmission loss, cross-range coherence, and horizontal refraction J. Acoust. Soc. Am. 111, 769.

Robinson A. and Lee D., (eds.) (1994). “Oceanography and Acous-tics: Prediction and Propagation Models”, AIP, New York, New York, 257 pp.

Tang D. J., Moum J., Lynch J., Abbot P., Chapman R., Dahl P., Duda, T., Gawarkiewicz G., Glenn S., Goff J., Graber H., Kemp J., Maffei A., Nash J., Newhall A. (2007). “Shallow water ’06 – a joint acoustic propagation/nonlinear internal wave physics experiment”, Oceanography, 20 (4),156-167 (2007).

Urick, R. J. (1967). Principles of Underwater Sound For Engineers, McGraw-Hill, New York.

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Introduction Recent articles in Acoustics Today have reviewed a number of difficult issues concern-ing wind turbine noise and how it can affect people living nearby (Leventhall 2013, Schomer 2013; Timmerman 2013). Here we present potential mechanisms by which effects could occur.

The essence of the current debate is that on one hand you have the well-funded wind industry 1. advocating that infrasound be ignored because the measured levels are below the threshold of human hearing, allowing noise levels to be adequately docu-mented through A-weighted sound measurements, 2. dismissing the possibility that any variants of wind turbine syndrome exist (Pierpont 2009) even when physicians (e.g., Steven D. Rauch, M.D. at Harvard Medical School) cannot otherwise explain some patients’ symptoms, and, 3. arguing that it is unnecessary to separate wind tur-bines and homes based on prevailing sound levels.

On the other hand you have many people who claim to be so distressed by the effects of wind-turbine noise that they cannot tolerate living in their homes. Some move away, either at financial loss or bought-out by the turbine operators. Others live with the discomfort, often requiring medical therapies to deal with their symptoms. Some, even members of the same family, may be unaffected. Below is a description of the disturbance experienced by a woman in Europe we received a few weeks ago as part of an unsolicited e-mail.

“From the moment that the turbines began working I experienced vertigo-like symp-toms on an ongoing basis. In many respects, what I am experiencing now is actually worse than the ‘dizziness’ I have previously experienced, as the associated nausea is much more intense. For me the pulsating, humming, noise that the turbines emit is the predominant sound that I hear and that really seems to affect me.

While the Chief Scientist [the person who came to take sound measurements in her house] undertaking the measurement informed me that he was aware of the low frequency hum the turbines produced (he lives close to a wind farm himself and had recorded the humming noise levels indoors in his own home) he advised that I could tune this noise out and that any adverse symptoms I was experiencing were simply psychosomatic.”

Alec N. Salt and Jeffery T. Lichtenhan

Department of OtolaryngologyWashington University

School of MedicineSt. Louis, MO 63110

How Does Wind Turbine Noise Affect People?The many ways by which unheard infrasound and low-frequency sound from wind turbines could distress people living nearby are described.

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We asked how she felt when she was away from the wind turbines, to which she replied:

“I did manage to take a vacation towards the end of August and for the two weeks we were away I was perfectly fine.”

The goal of our work in this field is to understand whether the physiology of the ear can, or cannot, explain the symp-toms people attribute to wind turbine noise. As it is generally the case when debate influences a specific industry’s financial interests and legal well-being, the scientific objectivity of those associated with the industry can be questioned. Liabil-ity, damage claims, and large amounts of money can hang in the balance of results from empirical studies. Whether it is a chemical industry blamed for contaminating groundwater with cancer-causing dioxin, the tobacco industry accused of contributing to lung cancer, or athletes of the National Foot-ball League (NFL) putatively being susceptible to brain dam-age, it can be extremely difficult to establish the truth when some have an agenda to protect the status quo. It is only when sufficient scientific evidence is compiled by those not working for the industry that the issue is considered seriously.

Origins of Our Involvement in Infrasound from Wind Turbines What is the evidence leading us to conclude that unheard infrasounds are part of the wind turbine problem, and how did we become involved in this debate? We are small group of basic and applied scientists, which means that our work addresses fundamental questions on how the ear works in normal and diseased states. While developing paradigms for our studies, we had been using a classic technique called “low-frequency biasing” – measurement of auditory responses to a test sound within the range of audibility, while simulta-neously presenting a low-frequency tone (e.g., 4.8 to 50 Hz) to displace the sensory organ of the inner ear. Some auditory responses saturate when displaced by the bias tone, which can be used to establish whether the sensory organ is vibrating symmetrically or whether a fluid disturbance has displaced it to one side. A condition called “endolymphatic hydrops,”

which is found in humans with Ménière’s disease, can displace the sensory organ as the space containing the fluid called endolymph swells. In our animal experiments we initially used 20 to 50 Hz bias tones, but for many reasons, and in large part based on a study in which we found that the ear responded down to 1 Hz (Salt and DeMott, 1999), we started using the lowest frequency our hardware could generate, 4.8 Hz, a frequency considered to be infrasound. Over the course of hundreds of experiments, we have found numerous biasing effects with 4.8 Hz tones at levels of 80 to 90 dB SPL (i.e., -13 to -3 dBA). We also found that the ear became about 20 dB more sensitive to infrasonic bias tones when the fluid spaces in the cochlear apex were partially occluded, as occurs with endolymphatic hydrops.

In late 2009, the first author received a report of a woman with Ménière’s disease whose symptoms – primarily dizziness and nausea – were severely exacerbated when she was in the vicinity of wind turbines. From our animal data, we knew this woman was likely hypersensitive to very low-frequency sounds. Our subsequent review of the literature on wind-tur-bine noise revealed two aspects that were absolutely astound-ing:

1. Almost all measurements of wind turbine noise are A-weighted, making the unjustified assumption that hearing is the only way by which infrasound generates physiologic effects. The few studies that reported un-weighted measure-ments of wind-turbine noise, or recalculated spectra by re-moving the A-weighting from published A-weighted spectra, clearly demonstrated increasing energy towards low frequen-cies with highest energy levels in the infrasound region. We were surprised that objective full-frequency measurements showed that wind turbines generate infrasound at levels capable of stimulating the ear in various ways. Under such circumstances, A-weighting measurements of turbine noise would be highly misleading.

“ Almost all measurements of wind turbine noise are A-weighted, making the unjustified assumption that hearing is the only way by which infrasound generates physiologic effects.”


2. Literature and websites from the wind industry often contained strong statements that wind turbine infrasound was of no significance. This view was largely based on publications by Leventhall (2006; 2007). Wind turbine noise was de-scribed as comparable to rustling leaves, flowing streams, air-conditioned offices or refrigerators heard from the next room. If wind turbine noise really was comparable to such sources then complaints would not be expected. But the turbines sounds are only comparable to these sources if the ultra-low frequencies emitted by the turbines are ignored through A-weighting. Stations that monitor infrasound or low frequency seismic (vibrational) noise for other purposes (for the detec-tion of explosions, meteors, volcanic activity, atmospheric activity, etc.) are well-aware that low frequency sounds ema-nating from distant wind farms, or coupling to the ground as vibrations, can influence their measurements. The UK, Ministry of Defense has opposed wind turbines cited within 50 km of the Eskdalemuir Seismic Array. We have seen no reports of the Ministry opposing the presence of refrigerators in the region, suggesting they appreciate that sounds emitted from wind turbines and refrigerators are quite different. It was thus quite astounding to see the vast majority of wind tur-bine noise measurements excluding the low frequency noise content. Given the knowledge that the ear responds to low frequency sounds and infrasound, we knew that comparisons with benign sources were invalid and the logic to A-weight sound measurements was deeply flawed scientifically.

The Ear’s Response to InfrasoundExperimental measurements show robust electrical responses from the cochlea in response to infrasound (Salt and DeMott, 1999; Salt and Lichtenhan 2013). This finding was initially difficult to reconcile with measures showing that hearing was notably insensitive to such sounds but the explanation became clear from now-classic physiological studies of the ear showing that the two types of sensory cell in the cochlea had very different mechanical properties (Cheatham and Dallos 2001).

The auditory portion of the inner ear, the cochlea, has two types of sensory cell. The inner hair cells (IHC; shown green in Figure 1) are innervated by type I afferent nerve fibers that mediate hearing. The stereocilia (sensory hairs) of the IHCs are free-floating and do not contact the overlying gelatinous tectorial membrane (shown gray). They are mechanically dis-placed by fluid movements in the space below the membrane. As their input is fluid-coupled to the vibrations of the sensory organ they exhibit “velocity sensitive” responses. As the veloc-ity of motions decreases for lower-frequency sounds, their fluid-coupled input renders the IHC insensitive to very low-frequency sounds. The other type of sensory cell, the outer hair cells (OHC; shown red in Figure 1) are innervated by type II afferent nerve fibers that are not as well understood as type I fibers and probably do not mediate conscious hearing per se. In contrast to the IHC, the stereocilia of the OHCs are inserted into the tectorial membrane. This direct mechani-cal coupling gives them “displacement sensitive” properties, meaning they respond well to low–frequency sounds and infrasound. The electrical responses of the ear we had been recording and studying originate from the sensitive OHCs. From this understanding we conclude that very low frequency sounds and infrasound, at levels well below those that are heard, readily stimulate the cochlea. Low frequency sounds and infrasound from wind turbines can therefore stimulate the ear at levels well below those that are heard.

The million-dollar question is whether the effects of wind turbine infrasound stimulation stay confined to the ear and have no other influence on the person or animal. At present, the stance of wind industry and its acoustician advisors is that there are no consequences to long-term low-frequency and in-frasonic stimulation. This is not based on studies showing that long-term stimulation to low-level infrasound has no influ-

Figure 1 : The sensory organ of the cochlea, showing inner and outer hair cell and neural anatomy.

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ence on humans or animals. No such studies have ever been performed. Their narrow perspective shows a remarkable lack of understanding of the sophistication of biological systems and is almost certainly incorrect. As we consider below, there are many physiologic mechanisms by which long-term infra-sound stimulation of the cochlea could have effects.

One important aspect of wind turbine noise that is relevant to its physiological consequences is that the duration of exposure can be extremely long, 24 hours a day and lasting for days or longer, depending on prevailing wind conditions. This is con-siderably different from most industrial noise where 8 hour exposures are typically considered, interspersed by prolonged periods of quiet (i.e., quiet for 16 hours per day plus all weekends). There are numerous studies of exposures to higher level infrasound for periods of a few hours, but to date there have been no systematic studies of exposure to infrasound for a prolonged period. The degree of low-frequency cochlear stimulation generated by wind turbine noise is remarkably difficult to assess, due to the almost exclusive reporting of A-weighted sound level measurements. It certainly cannot be assumed that cochlear stimulation is negligible because A-weighted level measurements are low. For example, with 5 Hz stimulation cochlear responses are generated at -30 dBA and stimulation is sufficient to cause responses to saturate (indi-cating the transducer is being driven to its limit) at approxi-mately 20 dBA (Salt and Lichtenhan, 2012; Salt et al., 2013). We have also shown that 125 Hz low-pass filtered noise at just 45 dBA produces larger responses than wide band noise with the same low-frequency content presented at 90 dBA (Salt and Lichtenhan 2012). We conclude that low frequency re-gions of the ear will be moderately to strongly stimulated for prolonged periods by wind turbine noise. There are a number of plausible mechanisms by which the stimulation could have effects:

1. Amplitude Modulation: Low-Frequency Biasing of Audible Sounds

Modulation of the biological mechano-electric transducer of the inner ear by infrasound is completely different from the amplitude modulation of audible sounds that can be measured with a sound level meter near wind turbines under some conditions. This can be demonstrated in low-frequency biasing paradigms in which a low-frequency tone and higher-frequency audible tone are presented simultaneously to a subject.

OHCs respond to both low- and high-frequency components and modulate the high-frequency components by either saturation of the mechano-electric transducer or by cyclically changing the mechanical amplification of high frequencies. IHCs, being insensitive to the low-frequency tone, see a high pass-filtered representation of the OHC response – an amplitude modulated version of the audible probe tone, as shown in Figure 2. As hearing is mediated through the IHCs that receive approximately 90-95% of afferent innervation of the auditory nerve, the subject hears the higher-frequency probe tone varying in amplitude, or loudness. A similar bias-ing influence on cochlear responses evoked by low-level tone pips was explained by the low-frequency bias tone changing OHC-based cochlear amplifier gain (Lichtenhan 2012). This same study also showed that the low frequency, apical regions of the ear were most sensitive to low-frequency biasing. Stud-ies like this raise the possibility that the amplitude modula-tion of sounds, which people living near wind turbines report

Figure 2 : Demonstration of biologically-generated amplitude modulation to a non-modulated stimulus consisting of an audible tone at 500 Hz tone summed with an infrasonic tone at 4.8 Hz. The cochlear microphonic response, which is generated by the OHC, in-cludes low and high frequency components. The IHC detect only the high frequency component, which is amplitude modulated at twice the infrasound frequency for the stimuli in this example.


as being so highly annoying, may not be easily explained by measurements with an A-weighted sound level meter. Rather, the low-frequency and infrasound levels need to be considered as contributing to the perceived phenomenon. Subjectively, the perceived fluctuation from an amplitude modulated sound and from a low-frequency biased sound are identical even though their mechanisms of generation are completely different. For the subject, the summed effects of both types of amplitude modulation will contribute to their perception of modulation. Acousticians therefore need to be aware that the degree of modulation perceived by humans and animals living near wind turbines may exceed that detected by a sound level meter.

2. Endolymphatic Hydrops Induced by Low Frequency Tones

As mentioned above, endolymphatic hydrops is a swelling of the innermost, membrane bound fluid compartment of the inner ear. Low-frequency tones presented at moderate to moderately-intense levels for just 1.5 to 3 minutes can induce hydrops (Figure 3), tinnitus (ringing in the ears) and changes in auditory potentials and acoustic emissions that are physi-ological hallmarks of endolymphatic hydrops (Salt, 2004, Drexl et al. 2013).

Unlike the hearing loss caused by loud sounds, the symptoms resulting from endolymphatic hydrops are not permanent and can disappear, or at least fluctuate, as the degree of hydrops changes. Return to quiet (as in Figure 3) or relocation away from the low-frequency noise environment allow the hydrops, and the symptoms of hydrops, to resolve. This which would be consistent with the woman’s description of her symptoms given earlier. As hydrops is a mechanical swelling of the membrane-bound endolymphatic space, it affects the most distensible regions first – known to be the cochlear apex and vestibular sacculus. Patients with saccular disturbances typi-cally experience a sensation of subjective vertigo, which would be accompanied by unsteadiness and nausea. As we mentioned above, an ear that has developed endolymphatic

hydrops becomes >20 dB more sensitive to infrasound be-cause the helicotrema becomes partially obstructed (Salt et al. 2009). The possibility of a positive feedback – low-frequency induced hydrops that causes the ear to be more sensitive to

low frequencies – has to be considered. To date, all studies of low-frequency tone-induced hydrops have used very short duration (1-2 min) exposures. In humans, this is partly due to ethical concerns about the potential long-term consequences of more prolonged exposures (Drexel et al., 2013). Endolym-phatic hydrops induced by prolonged exposures to moderate levels of low-frequency sound therefore remains a real pos-sibility.

3. Excitation of Outer Hair Cell Afferent Nerve Pathways Approximately 5-10% of the afferent nerve fibers (which send signals from the cochlea to the brain - the type II fibers mentioned above) synapse on OHCs. These fibers do not respond well to sounds in the normal acoustic range and they are not considered to be associated with conscious hearing. Excitation of the fibers may generate other percepts, such as feelings of aural fullness or tinnitus. Moreover, it appears that infrasound is the ideal stimulus to excite OHC afferent fibers given what has been learned about these neurons from in vitro recordings (Weisz et al, 2012; Lichtenhan and Salt, 2013). In vivo excitation of OHC afferents has yet to be attempted with infrasound, but comparable fibers in birds have been shown to be highly sensitive to infrasound (Schermuly and Klinke, 1990). OHC afferents innervate cells of the cochlear nucleus that have a role in selective attention and alerting, which may explain the sleep disturbances that some people living

Figure 3 : Brief exposures to low-frequency tones cause endolym-phatic hydrops in animals (Salt, 2004) and tinnitus and acoustic emission changes consistent with endolymphatic hydrops in humans (Drexel et al, 2013). The anatomic pictures at the right show the difference between the normal (upper) and hydropic (lower) cochleae The endolymphatic space (shown blue) is enlarged in the hydropic cochlea, generated surgically in this case.

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near wind turbines report (Nissenbaum et al. 2012). The likelihood that OHC afferents are involved in the effects of low-frequency noise is further supported by observations that type II innervation is greatest in the low-frequency cochlear regions that are excited most by infrasound (Liberman et al. 1990, Salt et al. 2009).

4. Exacerbation of Noise Induced Hearing LossSome years ago we performed experiments to test a hypothesis that infrasound was protective against noise damage (Harding et al. 2007). We reasoned that low-frequency biasing would periodically close the mechano-electric transducer channels of the sensory organ (reducing electrical responses as shown in the biasing studies above), and consequently reduce the amount of time that hair cells were exposed to the damaging overstimulation associated with noise exposure. The experi-mental study found that just the opposite was true. We found that simultaneous presentation of infrasound and loud noise actually exacerbated noise-induced lesions, as compared to when loud noise was presented without infrasound. Our interpretation was that low-frequency sound produced an intermixing of fluids (endolymph and perilymph) at the sites of hair cell loss resulting in lesions that were larger. A possibil-ity to be considered is therefore that long-term exposure to infrasound from wind turbines could exacerbate presbycusis and noise-induced hearing loss. Because these forms of hear-ing loss develop and progress slowly over decades, this could be a lurking consequence to human exposures to infrasound that will take years to become apparent.

5. Infrasound Stimulation of the Vestibular Sense Organs Recent exchanges in this journal between Drs. Leventhall and Schomer concerning the direct stimulation of vestibular receptors by sound at low and infrasonic frequencies deserve comment. Dr. Leventhall asserts that both Drs. Schomer and Pierpont are incorrect in suggesting that wind turbine infra-sound could stimulate vestibular receptors, citing work by Todd in which the ear’s sensitivity was measured in response to mechanical low-frequency stimulation applied by bone

conduction. Leventhall fails to make clear that there are no studies reporting either vestibular responses, or the absence of vestibular responses, to acoustically-delivered infrasound. This means that for all his strong assertions, Leventhall cannot refer to any study conclusively demonstrating that vestibular receptors of the ear do not respond to infrasound. Numerous studies have reported measurements of saccular and utricular responses to audible sound. Indeed, such measurements are the basis of clinical tests of saccular and utricular function through the VEMP (vestibular-evoked myogenic potentials). Some of these studies have shown that sensitivity to acoustic stimulation initially declines as frequency is lowered. On the other hand, in vitro experiments demonstrate that vestibular hair cells are maximally sensitive to infrasonic frequencies (~1 – 10 Hz). Thus, sensitivity to acoustic stimulation may increase as stimulus frequency is lowered into the infrasonic range. Direct in vivo vestibular excitation therefore remains a possibility until it has been shown that the saccule and other vestibular receptors specifically do not respond to this stimu-lation.

Low-frequency tone-induced endolymph hydrops, as dis-cussed above, could increase the amount of saccular stimula-tion by acoustic input. Hydrops causes the compliant saccular membrane to expand, in many cases to the point where it directly contacts the stapes footplate. This was the basis of the now superseded “tack” procedure for Ménière’s disease, in which a sharp prosthesis was implanted in the stapes footplate to perforate the enlarging saccule (Schuknecht et al., 1970). When the saccule is enlarged, vibrations will be applied to en-dolymph, not perilymph, potentially making acoustic stimu-lation of the receptor more effective. There may also be certain clinical groups whose vestibular systems are hypersensitive to very low-frequency sound and infrasound stimulation. For example, it is known that patients with superior canal dehis-cence syndrome are made dizzy by acoustic stimulation. Sub-clinical groups with mild or incomplete dehiscence could exist in which vestibular organs are more sensitive to low frequency sounds than the general population.

“ The million-dollar question is whether the effects of wind turbine infrasound stimulation stay confined to the

ear and have no other influence on the person or animal.”


6. Potential Protective Therapy Against Infrasound A commonly-used clinical treatment could potentially solve the problem of clinical sensitivity to infrasound. Tympanosto-my tubes are small rubber “grommets” placed in a myringot-omy (small incision) in the tympanic membrane (eardrum) to keep the perforation open. They are routinely used in children to treat middle ear disease and have been used successfully to treat cases of Ménière’s disease. Placement of tympanos-tomy tubes is a straightforward office procedure. Although tympanostomy tubes have negligible influence on hearing in speech frequencies, they drastically attenuate sensitivity to low frequency sounds (Voss et al., 2001) by allowing pressure to equilibrate between the ear canal and the middle ear. The effective level of infrasound reaching the inner ear could be reduced by 40 dB or more by this treatment. Tympanostomy tubes are not permanent but typically extrude themselves after a period of months, or can be removed by the physician. No one has ever evaluated whether tympanostomy tubes alleviate the symptoms of those living near wind turbines. From the patient’s perspective, this may be preferable to moving out of their homes or using medical treatments for vertigo, nau-sea, and/or sleep disturbance. The results of such treatment, whether positive, negative, would likely have considerable scientific influence on the wind turbine noise debate.

Conclusions and ConcernsWe have described multiple ways in which infrasound and low-frequency sounds could affect the ear and give rise to the symptoms that some people living near wind turbines report. If, in time, the symptoms of those living near the turbines are demonstrated to have a physiological basis, it will become apparent that the years of assertions from the wind industry’s acousticians that “what you can’t hear can’t affect you” or that symptoms are psychosomatic or a nocebo effect was a great injustice. The current highly-polarized situation has arisen

because our understanding of the consequences of long-term infrasound stimulation remains at a very primitive level. Based on well-established principles of the physiology of the ear and how it responds to very low-frequency sounds, there is ample justification to take this problem more seriously than it has been to date. There are many important scientific issues that can only be resolved through careful and objective research. Although infrasound generation in the laboratory is techni-cally difficult, some research groups are already in the process of designing the required equipment to perform controlled experiments in humans.

One area of concern is the role that some acousticians and societies of acousticians have played. The primary role of acousticians should be to protect and serve society from nega-tive influences of noise exposure. In the case of wind turbine noise, it appears that many have been failing in that role. For years, they have sheltered behind the mantra, now shown to be false, that has been presented repeatedly in many forms such as “What you can’t hear, can’t affect you.”; “If you cannot hear a sound you cannot perceive it in other ways and it does not affect you.”; “Infrasound from wind turbines is below the audible threshold and of no consequence.”; “Infrasound is negligible from this type of turbine.”; “I can state categorically that there is no significant infrasound from current designs of wind turbines.” All of these statements assume that hearing, derived from low-frequency-insensitive IHC responses, is the only mechanism by which low frequency sound can affect the body. We know this assumption is false and blame its origin on a lack of detailed understanding of the physiology of the ear.

Another concern that must be dealt with is the develop-ment of wind turbine noise measurements that have clinical relevance. The use of A-weighting must be reassessed as it is based on insensitive, IHC-mediated hearing and grossly mis-represents inner ear stimulation generated by the noise. In the scientific domain, A-weighting sound measurements would be

“ for years, they have sheltered behind the mantra, now shown to be false, that has been presented repeatedly in many forms such as ‘What you can’t hear, can’t affect you.’ ”

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unacceptable when many elements of the ear exhibit a higher sensitivity than hearing. The wind industry should be held to the same high standards. Full-spectrum monitoring, which has been adopted in some reports, is essential.

In the coming years, as we experiment to better understand the effects of prolonged low-frequency sound on humans, it will be possible to reassess the roles played by acousticians and professional groups who partner with the wind industry. Given the present evidence, it seems risky at best to continue the current gamble that infrasound stimulation of the ear stays confined to the ear and has no other effects on the body. For this to be true, all the mechanisms we have outlined (low-frequency-induced amplitude modulation, low frequency sound-induced endolymph volume changes, infrasound stimulation of type II afferent nerves, infrasound exacerbation of noise-induced damage and direct infrasound stimulation of vestibular organs) would have to be insignificant. We know this is highly unlikely and we anticipate novel findings in the coming years that will influence the debate.

From our perspective, based on our knowledge of the physiol-ogy of the ear, we agree with the insight of Nancy Timmer-man that the time has come to “acknowledge the problem and work to eliminate it”.

biosketches

Alec N. Salt is Professor of Otolaryn-gology at Washington University. He is a long-term member of the Acousti-cal Society of America, the Associa-tion for Research in Otolaryngology, and the American Otological Society. His research covers broad aspects of system-level cochlear physiology, with a major focus on the inner ear fluids,

drug delivery to the inner ear, and low-frequency sound ef-fects on the ear.

Jeffery T. Lichtenhan is Assistant Professor of Otolaryngology at Washington University in St. Louis. He recently completed his postdoc-toral fellowship in the Eaton-Peabody Laboratory of Auditory Physiology at Harvard Medical School. His research addresses questions on the mechanics of hearing to low-frequency acoustic sound, and the auditory efferent system. Ultimately, his work aims to improve the differential diagnostics of sensorineural hearing loss.

Cheatham, M.A., Dallos, P. (2001). “Inner hair cell response patterns: implications for low-frequency hearing,” Journal of the Acoustical Society of America. 110, 2034-2044.

Drexl, M., Überfuhr, M., Weddell, T.D., Lukashkin, A.N., Wiegrebe, L., Krause, E., Gürkov, R. (2013). “Multiple Indices of the ‘Bounce’ Phenomenon Obtained from the Same Human Ears,” Journal of the Association for Research in Otolaryngology. (e-pub, before print copy) 10.1007/s10162-013-0424-x

Harding, G.W., Bohne, B.A., Lee S.C., Salt A.N. (2007). “Effect of infrasound on cochlear damage from exposure to a 4 kHz octave band of noise,” Hearing Research. 225:128-138.

Leventhall, G. (2006). “Infrasound From Wind Turbines – Fact, Fiction Or Deception,” Canadian Acoustics 34:29-36.

Leventhall, G. (2007). “What is infrasound?,” Progress in Biophysics and Molecular Biology 93: 130–137.

References


Leventhall, G. (2013). “Concerns About Infrasound from Wind Turbines,” Acoustics Today 9:3: 30-38.

Liberman, M.C., Dodds, L.W., Pierce, S. (1990). “Afferent and efferent innervation of the cat cochlea: quantitative analy-sis with light and electron microscopy,” Journal of Compara-tive Neurology 301:443-460.

Lichtenhan, J.T. (2012). “Effects of low-frequency biasing on otoacoustic and neural measures suggest that stimulus-fre-quency otoacoustic emissions originate near the peak region of the traveling wave,” Journal of the Association for Research in Otolaryngology. 13:17-28.

Lichtenhan, J.T., Salt, A.N. (2013). “Amplitude modulation of audible sounds by non-audible sounds: Understanding the effects of wind turbine noise.” Proceedings of Meetings on Acoustics, Vol. 19: Journal of the Acoustical Society of America. 133(5), 3419.

Nissenbaum M.A., Aramini J.J., Hanning C.D. (2012). Effects of industrial wind turbine noise on sleep and health. Noise Health. Sep-Oct;14(60):237-43.

Pierpont, N. (2009). “Wind Turbine Syndrome.” K-Selected Books.

Salt, A.N., DeMott, J.E. (1999). “Longitudinal endolymph movements and endocochlear potential changes induced by stimulation at infrasonic frequencies,” Journal of the Acoustical Society of America. 106, 847-856.

Salt, A.N. (2004). “Acute endolymphatic hydrops generated by exposure of the ear to nontraumatic low frequency tone,” Journal of the Association for Research in Otolaryngology. 5, 203-214

Salt, A.N., Brown, D.J., Hartsock, J.J., Plontke, S.K. (2009). “Displacements of the organ of Corti by gel injections into the cochlear apex,” Hearing Research 250:63-75.

Salt, A.N., Lichtenhan, J.T. (2102). “Perception-based protec-tion from low-frequency sounds may not be enough,” Pro-ceedings of the InterNoise Symposium , New York.

Salt, A.N., Lichtenhan, J.T., Gill, R.M., Hartsock, J.J. (2013). “Large endolymphatic potentials from low-frequency and infrasonic tones in the guinea pig,” Journal of the Acousti-cal Society of America 133 :1561-1571.

Schermuly, L, Klinke, R. (1990). “Origin of infrasound sensi-tive neurones in the papilla basilaris of the pigeon: an HRP study,” Hearing Research 48, 69-77.

Schomer, P. (2013). “Comments On Recently Published Article, “Concerns About Infrasound From Wind Turbines,” Acoustics Today 9:4: 7-9

Schuknecht, H.F. (1977). “Pathology of Ménière’s disease as it relates to the sac and tack procedures,” Annals of Otology, Rhinology and Laryngology. 86:677-82.

Timmerman, N.S. (2013). “Wind Turbine Noise,” Acoustics Today, 9:3:22-29

Voss, S.E., Rosowski, J.J., Merchant, S.N., Peake, W.T.. (2001). “Middle-ear function with tympanic-membrane per-forations. I. Measurements and mechanisms,” Journal of the Acoustical Society of America 110:1432-1444.

Weisz, C.J., Lehar, M., Hiel, H., Glowatzki, E., Fuchs, P.A. (2012). “Synaptic Transfer from Outer Hair Cells to Type II Afferent Fibers in the Rat Cochlea,” Journal of Neuroscience. 32:9528-9536.

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page 30 - please romanize the citation for Schafer

ANSI/ASA S1.1-2013

AMERICAN NATIONAL STANDARD Acoustical Terminology This standard provides definitions for a wide variety of terms, abbreviations,

and letter symbols used in acoustics and electroacoustics. Terms of general

use in all branches of acoustics are defined, as well as many terms of special

use for architectural acoustics, acoustical instruments, mechanical vibration

and shock, physiological and psychological acoustics, underwater sound,

sonics and ultrasonics, and music.

To purchase an electronic copy of this ANSI Standard or other National or International Standards on Acoustics, Mechanical Vibration and Shock,

Bioacoustics, or Noise please visit the Acoustical Society of America's online store at:

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You can purchase hard copies of Standards by contacting our office at:

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Introduction The soundscape concept was first introduced as an approach to rethink the evaluation of “noise” and its effects on the quality of life. Now it has evolved into something much more. Soundscape suggests exploring all of the sound in an environment in its complexity, ambivalence, meaning, and context. Basically, the soundscape concept considers the conditions and purposes of its production and perception. Conse-quently, it is necessary to understand that the evaluation of noise / sound is a holistic approach.

This is why soundscape research represents a paradigm shift in the field of environ-mental sound evaluation. Moreover, it firstly relies upon human perception and then turns to physical measurement. The soundscape technique uses a variety of investiga-tion techniques, taxonomy, and measurement methods, soundwalks, questionnaires, interviews and recordings (Schafer, 1977). This is a necessary protocol to approach a subject or phenomenon, to improve the validity of the research or design outcome and to avoid systematic errors by relying only on one approach.

The soundscape approach enhances the use of available resources through adding the human capital: the “local expertise” of the particular environment’s inhabitants.

Exploring Our Sonic Environment Through Soundscape Research & TheoryHow can we know what people think of their sonic environment? Well, we ask them!

Bennett M. [email protected]

Brooks Acoustics Corp. Vernon, CT 06066

Brigitte Schulte-Fortkamp [email protected]

Technical University BerlinPsychoacoustics, Noise Effects,

Soundscape10587 Berlin, Germany

Kay S. [email protected]

Media VoigtSound Engineering

and Soundscape12435 Berlin, Germany

Alex U. [email protected]

University of Massachusetts LowellSound RecordingTechnology

Lowell, MA 01854





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This it is why it is of primary importance that physical noise criteria match perceptive descriptors with perception being the leading factor. As a result, we can better match the inhab-itants’ needs and desires with an implemented design scheme. For example, in the community noise field, we can correlate complaints of people living in a certain place with metrics for policy. In the architectural design field, we can create a built environment which aligns the designer’s aesthetic vision and the users’ comfort, effectiveness and sense of well-being. This process also has its parallels in the field of sound recording and musical composition. Concerning interdisciplinarity, the methods of psychology and sociology, to engineering and de-sign analyses are introduced to guarantee the combination of perceptual and physical tools for the planning of a multitude of land uses and building structures.

backgroundSoundscape studies have a rich tradition. The term as we use it today was introduced by R. Murray Schafer in 1977. Since then, this idea has been the subject of much research and application. A description of the work in progress up to now was presented in Acoustics Today (Schulte-Fortkamp et al. 2007), and in special issues in Soundscape (Schulte-Fortkamp and Dubois 2006) and the Journal of the Acoustical Society of America (Schulte-Fortkamp and Kang 2013).

Because the soundscape field has evolved differently around the world, as well as across disciplines, there is a diversity of opinions about its definition and aims. Consequently, the use of the term ‘soundscape’ has become idiosyncratic and ambiguous. The International Standard ISO/DIS 12913-1 (2013). aims to enable a broad international consensus on the definition of ‘soundscape,’ to provide a foundation for com-munication across disciplines and professions with an interest in soundscape (Brown, et al., 2011). The standard distin-

Figure 1 : Typical urban public space for soundscape studies. Alexan-derplatz, Berlin (2011)


guishes the perceptual construct (soundscape) from the physi-cal phenomenon (acoustic environment), and clarifies that soundscape exists through human perception of the acoustic environment. For the purpose of the International Standard, soundscape will be understood as a perceptual construct that is related to a physical phenomenon.

Current StatusSoundscape research represents a paradigm shift as it firstly counts on human and social sciences (e.g. psychology, sociolo-gy, architecture, anthropology, medicine) and then on physics, but also takes into account the diversity of soundscapes across countries and cultures. Governments have sponsored much of the recent soundscape research. So, given the simple objec-tive to reduce the noise level (the main focus, for example of the European Union (EU) environmental noise policy) it was found that the Environmental Noise Directive (2002/49/EC) does not necessarily lead to improved quality of life in urban/rural areas. Thus, a new multidisciplinary approach is essential as provided through the EU COST (European Cooperation in Science and Technology) Action TD0804 on Soundscape of European Cities and Landscapes, which includes 52 par-ticipants from 23 countries participating in COST, including 10 participants from outside Europe. As an outcome of this action a practical guidance in soundscape research is available (Kang, et al., 2013).

CollaborationsThere have also been collaborations with soundscape research-ers in other networks, such as the Global Sustainable Sound-scape Network (GSSN)www.greener-cities.eu. funded by the USA National Science Foundation, further COST Actions, and a number of EU projects including the “Holistic and Sustainable Abatement of Noise by optimized combinations of Natural and Artificial means“ (HOSSANA)www.greener-cities.eu. and the urban sound planning project SONORUS-www.fp7.sonorus, further EU networks such as European Network on Noise and Health (ENNAH)www.ennah.eu.

What is central to soundscape research focused on noise and its perception?While classical noise indicators are known to show strong limitations under certain sound conditions (low frequency noise, tonal components, multisource environments), it is central to soundscape research and implementation to fit the applied indicators to the perception and the appraisal of the concerned people. The fit of indicators also depends, however, on the type of investigated soundscape. It is extremely impor-tant that the fit of indicators reflects the situation and context (personal, social, cultural, land use, economic, geographic) which define the sonic listening space, and also enables trac-ing dynamic changes like time variances of the soundscape over the day or seasons (Figure 1 - previous page).

Overarching main requirements and some of the associated questions for indicators should be:• To support acoustical appraisal: Acoustic distinction of the

variety of soundscapes (Why does this place sound different? What is unique?)

• To support psycho-physiological appraisal: Assess the grade and type of neurophysiologic stimulation (Is the soundscape stressing, supporting or relaxing? Which emotions are linked to it?)

• To support context appraisal: Assess the person-environment fit (Are there sounds or sound components which interfere with intentions / expectations / meaning or support these? Are there other sensory factors [visual, vibration, odors] which interact with the sounds in a supporting or distorting way? Is the meaning of this place or the attachment to this place distorted, undermined or supported?)

• To support design or remedial action: Assessing the holistic potential of the place (Are control / coping options available / implementable? Can new meaning / emotions / attach-ment and social interaction be created to support adaptation and meet expectations?)

http://www.greener-cities.eu




http://www.ennah.eu

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In practice there is still a significant gap between soundscape indicators which are used in some standardized way in “mea-surement by persons” and those applied in “measurement by instruments.” For example, psychoacoustic, ecological and landscape acoustics need techniques to be more tightly inte-grated in such studies to mediate between personal experience and group-area-society requirements and needs. Moreover, only through proper integration of these techniques can the potential of the soundscape approach be implemented in planning and design.

Thus, the soundscape approach relies by definition on this strategy and in the strict sense it can be said: any study which does not use triangulation, that is, a combination of several differing investigative methods, cannot be considered a com-plete soundscape study. So we must look at each soundscape situation from several viewpoints to obtain a more complete picture of reality!

Why Triangulation?The concept of triangulation is borrowed from navigational and land surveying techniques that determine a single point in space with the convergence of measurements taken from

two other distinct points. The idea is that one can be more confident with a result if different methods lead to the same result. Accordingly, triangulation is a powerful technique that facilitates validation of data through cross verification from two or more sources (Figure 2). In particular, it refers to the application and combination of several research methodolo-gies in the study of the same phenomenon (Denzin, 2006;Jonsen and Jehn, 2009).

Soundscape as a resourceTraffic noise sources (Figure 3) do not only cause annoy-ance, but also offer non-visual orientation in one’s daily life. Subconscious routines reduce the effort of paying attention. To discuss the contribution of soundscape research in the area of community noise soundscape is understood as a resource, from which benefit is produced.

Typically, resources may be defined materials, money, services, staff, or other assets that are transformed to produce benefits to the interested parties, and in the process may be consumed or made unavailable. Benefits of resource utilization may include increased wealth, meeting needs or wants, proper functioning of a system, or enhanced well-being. From a hu-man perspective a natural resource is anything obtained from the environment to satisfy human needs and wants.Central to soundscape analysis is placing sound in a context, with noise and sound linked to activity at realistic study sites. The listener’s sensational reality depends on the combina-tion of their socio-cultural background and the psychological dimension with the acoustical setting. The acoustical social-ization (acoustical biography) and action frame of reference of the concerned residents will also influence environmental noise evaluation. Therefore, tools for the exploration of the soundscape, microscopic as well as macroscopic, are needed.Clearly, the concept of sound as a resource reaches across a broad range of applications. For example, in architectural design, the introduction of artificial “noise,” known as sound masking, can greatly improve the speech privacy, comfort, and effectiveness of workers in open-plan office environments.

Figure 2 : Basic triangulation model in soundscape research and practice (Lercher and Schulte-Fortkamp (2013)

Methodological triangulation

Led by investigator

Narrativeinterview,workshop

Led by the instruments

Led by the users of the space, the local experts

Sound analysis

Questionnairesurvey Soundscape


Similarly, in music composition and sound recording, the introduction of intense elements of volume or dissonance at the right moment can evoke the desired emotional response of the audience.

Needs – What must soundscape researchers and theorists do going forward?Beside the involvement of different disciplines, it is important to define areas of future research that will build the platform for further development. These include the areas of econom-ics, noise policy-standards, and combined effects. Also vital is research into common protocols, cross cultural studies, educa-tion about soundscape, combined measurement procedures, the perception of the character of sounds, and cross cultural questionnaires. Moreover, the importance of survey site selec-tion has to be emphasized, along with multi-sectorial environ-mental health impact assessment, the perspective on sustain-able development environmental zoning, citizen involvement, and preservation of quiet areas.

This rather long list of vital influences on understanding the complete soundscape may seem daunting. However, these are all within the reach of today’s scope of knowledge. These just need the continued attention of researchers to become effective tools for soundscape analysis. The benefit of develop-ing these tools is the realization of high quality sonic environ-ments that meet the needs and desires of their occupants.As we have learned from the Community Noise perspective, it is important to distinguish the totality of soundscape from

the limited idea of a quiet zone. Consideration of “sensitive areas” and the design of “supportive environments” require new insights into the existing annoyance data and new integrative research strategies. There is a common consensus about the necessity of additional parameters beside the A-weighted sound pressure level which exists in an environment. Psychoacoustic parameters contribute immensely to efforts to measure and assess environmental sound more properly. Us-ing psychoacoustic parameters, mainly based on standardized procedures of measurement and analysis, it will be possible to explain contributors of annoyance caused by environmen-tal noise. As for the evaluation procedure, it is needed to integrate contextual and subjective variables, to ensure that soundscape is not just a matter of noise level reduction but also accounts for people’s concerns and well-being.

Among qualitative methods there is a heterogeneous ‘research landscape’ which embodies different forms of observation, in-terviewing techniques with low level of standardization (such as open ended, unstructured interviews, partially or semi-structured interviews, guided or narrative interviews), and the collection of documents or archival data. Consequently, a host of methods are used, which rest on various theoretical and assumptions and methodological positions.

Yet, in spite of their differences, those approaches all share common ground, as advocates of the ‘interpretive paradigm’ agree on certain ideas about the nature of social reality, which is shaped by social meaning. So, for an environment’s inhab-itants, their perceived social reality is always a ‘meaningful’ reality. That is, the inhabitant thinks, consciously or sub-consciously, “What does this feature of the environment mean to me?” A particular feature could have great impact, or none at all, on an individual. Similarities and differences in percep-tion of the social reality among individuals may merge into a picture of consensus for a collective group of individuals. Due to the importance of meaning to the lives of these inhab-itants, their social reality refers to a context of action which they observe in other people, and about which they may form judgments. Social reality always depends on a certain point

Figure 3 : Traffic noise sources, Broadway, New York City (2012)

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of view or perspective and is therefore tied to social loca-tion. And lastly, since social reality is negotiated, it is always dynamic: social reality is a process. Clearly, this theoretical understanding of qualitative approaches will help to also understand what is meant by local expertise.

Research guided through local expertiseLocal experts are those people who live in the area under in-vestigation and provide their expertise to researchers and proj-ect designers through such processes as soundwalks and open interviews (Voigt and Shulte-Fortkamp, 2012). Soundwalks are participatory group sound and listening walks through the environment. During these exercises, soundscape analysts ob-serve and measure the perceptual responses of the participants to the acoustical, visual, aesthetic, geographic, social, and cul-tural modalities. Participation of local experts in soundwalks enables us, as researchers and practitioners, to collect and analyze acoustical as well as perceptive data. This enhances the investigator’s sensitivity for the particularities of the examined areas. As the multidimensional human perception cannot be easily reduced to singular values of physical unit, such as A-weighted decibels (Figure 4) there is an imperative to obtain higher order layers of local expert descriptions, which provide a path to the meaning of sounds - and what quality may make them perceived as noise, or conversely as a desired, even trea-sured resource. This emphasizes the importance of recognizing the composition of multiple sound sources. Based on earlier findings, the response to sound depends on the listener’s men-tal, social, and geographical relation with the sound source. Hiramatsu (2004) has proposed a method for comparing sonic environments on the basis of physical properties of and experiences and/or memories of sonic environments.

What are the inhabitants’ expectations?The attitude and the listener’s expectations and experiences are significant parameters which may be used to comprehend the different perceptions and evaluations due to specific stimuli. People unconsciously gather the most important key features of the sonic environment, by experiencing this area in daily life. Mining these data on soundwalks and in interviews, and then combining them with the analysis of acoustical measure-ments via triangulation, sheds light on the phenomenon from different aspects.

The soundwalk as an access tool to the sonic resourceThe soundwalk, as one of the most important tools in the soundscape method, has variable procedures regarding the context, scientific issues, and approach (Fiebig et al. 2010). Over the past decades its focus has shifted from obtaining the researcher´s view to determining the people´s understanding of places. Mainly, the evaluation on rating scales and anno-

Figure 4 : Example of physical measurements of traffic sound – see instrument box and display on pole. Seocho-dong, Seoul (2009)


tating people’s comments gains access to the experiences and expectations of the listening and observing attendee (Figure 5).

For example, the interview ques-tions may relate to the people’s agreement with a series of descriptions, on a verbal scale from “not-at-all” to “extremely.”

Experiences include comparisons of similar and oppositional situations and show the time-grown development of the peoples’ individual and collective mind (Voigt, 2013). They also refer to results of shifted strategies elaborated by previous decisions of acceptance and rejection of different soundscapes. This process of adjusting is described as “Passung” (Shulte-Fortkamp, 2010). That process considers all conscious and unconscious influences to the peoples’ mind as they judge the appropriateness of sounds to sources, places, or situations.

Expectations of a known place imply a bandwidth of accepted occurrences which are often indicated by noticing the devi-ances. Descriptions and ratings of the situation, the loca-tion, occurrence, and sound sources, are the most common comments in the non-hierarchical, multiple layers of written reflections. Expanding the evaluation through situational dis-course to an ad-hoc interview on the noted perception reveals additional layers of description.

In essence, data mining in the analysis of soundwalks goes beyond combining graphs vs. time with the notes of the attendees, and is already in process during data acquisition. The feedback given by the soundwalk participants after the original questioning enhances the analyst’s insight into the meaning of sound to those local experts, and identifies how a particular sound may be perceived as a positive feature, or as noise.

Considering moderatorsObviously, the soundscape approach and its methods enable us to learn about the process of perception and evaluation sufficiently as they take into account the context, ambience, the usual interaction between listener and sound, as well as the multidimensionality of sound perception. By contrast, conventional methods often reduce the complexity of real-ity to controllable variables, which supposedly represent the scrutinized object. Furthermore, traditional tests (2-AFC-method, A/B-comparison etc.) frequently neglect the context-dependency of human perception; they only provide artificial realities and diminish the complexity of perception to merely predetermined values, which do not completely correspond with perceptual authenticity. However, perception and evalu-ations entirely depend on the respective influences of the acoustic and non-acoustic moderators, as for example vegeta-tion, neighborhood, and life-style.

Application of soundscape analysis of local expertise to an outdoor public spaceThe development of the Nauener Platz in Berlin, a public place, is a pioneering example of how to collaborate in a soundscape approach with all project-relevant parties, or stakeholders. The Project “Nauener Platz - Remodelling for Young and Old” was conducted within the framework of the German government sponsored research program “Experi-mental Housing and Urban Development (ExWoSt)” of the “Federal Ministry of Transport, Building, and Urban Affairs (BMVBS)” by the “Federal Office for Building and Regional Planning (BBR)”.

Figure 5: Soundwalk with local experts, Berlin (2013)

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The key concept in the development of the outdoor public open place is the understanding that people living in the chosen area are the “real” experts concerning the evaluation of this place, according to their expectations and experiences of that place. Their knowledge is one of the most important investigative resources. The intention of the scientific research here is to learn about the meaning of the sounds and/or noise to those people, with respect to their living situation, and to implement adequate changes to effect an improvement of this place.

As the aim was to rebuild the place into one with social freedom, it was most relevant to involve those people who lived in the area from the very beginning (Figure 6). Therefore, different approaches were carried out to get residents involved by,

for example, public hearings about the intention of renovat-ing the place and meeting with different social groups to determine their different expectations through well-defined workshops. Attention was given to participants’ gender and age, and also to interdisciplinarity in collaboration among the researchers. “Sound walking” with all its evaluation features also provided the attendees of the several groups with a bond-ing quality to the development of “their” new place (Figure 7). This was crucial to the acceptance of the installed features, reflected by the low very level of vandalism after the renova-tion. In 2012 this project was honored through the European Soundscape Award (www.eea.europa.eu).

In the scientific research project “Dynamic arrangement of urban safety cultures” – in the framework of the German “Federal Ministry of Education and Research” (BMBF) – the soundscape approach delivered new insights on the influence of acoustics toward the feeling of safety toward public places. Soundwalks and subsequent narrative interviews with profes-sional security experts as well as local experts widened the field of understanding about modifying the quality of par-ticipant-declared unwanted sounds. The sonic characteristics of the unwanted sounds were traced to the occurrences and situations in those places, with the participants identifying on a subconscious level indicators which then demanded higher attention.

The process of “tuning” urban areas, based on the expertise of the people’s mind to improve the quality of life, is strongly related to the strategy of triangulation (Schulte-Fortkamp, 2010).This provides the theoretical framework within which to develop the solution and actualize the needed change in an area. In other words: approaching the field in this holistic manner is a necessary component for success. An effective and sustainable reduction of the number of highly annoyed people caused by noise, and increasing the number of people greatly pleased, is only possible with further scientific endeavors in the area of methods development, and the research and ap-plication of sonic effects.

Community noise implicationsIn the community noise field, noise level maps can start to provide an understanding of noise reactions and reliably iden-tify perception-related hot spots. Psychoacoustic parameter maps are particularly interesting in areas where the noise levels

Figures 7a (left) and 7b (right) : Nauener Platz, Berlin, in 2007 and 2009

Figure 6 : Scaling, Rating, Noting - Soundwalk, Berlin (2008)

http://www.eea.europa.eu


are marginal below the mandated noise level limits and offer an additional interpretation to identify the respective noise sources.

What we have to think of when we talk about innovation through soundscapeIn environmental health impact assessments (airports, rail tracks, roads) only the upper health limits of exposure are addressed. This leads to an attitude in government administra-tion and policy to “fill up” the noise exposure to the maxi-mum allowed.

Therefore, during the last 20 years noise exposure has spread from urban centers to suburban and rural areas and from day to nighttime - thereby reducing the viable options for restora-tion, undisturbed communication, while impairing public health and the environmental “quality of life.”

Due to this unfavorable development recent strategy papers, guidelines and directives have stressed a change in noise policy and administration towards more perception oriented and sustainable assessments, including the protection of quiet and sensitive areas and times.

For example: it was the task of WG-3 of COST Action TD0804 to reconcile and integrate classical and soundscape oriented means (“harmonizing”) and link those with quality of life and health related outcomes, in order to find appropri-ate strategies at different scales of assessment and implementa-tion (Lercher and Schulte-Fortkamp, 2013).

There is still a lack of willingness and often ignorance among policy makers to use soundscape techniques in noise action plans and for the protection of quiet areas. Funding agencies still hesitate to fund soundscape projects.

The situation differs, however, broadly from country to country: ‘Trying to do the right thing, play it straight, the right thing changes from state to state’ (Soul Asylum – Leave without a trace, 1992)

In order to take the full advantage of the benefits of the soundscape approach, it has to be accepted that:• the involvement of different disciplines is needed to identify

the resources in human and physical terms;• soundscape research is the appropriate platform for further

development in standards for improvement of the ecology and economy, as well as for noise policy-standards concern-ing the enhancement of quality of life;

• there is the need to link public Quality of Life and Health to Soundscape;

• there is the urgent need for the International Organization for Standardization (ISO) Working Group 54 of ISO / TC 43 / SC 1 to reach consensus on the soundscape defini-tion standard ISO/DIS 12913-1, to provide the necessary stimulus for further worldwide progress.

Architectural Design ImplicationsThe soundscape methods described above may be easily transferred to the fields of architectural and urban design, for projects which include building interior and exterior spaces, site planning, urban and transportation planning, public parks, and more (Brambilla and Maffei, 2010). The sound-scape method can be most effectively used to address acousti-cal concerns as early as possible in the architectural design process, even in the inspiration (vision) phase of a project.

Sonic perceptions of the built environment are often a vital part of the vision for a project, and must be expressed at the outset to be fully incorporated in the design. In this approach, design inputs are solicited from all stakeholders and design team members very early, before programming. Innovative project delivery methods and contract structures such as IPD (Integrated Project Delivery), unlike the tradi-tional design-bid-build method, assign shared risk and reward among the design, construction and management teams. This offers great opportunities for practitioners, through sound-scaping, to include acoustics in the initial project discussions, and to advance the implementation of quality sonic environ-ments.

“ Trying to do the right thing, play it straight, the right thing changes from state to state.” Soul Asylum – Leave without a trace, 1992

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There is a striking congruency between architectural design and sound recording for music in the application of sound-scape methods. How can the designer/composer ensure that their work will be successful? As Schafer said, “Orchestration is a musician’s business. I am going to treat the world as a macrocosmic musical composition” (Schafer, 1977). To quote Cage, “Music is sounds, sound around us whether we are in or out of concert halls”(Warner and Cox, 2004). The answer to these questions is intriguing.

So many soundscapes – found, archived, preserved or com-posed – consist of multiple sound elements. The interaction among these individual sounds can conflict and obscure, or complement and harmonize. The creation of sound record-ings through the multi-track production process offers a point of view into how an overall soundscape can be successfully created, and multiple sounds effectively orchestrated (Case, 2013). The parallels between the music production process and the architectural design process offer insights about how soundscape methods may help the composer/designer to cre-ate a meaningful “sense of place” within the listener.

What’s next?The link between the fruits of soundscape research and their application to sonic environments which provide a sense of comfort and well-being is currently being developed. The focus of project soundscape designers is to establish consistent means to gain the stakeholder acceptance needed to imple-ment these exciting, effective and creative tools.The ultimate goal here is for the soundscape tool to be rec-ognized as so powerful, so effective, and so influential that private developers, architects and urban planners will under-stand that they must use it, or risk the failure of their project. Perhaps too large a goal? We think not. The soundscape method is the logical and practical extension of an idea that was decades in the making, yet just now coming of age. There are many precedents to this approach in the built environ-ment community, which are now coming to the fore. The timing is propitious and the benefits are enormous.Stay Tuned!

biosketches

Bennett M. Brooks is President of Brooks Acoustics Corporation (BAC). He believes that environments should provide a sonic dimension which promotes a sense of well-being. He is a licensed Professional En-gineer, Fellow of the Acoustical Society of America, Member of the Institute of Noise Control Engineering, and Past President of

the National Council of Acoustical Consultants.

Brigitte Schulte-Fortkamp is Professor of Psychoacoustics and Noise Effects at the Institute of Fluid Mechanics and Engi-neering Acoustics, Technical University of Berlin, Germany and ASA Vice President, 2011-2012. She received the European Soundscape Award in 2012.

Kay S. Voigt was research assistant in the department of Psychoacoustics and Noise Effects of the Institute of Fluid Me-chanics and Engineering Acoustics in the Technical University of Berlin, Germany. Currently he is working as freelance re-searcher in acoustics and sound engineering.

Alex U. Case is Associate Professor of Sound Recording Technology at the University of Massachusetts Lowell, USA, a member of the Audio Engineer-ing Society, and a Fellow of the Acoustical Society of America. He is a former Chair of the AES Education Committee and the ASA Technical Committee for Architectural Acoustics.


Brambilla, G., and Maffei, L. (2010). “Perspective of the soundscape approach as a tool for urban space design,” Noise Control Engineering Journal, vol. 58, no. 5, pp. 532–39.

Brown, A.L., Kang, J., and Gjestland, T. (2011). “Towards standardization in soundscape preference assessment,” Applied Acoustics, vol. 72, no. 6, pp. 387–392.

Case, A. (2013). “Combining elements of the soundscape – lessons from the recording studio,” Journal of the Acoustical Society of America, vol. 134, no. 5, pt. 2, p. 4021.

Denzin, N. K. (2006) The Research Act: A Theoretical Intro-duction to Sociological Methods.(Aldine, Chicago, IL), p.300.

Fiebig, A., Acloque, V., Basturk, S., Di Gabriele, M., Horvat, M., Masullo, M., Pieren, R., Voigt, K. S., Yang, M., Genuit, K., and Schulte-Fortkamp, B. (2010). “Education in Sound-scape – A seminar with young scientists in the COST Short Term Scientific Mission “Soundscape – Measurement, Analy-sis, Evaluation,” Proceedings of 20th International Congress of Acoustics, ICA 2010, Sydney, Australia

Kang, J.,Chourmouziadiou, K., Sakantamis, K., Wang, B., Hao, Y. [editors] (2013). Soundscape of European Cities and Landscapes. (First Edition, E-book, Oxford, by Soundscape-COST TUD ActionTD0804)

Lercher, P., and Schulte-Fortkamp, B. (2013). “Soundscape of European Cities and Landscapes – Harmonising,” in Kang, J., et al. (2013). Soundscape of European Cities and Landscapes. (First Edition, Oxford by Soundscape-COSTTD0804), p.126.

Hiramatsu, K. (2004). “Soundscape: The Concept and Its Significance in Acoustics,” Proceedings of 14thInternational Congress of Acoustics, Kyoto, Japan

Jonsen, K., and Jehn, K. A. (2009). “Using triangulation to validate themes in qualitative studies,” Qualitative Research in Organizations and Management: An International Journal, vol. 4, no. 2, pp. 123–150.

Schafer, M. R.(1977). The Soundscape: Our Sonic Environ-ment and the Tuning of the World Destiny Books (Rochester, Vermont) pp.147; p. 5.

Schulte-Fortkamp, B. (2010).“The tuning of noise pollu-tion with respect to the expertise of people’s mind,” Plenary Lecture Internoise 2010, Proceeding Internoise 2010, Lisbon, Portugal

Schulte-Fortkamp, B., Brooks, B.M., and Bray, W. R. (2007). “Soundscape: An Approach to Rely on Human Perception and Expertise in the Post-Modern Community Noise Era,” Acoustics Today, vol. 3, no. 1, p. 7-15.

Schulte-Fortkamp, B., and Dubois, D. [guesteditor] (2006).Ed. Special Issue on Soundscapes - Recent advances in Sound-scape research, ActaAcustica Vol. 92, no. 6.

Schulte-Fortkamp, B., and Kang, J. [guesteditor] (2013). Special issue Soundscape, Journal of the Acoustical Society of America, vol.134, issue 1, pp. EL1-900.

Voigt, K. S., and Schulte-Fortkamp, B. (2012). “Quality of life – why does the soundscape approach provide the correct measures?,” Proceedings Inter-Noise 2012, New York City, USA

Voigt, K. S. (2013). “Soundwalk analysis of public spaces in the City of Berlin”, Tagungsband AIA-DAGA 2013, Merano, Italy

Warner, D., and Cox, C. (2004).Sound in continuing compo-sition: Soundscape, Indeterminacy and Ambient and Genera-tive music (New York, Continuum) p.30.

SO/DIS 12913-1, FDIS - Draft 1 (2013-10-03), ISO / TC43 / SC1/ WG54, perceptual assessment of soundscape quality, International Organization for Standardization.

www.greener-cities.euwww.eea.europa.euwww.ennah.euwww.fp7.sonoruswww.soundscapenetwork.org

References


http://www.eea.europa.eu

http://www.ennah.eu

http://www.fp7.sonorus

http://www.soundscapenetwork.org

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book Reviews

This issue of Acoustics Today introduces a “new” bOOK

REVIEWS section. In the past, Acoustics Today listed

new books that were referred to us (most often by au-

thors) and included the publisher’s description of the

book. While we will still continue to do this for books from

the new ASA Press, the primary goal of the book section

now will be to provide actual book reviews obtained by

the JASA and (now) Acoustics Today book review edi-

tor, Philip Marston. for the most part, the book reviews

in AT will be those that appear in JASA. The rationale for

this duplication is that most ASA members read JASA

only online and often overlook the very useful book re-

views. by sharing reviews between the two publications,

we give added exposure to the reviews, and thus to im-

portant new books in acoustics. Authors of new books

and publishers of new books in acoustics are most wel-

come to contact Philip Marston ([email protected]) and

arrange for copies to be sent to him for possible review.

book Review Editor

Philip L. MarstonPhysics and Astronomy Department

Washington State UniversityPullman, WA 99164-2814



book Review

Ultrasonic and Electromagnetic NDE for Structure and Material Characterization: Engineering and Biomedical Applications

Author: Tribikram Kundu (editor)Publisher: CRC Press, Taylor and Francis GroupISBN: 978-1439836637Pages: 890 (with 649 illustrations)Binding: HardcoverPublication Date: June 25. 2012Price: $139.95

This book edited by Tribikram Kundu is an expanded and updated version of Ultra-sonic Nondestructive Evaluation: Engineering and Biological Material Characteriza-tion (CRC Press, 2004, available in electronic form also.) This earlier book (henceforth referred to as I) dealt with ultrasonic techniques only and had 14 chapters, each written by well-known researchers in their field of interest. This new book follows the same tradition and has 18 chapters, some of which cover the same materials as in I , namely, mechanics of elastic waves and ultrasonic nondestructive evaluation (Chapter 1), mod-eling of ultrasonic fields by distributed point source method (Chapter 2), fundamentals and applications of nonlinear ultrasonic nondestructive evaluation (Chapter 6), theory and application of laser ultrasonic techniques (Chapter 7), ultrasonic characterization of biological cells (Chapter 12), and ultrasonic characterization of hard tissues (Chapter 13). New topics included in this book are: electromagnetic nondestructive evaluation (Chapter 3), distributed point source method for modeling and imaging in electrostatic and electromagnetic problems (Chapter 4), material characterization by nonlinear ultrasonic technique (Chapter 8), toward structural health monitoring solutions for bolted joints (Chapter 9), clinical applications of ultrasonic nondestructive evalua-tion (Chapter 14), terahertz radiation for nondestructive evaluation (Chapter 15), and fiber –optic sensors for structural health monitoring. Other topics covered in the book which were also included in I are: guided waves for plate and pipe inspection (Chapter 5), measurements of the elastic properties of solids by Brillouin Spectroscopy (Chapter 10), and theory and applications of scanning acoustic microscopy and scanning near – field acoustic imaging (Chapter 11). The book is a collection of review articles, some of which are comprehensive and include extensive up-to-date references.

RE VIE W bY

Subhendu K. DattaProfessor Emeritus

Department of Mechanical Engineering

University of ColoradoBoulder, CO 80309-0427

1

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Chapter 1 (by T. Kundu) in this book is the same as that in I and it deals with basic equations governing the deformation of a linearly elastic continuum. The treatment of plane har-monic wave propagation in infinite, semi–infinite, and layered media follows that found in standard textbooks. This chapter also contains discussion of sound waves in homogeneous fluids and solids surrounded by fluids. The chapter has several worked out problems as well as exercise problems that should be useful to the graduate students. Researchers and practitio-ners will find this chapter lacking in a comprehensive treat-ment of elastic waves in anisotropic and composite media. A clear discussion of phase, group, and energy velocities and slowness surfaces is also missing. A very brief (and necessarily incomplete) description of waves in anisotropic media can be found later in Chapter 10.

A numerical technique using distributed point sources (DPSM) to model the acoustic and elastic fields generated by a transducer placed in the fluid in contact with another fluid or an isotropic elastic solid is presented in Chapter 2 (by T. Kundu, D. Placko, S. Das, T. Bore, and E.K. Rahani). The authors have developed this method in recent years to solve several problems of practical interest. The method was pre-sented in I (Chapter 2, by D. Placko and T. Kundu). Chapter 2 in this book is an updated version of the previous review.

Electromagnetic nondestructive evaluation techniques are reviewed in Chapter 3, by P.B. Nagy. A brief introduction to electromagnetic wave propagation is given first. This is fol-lowed by the theory of eddy currents and Dielectric inspec-tion, and thermoelectric inspection. This chapter has many example problems and extensive references that will be very useful to students and practitioners.

The DPSM discussed in Chapter 2 is extended to solve elec-trostatic and electromagnetic problems in Chapter 4. Here Placko, Bore and Kundu review their work on modeling and imaging the effects of cracks or interfaces on the fields gener-ated by probes.

Guided elastic waves in homogeneous and layered plates have been extensively studied in recent years. Two recent mono-graphs, Elastic waves in composite media and structures:

with applications to ultrasonic nondestructive evaluation, by S.K. Datta and A.H. Shah, and Physical ultrasonics of composites, by S.I. Rokhlin, D. E. Chimenti, and P.B. Nagy, contain comprehensive treatments (with extensive references) of guided waves in single and multiple layered composite plates. They also discuss waves in periodic layered composite plates which is important in the context of multiple layered composite plates. T. Kundu presents a somewhat incomplete review in sections 5.1 – 5.7 of Chapter 5 (Guided waves for plate and pipe inspections) with very few references and this is the same review that appeared in I (Chapter 4). Sections 5.8 – 5.9 are devoted to circumferential and axial wave propaga-tion in cylindrical pipes. A more comprehensive treatment of circumferential waves in pipes was presented by J. Qu and L. Jacobs in I (Chapter 5). A comprehensive treatment of axial waves in composite cylinders can be found in the monograph by Datta and Shah.

Nonlinear ultrasonic waves provide an important tool to characterize material defects (dislocation, cracks, and metal fatigue), microstructure, effects of precipitation, etc. Chapter 6 (by J.H. Cantrell) is a good review of fundamental equa-tions and their applications to the measurements of acoustic harmonics generated from the nonlinear interactions of an incident wave with basic lattice configurations of anharmonic materials, microstructures, etc. The review also includes study of acoustoelasticity to measure state of stress in the material. The material covered in this chapter is basically the same as in Chapter 6 of I, with an update of recent works on fatigue damage, precipitate induced harmonic generation, and non-linear dislocation dynamics.

Nonlinear elastic waves in a bounded homogeneous isotropic solid are investigated in Chapter 8 (by J.-Y. Kim, L. J. Jacobs, and J. Qu). Here, the focus is on secondary wave generation from a primary wave due to quadratic nonlinearity. Rayleigh waves in a semi – infinite medium and Lamb waves in a plate are treated as examples. This provides a good review of current work and motivation for further research.

Theory and application of laser generated ultrasonic waves in the thermoelastic regime has been reviewed in Chapter 7 (by S. Krishnaswamy and F. Zhang). This is an updated version

“ a valuable addition to the literature on nondestructive evaluation of materials and structures”


of that found in Chapter 7 in I. Laser ultrasonic techniques have been investigated by many researchers and practitioners since the early work by White. The theory and application of laser ultrasonic NDE are presented here in a comprehensive manner with extensive references. Brillouin light scattering is also a noncontact technique to measure elastic properties of material. A comprehensive review of this technique, which is particularly suited for measurements of elastic anisotropic bulk properties of small samples and anisotropic properties of thin films, is presented in Chapter 10 (by M.C. Beghi, A.G. Every, V.B. Prakapenka, and P.V. Zinin). This is an updated version of Chapter 10 in I. A brief review of bulk and surface waves in anisotropic solids is presented in this chapter. Exten-sive references are given to guide the readers to the published literature.

Chapter 11 (by P.V. Zinin, W. Arnold, W. Weise, and S. Berezina) provides a review of the theory and application of scanning acoustic microscopy and imaging by acoustic microscopy. Since the development of acoustic microscopy for imaging near – surface microstructure of opaque materials and defects in the 1980s and 1990s, there have been many improvements in the technology that allow characteriza-tion and imaging of two and three dimensional sub-surface features in isotropic and anisotropic materials. This review, which is an expanded version of the review in I, discusses the theory and applications of this technique for imaging of engi-neering and biological materials. This chapter contains many illustrative examples and figures. Extensive references are also given for the reader to learn and explore the technique.

Characterization of mechanical properties of biological mate-rials and their mechanical behavior have been investigated by many researchers since the 1970s. Ultrasonic characterization of biological materials, like cells and bones, has been under active investigation since the 1980s. The advances in acoustic microscopy have enabled researchers to measure mechanical properties and to image them. Chapters 12 (by C. Blase and J. Bereiter-Hahn) and 13 (by K. Raum) deal with these top-ics. Modeling and measurement issues are well reviewed with

many references in these chapters. Clinical applications of ul-trasound are also treated in Chapter 14 (by Y. Saijo). This is a good review of the developments in medical ultrasound since the 1940s. The readers of this book will find these chapters very informative and useful in their work.

Terahertz radiation and its uses have been the subject of intense investigation in the last two decades or so. A recent book by Y.-S. Lee gives a good description of terahertz science and technology. Chapter 15 (by E.K. Rahani and T. Kundu) reviews some applications of terahertz technology in non-de-structive evaluation of solid foam and heat–treated materials. Both time and frequency results are presented. Modeling by the DPSM (see Chapter 4) and applications to heat damaged block material are discussed. This review will be useful to stu-dents and researchers interested in this interesting technology.

Assessment of damage state and failure prediction of aeronau-tical/aerospace, civil, and mechanical structures in use have become critically important problems worldwide. There are many ongoing efforts to develop efficient sensing technolo-gies. Chapters 9 (by A. Rakow and F.-K. Chang) and 16 (by N. Takeda, Y. Okabe, and S. Minakuchi) describe develop-ments in two technologies: embedded eddy current sensors for bolted joints and fiber; optic sensors for fiber reinforced composites. The authors present theory and applications in details for the readers to appreciate the challenges involved and opportunities for significant advancement. Adequate references are included for further exploration.

Overall, some of the chapters in this book are a good refer-ence source of information on the state–of–the–art of current researches. They will be very useful to graduate students and researchers. But not all the chapters are equally comprehen-sive. Rather, they are specialized to particular techniques or problems and thus, are narrow in scope. This gives the book an uneven character. In spite of these deficiencies, though, the book is a valuable addition to the literature on nondestructive evaluation of materials and structures.

book Reviews “ Extensive references are given to guide the readers to the published literature”

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book Review

A Dictionary of HearingAuthor: Maryanne MaltbyPublisher: Thieme Medical PublishingISBN: 978-1604068283Pages: 272 Binding: HardcoverPublication Date: February 26, 2013Price: $49.99

As the title of the publication indicates, this a dictionary; a book of approximately 4000 entries covering many terms used in the diagnosis and treatment of hearing loss. The dictionary is intended for students, practitioners, and scholars in the fields of hearing, especially those involved with the clinical/audiological aspects of hearing. The dictionary provides the term, any acronyms, the part of speech (e.g., noun), current status of the term’s use, usual pronunciation, plural/singular forms of the term, the term’s etymology and brief onomastic information, known synonyms, and meaning/definition. In addition, the book includes a list of additional common acronyms used in hearing research and clinical practice. The definitions do not contain any equations or figures, and units of measurement are usually expressed in SI (Système Internation-al d’Unités) units. The author is a British audiologist, teacher of the deaf, and author of several books and other dictionaries in the field of audiology.

While it would always be possible to find terms not covered in a dictionary like this one, A Dictionary of Hearing misses very few. Those that I thought of (e.g., dead regions/zones or informational and energetic masking) were very current and mainly represented the more experimental, as opposed to clinical, aspects of hearing. The author’s inclusion of the origin of many of the terms, especially regarding researchers and clinicians responsible for the term, added an enjoyable and informative aspect to what would normally be rather dry reading. While one might question the inclusion of many terms that are no longer used, I found the meaning of most of these terms to be informative in regards to their origins and the fact that the term was obsolete or had been replaced by a different term. The use of cross-referencing was rather limited and somewhat idiosyncratic, requiring more “leafing back and forth” than I wanted to do. And, the same terms are sometimes defined somewhat differently in different parts of the book.

The dictionary’s strength is also its weakness. The definitions are as the author indi-cates, “stated in clear and simple language.” Indeed, almost anyone would be able to

RE VIE W bY

William A. YostSpeech and Hearing Science

Arizona State University Tempe, AZ 85287

2


glean the meaning of a term listed in the dictionary. Thus, students and those not close to the field would gain an ap-preciation of the meaning of most of the 4000 terms listed in the dictionary. The informal style of definition comes at the cost of a lack of accuracy in some cases. A definition like that for emission, otoacoustic (OAE)’ as “sounds produced by the outer hair cells……” provides a hint of what an OAE might be, but “tiny” is notan appropriate characterization of sound.

My major disappointment about A Dictionary of Hearing is the lack of any reference to definitions and measurements that have been standardized both nationally and internationally. The list of acronyms in the dictionary contains ISO (Inter-national Standards Organization) and IEC (International Electrotechnical Commission), as well as the obsolete ASA (American Standards Association, neither ANSI-American National Standards Institute- nor Acoustical Society of Ameri-ca are listed). Moreover, no mention is made of the defini-tions of a large number of acoustic and psychoacoustic terms provided in several standards published by these organizations and used worldwide. In many cases the differences between

the definitions provided in A Dictionary of Hearing and those found in national and international standards are small, and probably inconsequential; in other cases the differences are significant. For instance, pitch is defined as “The individual listener’s subjective impression of frequency. High-frequency tones are heard as high pitch and low-frequency tones are heard as low pitch.” Tying the term “pitch” to only the fre-quency of tonal sounds ignores 150 years of research on pitch perception documenting the complex relationship between the term “pitch” and the acoustic conditions (e.g., the pitch of a person’s voice) that lead to the perception of pitch.What is good about A Dictionary of Hearing is the large number of terms that are defined, especially those dealing with diagnosing and treating hearing loss. I am not aware of dictionaries or other references that cover such a large number of terms. If A Dictionary of Hearing were used in combina-tion with standardized definitions of terms and measure-ments, both students and professionals could discover useful meanings of terms used in the fields of hearing. And many, like this reviewer, are likely to enjoy the brief historical refer-ences to people in the field provided in the onomastic descrip-tions.

book Reviews “ While it would always be possible to find terms not covered in a dictionary like this one, A Dictionary of Hearing misses very few.”

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book Review

Computational Aeroacoustics: A Wave Number Approach

Author: Christopher K. W. TamPublisher: Cambridge University PressISBN: 978-0521806787Pages: 492 (with 281 illustrations)Binding: HardcoverPublication Date: September 2012Price: $125.00

Chris Tam has given in this book a valuable and very pleasing account of howto resolve the peculiar difficulties encountered in the numerical treatment ofaeroacoustics (‘CAA’). The fact that only a tiny fraction (typically 10^-5) of the energy of a mean flow is radiated as sound throws up an array of algorithmic problems that are usually of no significance in traditional computational fluid dynamics (‘CFD') -- and a naive extension to acoustics of CFD methodology usually leads to grossly ineffective and misleading predictions.

A typical unsteady and noisy flow involves a broad range of frequencies withmany different length scales. In CFD unsteady phenomena are often localized,but the acoustic problem involves also small amplitude sound waves that can bewell correlated over many hydrodynamic length scales, and perhaps superimposedon an intermediate or larger scale background mean flow through which thesound must propagate to the ‘far field’, frequently over long (manywavelengths) and sinuous, time dependent paths. This presents a formidablechallenge to the numerical analyst who must devise schemes that can resolvepropagating short wavelength, high frequency sound waves while taking properaccount of damping, wave dispersion and convection by the variable, backgroundflow, and at the same time removing from the weak acoustic signal the‘numerical noise’ accumulated by the computational scheme. It is alsonecessary to minimize the spurious dissipation and dispersion caused by thenumerical procedure itself. In contrast to most CFD problems, a special‘non-reflecting’ boundary condition must be imposed at the outer edges of thecomputational zone to avoid the anomalous ‘numerical’ reflection of soundwaves back into the aeroacoustic source region.

RE VIE W bY

Michael S. HoweBoston University

110 Cummington MallBoston, MA 02215

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The main thrust of this book is an account of how these problems are handled by clever modification of traditional finite difference approximations to the governing equations. Accurate resolution of small scale motions is achieved in CFD by requiring 18 - 25 mesh points per hydrodynamic wave-length. This is impracticably large for CAA, which usually requires much more extensive gridding to reach an acceptable approximation to the acoustic far field. The special schemes developed by Tam yield adequate resolutions of sound waves with about six or seven mesh points per wavelength. Roughly speaking, the secret lies in optimizing the coefficient values in a finite difference approximation to ensure that the dispersive characteristics -- such as ‘group velocity’ -- of the exact system of equations are replicated in the numerical model.

The first five or so chapters deal with the ‘wavenumber’ ap-proach to finite difference optimization, both for spatial and temporal variations. Essentially, because differentiation is equivalent to wavenumber multiplication of the Fourier trans-form, the selection of the finite difference coefficients is made by minimizing the averaged mean square difference between the exact wavenumber and its finite difference approximation, the average being over a wavenumber range that ensures aresolution of, say, one wavelength per 7 mesh points. The pro-cedure is actually a little more complicated, involving group velocity and some numerical experimentation, but the details are adequately explained by Tam. The purist might object to such empiricism -- which, however, seems to pervade the world of CAA!

The application of non-reflective radiation conditions and mean outflow boundary conditions are discussed in Chapter 6, and the following four chapters review subsidiary mate-rial and special cases, including the introduction of artificial damping to remove ‘numerical noise’ and associated instabili-ties from small scale variations not fully resolved by the opti-mized difference equations. Special cases include the accurate

capture of wave steepening and shock formation due to non-linear propagation, the influence of variable mean flow and the application of dissipative wall boundary conditions. The remainder of the book is devoted to illustrative applications, including wave scattering by solid bodies, rotor noise, wall cavity noise, the use of oversetting grids, and the prolongation of a numerical acoustic near field into the distant far field, culminating (Chapter 15) in an extensive discussion of airfoil noise and the sound generated by an imperfectly expandedsupersonic jet. Each chapter ends with a series of problems for the reader. A set of useful sample Fortran codes is docu-mented in the appendix.

The book is described as both a professional research reference and a graduate level text. But CAA is a rapidly expanding and highly competitive subject, and Computational Aeroacoustics is more likely to be received as a substantive repository of one research group's approach to solving CAA problems. Prior exposure to the numerical treatment of partial differential equations is not required of the reader, although the text is difficult in parts and especially so for the uninitiated. The cur-rent trend encouraging the gradual demotion of undergradu-ate engineering mathematics in favor of commercial software tools could very possibly increase the difficulties faced by prospective student readers, who may not possess the ‘general understanding of partial differential equations’ assumed by the author.

“ Special cases include the accurate capture of wave steepening and shock formation due to nonlinear propagation, the influence of variable mean flow and the application of dissipative wall boundary conditions”

book Reviews

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book Review

Unsteady Combustor Physics

Author: Tim C. LieuwenPublisher: Cambridge University PressISBN: 978-1107015999 Pages: 424 (with 333 illustrations and 12 tables)Binding: HardcoverPublication Date: February 26, 2013Price: $125.00

This single authored text offers excellent readability, a consistent approach to the presentation of material, and an adherence to the overarching goal of providing a sys-tematic treatment of the complex topic of unsteady combustion. By necessity, prob-lems involving unsteady combusting must incorporate combustion chemistry, fluid mechanics, and acoustics. The author avoids the easy path of treating each of these aspects in isolation. Instead, the material is organized in such a way to allow the reader to understand how each of these aspects interacts in a dynamic combustion environ-ment.

The author claims to achieve something remarkable by offering the first ever, system-atic treatment of the subject. Indeed, a student or researcher approaching this topic would generally be required to comb through a vast sea of journal publications to compile the knowledge presented succinctly in this text. The author’s task would have been impossible had he attempted to address all possible combustion scenarios encountered in today’s combustion based energy conversion applications. Modern systems can involve advanced fuels, solid additives, and enhanced oxidizing agents. To keep the approach tractable, the author restricts the discussion to air-breathing systems and thus neglects molar production throughout. The primary aim is to pres-ent the threefold coupling of acoustics, flame dynamics, and hydrodynamic stability in order to gain an improved understanding of the time-averaged and unsteady features of combustion dynamics.

Acoustics, fluid dynamics (stability), and physical chemistry are all mature subjects in their own right. Those subjects bring to mind texts by Pierce, Batchelor, Landau & Lifshitz, and Engel & Reid. This text fills a significant gap in the available reference literature by bringing these topics together in a balanced framework; not trying to recapitulate but focusing on the interactions between their characteristic disturbances.

RE VIE W bY

Nathan E. MurrayNational Center for

Physical Acoustics University of Mississippi

University, MS 38677

4

Continued on page 59


Kim C. Benjamin1954-2013

Kim C. Benjamin, a Fellow of the Acousti-cal Society of America, passed away at his home on Tuesday, 05 May 2013 after a 23 month illness. Mr. Benjamin was born in Providence, Rhode Island on 21 Oc-tober 1954. In 1974 he received his A.S. degree in Physics from Rhode Island Junior College

and, in 1977, the B.S. degree in Physics from the University of Rhode Island. Kim completed his M.S. degree in Ocean Engineering in 1980 at the University of Rhode Island with Professor Peter R. Stepanishen as his Advisor.

Mr. Benjamin’s M. S. thesis, “Forward and Backward Pro-jection of Acoustic Fields using FFT Methods,” provided groundbreaking understanding of the interaction and inter-pretation of how acoustic waves can be transposed. Portions of this work were presented at the 97th Meeting of the ASA in Boston in June 1979 and at the 101st Meeting of the ASA in Ottawa in May 1981. The subject of the second presentation was published in JASA in April 1982. Kim had over 50 con-ference presentations and 20 publications during his career.

From 1981 to 1995 (with a 7 month absence at Woods Hole Oceanographic Institute in 1985), Kim was an Acoustic De-sign Engineer at Raytheon Company’s Submarine Signal Divi-sion in Portsmouth, RI where he specialized in the design and development of underwater acoustic transducers. Mr. Ben-jamin enjoyed a reputation early in his career for developing new acoustic transduction materials from laboratory curiosities into advanced transduction devices. One of the first materials he investigated was magneto-strictive metallic glassy ribbon for use as a gradient hydrophone. This was later followed with experimental efforts to evaluate material parameter coefficients for glass reinforced composite flex-tensional transduction shells and transduction properties for length expander mag-neto-strictive rods. For the remainder of his Raytheon career (1985-1995), key efforts by Kim include: the development of a very large, 2D, ultrasonic imaging array; design and develop-

ment of a toroidal volume search sonar (TVSS); development multi-layered, broadband copolymer for acoustic transmit applications; and production support for numerous U.S. Navy fleet transducers. In 1990, Mr. Benjamin worked jointly with The Pennsylvania State University in fabricating the first 1-3 piezo-composite transduction prototypes used for acous-tic transmission applications. This early effort would later become the focus for much of Mr. Benjamin’s career when he joined the Naval Sea Systems Command Division Newport in November 1995.

Throughout his Navy civilian career, Mr. Benjamin focused primarily on advancing 1-3 piezocomposite materials into unique underwater acoustic devices. Among his key accom-plishments are the following: design and fabrication of 1-3 piezocomposite-based beam steered parametric mode trans-ducers with integral high-gain receivers; design and delivery of parametric mode sub-bottom profiler transducers; develop-ment of U. S. Navy calibration transducer standards F82 and F83; use of 1-3 piezo-composites materials with area--shaded electroding to realize a new class of transduction which main-tains a constant beam-width over a two octave bandwidth; novel use of singly and double curved piezo-composites for applications in ultrasonics and structural receivers; design and segment demonstration of a cylindrical array module that is coupled linearly to form a towed line array with 3D spa-tial discrimination; design and fabrication of a 120 element conical octahedral homing array for high speed (> 150 knots) applications; design and development of wideband piezo-com-posite-based transducers for acoustically tracking high speed underwater projectiles traveling near the speed of sound of wa-ter; design of all tooling used for the development of a singly curved array of cymbal panels for low profile, low frequency transduction application. Kim has been granted eight U.S. patents and has another seven patent disclosures currently under consideration at the United States Patent Office.

Mr. Benjamin was active in the Acoustical Society of America beginning with his first presentation in 1979 and continued with numerous presentations and publications throughout his career. He was the former Chair of the ASA Engineering Acoustics Technical Committee (2003-2006) and long term member of the ASA Medal and Awards Committee (2006-2013).

Kim enjoyed sailing and spending time at his vacation home in the woods of Tamworth, New Hampshire. He is survived by his wife Pamela. – Thomas R. Howarth

Passings

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Stephen H. Crandall1920-2013

Stephen H. Crandall, a Fellow of the Acoustical Society of America and a former recipient (1978) of the Society's Trent-Crede Medal passed away on 29 October 2013 in Needham, Massachusetts. He was 92 years old.

Crandall was born in Cebu, in the Philippine Islands, on December 2, 1920. He began undergraduate studies

at Stevens Institute of Technology in 1936. A note written by Crandall many years later reveals the personal difficulties he experienced during his undergraduate years.

"I have enjoyed better than average health over the last 50 years, but I was not so lucky when I was a student at Stevens. Because of a spinal infection, I spent more time in hospitals than I did in classrooms. I entered Stevens with the class of '40, then slipped back to the class of '41, and eventually graduated with the class of '42 . Although my attendance in classes was spotty, I did well academically. In those days I was a quick study."

It is quite likely that, by the time Crandall graduated from Stevens, his self-study activities had given him a superb gradu-ate level grounding in the mathematics related to engineering. He graduated with a B.S. in Mechanical Engineering from Stevens in 1942, shortly after the U. S.'s entry into World War II. He found employment as a staff member of the Ra-diation Laboratory of MIT and was able to pursue a doctorate while working at the Radiation Laboratory, receiving a Ph. D. in mathematics in 1946. Shortly thereafter, he joined the Mechanical Engineering faculty at MIT. He was appointed Assistant Professor in 1947, Associate Professor in 1951, Pro-fessor in 1958, and was named Ford Professor of Engineering in 1975. He retired from MIT in 1991 with the title of Ford Professor Emeritus, but continued to teach through 2002.

Across MIT and by his former students and colleagues, scat-tered all over the world (many of whom are active in this So-ciety), Crandall is remembered as an outstanding teacher and

scholar, noted for the clarity of his lectures: He spoke slowly, but managed to cover plenty of material. While at MIT, he led the transformation of mechanics into an engineering sci-ence, acting as editor of three groundbreaking texts: Random Vibration (1958), An Introduction to the Mechanics of Solids (1959), and Dynamics of Mechanical and Electromechanical Systems (1968). Crandall was a pioneer of random vibrations research, offering the first academic course on the subject in 1958. He co-founded, with the late Patrick Leehey, the in-terdepartmental Acoustics and Vibration Laboratory at MIT in the mid 1960's and subsequently directed that laboratory for 33 years. This laboratory served as the interdepartmental focal point for research and education in acoustics at MIT and attracted a long sequence of students and post-graduate scholars. Crandall published a total of eight books and 160 technical papers.

In the same note mentioned above that was written somewhat late in his life, Crandall reminisced-

"I was fortunate to start my teaching career during World War II. The past half-century has been an exceptional period in American history. Until quite recently it has been a time of continually expanding horizons. In engineering education we made revolutionary changes as we moved to a stronger engi-neering science curriculum. As an enthusiastic proponent of this movement I had the benefit of working with exception-ally able students in the classroom and the laboratory."

Crandall was active in many technical societies. He served as chairman of the Executive Committee of the Applied Me-chanics Division and as vice president of Basic Engineering for the American Society of Mechanical Engineers (ASME); he also served as president of the American Academy of Me-chanics. He served as chairman of the U.S. National Commit-tee for Theoretical and Applied Mechanics and of the Solid Mechanics Panel of the International Union of Theoretical and Applied Mechanics. He was also a member of the Board of the International Commission for Acoustics.

Crandall’s professional contributions have been widely recog-nized. He was elected to the American Academy of Arts and Sciences, the National Academy of Sciences, the National Academy of Engineering, and the Russian Academy of Engi-neering.

The Acoustical Society of America awarded him the Trent-Crede Medal in 1978, and the American Society of Civil En-gineers awarded him both the Theodore von Karman Medal,


Passings

in 1984, and the Freudenthal Medal, in 1996. The ASME awarded Crandall the Worcester Reed Warner Medal in 1971; the Timoshenko Medal in 1990; the Den Hartog Award in 1991; and the Thomas K. Caughey Dynamics Award in 2009. He was inducted as an honorary ASME member in 1988.

In addition to his eminent research activities, Crandall was a strong proponent of international collegiality. Both Crandall and his wife, Pat, had strong interest in the teaching and sup-porting of foreign students. This interest was partly initiated by their first sabbatical at Imperial College London in 1949 and reinforced by subsequent sabbaticals and lecture tours in Mexico, France, Germany, Israel, Russia, China, Japan, Aus-

tralia, and South Korea. Crandall learned to speak Spanish, French, and Russian, and enjoyed giving lectures in the local language. Pat chaired MIT’s faculty wives committee, which organized English-language classes for the wives of foreign students. She also enjoyed playing Dixieland piano and was a member of the Tabor Hill Jazz Band for several decades, hosting their rehearsals at their home on Tabor Hill Road in Lincoln, Massachusetts. Crandall's wife Pat, his close companion for 62 years, died in 2011. He is survived by his daughter, Jane (Crandall) Kontri-mas, her husband Peter, and son Stephen; and by his son, William B. Crandall. – Allan D. Pierce

William C. Cummings1932-2013

William C. Cummings, a Fellow of the Acoustical Soci-ety of America, passed away on August 20, 2013 at the age of 81. Dr. Cummings was a principal participant in the actions that led to the forma-tion of the ASA’s Animal Bioacoustics Technical Com-mittee in 1997. This Techni-cal Committee began as a Technical Specialty Group,

and Cummings served as the Group’s founding chair from 1988 to 1994. He was also a former vice president and presi-dent of the San Diego ASA Regional Chapter He served on the ASA coordinating committee on environmental acoustics (an ad hoc committee) and organized various special sessions at ASA meetings, especially during the formative years of the Technical Specialty Group. Cummings is widely-recognized in the animal bioacoustics community for his work concerned with the sounds of whales. He frequently presented papers at ASA meetings, including papers in honorary sessions to com-memorate former colleagues D. V. Holliday, Robert Gales, and P. O. Thompson. Cummings coauthored several papers with both Holliday and Thompson. For example, Holliday was a coauthor with Cummings on a paper, “Passive acoustic location of bowhead whales in a population census off Point Barrow, Alaska,” published in JASA in 1985. Thompson was

a coauthor with Cummings of a paper “Underwater sounds of migrating gray whales, Eschrichtius Glaucus (Cope),” pub-lished in JASA in 1968.

A special session in Cummings honor was part of the 140th ASA meeting in Newport Beach, CA on 3-8 December, 2000. Throughout his 50 years of active membership in the ASA, Bill strived to provide a more accommodating environ-ment for young professionals within the organization, while serving as a mentor to young colleagues and graduate stu-dents.

Dr. Cummings received his B. S. in biology and chemistry from Bates College, Lewiston, Maine, in 1954. He served in the U.S. Army from 1954-1956 and then went on to his graduate studies at the University of Miami, Florida, where he earned his M.S. in 1958 and his Ph. D in 1967. As a dedicated biological oceanographer and bioacoustician, Bill conducted research on marine invertebrates, fishes, and mam-mals throughout ocean basins around the globe. During his graduate work at the University of Miami, Bill studied the reproductive biology of fishes and shrimp along the Western Atlantic and Caribbean. He also investigated near-shore and salt pond ecology while at the University of Rhode Island before initiating work on ambient noise and acoustic propa-gation across Florida Strait. Bill then teamed up with John Steinberg, among others, to install and operate a hydrophone array off the Bahamas where he operated an innovative acoustic-video station from 1959-1965. While working on the long-term monitoring project in Bimini, Bill met Robert Gales (a former ASA President). Gales invited Bill to give a lecture on his work at the Naval Undersea Center in San

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Diego. Soon, Bill was offered a job working as an oceanogra-pher for the Naval Electronics Laboratory on Point Loma in San Diego. Working at the Navy laboratory, Bill was among the earliest to describe the calls of blue whales, gray whales, right whales, Bryde’s whales, and finback whales. Much of this work was published in JASA. Bill served as chief scien-tist for expeditions aboard the 95-foot sailing yawl Saluda, an especially quiet platform for recording bioacoustics. In 1969, Bill made dives in the submersible Deep Star with Dr. Richard Rosenblatt of Scripps Institution of Oceanography. The purpose of these dives was to prepare for bottom acoustic monitoring of marine life for the SEA-LAB III site off San Clemente Island, California. At Point Loma, Bill advanced to head of the Applied Bioacoustics Branch at the Naval Ocean Systems Center where he conducted numerous projects throughout the Pacific from 1967-1977.

In 1977, Bill moved on to become chief curator for the San Diego Natural History Museum where he supervised 26 research scientists and expanded research activities for all scientific departments at the museum. Bill led research voy-ages to remote locations from Chile to the Arctic Circle in the Pacific, the North and South Atlantic Ocean, and throughout the Caribbean, Scotia, Weddell, Bering, Chukchi, Beau-fort, Okhotsk, Philippine, East China, and Japan seas. Bill participated in 36 oceanographic cruises, was awarded four U.S. patents for the design and development of underwater acoustic communication devices, and published more than 75 scientific papers. Overall, Bill’s work filled numerous data gaps in the field of bioacoustics and aided in the conservation of marine resources.

Bill continued his work through various setbacks including the death of his beloved wife Joan from cancer in 1994 and injuries from a later hunting accident which left 50 shotgun pellets from another’s gun deeply imbedded throughout his body. Bill remained active as an ASA member at large and within the San Diego community throughout his later life. He enjoyed photography, sailing, woodworking, exploring his family genealogy, and especially fishing with friends. He regaled his friends and family with stories of previous expedi-tions, associates and adventures, interspersed with a hearty belly laugh that could only make one smile. Bill’s life and stories are carried on by his brother Bob, two sons Phillip and Mark, daughter-in-law Theresa, and five grandchildren and great-grandchildren. – Scott Aalbers and Sam H. Ridgway

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ASANews

barbara Shinn-Cunningham Receives Mentoring Award During the December 2013 meeting of the Acoustical Society in San Francisco, Barbara Shinn-Cunningham (Boston University) received the ASA Student Council Mentoring Award. The Student Council Mentoring Award is designed to recognize a person who has demon-strated exceptional ability in guiding the academic and/or professional growth of his/her students and junior colleagues. Previous winners of the award are David Blackstock, Lawrence Crum, David Dowling, Kenneth Suslick, Christy Holland, and Stephen Dance. The presentation of the award to Professor Shinn-Cunningham took place at the Wednesday night student social event (4 December 2013), which was attend-ed by over 100 students

Smartphone APP Student Competition

A special poster session was held dur-ing the meeting in San Francisco. The session was organized by the Signal Pro-cessing Technical Committee, chaired by Kevin Cockrell. The purpose of the session was to display entries in the Smartphone Acoustic Signal Processing Student Competition. A list of the titles and abstracts is on pages 4134 -4135 of the November 2013 issue, part 2, of the Journal of the Acoustical Society of America. The competition had an open-ended format to allow students to be as creative as possible.

Entrants were required to present a poster describing a smartphone “app” that utilizes acoustic signal processing. Creative ideas and development strate-gies were left up to the students. The six entries were ambitious and crossed

many different disciplines represented by the ASA. Third runner up, an entry from K. J. Bodon and Zachary Jensen (Brigham Young University) was for an app that asks the user to draw out the shape of his or her living room and then suggests optimal speaker placement. The second runner up, submitted by Jorge Herrera and Hyung-Suk Kim (Stan-ford University), used audible signals to estimate inter-smartphone distances and geometry. The 2013 Smartphone Acoustic Signal Processing Student Competition winner was submitted by Rene L. Utianski, Steven Sandoval, Nicole Lehrer, Visar Berisha, and Julie Liss (Arizona State University). This app was designed to assess the integrity of speech production for the purposes of providing an augmentative tool for tele-medicine. The first, second, and third place teams were awarded $1,000, $500, and $300 respectively.

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near future, news items will be posted, shortly after receipt, on the forthcoming Acoustics

Today web site.

There was lively interest for the student app competition that was organized by ASA’s Signal Processing Technical Committee for the San Francisco meeting.

Attendees at the ASA student social on December 4 congratulate ASA student mentoring award winner Barbara Shinn-Cunningham.

Joshua Bodon explaining the soundmap app at the smartphone session at the December meet-ing of ASA in San Francisco.




ASANews

The Signal Processing Technical Com-mittee is planning to host a second smartphone competition at the ASA meeting in Pittsburg in spring 2015.

James A. Simmons Receives Gerrit S. Miller Award

ASA fellow James A. Simmons has been awarded the 2012 Gerrit S. Miller Award by the North American Society for Bat Research (NASBR)" in rec-ognition of outstanding service and contributions to the field of chiroptean biology." Simmons is a professor of neu-roscience at Brown University. He re-ceived the ASA’s Silver Medal in Animal Bioacoustics in 2005. According to the Brown University website, there is an interesting story about the timing of the award. Simmons actually won the 2012 Gerrit S. Miller Award. Apparently, the awardee must be present at the meeting where the award is given, and the award is kept as a surprise. The intent was that the Award be presented at a meeting in Puerto Rico in 2012, but Simmons

could not make it to this meeting, so the Society deferred its presentation until the next meeting, which was this past August (2013) in Costa Rica. All this was kept secret from Simmons, who subsequently affirmed that the delayed timing was serendipitous.

"This award comes at a time when my lab has completed a decades-long effort to understand how bat sonar ‘works’ as a system, with the goal of designing a bio-logically inspired sonar for the Office of Naval Research. The award means a lot to me because it was given by colleagues of long standing whose work I respect.” Readers interested in the North Ameri-can Society for Bat Research are invited to explore its web page at http://www.nasbr.org/. Information concerning the Gerrit S. Miller award can be found at http://www.nasbr.org/miller.html. The NASBR’s next meeting will be in Octo-ber 2014 in Albany, NY.

Editorial Manager to Replace PXP

The Acousti-cal Society of America is in the process of tran-

sitioning to a new online manuscript submission and management system. At a special teleconference meeting on Sep-tember 10, 2013, the voting members of the Executive Council unanimously agreed to replace the current manuscript submission system (Peer X-Press, offered by the AIPP) by an alternate system, Editorial Manager. A contract with Aries, the vendor that offers Editorial Manager, was subsequently signed by Susan Fox, the ASA Executive Direc-tor, on January 10, 2014. This change will affect JASA, JASA-EL, and POMA.

Ultimately, submissions to Acoustics Today will also use the new submissions system.

General information concerning Edito-rial Manager can be found at the site www.editorialmanager.com

The chief attraction of Editorial Man-ager is that it is fully featured and highly configurable. Editorial Manager grew out of Editorial Assistant, a desktop manuscript-tracking application used by journals since the early 1990s. Editorial Manager was launched in the spring of 2001 and has been rapidly adopted by scholarly societies and publishers. It is used by over 5,000 journals and mil-lions of registered users. Many of our sister journals associated with acoustics are currently using Editorial Manager.

Aries Systems is located in North Ando-ver, Massachusetts, USA, with local staff representing the company in Germany and the United Kingdom. The company hosts an annual two-day Editorial Man-ager user’s conference in Boston every summer, the next one scheduled for June 19-20, 2014. ASA staff and some of our editors will attend this confer-ence. Aries also hosts similar meetings in Europe and Japan, so there may be ample opportunity for ASA’s overseas editors to attend such meetings.

The transition to Editorial Manager will require some extensive training of the ASA staff associated with publications, and there will be an extended period to configure the software system so that it is fully compatible with what the ASA desires for such a system. There will be separate configurations for JASA, JASA-EL, and POMA, and the editors and

James A. Simmons

http://www

http://www.nasbr.org/miller.html

http://www.editorialmanager.com

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associate editors for all three publica-tions will participate. There is no fixed date for the transition to be completed, but it is expected to extend for up to 6 months. There may be some overlap in the use of the Editorial Manager and the current system, but for each publica-tion, a date will arrive at which all new submissions must be submitted via the Editorial Manager. Transition will not be a trivial task, but Aries has helped many other organizations make such transitions in the past, so the ASA an-ticipates no insurmountable difficulties.

POMA Submission Requirements May Change

Currently, the ASA’s open-access online journal,

Proceeding of Meetings on Acoustics (POMA), is configured so that each new volume corresponds to a distinct con-ference. Since the ASA has two meet-ings a year, there are at least two new POMA volumes each year. In addition, the organizers of several co-sponsored meetings have elected to use POMA for the publication of their conference proceedings, so that there can be more than two volumes associated with any given calendar year. (Currently, POMA has a total of 20 volumes posted online. Volume 1 is dated February 2007, but one has to download a specific article to find that this volume corresponds to the ASA meeting in Salt Lake City in June 2007.)

Problems with POMA volume num-bers were discussed extensively by the POMA editors, the ASA Publication Policy Committee, and the Executive Council at the meeting in San Francis-

co. It was recognized that the process of transitioning to Editorial Manager represented a unique opportunity for reconfiguring POMA.

The tentative plan, which was approved by the Executive Council, is that there will generally be one (though some-times two) new POMA volumes each year. The volume numbers will not correspond to distinct conferences. Instead the contents of a given volume will consist only of papers that were accepted for publication during the time period associated with the volume. Thus, for example, a volume corre-sponding to 2015 could contain a paper that corresponds to a presentation that took place in, for example, 2001. Each volume will be organized according to the technical committees of the Society, and papers will appear in the relevant section in the order in which they are accepted, regardless of just when they were presented at a meeting. (This system of posting is referred to as e-first publication. A given volume will build until the time deadline is reached for last acceptance of a paper.)

Currently, there are no fees for publica-tion in POMA and all papers published in POMA are open access. This does incur some financial expense to the ASA, but a possible rationale is that the Society has already collected a registra-tion fee from the author at the time the author attended the meeting at which the paper was given. The actual expense of publishing a paper in POMA is generally significantly less than a typical registration fee.

ASA books Offered Online at Membership Prices

The ASA has been publishing books since 1983 and most of the published books are reprints of older books that had gone out of print.

Over the years, these books have been offered for sale, principally by mail-order, with different prices for members and nonmembers. If the books are sold via an online vendor, such as Amazon, it has been difficult to distinguish between members and nonmembers, so members purchasing online must pay the non-member price.

Since fall 2013, the ASA Publications Office has been shipping some of the ASA books in bulk quantities to des-ignated Amazon sites so that Amazon itself could fulfill any orders for these books directly by shipping from one of its warehouses. The cost for this service to ASA is nominal, and it is advertised by Amazon as Fulfillment by Ama-zon. Customers are charged $3.99 for shipping within the United States, and the Acoustical Society is not charged for shipping and handling. ASA Prime members get free shipping and two-day delivery.

ASA books sold by Amazon are adver-tised as being offered by the ASA Press, which is now the official trademark for all ASA publications. Moreover, the Executive Council, upon recommenda-tion of the Publications Committee, agreed to allow the pricing of all books sold by Amazon to be at the member prices. Thus one finds the ASA’s better selling books offered by ASA Press on the Amazon site at member prices.


Acoustical Society foundationThe mission of the Acoustical Society Foundation (ASF)is to support the mission of the ASA by developing financial resources for strategic initiatives and special purposes.

Many years ago, a number of dedicated and forward-looking ASA members established the Foundation in order to grow an endowment to support and enhance the goals of the Society. Starting from this base, ASA is now expanding its efforts in seeking philanthropic support to help the Society move forward to meet future challenges. Details concerning the Acoustical Society Foundation Fund can be found on the website: www.acousticalsociety.org/membership/as_foundation_fund

Funds from the Foundation serve as the basis on which the Society grants deserving student stipends, awards service acknowledgements and prizes, and develops new outreach initiatives as directed by the Executive Council. With new momentum, the Foundation plans to expand these activities and help the Society focus on the growth of our profession. Tax-deductible opportunities abound, from the check-off donations on ASA dues renewals, major donations, bequests, and life-time giving to the Pooled Income Fund.

The ASF Fund’s activities are directed by the Acoustical Society Foundation Board, chaired by Carl J. Rosenberg. The Board plans to present its goals and aspirations to the ASA membership in future issues of ASA publications. Anyone having ideas or questions they would like to share should send an e-mail to the Board’s Chair, using the e-mail address [email protected].

Acoustics Today UpdatesStarting with 2014, we will include “Letters to the Editor” as a feature in each issue. Letters can be on any topic related to acoustics, and may be comments on material in recent issues. See the Letters Section for more information.

We are seeking articles for Acoustics Today. If you have an idea for an article that you would like to write, or the sugges-tion for an article, please contact the editor. Please do not, however, submit articles without discussions with the editor. Articles can be on any topic within the range of areas covered by ASA. Articles should generally be reviews, with perhaps a bit of emphasis on material that covers “hot areas” in acous-tics. Articles should be written so that they are of interest to, and understandable by, all members of ASA.

We welcome ideas for special issues of Acoustics Today. Special issues would include three or four articles on the same general theme and be done with a guest editor who would be respon-sible for design of the overall theme and the individual papers. If you have an idea for a special topic, and/or would like to be a guest editor on a topic, please contact the editor.

Acoustics Today InternsAcoustics Today announces the start of Acoustics Today Interns (ATI), an opportunity for graduate students and early career acousticians (individuals within three years of their terminal degrees) who are members of ASA to serve the Society in a unique and different way, and, at the same time, gain expe-rience in publication of a major science magazine. Intern appointments will be for one year (generally starting June 1) and will be expected to devote 10-20 hours/month to their internship responsibilities.Interns will work directly with an individual mentor in ASA on a specific project directly related to the magazine. Mentors might be the Acoustics Today editor, publications manager, IT manager, etc. The specific role of each ATI will depend on her/his interests and experience and the needs of the maga-zine. The expectation is that the interns will enhance the val-ue of the magazine by taking on specific tasks. For example, an intern may be assigned the gathering and writing of short news articles that will appear on the forthcoming Acoustics Today web site and/or in the magazine, helping Acoustics Today

Acoustics Today regularly publishes announcements of ongoing and future activities that

may be of interest to the acoustics community. Anyone having an announcement they would

like to have considered for inclusion should send the relevant information via e-mail to the

Editor ([email protected]), with a copy to the ASA Publications Office (maryguillemette@

acousticstoday.org). The Editor and the Publications staff will routinely rewrite or rephrase

whatever is sent to make it compatible with the format of Acoustics Today.

ASA Announcements


http://www.acousticalsociety.org/membership/as_foundation_fund


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develop a presence in social media, etc. Interns will be selected competitively by the Acoustics Today Advisory Committee at the May meeting of ASA. Selected individuals will receive a small honorarium at the end of their internship as well as free registration at ASA meetings (if they attend) while they are interns. Interns will also be listed on the magazine masthead during their internship and will be invited to participate in

meetings of the Advisory Committee. Individuals interested in becoming Acoustics Today Interns should contact the maga-zine editor for an application packet ([email protected]). For best consideration, applications should be submitted no later than May 1, 2014 for the first “class” of interns. Up to three interns will be selected.

book Review Continued from page 49

Still, in order to keep the text accessible for a graduate student audience, the author does well not to assume the reader is an expert in any one of these fields and includes enough back-ground for the text to stand on its own.

Chapter 1 presents an overview of all the basic equations and notational to set the stage for the rest of the text. This allows the reader to quickly become comfortable with the nota-tion which is complicated because of the broad nature of the content. The four page nomenclature section at the end of Chapter 1 is nicely formatted, but I would have preferred that is was printed on the inside of the front/back cover to make it easier to access.

The remainder of the text is arranged into three main sections. Section one (chapters 2–6) lays the framework for the fol-lowing sections by examining acoustic, vortical, and entropy disturbances in turn assuming the reader has had only an introductory course in fluid mechanics. Section two (chapters 7–9) deals with flame-flow interactions assuming the reader has only an undergraduate exposure to combustion. The discussion deals with ignition and internal flame processes such as burning rates and extinction. The discussions on flow disturbances are tied into their impact on flame dynamics.

Finally, section three (chapters 10–12) looks at transient and time-harmonic phenomena such as flashback and methods for stabilization. The final two chapters deal with forced response both from the perspective of the flame dynamics and the heat release. These are the most applied chapters in the text and offer many suggestions and topics for further exploration.The layout of the book has some nice features. Each chap-ter has its own references section and, with the exception of Chapter 10, a set of exercises. The exercises are primarily ana-lytical in nature (derivations, proofs, etc.), which is appropri-ate for the target audience. There are “aside” sections within

the text that offer focused discussions of related topics that either clarify or expand on topics in the main text. For ex-ample, the section on “general results for temporal instability” in Chapter 3 includes an aside on “vortex mutual induction.” This gives the reader a glimpse into topics that are beyond the scope of the text but are central to a full understanding of combustion dynamics.

As with any text written concurrent to active research, some concession must be made on topics of contention. For example, in Chapter 2, the basic discussion of flow perturba-tions is couched in terms of a triple decomposition such that a flow quantity is separated into a base value, an ensemble mean quantity exhibiting the coherent structures, and a time varying component identified with turbulent fluctuations.

The author comments that the time average, or base value, is representative of the laminar flow that would exist if the same boundary conditions were imposed in the absence of turbu-lence. This is a debatable position because it is simple to prove that turbulence itself modifies the mean flow in an insepa-rable manner, so it is not correct to assume that the base flow can be equated to a laminar flow. For this reason, the triple decomposition is difficult to justify and even more difficult to demonstrate in practice. But, in the absence of some other better formulation, the author adopts this common approach.The result of the author’s approach is a text that is very acces-sible and can also act as a valuable reference for the seasoned researcher. Because of the assumed knowledge base of the target audience, the text can act as an introduction to com-bustion for those coming strictly from a physical acoustics or fluid mechanics background. The inclusion of numerous references provides an excellent starting point for a more focused study. And finally, the avoidance of electronic means of enhancing the text ensure that longevity of this work as an excellent resource.



P O S I T I O N A N N O U N C E M E N T

EDITOR-IN-CHIEFAcoustical Society of America

The ASA seeks candidates for the position of Editor-in-Chief (EIC) to fill the vacancy

that will open upon the retirement of the current EIC, Allan D. Pierce.

This is a great opportunity for an outstanding individual with a serious professional interest in

acoustics to direct and influence the activities of the ASA flagship publication,

The Journal of the Acoustical Society of America (JASA), and others including JASA-Express Letters

(JASA-EL), Proceedings of Meetings on Acoustics (POMA), Acoustics Today, Echoes, and the book

publishing activities of the Society.

Since 1929, The Journal of the Acoustical Society of America (JASA) has been the leading source of

theoretical and experimental research results in the broad interdisciplinary study of sound. Subject

coverage includes: linear and nonlinear acoustics; aeroacoustics; underwater sound and acoustical

oceanography; ultrasonics and quantum acoustics; architectural acoustics; musical acoustics; noise;

structural acoustics and vibration; speech communication; psychology and physiology of hearing;

signal processing; engineering acoustics; transduction; biomedical acoustics; and animal bioacoustics.

D U T I E SThe responsibilities of the ASA EIC include:

• Oversees the ASA Publications Manager and editorial office staff

• Maintain publication policies for JASA, JASA-EL and POMA

• Manage Editors and Associate Editors

• Chair ASA Editorial Board meetings

• Serve as the key liaison between the ASA and the publisher

• Report to the ASA Executive Council on the publishing activities of the Society

• Configure the ASA online Editorial System and maintain the Reviewer Database

• Stimulate the growth of ASA publications

The routine activities of the Editor-in-Chief of a prestigious and archival scientific society journal in-

clude extensive correspondence with ASA office staff, authors, reviewers, Editors, Associate Editors,

and ASA committee chairs. The EIC solicits review papers to be submitted to JASA and recruits new

ASA members by screening each JASA author.

| 61

Q U A L I f I C AT I O N S

The successful candidate must be a member of the ASA. Other desired attributes include having pub-

lished as a JASA author, and preferably having served as a JASA Associate Editor, or having equivalent

experience in other publications. The candidate must demonstrate excellent written and verbal com-

munication and proven managerial skills. Mediation expertise or experience with conflict resolution is

preferred. An international perspective and diplomatic communication style is beneficial.

The candidate should have a working knowledge of the challenges of open access, be able to articulate a

strategy to embrace the changing world of publishing and different publishing formats, and be comfort-

able with emerging publication technologies, including software and search engine tools.

The successful candidate will be a thought leader, having demonstrated inspirational leadership in an

academic or industrial sector. This person will have a broad awareness of the need to balance the widely

ranging acoustics disciplines and ASA technical committees, and will express a clear vision for the future

of ASA publications. This person will be a highly responsible individual who is able to protect the integ-

rity of ASA publications and particularly, JASA.

The ASA Editor-in-Chief post is a 40 percent FTE position.

Occasional travel is required. Compensation is competitive.

H O W T O A P P LY

Candidates are invited to respond with a letter of intent and C.V. by 1 April 2014 to:

EiC Search Committee

Attn: Helen Wall Murray

ASA Publications Office, P.O. Box 274, West Barnstable, MA 02668Email: [email protected]



Classif ieds

ACOUSTICS TODAY RECRUITING AND INFORMATION CLASSIFIED ADVERTISEMENTS:Positions Available/Desired and Informational Advertisements may be placed in ACOUSTICS TODAY in two ways: — display advertisements and classified line advertisements.

Recruitment Display Advertisements:Available in the same formats and rates as Product Display advertisements. In addition, recruitment display advertisers using 1/4 page or larger for their recruitment display ads mayrequest that the text-only portion of their ads (submitted as an MS Word file) may be placed on ASA ONLINE — JOB OPENINGS for 2 months at no additional charge. All rates are com-missionable to advertising agencies at 15%.

Classified Line Advertisements:2014 RATES: Positions Available/Desired and informational advertisements

One column ad, $38.00 per line or fractions thereof (44 characters per line), $200 minimum, maximum length 40 lines; two-column ad, $50 per line or fractions thereof (88 characters per line),$350 minimum, maximum length 60 lines. ( Positions desired ONLY – ads from individual members of the Acoustical Society of America receive a 50% discount)

Submission Deadline: 1st of month preceding cover date.

Ad Submission: E-mail: Christine DiPasca at [email protected]; tel. : (516) 576-2434. You will be invoiced upon publication of issue. Checks should be made payable to the Acoustical Soci-ety of America. Mail to: Acoustics Today, Acoustical Society of America, 2 Huntington Quadrangle, Suite 1NO1, Melville, NY 11747. If anonymity is requested, ASA will assign box numbers.Replies to box numbers will be forwarded twice a week. Acoustics Today reserves the right to accept or reject ads at our discretion. Cancellations cannot be honored after deadlinedate.

It is presumed that the following advertisers are in full compliance with applicable equal opportunity laws and, wish to receive applications from qualified persons regardless of race,age, national origin, religion, physical handicap, or sexual orientation.

Please contact:

DEBBIE BOTTAdvertising Sales Manager

AIP PublishingTwo Huntington Quadrangle

Suite 1NO1, Melville, NY 11747

Tel: (800) 247-2242 (516) 576-2430Fax: (516) 576-2481 Email:[email protected]

To view a pdf of the media kit visit :http://scitation.aip.org/upload/ASA/AT/atmediakit2014.pdf

FFOROR AADVERTISINGDVERTISING RRESERVATIONSESERVATIONSANDAND IINFORMATIONNFORMATION

ACOUSTICS TODAY RECRUITING AND INFORMATION CLASSIFIED ADVERTISEMENTS:Positions Available/Desired and Informational Advertisements may be placed in ACOUSTICS TODAY in two ways: — display advertisements and classified line advertisements.

Recruitment Display Advertisements:Available in the same formats and rates as Product Display advertisements. In addition, recruitment display advertisers using 1/4 page or larger for their recruitment display ads mayrequest that the text-only portion of their ads (submitted as an MS Word file) may be placed on ASA ONLINE — JOB OPENINGS for 2 months at no additional charge. All rates are com-missionable to advertising agencies at 15%.

Classified Line Advertisements:2014 RATES: Positions Available/Desired and informational advertisements

One column ad, $38.00 per line or fractions thereof (44 characters per line), $200 minimum, maximum length 40 lines; two-column ad, $50 per line or fractions thereof (88 characters per line),$350 minimum, maximum length 60 lines. ( Positions desired ONLY – ads from individual members of the Acoustical Society of America receive a 50% discount)

Submission Deadline: 1st of month preceding cover date.

Ad Submission: E-mail: Christine DiPasca at [email protected]; tel. : (516) 576-2434. You will be invoiced upon publication of issue. Checks should be made payable to the Acoustical Soci-ety of America. Mail to: Acoustics Today, Acoustical Society of America, 2 Huntington Quadrangle, Suite 1NO1, Melville, NY 11747. If anonymity is requested, ASA will assign box numbers.Replies to box numbers will be forwarded twice a week. Acoustics Today reserves the right to accept or reject ads at our discretion. Cancellations cannot be honored after deadlinedate.

It is presumed that the following advertisers are in full compliance with applicable equal opportunity laws and, wish to receive applications from qualified persons regardless of race,age, national origin, religion, physical handicap, or sexual orientation.

Please contact:

DEBBIE BOTTAdvertising Sales Manager


Suite 1NO1, Melville, NY 11747

Tel: (800) 247-2242 (516) 576-2430Fax: (516) 576-2481 Email:[email protected]

To view a pdf of the media kit visit :http://scitation.aip.org/upload/ASA/AT/atmediakit2014.pdf

FFOROR AADVERTISINGDVERTISING RRESERVATIONSESERVATIONSANDAND IINFORMATIONNFORMATION



http://scitation.aip.org/upload/ASA/AT/atmediakit2014.pdf



| 63

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For advertisement reservations or further information please contact:

Deborah BottAdvertising Sales Manager

Acoustics Todayc/o AIPP Advertising Department2 Huntington QuadrangleSuite 1NO1Melville, NY 11747Phone: (800) 247-2242 or (516) 576-2430Fax: (516) 576-2481Email: [email protected]

For advertisement production inquiries, please contact/send files to:

Christine DiPascaSenior Advertising Production Manager

Acoustics Todayc/o AIPP Advertising 2 Huntington QuadrangleSuite 1NO1Melville, NY 11747Phone: (516) 576-2434Fax: (516) 576-2481Email: [email protected]

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volume 10 | issue one winter 2014 acoustics today · 2014. 10. 26. · regarding the magazine....

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