3nd-papo · sf 013 1101, task 1357, "room constants for shipboard compartments" of *18...

3ND-Papo.24st

U. S. NAVAL APPLiED SCIENCE LABORATORY

NAVAL BASErBROOKLYN 1, NEW YORL rj

EACH TRANSMITTAL Of THIS DOA-J.MEIT }UTSIDESoTWE DFPARThiENT OF DEf ENSE IUST HAVE PRIOR

4APPROVAL OF THE COMMAND"R, HAVAL SIPSYSTEMS c(OAMANIff WARMrT1n p m jTor ~r~

DISCLAIMER NOTICE

THIS DOCUMENT IS BEST QUALITYPRACTICABLE. THE COPY FURNISHEDTO, DTICCONTAINED A SIGNIFICANTNUMBER OF PAGES WHICH DO NOTREPRODUCE LEGIBLY.

REPORT OF DEIIELOP4ENT

IESIMAIN METHOD FOR " '

-.7 AUGUST 1964 T h 7

Final Repo rtI~

TL: J: HOLGATE

Material Sciences Division . ,D. H. KALAS, Head -A Lt-J t-

Approved:E. J. JAH Approved:

,.Technica ecor I. F. FE CAPT., USN-/ -

' Commanding Officer and Director

U. S. NAVAL APPLIED SCIENCE IORATORY; NAVAL BASE

,BROOKLYN, NEW YORK 11251

Lab. Project 5662-2Final Report

A method for predicting noise levels, in terms of sound power in octavebands, generated by air conditioning or ventilation systems on submarines andsurface vessels has been developed and reported herein.

This method will enable the designer, within certain limitations, topredict system noise prior to construction and where necessary, reduce systemnoise to specified limits by the use of noise reduction devices.

2

. ....

Lab. Project 5662-2

Final Report

TABLE OF CONTENTS

Page No.

SUMMARY 2

ADMINISTRATIVE INFORMATION 4

BACKGROUND 5

OBJECT 6

DESCRIPTION 6

PROCEDURE 6

RESULTS 13

CONCLUSIONS 14

RECOMENDATIONS 15

FUTURE WORK 15

3L"

fI

Lab. Project 5662-.2Final Report

ADMINISTRATIVE INFOR.MATION

Ref: (a) BUSHIPS ltr F 013 O801, F 013 0803, F 013 1106 Ser 649S-1824,Program Review, of 16 Aug 1960

(b) BUSHIPS ltr NY/3/N26(649S) Ser 649S-3258 of 30 Jul 1958%c) BUSHIPS ltr S38/3 (549S) Ser 549-5515 of 26 Aug 195-4(d) MATLAB NAVSHIPYDNYK, Project 5662-1, Progress Report 1,

NS 713-215, Subtask 18, "A Method for Predicting Octave Band Levelsof Ventilation System Noise in Shipst Spaces" of 18 Aug 1955

(a) MATLAB NAVSHIPYDNYK, Project 5662-1, Progress Report 2,NS 713-215, Subtask 18, "Air Conditioning Systems, Estimating OctaveBend Levels of Noise" of 26 Sep 1956

(f) N1ATLAB NAVSHIPYDNYK, Project 5662-1,Progress Report 3, NS 713-215,Subtask 18, 0Air Conditioning Systems, Estimating Occave Band Levelsof Noise" of 31 Jan 1957

(g) MATLAB NAVSHIFYDNYK, Project 5662-2, Progress Report 1, SF 013 1106,Task No. 4071, "A Method for Estimating Noise Attenuation in Plenumsand Intake Boxes" of 16 Feb 1961

(h) MATLAB NAVSHIPYDNYK, Project 5662-2, Progress Report 2, SF 013 1106,Task No. 1073p "A Method for Estimating Noise Attenuation in Fan IntakeBoxes" of 3 Jul 1961

(i) MATLAB NAVO-.±rLi K , ?roject 5662-2, Progress Report 3, SF 013 1106,Task No. 4071, "1 Method for Zsbimating Noise Attenuation in Fan IntakeBoxes" of 20 Sep .961

(j) NAVAPLSCIENLAB, Project 5662-2, Progress Reporb 4, SF 013 1106, TaskNo. 4071, "Noise Atbenuation in Plenums Housing a Fan" of 19 Jul 1963

(k) NAVAPLSCIENLAB, Project 5662-2, Technical Memorandum #1, SF 013 1109,Task 4071, "Sound Power .Generated by U. S. Navy Vaneaxial and CentrifugalFans" of 14 May 1964

(1) NAVAPLSCIENLAB, Project 5662-2, Progress Report 5, SF 013 1109, Task4071, "Generation and Attenuation of Sound Power by Navy Terminals forAir Conditioning Systems" of 23 June 1964

(m) NAVAPLSCIENLAB, Project 5280-30, Technical Memorandum Final Report,SF 013 1101, Task 1357, "Room Constants for Shipboard Compartments" of*18 Nov 1963

Sn) General Specifications for Ships of the U. S. Navyo) Noise Reduction, edited by L. L. Beranek, McGraw-Hill Book Co., 1960(p) ASHRAE Progress Report No. 3-, Contract No. 72291, to BUSUTFS for May

1960. dated 13 Jun 19n(q) kcFRisE Progress Report No. 38, Contract No. 72291, to BUSHIPS for June

1960, dated 15 Jul 1960.

(r) Ag1RE ltr to BUSHIPS (Code 549S) of 19 may -059 with Final Report onFirst Phase of Contract No. 72291, "Attenuation and Generation of Soundin Elbows with Turning Vanes" by W. F. Kerka.

(s) Paper "Attenuation of Sound in Lined Ducts With and Without Air Flow"by W. F. Kerka presented at ASIRAE Semi-annual Meeting, Feb 11-14, 1963(Research sponsored by BUSHIPS,.

4

Lab, Project 5662-2

Fi-lal Report

(t) NAVAPSCIENLAB, Project 5662-3, Technical Memorandum #1, SF 013 1109,Task No. 4071, "Pressure Losses of Fan Intake Boxes" of 12 Nov 1963

(u) NAVAPLSCIENLAB, Project 5662-3, Technical Memorandum, Final Report,SF 013 1109, Task 4071, "Airflow Pressure Losses in Plenums Housinga Fan" of 22 Nov 1963

Encl: (1) Estimating Method for Predicting Octave Band Levels of Ventilation orAir Conditioning System Noise (32 pp)

1. In references (a), (b), and (c) the Bureau of Ships authorized the Naval AppliedScience Laboratory (formerly the Material Laboratory) to develop for design purposesa method for estimating noise generated by air conditioning systems. In reference(c), the Laboratory was requested to convert an existing method predicated on overallsound pressure levels to one predicated on sound in octave bands and to conductnecessary laboratory evaluations to obtain required data for all components inair conditioning systems. In reference (b), the Laboratory was requested to enlargethe scope of the work to include attenuation of noise provided by plenums housingfans, and by fan intake boxes. In conferences mentioned in reference (b), it wasagreed that the method should be based on sound power levels rather than on soundpressure levels previously used. In reference (a), the Bureau approved continuationof the work under the established Laboratory Project 5662-2.

2. In reference (b)the Bureau requested the Laboratory to experimentally determineairflow pressure loss coefficients for intake boxes and for plenums. This work wasreported separately under references (t) and (u) and will not be further discussedherein.

BACKGROUND

3. Air-borne and structure-borne noise generated by air conditioning and ventilationsystems on submarines and surface vessels interferes with sonar and communicationssystems and provides a means for detection by the enemy. Low noise levels are re-quired and the need exists for a realistic method for designing ventilation andair conditioning systems whose noise levels, in octave bands, are within specificationrequirements. The method should provide means to determine the character and intensityof system noise from drawings so that corrective action, if necessary, can be takenat an early design stage prior to construction. Use of such a method will preventthe need for costly modifications to completed systems where noise levels have beenfound to be excessive, and will reduce costs by eliminating overdesigned acousticaltreatment.

5


OBJECT

4. The object of this work is to develop a method for estimating noise originatingin ventilation or air conditioning systems on submarines and surface vessels. Themethod is to be suitable for use by designers prior to construction, for predictingnoise levels in octave bands in spaces served by the systems.

DESCRIPTION

5. There are two principal types of noise normally encountered in ventilationand air conditioning distribution systems. These two types of noise are brieflydescribed as follows:

a. Fan Noise - This is the type of noise originating in fans and is trans-mitted through the distribution system. This particular type of noise may becompared to the noise generated by a loudspeaker.

b. Air Flow Noise - This type noise is principally due to air turbulencecaused by the wrindstream passing over system components such as elbows, filters,coils, etc. Although relatively minor, the ducting itself is a scurce of noisegeneration at higher air velocities. This is primarily due to boundary turbulenceof airflow through the duct.

PROCEDURE

6. The first draft of a method for predicting octave band levels of noise inventilation systems from design drawings prior to construction of the systems wasprepared in a step by step procedure. Authoritative data for generation or attenua-tion of noise by components were not available but estimates and approximations ofscund pressure levels in octave bands were ased and were subjec- to later verificationor correction. This first draft of the method ,.as reported in reference (d).

7. Additional sound pressure data uexe developed for noise generated by centrifugalfans, for noise reduction by exterior duct wrapping and for transmission of fannoise through partitions. These data were reported ir reference (e). Additional datafoi attenation of airborne noise by sound absorbing duct linings of 1 inch and 2inch thick fiberglass covered by perforated metalweze developed and reported inreference (f).

8. At this point, decision was made to convert the estimating method from P"o"dure based on sound . ,o one bpaed on sound power . New experimentalevaluations of noise generated by Navy fans were made in terms of sound power gener-ated. Principal components of systems were evaluated experimentally to determinethe sound power generated by air flow through the components, as well as to determinethe sound attenuation or amplification of system noise provided by the componentindependent of the noise generation effects due to air flow through the component.

6


9. Fan intake boxes, and plenum chambers housing a fan, were evaluated experimentallyto determine sound power generated or at.tenuated in octave bands by air flow throughthese cooponents. Principal operating variables included in the investigation werethree sizes of intake boxes, three sizes of plentums, three conditions of soundabsorbent lining, three sizes and three locations of flow opening, the addition ofthree types of hoods on the flow opening, and four different air velocities. Theseinvestigations were reported in references (g) through (j).

10. Thirteen Navy Standard fans, including eight vaneaxial fans and five centrifugalfans, were experimentally evaluated to determine the sound porer in octave bandsgenerated by the fans. This investigation was reported in reference (k).

U1. Three types of Navy air distribution terminals were experimentally evaluated todetermine the sound power generated in octave bands by the terminals due to air flowthrough The terminals and to determine the attenuation or amplification of soundgenerated by fans or by other components elsewhere in the system. The three typeswere the diffusing terminal, the cone terminal, and the exhaust terminal. Theinvestigation included three sizes of each tenminal and three different air velocities.This work was reported in reference (1).

12. Concuirrently with the work at the Naval Applied Science Laboratory describedabove, the American Society of Heabing, Refrigerating and Air Conditioning Engineers(ASHRAE) investigated sound power generated by air flow in elbows, in straightunlined ducts, and in straight ducts lined with Navy Standard fiberglas covered byperforated aluminum. This work was done under contract with the Bureau of Ships andwas reported in references (p) through (s).

13. The Applied Science Laboratory revised the first draft of the method for pre-dicting noise in ventilation systems which was reported i. reference (d). All datafor noise generated by fans or by air flow through system components have been ex-pressed in terms of sound power instead of in terms of sound pressure. Approximationsof noise attenuated by components and of noise generated by components have been

replaced by experimentally determined values of sound power for those componentsr6ported in references (k), (1), and (p) thrcugh (s). The remaining portion of thisreport deals with the conversion of the first draft of the method reported in reference(d) to the revised method and coordinated procedure appearing at the end of thisreport.

14. It is considered that a method for predicting noise levels developed byventilation and air conditioning systems, in terms of sound power, includes the_following necessary elements:

7.,


(a) Procedure for the calculation of sound power levels developed by thesystem and delivered at the openings to the system,

(b) The attenuation and generation characteristics of all the components ofthe system, in terms of sound power; with and without airflow.

(c) Proccdure for determining the acoustic properties of spaces being servedby the system.

(d) Procedure for calculating the sound pressure levels at any listening lo-cation in the space based on the acoustic properties of the space, the directivityfactors of the terminals and the distance between the listener and the noise source.

(e) Allowable noise criteria for various types of spaces.

(f) Procedure for reducing noise levels of systems which are in excess of theallowable noise criteria.

15. The attenuation and generation characteristics of system components were obtainedfrom the available data developed by the Laboratory and other investigative sources.Listed in the tabulation below are the principal components considered and thereference sources of information relative to the acoustical characteristics of thecomponents, with and without airflow.

I!

8

III


Reference Source forNoise Attenuation Reference Source forand Generation Noise GenerationCharacteristics, Characteristics

4Component Without Airflmi Due to Air Flow

a. Fans None LP 5662-, Tm #1, ref. (k),enclosures (3), (4)

b. Unlined Duct ASHRAE ltr-.ref.(r) ASHRAE !tr - ref. (p),Table 3a figures 2, 3

ASHRAE ltr - ref. (q),figure 1

c. Lined Duct LP 5662-1, rog. ASHRAE Paper,

Report 3, ref. (f), ref. (s),figures 1, 2 figure 10

d. Vaned Elbows ASHRAE ltr - ref. (r), ASHRAE ltr - ref. (r),Table 4a figures .1-24, incl.

e. Fan Intake Boxes LP 5662-2 - Prog. Report 3. ref. (i), figure 17*and

Plenums LP 5662-2 - Frog. Report 4. ref. (j), figure 15*

f. Cooling Coils and LP 5662-1., Frog.Air Filters Report 1 ref. (d). NoneTable 3

g. Heating Coils LP 5662-1, Frog.Report 1., ref. (d)., NoneTable 3

h. Terminals LP 5662-2, Frog. LP 5662-2, Frog.Report 5, ref. (1), Report 5, ref. (1),Figure 3 figures 4, 52 6

i. Duct Branches "Noise Reduction" None

by L. BeranekS(McGraw-Hill) I

Data were obtained while air was flowing from the fan, and they represent netattenuated fan noise and generated noise due to air flow.

9


16. The estimated noise levels as reported herein, depend primariay upon anevaluation of sound power levels throughout the duct system. Consequent:Ly, acousticaldata, referenced in the table above, that were found to be in terms of sound pressurewere converted to sound power for purposes of this report. The conversion of soundpressure level to sound power level, where necessary, was based upon fundament:aiacoustic principles. A brief summary of the modifications for the components listedin the above table, follows:

a. Fans - A tabulation of sound power levels for vaneaxial and centrifugal typefans is given in Table 3 of enclosure (1). This tabulation was obtained from reference(k), enclosures (3), (4) and (5), and includes a reduction of 3 db for each of thesound power levels shown in reference (k). This reduction was necessary since the

sound power levels shown in reference (k) represent the combined sound power developedat both the inlet and outlet of the fans, wheieas the sound power levels shown onTable 3 (enclo:lure (1)), represent the sound power levels at either the inlet oroutlet of the fans. The sound power levels shown on Table 3 are considered moreexpedient for calculation purposes.

b. Unlined Ducts - The attenuations provided by unlined ducts in terms ofsound pressure were evaluated in reference (r), Table 3ap for various duct sizes

and aspect ratios. In view of the relative uniformity of the tabulated attenuationfactors, average attenuations per foot were calculated which were considered to berepresentative for all duct sizes and aspect ratios in any given octave band. Theseaverage attenuation factors are also applicable for sound power level attenuation andare noted in Table 4 of enclosure (1). Sound pressure levels generated by variousair velocities in three different square sizes of unlined ducts were reported inreference (p), Figures 2 and 3, and in reference (q), Figure 1. These soun1 pressurelevels were converted to sound power ?evels and are shown in Figure 4 of enclosure (1).The convrrsion from Lound pressure level to sound power level was accomplished by useof the following relationship given in reference (6), Page 179.

PUL = SPLd + 10 logo S'dwhere 1o l 3

PWL = sound power level, db re 10 wattSPIJ = mean-square sound pressure level,

db re 0.0002 microbarsp obtainedover cross-sectional area Sd of duct2 ft 2

c. Lined Ducts - Attenuationsp in decibelso provided by ducts of variousperimeter-cross sectional area ratios and lined with l" and 2" thick sound absorbent

lining (MIL-I-15365B) under perforated aluminum, without airflow, were reported in

reference (f)p Figures I and 2. Since decibel attenuation is identical in bothsound pressure level and sound power level work, Figures 10 and 11, reported herein,

are similar to Figures 1 and 2, reference (f). Sound pressure levels generated by

10

if.


various air velocities through a 12" x 12" duct lined with a 1" thick lining, described

above, were reported in reference (s), Figure 10. In a manner similar to that usedfor unlined ducts, sound pressure levels were converted to sound power levels, andare shown on Figure 12 of enclosure (1). In completing Figure 12., it was assumed thatthe sound power levels generated with airflow on a 2" thick lining are the same as.or a 1" thick lining. It was also assumed that the differences in sound power levelbetween different sizes of ducts will be uhe same in lined duct as in unlined duct,

d. Vaned Elbows - The data for vaned elbows, presented in reference (r), Table4a, represent attenuations in sound pressure levels, without airflow, for differentsizes, aspect ratios and angles of bend. In view of the relative uniformity of thedata, average attenuations were calculated which are considered representative of thethree parameters. These attenuations, which are again applicable in sound power work,are included in Table 4 of enclosure (1). Sound pressure levels generated by variousair velocities through unlined vaned elbows of different sizes, aspect ratios andangles of bend are shown in reference (r), Figures 11 through 24. Again, as previouslydescribed, average sound power levels of vaned elbows were determLned and aregraphically shown in Figure 5 of enclosure (1).

e. Other Elbows - It was assumed that sound power level data for elbows otherthan vaned, with and without airflow, are the same as that for vaned elbows, and areshown on Table 4 and Figure 5, respectively, in enclosure (1)o

f. Intake Boxes and Plenums - Sound power attenuation provided by lined intakeboxes and plenums have been reported in reference (i), Figure 17 and reference (j),Figure 15. Graphical representation of these sound power attenuation characteristicsare included in enclosure (1) as Figures 13 and 14, respectively. Figures 13 and 14are predicated on the assumption that the sound absorption coefficients of liningmaterials meeting the requirements of MIL-I.15365- will be similar to bhose shomfor Owens-Corning PF-334 in reference (j).

g. Cooling Coils and Air Filters - Attenuations provided by cooling coils and

air filters, without airflow, were reported in reference (d), Table 3, and are in-cluded in Table 4 of enclosure (1).

h. Heating Coils - Attenuation data~provided by heating coils., were likewise

reported in reference (d), Table 3 and are also included in Table 4 of encolosure (1).

i. Terminals - Sound power level attenuation and generation characteristics ofthree Navy type terminals, with and without airflow, were reported in reference (1),

Figures 3, 4, 5 and 6 and are included in enclosure (1) as Figures 69 7, 8 and 9.

J. Duct Branches - Sound energy, t-aveling along a main duct. divides on anenergy basis when reaching a junction of two or more branches. The reduction insound power level from a main duct to a branch duct is based on the following

• j

L?.


relationship developed from a formula given in reference (o), page 556:

PWL (Branch) = RL (Duct) - 10 logic A,

Ad

where:

PWL (Branch) = Sound power level in particular branchnTL (Duct) = Sound power level in main duct at branch pointA = Total cross section area of all branch ducts leaving junction

Ad = Cross section area of particular branch

Figure 3 of enclosure (1) shows a graphical means by which the sound power levelreduction between a main duct and a branch duct can be determined.

17. The acoustic properties of spaces being served by a system become relevant factorsin translating the sound power levels at the face of a terminal to sound pressurelevels at a listener or working station. Values for room constant were obtained byuse of the following relationship given in reference (o), page 237:-

R= SAi-

where:R = Room constant, in sq. ft.

= Average sound absorption coefficientS = Total surface area, in sq. ft.

Figure 1 of enclosure (1) was developed using the above relationship and it providesfor designers a means for estimating the Room Constant of a space as a function ofthe six boundary surface areas and the average sound absorption coefficients of thespace contents, in octave bands. Data for Room Constants were obtained from resultsreported in reference (m) fi- spaces of known "Noise Category" aboard the EAG 153,USS COMPASS ISLAND. Additional data were also obtained for the Ventilation AcousticChamber in the Laboratory, which was considered analagous to a Noise Category "C"type of space. For compactness, a tabulation of sound absorption coefficients for

spaces of different "Noise Ca+egories" is also showm in Figure 1 cf enclosure (1).

18. The procedure for determining the sound pressure levels at any listening locationin a space based on the acoustic properties of the space, the directivity factors ofth-e ter.als , and the do coen the listener and the noise source was aev-Iopedfrom the expression:

12

Lab. Project 5662-2"-1 nal Report

where:

FWL = Sound power level at terminal (db - e O13 watt)

SPL = Sound pressure level at listening location (db - re 0.0002 microbars)

r = Distance between face of terminal and listening location, in feet

R = Room constant of space (sq. ft.)

= Directivity factor of terminal

For purposes of expediency, an average directivity factor of Q=2 was assumed for allterminals. Figure 2 of enclosure (1) shows in graphical form the relationshipsdeveloped from the above expression.

19. Allowable noise criteria for various types of spaces are given in Section Sl-l0of the general Specifications for Ships of the U. S. Navy. For noise categories A or Ewhere Speech Interference Levels (SIL) are specified, a distribution of allowablelevels was assumed in the four octave bands from 300 cps to 4800 cps. The distributionwas based on descending 4 db per octave band with ascending frequency, and with theaverage of the four octave band levels equal to the SIL specified. The distributionof allowable levels for SIL Categories A and E are shown in Table 1 of enclosure (1).

RESULTS

20. An esAiatin,; method for predicting octave band levels of ventilation or airconditioning system noise is presented in enclosure (1) herewith, which includesfour tables and fifteen figures. Table 1 provides a step by step procedure of themethod and includesg

a. Setting up of the problem based on a specific system.

b. The determination of the maximum allowable sound pressure levels of spaces

served by the system.

c. The method for calculating the sound power levels delivered by the system at

the terminals.

d. The determination of the acoustical characteristics of the spaces served bythe system.

e. The determination of the sound pressure levels at the working stations of aspace resulting from the sound power levels at the terminals in the space.

13


f. The determination of the attenuation required in a system where soundpressure levels at the Vorking stations exceed specification requirements.

g. Design of sound absorbing duct work, fan intake boxes, or plenum housingthe fan, to provide the attenuation requirements.

21. Table 2 is a sound control work sheet which is used to implement the step bystep procedure described in Table 1. Incorporated in Table 2 is an example, inone octave band, of the application of the method for a typical air conditioningsystem.

22. The calculation of the sound power levels delivered by a system at theterminals can be accomplished as indicated in Step III of Table 2. Supportingexperimental and estimated data relative to the sound power level attenuation andgeneration characteristics of system components are shown on Tables 3 and 4, andFigures 3 through 9 and 15.

23. Figure 1 provides a means by which the acoustical characteristic, room constantR, of spaces served by a system can be determined. In conjunction with resultsobtained from Figure 1, Figure 2 provides the means by which the difference betweenthe sound power levels at the terminals and the sound pressure levels at the workingstations can be determined, which in turn is used to establish the sound pressurelevels at the working stations. A comparison between the sound pressure levels atthe working stations and those permitted in the space by reference (n), indicatesthe octave bands in which reductions in sound pressure levels are necessary to meetspecifications. Figures 10 through 14 provide the means for obtaining the necessaryIoise reduction in the system. CONCLUSIONS

24. It is concluded that:

a. Enclosnire (1), with Tables 1 tlrou i 4 and Figures 1 through 15 providesfor ventilation -and air conditioning systems:

(1) A suitable method for estimating noise developed by such systems ona sound power basis.

(2) A procedure for translating sound power delivered at the terminals ofsuch systems to sound pressure levels that will exist and can be measured at variouslocations in a room.

i14g21


(3) A means by which noise levels developed by these systems can bereduced by relocation of terminals, by the acoustical treatment of duct work, orby the use of acoustically lined intake boxes and plenums housing a fan.

b. The revised noise estimating method shown in enclosure (1) provides thefollowing advantages over the first draft of the method, reference (d):

(1) A noise estimating method based on sound power, a fixed acousticalcharacteristic, provides a fundamental and more desirable basis for estimatingand comparing ventilation and air conditioning systems and system components thanone based on rcom sound pressure levels.

(2) Experimental data are used in lieu of estimated data for many system

components.

RECOMMENDATIONS

25. It is recommended that the method for estimating octave band levels of noisereported in enclosure (1), be distributed for use by Naval designers. It issuggested that the design agencies report to thp Bureau, the extent of agreementfound between the noise levels predicted by the method and those found by actualmeasurement in completed systems.

FUTURE WORK

26. The U. S. Naval Applied Science Laboratory has no plans for continuing workon this project after June 1964. This is a final report.

27. While experimental data for generation and attenuation of noise by the principalgenerators and attenuators among system components have been obtained and integratedinto the procedure reported herein, consideration should be given to obtainingsimilar experimental data for the follow-ing e stem components : heating and cooling

coils including their duct transformations, branch take-offs, elbows other thanvaned elbows, flame arresters, watertight closures, silencers and mufflers.

28. Attenuation in 12" x 12" straight ducts lined with orn inch thick fiberglasscovered by perforated metal was measured as part of the work reported by ASHRAEin reference (s). Consideration should be given to experimental determination ofattenuation for other sizes and other aspect ratios of duct, and for two inchthick linings.

15

Lab. Project 5662-2Final ReportEnclosure (1)

Page 1 of 32

ESTIMATING METHOD

FOR PREDICTING OCTAVE BAND LEVELS OF

VENTILATION OR AIR CONDITIONING SYSTEM NOISE

U. S. NAVAL APPLIED SCIENCE LABORATORY

NAVAL BASE

BROOKLYN, NEW YORK 11251

U. S. Naval Applied Science Laboratory Lab. Project 5662-2final Report

Enclosure (1)Page 2 of 32

ESTI!-ATING NITHOD

FOR FREDICTING OCTAVE BAND LEVClS OF

VENTILATION OR AIR CONDITIONING SYSTEM NOISE

Tables 1 through 4, and Figures I through 15 form a package which contains allinformation necessary for using and applying the estimating method. Table 1outlines the procedure and refers to item numbers on Table 2 which is a suggestedwork sheet on which a typical example has been worked out. Tables 3 and 4, andFigures I through 15 contain data used in the various steps of the procedure.

Tables:

1. - Procedure for Prediction of Octave Band Levels of System Noise.

2. - Sample Sound Control Work Sheet and Example for Predicting Noise Levels.

3. - Sound Power Levels at Either Inlet or Outlet of Navy Standard Fans.

4. - Sound Power Level Attenuation of System Components without Airflow.

Figures:

1. Design Curves for Estimating the Room Constant (R) of a Space as a Functionof the Surface Area of the Space and the Average Sound Absorption Coefficient (0c).

2. Design Curves for Predicting the Sound Pressure Levels in a Space as a Functionof the Roor Constant (R) and the Distances from the Noise Source to Listener.

3. Reduction in Sound Power Level from a Main Duct to a Branch Duct.

4. Sound Power Level Generated in Octave Bands Due to Airflow in Straight Ductswith No Lining,, for Any Length of Duct.

5. Sound Power Level Generated in Octave Bands Due to Airflow in Vaned Elbowsof Any Angle of Bend, with No Lining.

6. Sound Power Level Attenuation or Generation Characteristis of Navy StandardDiffuser, Exhaust and Cone Type Terminals (Without Airflow).

II

U. 3, Naval Applied Science Laboratory Lab. Projev 5662-2Final ReportEnclosure (I)Page 3 of 32

7, Average Sound Power Levels of Navy Standard Cone Terminals, Due to Airflow.

8. Average Sound Power Levels of Navy Standard Exhaust Terminals, Due to Airflow.

9. Average Sound Power Levels of Navy Standard Diffuser Terminals, Due to Airflow.

10. Sound Power Level Attenuation in Octave Bands in Straight Ducts Lined onFour Sides with l" thick Navy Standard Fiberglass and Perforated Aluminum,No Airflow.

-1. Sound Power Level Attenuation in Octave Bands, in Straight Ducts Lined on FourSides with 2" thick Navy Standard Fiberglass and Perforated Aluminum, NoAirflow.

12. Sound Power Level enerated in Octave Bands Due to Airflow in Straight DuctsLined 1" or 2"thick Navy Standard Fiberglass and Perforated Aluminum, forAny Length of Duct.

13. Design Curves for Predicting Sound Power Level Attenuation of RectangularIrtake Boxes (Without Inbernal Baffles and Lined with Navy Standard Fiber-lassand Perforated Aluminum) as a Function of Sound Absorption Coefficient (.4 andTotal Internal Surface Area.

14. Design Curves for Predicting Sound Power Level Attenuation of RectangularPlenums Housing a Fan (Without Internal Baffles and Lined with Navy StandardFiberglass and Perforated Aluminum) as a Function of Sound AbsorptionCoefficient ( c) and Total Internal Surface Area.

15. Chart for Combining Noise Levels.

U. S. Naval Applied Science Laboratcry Lab. Project 5662-2Final RepcrtEnclosure (1)Page 4 of 32

TABLE I

PROCEDURE FOR PREDICTING OCTAVE BAND LEVEIS OF SYSTEM NOISE

Step I

Identifying Information

a. Enter information indicated in items 1, 2, 3 on Table 2.

b. In Item 4., draw a single line diagram of entire system, showing all duct workand components. letter and number the junction points of the system toseparate mains, branch-mains and branches. Show all spaces in which there areinlet or discharge openings for the system, hereafter referred to as terminals.Show space dimensions. Indicate air velocities in fpm; duct lengths in.feet-;.and the sizes of all ducts and system components.

c. In Item 5, enter the information indicated, including thcz distance from eachterminal to the nearest listener (nearest working station).

d. In Item 6, enter the information indicated, for each space served by the system.

Step II

Maximum Allowable Sound Pressure Levels in Space

a. In item 7, enter the designation for noise category of each space. Selectcategory from Sectioi. -28-3-c of General Specifications for Ships of theUnited States Navy.

b. For noise categories B, C, or D, select from Section Sl-lO-c of GeneralSpecifications the allowable sound pressure levels in each octave band andenter them in Item 8. Use space volume, item 6, when making selection.

c. For noise categories A or E where speech interference levels(SIL) are specified,assume distribution of allowable levels in the octave bands as follows:

U. S. Naval Applied Science Laboratory lab. Project 5662-2f inal ReportEnclosure (])Page 5 of 32

- - ALLOWABLE SOUND FRESSURE LEVEL, db

Vol. of Octave Bands cMNoise Room 300 ()00 1200 2400Category (cu. ft.) SIL 600 1200 2400 4800

500 to 1999 60 66 62 58 54

A 2000 to 7999 55 61 57 53 49

8000 or larger 50 56 52 48 44

72 78 74 70 66

Select allowable levels in four octave bands from appropriate line in tabulationabove and enter them in item 8.

d. If other important noise sources are present in the space, which are likely toproduce noise levels equal to those created by the air conditioning system, deduct3 db from the levels selected under (b) or (c) before entering them in item 8.

Step III

Calculation of Predicted Noise Developed by System

a. In items 9 and 10, enter data indicated.

b. For purposes of calculation, the fan is considered the start of the system and thesound power levels at the terminals are to be computed independently from thedischarge side of the fan to each discharge termainal and from the intake side ofthe fan to the intake of the system. From the fan, and for either the upstream ordownstream side of the system, the available sound power level attenuation andgeneration data of all system components, under both airflow and no flow conditions,are to be integrated into the calculation in consecutive order until the sound powerlevel at the face of the intake or terminal opening to the system is determined.

U. S. Naval Applied Science iaboratory Lab. Project 5662-2Final ReportEnclosure (1)

Page 6 of 32

o All available data for the calculation are given on Tables 3 and 4, and Figures1 through 9 and 13 through 15. Data for sizes of components other. than given inthe aforementioned tables and figures are to be obtained by interpolation. Datafor configurations of components other than those given in the aforementionedtables and figures are to be obtained by cloosing from the given components, oneclosely resembling the component in qu.estipn. Whre data are not available foreither the airflow or no flow condition of the given component, it is to be assumedthat these acoustical characteristics are not pertinent to the calculation andshall be omitted. -

d. By way of example, and for purpos$a. .. explanatiorL. and clarity ,.the steps in thecalculation for one octave band are shown in item 11 of Table 2 for thz system as,ahown in item 4. This prbcedure dhould also be applied to all other octave bandsin the frequency range of 75 cps through 9600 cs.

Step IV

Dotermination of Necessary Attenuation

a. Necessary attenuation in each octave band is the number of decibels by which thecalculated sound pressure levels at the listener, determined in column !0 of Table2, exceeds the maximum allowable levels in the same octave bands as shown in Item 8.In the tabulation, item 12, Table 2, enter the data indicated.

Step V

Obtaining the Necessary Attenuation

a. Determine from Figuire 2, if the necessary attenuation can be obtained by increasingthe distapce between the terminal, or the fan inlet, and the listener at the workstation. If feasible, select new location of terminal or fan inlet and show it initem.13.

b, If a terminal cannot be moved to obtain, the necessary attenuation, use Figure 10cr 11 to determine the minimum length of sound absorbing lined duct which isrequired to reduce each octave band level to the maximum allowable sound pressurelevel in the space. -Te the longest length required by any of the several octavebands. If the required length of lined duct exceeds the length of duct in the

branch, sub-divide the duct into cells with duct lining to provide greater attenua-tion in a given length. The amount of noise reduction attainable by sound absorbingduct lining:

I

U. S. aval Applied Science Laboratory Lab. Project 5662-2Final Reportb

a Enclosure (1)Page 7 of )2

1. Is limited to a rnximum attenuation of 25 db.2. Is limited by the generated sound pressure level of the terminal (column 7

minus column 9 in item 11).3. Is limited by generated sound pressure level of lined duct work. (PWL from

Figure 12 minus column 9 in item 11).\ Show calculations in item 14.

c. .. -b e fan inlet cannot be moved to obtain the necessary attenuation, select anintake box to be installed on the fan inlet, or a plenum to be installed aroundthe fan, by use of Figure 13 or 14. Use a box or plenum having the largest liningarea required by any octave band. Show calculation in item 15. Provide an airinlet opening to the box having an area from 1.0 to 1.5 times the face area of thebellmouth on the fan. Show calculation in item 16.

v. f.

U. S. Naval Applied Science Laboratory Lab. Project 5662-2Final ReportEnclosure (1)Page 8 of 32

TABLE 2

SAMPLE SOUND CONTROL WORK SHEET

AND EXAMPLE FOR PIREDICTING NOISE LEVELS

Step 1

Identifying InformationItemNumber

1 Name and number of vessel:

System number:

2 Type and size of fan: Vaneaxial, A2

3 Name of space served:Number of space served:

4 System diagram: (see nex. page)

Lr

I

LaboProject 5662-aU.S. Naval App ed Science Laboiatory Final Report

Enclosure (1)TABLE 2 (SHEET 2) Page 9 of 32

_ SSTEM_ fiRAM

9" OIA. C-TSE DMNSIONS 9" DIA. TH. VEL = 2050LENGTH - 40' 900 VEL= 2050 900 CFMWIDTH 20' V.EL L 20'HEIGHT -- 9' PWL

1 84 8

8 8" DIA.90° VEL 1&0 90°V. EL. L= 10' L=5' V. EL.

BR. T.0.C 45 EL

PWL80 DB- F 6" DA

PWL "VEL: 1550899 L--B J 6" DIA. L=I0

PWL VEL=O89 D)8 \L=5

[ 8~R.TO.\A 2 45° EL 90° V.EL.2500 i- SPLITSCFM 11" DIA. 90f V.EL.

V rL2,40 0 PWLz 69 D8---- 5'6"OIA. DF-TA 350 CFM

INTAKE PTH. VEL. =18008CXK 92 OB

12"X12"9" DIA.VEL.: POO VEL= 2150L 5 L =15' -#4

PWL 68.5 066" DIA. DIF-1

300 CFMTH. VEL=i550

PWL 78 D69" DIA. DIF-T950 CFM

TH. VEL: 2150

SALE, NQNE

LEGEND:VEL. -VELOCITY OF AIR IN FPM C-T - GONE TERMINALTH. VEL.-THROAT VELOCITY OF AIR IN FPM L - LENGTH OF DUCT, IN FT.

PWL - SOUND POWER LEVEL, IN DB V. EL - VANED ELBOWSPL - SOUND PRESSURE LEVEL, IN D EL .- ELBOWDIF - T - DIFFUSION TERMINAL B. T.O. -BRANCH TAKEOFF

'I

'U. 3. Naval Applied Science Laboratory Lab. Project 5662-2Final ReportEnclosure (Page 10 , 32

Atem

'41urber

5 Terminal Data:

Terminal No. - Distance toon Diagrm . Type Size Listener

#1 Cone 9h P-a. 5'#2 Diffusirg 912 Dia. 8'#3 Diffusing 6" Dia. l0 t

#4 Diffusing 6" Dia. 15'#5 Intake Box 1 O'

6. Space Dimensions:

Length 40tWidth 20Height 9?Surface area of space (6 boundaries), in sq. ft. 2680Volume of space, in cu. ft. 7200

Step II

Maximum Allowable Sound Pressure Levels in Space

7. Space Noise Categoryg

See Section 28-3--c; General SpecificationsCategory "C" (assumed for example)

8. Maximum Allowable Sound Pressure Levels in Space at Listeners:

See Section Sl-l0, General Specifications

Octave Pass Bands, cps -

75 ' -5 1 3001 600 112001 2400 f 8001600 120 2400 4800 9600 1

Max. SPL, db 72 68 64 60 56 52 48

L

SII

U. S. Naval Applied Science Laboratory Lab. Project 5662-2Final Report

Enclosure (1)

ItnPage 11 of 32

N"umber

Step III

Calculation of Predicted Noise Developed by System

9. Room Constants "R" for Spaces Serveds

Noise category of space: 11011

Total surface area: 2680 sq. ft.

From Figure 1:

Octave Pass Bands, cps

75 150 300 600 1200 2400 480015o 300 600 1200 2400 4800 9600

"R' Ii_1150

10. Difference between FdL at Terminals and SPL at Listener, in db(from items 5, 9, an, 'igure 2):

jOctave Pass Bands, cpsDistance to I 75 150 300 600 1200 24OO 48oo

rerminal Listener 150 300 600 1200 - 2400 4800 9600

#1 5' I20.0#2 8' 92.0#3 10 t 22o5

4 1.5' 24.0#5 10' 22.5

_____ A_____ ___-_ _

a) (D I tI I II I222 I I I I I I9 C~ D-1f 211 (M

C'. 0 b. C', 'ZO.C9. : 22b HV2I 1 1 1 t 1 It2 2 21 21 1 2 1 4

_ _ _ _ r. c'.0 PL,

I) r@CI I 21 I 2222t \0--I C O -GH 1bO 2\ I2 m2 2 222t C I -* MI

4z 0 't It~0 f0 VU000 I 0000188

_ _4 2 2'0 I.4..4. I.. . c CC-'

oH 0 \ I ooo0

1A O' ~ 0 tr\0 1A \0 0 0 x\1 i r 0000~ 4 ,F1 a. ~0 0000I

0 ( 09 i, P fN r\0 VIOH r 0C Co0 0 1^0 0.0 0000

.r0ro)0-- li 6 A Zc gxA 4 r4 i

0 0

N~ 0 i 0 co~~ 0,0.r~ 22.

c+1 -~f0~ _________tI4'P C. ,g C

I) 0

"q P-0I.-

t 0 S, a, 0 2 I

0 ~ 4-5.~-C'J H w~~ a')1 26

c'J\0110 P'd S I

01 0~ 231 I ~.r-3 c' Pc, co 262 * 2,0 ( 4-4 E- CO\ 0 0214 '

rM0 0 (1 HI0 0,'8 i~x\o o 000000 0

:' > b 0 a ) *C o C 0 E 0 0 0 0 0 0 0 0 C C 0a

(1) C-> 0S I ol"

a) .13.4 IJ' Q0 0 0 0g.20000 0 0

43 Ic\Jc'Jc'J'o 'o 0 0

nq0 Id

4:) 4(D'd 1A'\X\0O 000000 0

V~ ) U CC) C 000 L0000 C oo oc C D .

C.. 4 r.'~ c02 0o'bf

oc(D0 .43 IAHI 0 0 0

04 0*

co coJ00

0 0 A E4 f r

0' 0aO4 76-, 4H C -

C/2 0

U. S. Naval Applied Science Laboratory Lab. Project 5662-2Final- ReportEnclosure (].Page 14 of 32

ItemS

Number

Stop IV

Determination of Necessary Attenuation

12. Necessary Attenuation, in decibels:

Octave Bands cps75 150 300 600 1200 2oo h800

150 300 600 1200 240 4800 9600

Maximum AllowableSPL at Listener-i- 72 68 64 60 56 52 48

Section Al, SPL* 64.0Nec. Atten. 4.o

Section B2, SPL* 56.0Nec. Atten. None

Section C3, SPL* 46.5Nec. Atten. None

Section C4, SPL* 44.5Nec. Atten. None

Section F5, SPL* 76.5Nec. Atten. 16.5

* SPL at listener from column 10 Item 11.

Vi

U. S. Naval Applied Science Laboratory Lab, Project 5662-2Final Report- -:losure (1'

k 5 32

Item

Number

Step "

Obtaining the Necessary Attenuation

13. Move terminal No. to .Move fan inlet to ....__

14. Length of lined duct requireds

Section Al, 1" thick lining, octave band 600-12001P/A ratio = .44; Attenuation - 3.0 db per ft. of dact (from Figre 10);Lined duct required = 4.0- 3.1 : .3 feet for octave band 600-1200.(Calculate length required for each of the other octave bands).

15. Selection of intake box for fan:

On Figure 13, select l' thick lining. Coefficient cC= 0.69 for octaveband 600-1200. For 16.5 db necessary attenuation and 4= 0.69,. the internalsurface area of lined intake box must be 46.5 s.f. for octave band 600-1200.Calculate area required for each of the other octave bands.

16. Selection of air inlet opening to intake box:

Face area of bellmouth for A2 fan = 2.16 s.f.Area of opening in intake box = 1.25 x 2.16 = 2.7 s.f.

I

Ii.

I

U. S. Naval Applied Science Laboratory Lab. Project 5662-2Final ReportEnclosure (I1Page 16 of 32

TABLE 3

SOUND POER LEVEL AT EITHER INLET OR OUTLET

OF NAVY STANDARD FANSDB - RE lO-13 WATTS

Octave Pass Bands -c . -

Fan Std. Navy 75 150 300 600 1200 2400 4800Type Fan Size 150 300 600 1200 2400 4800 9600

Vaneaxial A 1/4 79 97 93 89 87 82 77if A 1/2 69 80 88 89 89 85 78it A 1 73 85 87 86 88 85 77SA. 1 1/2 76 88 95 98 99 93 86"l A 2 84 93 96 99 98 91 90it A 3 84 91 89 88 87 83 77M A 4 88 98 99 94 93 86 83" A 6 92 101 101 100 95 86 80

Centrifugal C 1/4 86 100 88 83 82 75 680 CC 1/2 89 90 88 85 83 77 71

" CC 2 94 92 92 90 94 85 77It CC 3 98 91 93 90 93 90 79"1 CC 5 104 95 97 95 98 92 84

I.

U. S. Naval Applied Science Laboratory Lab. Project 5662-2Final ReportEnclomre (3Page 17 of 32

TABLE 4

SOUND POWER LEVEL ATTENUATION OF SYSTE4 COMPONENTS

WITHOUT AIR FLOW, DECIBEIS

Octave Pass Bands, cps

75 150 300 600 1200 -240 480Component 150 300 600 1200 2400 4800 9600

Cooling Coil& Air Filter 0.5 1.5 3 4.5 5.5 7.5 8.5

Heating Coil 0.5 1 1.5 2.0 2.5 3.0 3.5

Unlined Duct, -- ___ ___ - _____-

db per ft. 0.22 0.16 .20 .10 .12 .15 .18

Vaned Elbows 0 2 2 2 2 3 3

Other Elbows(Estimated) 0 2 2 2 2 3 3

Lined Duct Shown in Figures 10 and 11

Intake Boxes& Plenums Shown in Figures 13 and a4*

hay Ter-nals-- Shw in Fi 6

Duct Branches Shown in Figure 3

* Data were obtained while air was flowing from the fan, and they represent netattenuated fan noise and generated noise due to air flow. I

U . NAVAL APPLIED SCIENCE L.ABORATORY LAB. PROJECT 5662-2FINAL REPORT

10PO --- Enclosure (1) page 18 of 328POC

6pooc FIGURE1DESIGN CURVES FOR ESTIMATING THE ROOM

4P00 CONSTANT (R) OF A SPACE AS A FUNCTIONOF THE SURFACE AREA OF THE SPACE ANDTHE AVERAGE SOUND ABSORPTION

2,000 COEFFICIENT (05____

l,000-

SP C 8057CI O 3 0 60 2 0 24 0 4 0

100

AVRG S" ABOPTO (XECN 060OSURF PACE RATOF IE 0ADFROTV ADSPACE (3N SQ FT. 1 0 30 60110 40 40

(4 WALS CEIIN AND FLOOR)1240 80 90

U. S. NAVAL APPLIED SCIENCIE LABORATORY LAB PhOJE6A 5662-?.FINAL REPORTEnclosure (1)Page 19 of' 32

FIGURE 2

DESIGN CURVES FOR PREDICTING THE SOUND PRESSURELEVELS IN A SPACE AS A FUNCTION OF THE ROOM CONSTANT(R) AND THE DISTANCE FROM THE NOISE SOURCE TO LISTENER

2I

____ R :100 ( SQ. FT.)

z~

-i

ow

2000

9 - 000

UQ~3 ___ i __ 50

*1W 221 _____ I

56800 3 4006 100

DITAC FRO NOIS SORET ITNR NFE

wo aolv S

I87

m 13

0) LO -2)U-W 0

H m0

z ~z

ww

zzM-I-

00z 15

0 0

-o

0

cr-a

A~

US NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5662-2FINAL REPORTEnclosure (1)

110 -15-15 rPSPage 21 of 32

100 FIGURE 4

80 SOUND POWER LEVEL GENERATED70 611IN OCTAVE BANDS DUE TO AIRFLOW IN

60 _ 6_ STRAIGHT DUCTS WITH NO LINING, FOR50___ ANY LENGTH OF DUCT

40 __ 10-40 P

80-

70 -T

0

10100r- 80900'

90- 90-

30 -X 400 300 200-O

VEWCT OF1 2AIR (F.EMN

U. S. NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5662-2FiNAL REPORTEnclosure (1)Page 22 of' 32

1075 -15O CPS FIGURE 5

/ '~ "SOUND POWER LEVEL GENERATEDIN OCTAVE BANDS DUE TO AIRFLOW

70 wiIN VANED ELBOWS OF ANY ANGLE61T1 OF BEND, WITH NO LINING

50 NOTE: USE THESE DTA ALSO FOR ELBOWS WITHOUT VANES

0 :1

7-10 100x6 -

~ 21 1530- 00 CPS __i2 ___400___

00

-2 -k 6 60010 P 80ROC~

6""

U) 40.40 -

5!1004J 300 -60U10 2000 4800 CPVEOCT OFj 9I0(T PRMI.

Jrr

U.S. NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5662-2IINAL REPORT

FIGURE 6 taeSOUN~D POWER LEVEL ATTENUATION -OR GENERATION CHACTERISTICS OFNAVY STANDARD DIFFUSER, EXHAU1 ST AND CONE TYPE TERMINALS

_______ (WITHOUTAIRFLOW)

+2 _______ER

TERMINALS.

0

+0

z

a -4

-6

z

r 4

> +21

0-

0~ +8CONE

TERMINALS

+6 -

75 15 1200 2400 41300150 30 2400 4800 9600

OCTAVE PASS BANDS IN CYCLES PER SECOND

FIN

r2 NAAPLE UtLBROX(DUE TO AIRFLOYW) 9____INCH ______

75-Q~ CONETERMNAL

70

65

~ 0

0

> 6 INCH DIA.ti TERMINALj 75 .w

265

6C

R 3 INCH DIA.

075TERMINAL___

6C--

55'150 300 600 1200 2400 4800 9600


U S. NAVAL APPLIED SCIENCE LABORATORY LAS. PROJECT 5662-2FINA1_EOg

FIGURE 8 Page 25 of 32AVERAGE SOUND PWER LEVELS OF NAVY

SNDAD EXHAUST TERMINALS

700

65 THROAT_________

~60

rn7

w

765wU0

-Jw

675

55orU)

80

65NH I.

______________________T ____________________ ___________________

65

300 ~o00

150 300 600 1200 2400 4800 9600


U.S NAVAL APPLIED SCIENCE LABO0RATORY LAB. PROJECT 5662-2FINAL REPORT

FIGURE 9 Enclosure (1)

AVERAGE SOUND POWER LEVELS OF NAVY Pae6 f3STANDARD DIFFUSER TERMINALS

80. _______ _____(DUE TO AIRFLOW) _________

. 7~ ~5____

70CC

65

~60

7055

I-

>j 6 INCH DIA.-

~75j

~70

*w ~ 65

zJ60

55

a. 3- 1/2 INCH( 0A.3 I_______ ______________ _____ TERMINAL

70

60 10

55 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _75 150 300 600 i200 2400 4800150 300 600 1200 2400 4800 9600

OCTAVE PASS BANDS IN CYCLES K~R SECOND.t

U. S. NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5662-2REPOF

FIGURE 10 Pncosure Pg.27 of 32

SOUND POWER LEVEL ATTENUATION IN OCTAVE BANDS INSTRAIGHT DUCTS LINED ON FOUR SIDES WITH I" THICK NAVYSTANDARD FIBERGLASS AND PERFORATED ALUMINUM, NO AIR FLOW

I INCH THICK LINING "INC __ _ 4-... .

4.-

zI

15 300 P00 RATIO0 80 90

13._ _ _ _L_

Z2

wT

75 150 300 600 1200 2400 _A000I150 300 600 1200 2400 4890 9600


NOTES:1. .__PERIMETER (INCHES) PERIMETER AND AREA ARE INSIDE DUCT LINING.

A CROSS SECT. AREA (SQ.IN.) I2- CURVES SHOWN MAY NOT BE USED FOR SINGLE FREQUENCY SOURCES.3. FOR EITHER ROUND OR RECTANGULAR DUCTS WHOSE P/A RATIO IS NOT LISTED,

ESTIMATES OF ATTENUATION MAY BE MADE BY INTERPOLATING BETWEEN CURVES.4. 25 DB IS THE PRACTICAL MAXIMUM ATTENUATION WHICH CAN BE ATTAINED IN DUCTS

IN WHICH AIR FLOWS. THIS DETERMINES OPTIMUM LENGTHS OF DUCT LININGS FORTHE VARIOUS OCTAVE BANDS.

U.S. NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5662-2FINAL REPORT

FIGURE II Enclourc ()SOUND POWER LEVEL ATTENUATION IN OCTAVE BANDS IN Page 28 of32STRAIGHT DUCTS LINED ON FOUR SIDES WITH 2' THICK NAVYSTANDARD FIBERGLASS AND PERFORATED ALUMINUM, NO AIRFLOW

2 INCH THICK LINING::

0 .

w Z OZ.

wt

< -

5P/A A 10 Z

10 ____0_00 200 400 90

0.8

z2 0.6 - -4

OA4

75 150 300 600 1200 2400 4800150 .300 600 1200 2400 4800 9600


.,C . PEIMTR ICHS. CROSS SECT. AREA (SQ. IN.) PERIMETER AND AREA ARE INSIDE DUCT LINING.

2. CURVES SHOWN MAY NOT BE USED FOR SINGLE FREQUENCY SOURCES.3. FOR EITHER ROUND OR RECTANGULAR DUCTS WHOSE PA RATIO IS NOT LISTED,

ESTIMATES OF ATTENUATION MAY BE MADE BY INTERPOLATING BETWEEN CURVES.4. 25 DB IS THE PRACTICAL MAXIMUM ATTENUATION WHICH CAN BE ATTAINED IN

DUCTS IN WHICH AIR FLOWS. THIS DETERMINES OPTIMUM LENGTHS OF DUCT LININGSFOR THE VARIOUS OCTAVE BANDS.

U. S. NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5652-2FINAL REPORT

Enclosure (1)Page 29 of 32

_00 FIGURE 12

60 ~SOUND POWER LEVEL GNERATED70 IN OCTAVE BANDS DUE TO AIRFLOW IN6 ~STRAIGHT DUCTS LINED WITH I" OR 2 '

50__ THICK NAVY STANDARD FIBERGLASS___ ____AND PERFORATED ALUMINUM, FOR ANY

LENGTH OF DUCT.

to 90i

-k 10 70

800- 60P70-

500 3 0 00 30 00 10

4EO0T OFAR (F.PR0I.

H 0~

13 0 U o - _

N 0

0 Li 0

0o

z W

00

b.jQ (DWO 0 O

0 NW

dZZ zz 00 0_ 0

00 i- V ,x00 u 0(p

_dd X i i m-_L

-\%

E.)~(S±V <IO to 80)08 11- CD

z j

wI 00

-2 , t 0 0

to r

(rcrI0. c

-

LL~ZL 0OD U,

DLLJ

ci z

0 0

00 ~ -_

Li. 00(f) Cj 0

ILL 1' 10 0 _ _

W _& K 0 d

9~ ~ 0 0 0 .U

m 0

z~U~ 4 U) 00 0 D

(DSLV 01 UZ 80) 1C~

z j

I0Il

U. S. NAVAL APPLIED SCIENCE LABORATORY LAB. PROJECT 5662-2FINAL REPORTEnclosure (1)Page 32 0f 32

FIGURE 15

CHART FOR COMBINING NOISE LEVELS

H

0.

00 6 7 8 10 11 12 I3 14

DIFFERENCE IN DECIBELS BETWEEN TWO LEVEL.SBEING ADDED

b~0 )bo 0 4) 061)

16 0 3- I)4 'j

0, .44 4) .4) . * - 4Z -) cl. 0

4- z ca) .

in. 0 *1-4*4 c " G .1>-0 -4>

0 B

NO) 4.' .

4 )-c( .c.0 > r4)1.4- z )- :3)4)). 00 1-4 4)3 0.4).4Z.40

I4~~C .'>4) <

0.6. 4)4 0 o~~U 6 Q 0

ca 0.14) 4cc .. 4).. .)0.14 . IX4)c4) 04) 0>

ON !Q C04.4 .0 06C c

.2 4)*4)04).00 19 In0 -.- . 11 r).'.)

CD t.)04) .ca0; w. C0 (x4)1a 04)4)) . 0' ' 4))' 4) '-)) .000 4.') 0>

0 >. 0.4 W~ *- 0 4) 0..Q 0. > C t -V 4)

O>< v E vCO>< 4)4))4E 4) Ww~-4)f Z< W4'. v> 0 4) Oc3 Z4) . to.'.> .0 4)

Z0 - '04)0 00 r u 04)c0 n 4) 4'A 41 '0.O 4) -8.040)1. C

* ~ ~ . '4) .0 0- u~- 5-..)'"4' u4I-..N 0' )0 )

0 r1.4)0.0 k u 0 o w) u-

0 0 ' 04 .40 .0) 04 >.0 04o )

*00-4 c 4) w 0.~- m Z: M '00.w. ( 04)ai w z's ) 4) c0x0)> m4)0>4c4

e* rz (nZ 0 40 t U4 ~ U C'0 40 m

v 0v - 4)'. m r.4 "0-0 <c, 4) D

)C a > 4) 0 c4)0 -t, 06 4) 44 0 4

0 L:44). 6ex " 1.40 4)1= kA00-4 * ) 04 00 0 4 > 0

00 c).-" 4Z. '0 m4)0.-9z C'4CC 60.'- "a 00 .. '"04 0

Q. 0.0 C:4. m/ mz 0.0 >10. 0>4.% 0 4Cf ad 24'44)C) C:/)

D 'w 0 Ix4) 0' w. 1

o1- s.1 4.

C 0 C ~~4 0C

o 04 w 04

44))> k%00040.0 ~ ~~~~~ CC 4))1 0 .244 0 ) 41

0 c It1. In C4C).42 V 4C4.4.

-' " > 04'- -00 4)1 .. .

'0 cOa 44 4) (n" ~ '0 m0 OW 4n u)-41~,c>4 0'0 0) 1.c4 0')0

... 4.0 0.4 <-4 4 1.0)"C>

04) >4' 0) .4 ('4) 0) >.' 04

Cd) ('1 0 44 g '0 '402 d z C 4 ' 4 0

*~~~~~~~~~~ 1*"". C0 44. .- ''C04)

__ w __ _ _ _ _____ ____ ____

.0 V.4)M: l14 .

VI (

*44 0 4 0 0 " 0- 40

> 0 0-. 0**u'~ "D 0. 4) * 0

.0 0 c0 .)' "C 04. L . 1C.4*~~~~~k Cc >.O''0 40.'.14E' V) C

0 C 3 > W "" 0 U 0 C . ' A '-

n 0= *z < ~0=

z -0

0.04C 0.

0 *. E u ) '''4 )0 **."41. n) '1'4

ON -! ON. "En C.UC.0 C M-

d "4 '0~. 06 Q 0

C* ) 8 ; 14 .44 0440c0. 0 .. 4.4CL)

0. 0 0>i 4)4W 0 4) 0 >

S..~4 Z.' V).. 0 : 1 4

4o) 0)..4 .00 jU 0o4 0'S0 0 )'. 0 0A0 0 CC w)4a'. Q

14)4444 r).C 4 4 0 21))U . C* 40 4)0 X 2M4) 14'.00" 4' ) 6.4 .00.04'"44)u

U.41a. caJ 0 c 0. 0'4 0-0. 0.4 r4 a*-.r 0 4> 04 Q .40 C4)'-..c04!2 =. 4- . >c m40 C4"..0 Q

U) C44 m.0. .4- u- U) W ~ .. 0' U .~)'00 r 'O.c 0 0 alp '0OCa 0

.. 4 4tR ~ 4 .0. 4)'. c!4 Z.~' 0.' " 40u )*Ct4'A.40'.' 6443 '.4''0

0. 'O~~S 4.4 0..4.0 eaf)4. C ' .0) 060. 1-4) 0 > 04) 0.X m) >4 0 4)

.. 44 . 44 M.0 4 .4 . 0-4 1. ' 3 .0 0 "4.401'400 01 04O >1 X 0 - a..0>>4)L 04) C -.C0'."c .0 -4<404 0 0'" .0

0; 0 .02 0'0.-0

C 0. 11 4 C - 0444 4 444m 0 v4)

to0.4 04 toO 4 0 0

*.0 40 ..0 0 '-Z0 40*- 0

'0 4)0 0 Z4 ' U 4)0 0"

04 r )." .4.2 U 4) 4).44 .0.20 U)u4.4 444. <

>1~~~~d 00)- ~ -'0..4>* ~ 4 4) 04 0C6.

0>< 4, 0 ". , mC.) u.0'a Ua O)< V4ton C:4.00S '0

En~0 -.- u >'04 Co Er< 0. .- 4it)><4Om0 4)"0U4) *404" 0

r d - '440 C o" ".'0.40 0d-~1 0 0 4 ).03

C. 00. 4'40 3 .0.0 .Z'4Q4 0.4 444 0 04 >'.1 .0 44 '4 04

6 4: 4444." 44) ul a. 'C ' Z a 0 "0 ."4 .00 44 "o o"- . 0

r40: a004 00 Z'0 '000 00

4).00.4. to .0 ). 0 No4 0,%o. 04 A404 04 >" 04

03 " a,.. U)'o - 0.' <0r4)244)Wmra O di -' 0 4)40. 41" >"0 0 D 0 0 "a> 4 7 0, 0>

*~ 0.'4. .. '. "a'4. C)4 .-.- 0~ 20. X. M0 v) 4 > 0' .. 0) k)o C 0 0 >0 42

C* . 0 c 4 ~ " 0 0 >1 ' C3 0 a 3 .001

> Vc 75- 0.1 $- 00.4. C 04 a-UU -0 .4o- C 0$..a

La- ' .

3nd-papo · sf 013 1101, task 1357, "room constants for shipboard compartments" of *18...

Documents