7/30/2019 Acoustic 97

1/16

TERM PAPER

WAVES,ELECTRICITY AND MAGNETISM

PHY 111

TOPIC:- Acoustic

DOA:17-02-2010DAR:17-03-2010

DOS:05-05-2010

SUBMITTED TO: SUBMITTED BY:

MR.Amandeep Singh Manhar param jout singh

Deptt of physics Roll no:RC4902B32Reg.no: 10900912

Class:B.Tech-M.Tech(Dual Degree) M.E

7/30/2019 Acoustic 97

2/16

ACKNOWLEDGEMENT

I take this opportunity to present my votes of thanks to all those guidepost who reallyacted as lightening pillars to enlighten our way throughout this project that has led to

successful and satisfactory completion of this study.

We are really grateful to our HOD for providing us with an opportunity to undertakethis project in this university and providing us with all the facilities. We are highly

thankful to Mr. Amandeep for his active support, valuable time and advice, whole-

hearted guidance, sincere cooperation and pains-taking involvement during the studyand in completing the assignment of preparing the said project within the time

stipulated.

Lastly, We are thankful to all those, particularly the various friends , who have been

instrumental in creating proper, healthy and conductive environment and including new

and fresh innovative ideas for us during the project, their help, it would have beenextremely difficult for us to prepare the project in a time bound framework.

Name MANHAR

Regd.No-10900912

Rollno.RC4902B32

7/30/2019 Acoustic 97

3/16

Abstract

Acoustic can be defined as a science that deals with the characterstics of sound. It dealswith frequency, amplitude and complexity of sound waves and how sound waves interact

with various environments. Its main branches are architectural, environmental, musical,

and engineering acoustics, and ultrasonics. Musical acoustics deals with the design and useof musical instruments and how musical sounds affect listeners A scientist who works in

the field of acoustics is an acoustician.

The application of acoustics in technology is called acoustical engineering.The area of

physics that deals with acoustics is devoted to the study of the production, transmission,and reception of sound wave. The medium of sound transmission is the important key

factor.

TABLE OF CONTENTS:-

http://www.answers.com/topic/architecturehttp://www.answers.com/topic/ultrasonicshttp://en.wikipedia.org/wiki/Acousticianhttp://en.wikipedia.org/wiki/Acoustical_engineeringhttp://www.answers.com/topic/architecturehttp://www.answers.com/topic/ultrasonicshttp://en.wikipedia.org/wiki/Acousticianhttp://en.wikipedia.org/wiki/Acoustical_engineering

7/30/2019 Acoustic 97

4/16

1.Introduction

1.1 Acoustic1.2 Concept

1.3 Mrchanism of Wave Motion And Sound Waves

1.4 Properties of sound Wave

2. History Of Acoustic

3. Fundamental Concepts of Acoustics

4. Transduction in Acoustics

5. Division of Acoustic

INTRODUCTION

1.1 ACOUSTICS

7/30/2019 Acoustic 97

5/16

Acoustics is the study of the physical characteristics of sound. It deals with things like the

frequency, amplitude and complexity of sound waves and how sound waves interact with

various environments. It can also refer to the over-all quality of sound in a given place.

Science of production, control, transmission, reception, and effects ofsound. Its principal

branches are architectural, environmental, musical, and engineering acoustics, andultrasonics. Environmental acoustics focuses on controlling noise produced by aircraft

engines, factories, construction machinery, and general traffic. Musical acoustics deals withthe design and use of musical instruments and how musical sounds affect listeners.

Engineering acoustics concerns sound recording and reproduction systems. Ultrasonics

deals with ultrasonic waves, which have frequencies above the audible range, and theirapplications in industry and medicine

Acoustics is the interdisciplinary science that deals with the study ofsound,ultrasound and

infrasound (all mechanical waves in gases, liquids, and solids). A scientist who works in

the field of acoustics is an acoustician. The application of acoustics in technology is called

acoustical engineering. There is often much overlap and interaction between the interests ofacousticians and acoustical engineers.

Hearing is one of the most crucial means of survival in the animal world, and speech is one

of the most distinctive characteristics of human development and culture. So it is nosurprise that the science of acoustics spreads across so many facts of our societymusic,

medicine, architecture, industrial production, warfare and more. Art, craft, science and

technology have provoked one another to advance the whole, as in many other fields ofknowledge.

The word "acoustic" is derived from the Greekword , meaning "of or for hearing, ready to

hear and "heard, audible". After acousticians had extended their studies to frequenciesabove and below the audible range, it became conventional to identify these frequencyranges as "ultrasonic" and "infrasonic" respectively, while letting the word "acoustic" refer

to the entire frequency range without limit.

1.2 Concept:-

The area of physics known as acoustics is devoted to the study of the production,transmission, and reception of sound. Thus, wherever sound is produced and transmitted, it

will have an effect somewhere, even if there is no one present to hear it. The medium ofsound transmission is an all-important, key factor. Among the areas addressed within the

realm of acoustics are the production of sounds by the human voice and various

instruments, as well as the reception of sound waves by the human ear.

http://www.answers.com/topic/sound-1http://www.answers.com/topic/architecturehttp://www.answers.com/topic/ultrasonicshttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Infrasoundhttp://en.wikipedia.org/wiki/Acousticianhttp://en.wikipedia.org/wiki/Acoustical_engineeringhttp://en.wikipedia.org/wiki/Hearing_(sense)http://en.wikipedia.org/wiki/Speechhttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Frequencieshttp://www.answers.com/topic/sound-1http://www.answers.com/topic/architecturehttp://www.answers.com/topic/ultrasonicshttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Ultrasoundhttp://en.wikipedia.org/wiki/Infrasoundhttp://en.wikipedia.org/wiki/Acousticianhttp://en.wikipedia.org/wiki/Acoustical_engineeringhttp://en.wikipedia.org/wiki/Hearing_(sense)http://en.wikipedia.org/wiki/Speechhttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Frequencies

7/30/2019 Acoustic 97

6/16

1.3 Mechanism:-

1.3.1 Wave Motion and Sound Waves

Sound waves are an example of a larger phenomenon known as wave motion, and wave

motion is a subset of harmonic motion i.e. repeated movement of a particle about a positionof equilibrium. In the case of sound, the "particle" is not an item of matter, but of energy,

and wave motion is a type of harmonic movement that carries energy from one place to

another without actually moving any matter.

Particles in waves experience oscillation, harmonic motion in one or more dimensions.

Oscillation itself involves little movement, though some particles do move short distances

as they interact with other particles. The waves themselves, on the other hand, move acrossspace, ending up in a position different from the one in which they started.

A transverse wave forms a regular up-and-down pattern in which the oscillation is

perpendicularto the direction in which the wave is moving. Sound waves are longitudinalwaves, in which oscillation occurs in the same direction as the wave itself.

These oscillations are really just fluctuations in pressure. As a sound wave moves through amedium such as air, these changes in pressure cause the medium to experience alternations

of density and rarefaction (a decrease in density)and compressions(increase in density).

This, in turn, produces vibrations in the human ear or in any other object that is receivingthe sound waves.

1.4 Properties of Sound Waves:-

1.4.1 Cycle and Period

The term cycle means that varies slightly, depending on whether the type of motion beingdiscussed is oscillation, the movement of transverse waves, or the motion of a longitudinal

sound wave. In the latter case, a cycle is defined as a single complete vibration.

A period ( T) is the amount of time required to complete one full cycle.

http://www.answers.com/topic/oscillationhttp://www.answers.com/topic/myelitis-1http://www.answers.com/topic/perpendicularhttp://www.answers.com/topic/longitudinalhttp://www.answers.com/topic/rarefactionhttp://www.answers.com/topic/vibrationhttp://www.answers.com/topic/oscillationhttp://www.answers.com/topic/myelitis-1http://www.answers.com/topic/perpendicularhttp://www.answers.com/topic/longitudinalhttp://www.answers.com/topic/rarefactionhttp://www.answers.com/topic/vibration

7/30/2019 Acoustic 97

7/16

1.4.2 The Speed of Sound in Various Mediums

People often refer to the "speed of sound" as though this were a fixed value like the speed

of light, but, in fact, the speed of sound is a function of the medium through which ittravels. What people ordinarily mean by the "speed of sound" is the speed of sound through

air at a specific temperature. For sound traveling at sea level, the speed at 32F (0C) is 740MPH (331 m/s), and at 68F (20C), it is 767 MPH (343 m/s)..

The speed of sound through a gas is proportional to the square root of the pressure dividedby the density. According to Gay-Lussac's law, pressure is directly related to temperature,

meaning that lower the pressure, lower is the temperatureand vice versa. At high

altitudes, the temperature is low, and, therefore, so is the pressure; and, due to the relativelysmall gravitational pull that Earth exerts on the air at that height, the density is also low.

Hence, the speed of sound is also low.

It follows that the higher the pressure of the material, and the greater the density, the faster

sound travels through it: thus sound travels faster through a liquid than through a gas. Thespeed of sound in water varies from about 3,244 MPH (1,450 m/s) to about 3,355 MPH

(1500 m/s). Sound travels even faster through a solidtypically about 11,185 MPH (5,000

m/sas compared to liquid

1.4.3 Frequency

Frequency ( f) is the number of waves passing through a given point during the particular

interval oftime. It is measured in Hertz (Hz), named after nineteenth-century German

physicist Heinrich Rudolf Hertz (1857-1894) and a Hertz is equal to one cycle ofoscillation per second. Higher frequencies are expressed in terms ofkilohertz (kHz; 103 or

1,000 cycles per second) ormegahertz (MHz; 106 or 1 million cycles per second.)

The human ear is capable of hearing sounds from 20 to approximately 20,000 Hza

relatively small range for a mammal, considering that bats, whales, and dolphins can hearsounds at a frequency up to 150 kHz. Human speech is in the range of about 1 kHz, . The

quality of harmony when two notes are played together is a function of the relationship

between the frequencies of the two.

Frequencies below the range of human audibility are called infrasound, and those above it

are referred to as ultrasound. There are a number of practical applications forultrasonictechnology in medicine, navigation, and other fields.

1.4.4 Wavelength

Wavelength (, lambda)can be defined as distance between a crest and the adjacent crest, ora trough and an adjacent trough, of a wave. The higher the frequency, the shorter the

http://www.answers.com/topic/ordinarilyhttp://www.answers.com/topic/kilohertzhttp://www.answers.com/topic/megahertzhttp://www.answers.com/topic/khzhttp://www.answers.com/topic/audibility-acousticshttp://www.answers.com/topic/infrasoundhttp://www.answers.com/topic/ultrasoundhttp://www.answers.com/topic/ultrasonichttp://www.answers.com/topic/ordinarilyhttp://www.answers.com/topic/kilohertzhttp://www.answers.com/topic/megahertzhttp://www.answers.com/topic/khzhttp://www.answers.com/topic/audibility-acousticshttp://www.answers.com/topic/infrasoundhttp://www.answers.com/topic/ultrasoundhttp://www.answers.com/topic/ultrasonic

7/30/2019 Acoustic 97

8/16

wavelength, and vice versa. Thus, a frequency of 20 Hz, at the bottom end of human

audibility, has a very large wavelength of about 56 ft (17 m)..

Wavelengths of visible light have a higher frequency of about 109 MHz. This means thatthese wavelengths are incredibly small, and thats why light waves can easily be blocked

out by using one's hand or a curtain.

The same does not hold for sound waves, because the wavelengths of sounds in the range

of human audibility are comparable to the size of ordinary objects. To block out a soundwave, one needs something of much greater dimensionswidth, height, and depththan a

mere cloth curtain. A thick concrete wall may be enough to block out the waves.

1.4.5 Amplitude and Intensity

Amplitude can be defined as the maximum displacement of a wave from its meanposition,it is the "size" of a wave. The greater the amplitude, the greater the energy the

wave, amplitude indicates intensity, commonly known as "volume," which is the rate atwhich a wave moves energy per unit of a cross-sectional area.

Intensity can be measured in watts per square meter, or W/m2. A sound wave of minimumintensity for human audibility would have a value of 1012 W/m2. As a basis of comparison,

a person speaking in an ordinary tone of voice generates about 104, or 0.0001, watts. On

the other hand, a sound with an intensity of 1 W/m2 would be powerful enough to damage a

person's ears.

2. History of acoustics

2.1 Early research in acoustics:-

http://www.answers.com/topic/curtainhttp://www.answers.com/topic/curtain

7/30/2019 Acoustic 97

9/16

The fundamental and the first 6 overtones of a vibrating string. The earliest records of the

study of this phenomenon are attributed to Ancient Chinese 3000 BC.

Many books and websites about musical theory written by Western musicologists mentionPythagoras as the first person studying the relation of string lengths to consonance.

However, from at least 3000 BC, the Chinese were already using a scale based on the

knotted positions of overtones that indicated the consonantpitches related to the openstring, present at theirGuqin. Like the Chinese, Pythagoras wanted to know why some

intervals seemed more beautiful than others, and he found answers in terms of numerical

ratios representing the harmonicovertone series on a string. Aristotle (384-322 BC)understood that sound consisted of contractions and expansions of the air "falling upon and

striking the air which is next to it...", a very good expression of the nature ofwave motion.

In about 20 BC, the Roman architect and engineerVitruvius wrote a treatise on the

acoustical properties of theatres including discussion of interference, echoes, andreverberationthe beginnings ofarchitectural acoustics.

The physical understanding of acoustical processes advanced rapidly during and after the

Scientific Revolution.Galileo (15641642) and Mersenne (15881648) independentlydiscovered the complete laws of vibrating strings (completing what Pythagoras had started

2000 years earlier). Galileo wrote "Waves are produced by the vibrations of a sonorous

body, which spread through the air, bringing to the tympanum of the eara stimulus which

the mind interprets as sound", a remarkable statement that points to the beginnings ofphysiological and psychological acoustics. Experimental measurements of the speed of

sound in air were carried out successfully between 1630 and 1680 by a number of

investigators, prominently Mersenne. Meanwhile Newton (16421727) derived therelationship for wave velocity in solids, a cornerstone of physical acoustics (Principia,

1687).

2.2 The Age of Enlightenment and onward:-

http://en.wikipedia.org/wiki/Fundamental_frequencyhttp://en.wikipedia.org/wiki/Overtonehttp://en.wikipedia.org/wiki/Pythagorashttp://en.wikipedia.org/wiki/Consonancehttp://en.wikipedia.org/wiki/Consonanthttp://en.wikipedia.org/wiki/Guqinhttp://en.wikipedia.org/wiki/Pythagorashttp://en.wikipedia.org/wiki/Harmonichttp://en.wikipedia.org/wiki/Overtone_serieshttp://en.wikipedia.org/wiki/Aristotlehttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Vitruviushttp://en.wikipedia.org/wiki/Architectural_acousticshttp://en.wikipedia.org/wiki/Scientific_Revolutionhttp://en.wikipedia.org/wiki/Galileohttp://en.wikipedia.org/wiki/Mersennehttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Earhttp://en.wikipedia.org/wiki/Speed_of_soundhttp://en.wikipedia.org/wiki/Speed_of_soundhttp://en.wikipedia.org/wiki/Philosophi%C3%A6_Naturalis_Principia_Mathematicahttp://en.wikipedia.org/wiki/File:Harmonic_partials_on_strings.svghttp://en.wikipedia.org/wiki/Fundamental_frequencyhttp://en.wikipedia.org/wiki/Overtonehttp://en.wikipedia.org/wiki/Pythagorashttp://en.wikipedia.org/wiki/Consonancehttp://en.wikipedia.org/wiki/Consonanthttp://en.wikipedia.org/wiki/Guqinhttp://en.wikipedia.org/wiki/Pythagorashttp://en.wikipedia.org/wiki/Harmonichttp://en.wikipedia.org/wiki/Overtone_serieshttp://en.wikipedia.org/wiki/Aristotlehttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Vitruviushttp://en.wikipedia.org/wiki/Architectural_acousticshttp://en.wikipedia.org/wiki/Scientific_Revolutionhttp://en.wikipedia.org/wiki/Galileohttp://en.wikipedia.org/wiki/Mersennehttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Earhttp://en.wikipedia.org/wiki/Speed_of_soundhttp://en.wikipedia.org/wiki/Speed_of_soundhttp://en.wikipedia.org/wiki/Philosophi%C3%A6_Naturalis_Principia_Mathematica

7/30/2019 Acoustic 97

10/16

The eighteenth century saw major advances in acoustics at the hands of the great

mathematicians of that era, who applied the new techniques of the calculus to the

elaboration of wave propagation theory. In the nineteenth century the giants of acousticswere Helmholtz in Germany, who consolidated the field of physiological acoustics, and

Lord Rayleigh in England, who combined the previous knowledge with his own copious

contributions to the field in his monumental work "The Theory of Sound". Also in the 19thcentury, Wheatstone, Ohm, and Henry developed the analogy between electricity and

acoustics.

The twentieth century saw a burgeoning of technological applications of the large body of

scientific knowledge that was by then in place. The first such application was Sabinesgroundbreaking work in architectural acoustics, and many others followed. Underwater

acoustics was used for detecting submarines in the first World War. Sound recording and

the telephone played important roles in a global transformation of society. Soundmeasurement and analysis reached new levels of accuracy and sophistication through the

use of electronics and computing. The ultrasonic frequency range enabled wholly new

kinds of application in medicine and industry. New kinds of transducers (generators andreceivers of acoustic energy) were invented and put to use.

3. Fundamental concepts of acoustics:-

Jay Pritzker Pavilion

http://en.wikipedia.org/wiki/Helmholtzhttp://en.wikipedia.org/wiki/John_Strutt,_3rd_Baron_Rayleighhttp://en.wikipedia.org/wiki/Sound_recordinghttp://en.wikipedia.org/wiki/Jay_Pritzker_Pavilionhttp://en.wikipedia.org/wiki/Helmholtzhttp://en.wikipedia.org/wiki/John_Strutt,_3rd_Baron_Rayleighhttp://en.wikipedia.org/wiki/Sound_recordinghttp://en.wikipedia.org/wiki/Jay_Pritzker_Pavilion

7/30/2019 Acoustic 97

11/16

At Jay Pritzker Pavilion, a LARES system is combined with a zoned sound reinforcement

system, both suspended on an overhead steel trellis, to synthesize an indoor acousticenvironment outdoors.

The study of acoustics revolves around the generation, propagation and reception of

mechanical waves and vibrations.

The steps shown in the above diagram can be found in any acoustical event or process.

There are many kinds of cause, both natural and volitional. There are many kinds of

transduction process that convert energy from some other form into acoustical energy,producing the acoustic wave. There is one fundamental equation that describes acoustic

wave propagation, but the phenomena that emerge from it are varied and often complex.

The wave carries energy throughout the propagating medium. Eventually this energy istransduced again into other forms, in ways that again may be natural and/or volitionally

contrived. The final effect may be purely physical or it may reach far into the biological or

volitional domains. The five basic steps are found equally well whether we are talking

http://en.wikipedia.org/wiki/Jay_Pritzker_Pavilionhttp://en.wikipedia.org/wiki/LAREShttp://en.wikipedia.org/wiki/Sound_reinforcement_systemhttp://en.wikipedia.org/wiki/Sound_reinforcement_systemhttp://en.wikipedia.org/wiki/File:Cause-effect_diagram_for_acoustics.svghttp://en.wikipedia.org/wiki/File:20070919_Pritzker_Pavilion_speakers.JPGhttp://en.wikipedia.org/wiki/File:20070919_Pritzker_Pavilion_from_stage.JPGhttp://en.wikipedia.org/wiki/Jay_Pritzker_Pavilionhttp://en.wikipedia.org/wiki/LAREShttp://en.wikipedia.org/wiki/Sound_reinforcement_systemhttp://en.wikipedia.org/wiki/Sound_reinforcement_system

7/30/2019 Acoustic 97

12/16

about an earthquake, a submarine using sonar to locate its foe, or a band playing in a rock

concert.

The central stage in the acoustical process is wave propagation. This falls within thedomain of physical acoustics. In fluids, sound propagates primarily as a pressure wave. In

solids, mechanical waves can take many forms including longitudinal waves,transversewaves and surface waves.

Acoustics looks first at the pressure levels and frequencies in the sound wave. Transductionprocesses are also of special importance.

3.1 Wave propagation: pressure levels:-

In fluids such as air and water, sound waves propagate as disturbances in the ambient

pressure level. While this disturbance is usually small, it is still noticeable to the humanear. The smallest sound that a person can hear, known as the threshold of hearing, is nine

orders of magnitude smaller than the ambient pressure. The loudness of these disturbancesis called the sound pressure level, and is measured on a logarithmic scale in decibels.

Mathematically, sound pressure level is defined

where pref is the threshold of hearing and p is the change in pressure from the ambientpressure. The following table gives a few examples of sounds and their strengths in

decibels and pascals.

Example of Common

Sound

Pressure

Amplitude

Decibel

Level

Threshold of Hearing 2010-6 Pa 0 dB

http://en.wikipedia.org/wiki/Earthquakehttp://en.wikipedia.org/wiki/Fluidshttp://en.wikipedia.org/wiki/Longitudinal_waveshttp://en.wikipedia.org/wiki/Transverse_waveshttp://en.wikipedia.org/wiki/Transverse_waveshttp://en.wikipedia.org/wiki/Surface_waveshttp://en.wikipedia.org/wiki/Sound_pressure_levelhttp://en.wikipedia.org/w/index.php?title=Threshold_of_Hearing&action=edit&redlink=1http://en.wikipedia.org/wiki/Earthquakehttp://en.wikipedia.org/wiki/Fluidshttp://en.wikipedia.org/wiki/Longitudinal_waveshttp://en.wikipedia.org/wiki/Transverse_waveshttp://en.wikipedia.org/wiki/Transverse_waveshttp://en.wikipedia.org/wiki/Surface_waveshttp://en.wikipedia.org/wiki/Sound_pressure_levelhttp://en.wikipedia.org/w/index.php?title=Threshold_of_Hearing&action=edit&redlink=1

7/30/2019 Acoustic 97

13/16

Normal talkingat 1 m 0.002 to 0.02 Pa 40 to 60 dB

Power lawnmowerat 1 m 2 Pa 100 dB

Jet engine orrock concert 20 Pa 120 dB

Threshold of Pain 200 Pa 140 dB

3.2 Wave propagation: frequency:-

Physicists and acoustic engineers tend to discuss sound pressure levels in terms of

frequencies, because this is how ourears interpret sound. What we experience as "higher

pitched" or "lower pitched" sounds are pressure vibrations having a higher or lower numberof cycles per second. In a common technique of acoustic measurement, acoustic signals are

sampled in time, and then presented in more meaningful forms such as octave bands ortime frequency plots. Both these popular methods are used to analyze sound and better

understand the acoustic phenomenon.

The entire spectrum can be divided into three sections:- audio, ultrasonic, and infrasonic.

The audio range falls between 20 Hz and 20,000 Hz. This range is important because its

frequencies can be detected by the human ear. This range has a number of applications,

including speech communication and music. The ultrasonic range refers to the very highfrequencies: 20,000 Hz and higher. This range has shorter wavelengths which allows better

resolution in imaging technologies. Medical applications such as ultrasonography and

elastography rely are on the basis of the ultrasonic frequency range. On the other end of the

spectrum, the lowest frequencies are known as the infrasonic range. These frequencies canbe used to study geological phenomenon like earthquakes.

4. Transduction in acoustics:-

http://en.wikipedia.org/wiki/Talkinghttp://en.wikipedia.org/wiki/Talkinghttp://en.wikipedia.org/w/index.php?title=Power_lawnmower&action=edit&redlink=1http://en.wikipedia.org/wiki/Jet_enginehttp://en.wikipedia.org/wiki/Rock_concerthttp://en.wikipedia.org/wiki/Threshold_of_Painhttp://en.wikipedia.org/wiki/Earshttp://en.wikipedia.org/wiki/Hertzhttp://en.wikipedia.org/wiki/Talkinghttp://en.wikipedia.org/w/index.php?title=Power_lawnmower&action=edit&redlink=1http://en.wikipedia.org/wiki/Jet_enginehttp://en.wikipedia.org/wiki/Rock_concerthttp://en.wikipedia.org/wiki/Threshold_of_Painhttp://en.wikipedia.org/wiki/Earshttp://en.wikipedia.org/wiki/Hertz

7/30/2019 Acoustic 97

14/16

An inexpensive low fidelity 3.5 inch driver, typically found in small radios

A transduceris a device which is used for converting one form of energy into another. Inan acoustical context, this means converting sound energy into electrical energy (or vice

versa). For nearly all acoustic applications, some type of acoustic transducer is necessary.Acoustic transducers include loudspeakers,microphones,hydrophones and sonarprojectors. These devices convert an electric signal to or from a sound pressure wave. The

most widely used transduction principles are electromagnetism (at lower frequencies) and

piezoelectricity (at higher frequencies).

A subwoofer, used to generate lower frequency sound in speaker audio systems, is anelectromagnetic device. Subwoofers generate waves using a suspended diaphragm which

oscillates, sending off pressure waves. Electret microphones are a common type of

microphone which employ an effect similar to piezoelectricity. As the sound wave strikesthe electret's surface, the surface moves and sends off an electrical signal.

5. Divisions of acoustics:-

Countless subfields have been created as we have perfected our understanding of the

underlying physics of acoustics. The table below shows seventeen major subfields of

http://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Loudspeakershttp://en.wikipedia.org/wiki/Microphoneshttp://en.wikipedia.org/wiki/Hydrophoneshttp://en.wikipedia.org/wiki/Sonarhttp://en.wikipedia.org/wiki/Electromagnetismhttp://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/File:3.5_Inch_Speaker.jpghttp://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Loudspeakershttp://en.wikipedia.org/wiki/Microphoneshttp://en.wikipedia.org/wiki/Hydrophoneshttp://en.wikipedia.org/wiki/Sonarhttp://en.wikipedia.org/wiki/Electromagnetismhttp://en.wikipedia.org/wiki/Piezoelectricity

7/30/2019 Acoustic 97

15/16

acoustics established in the PACS classification system. These have been grouped into

three domains: physical acoustics, biological acoustics and acoustical engineering.

Physical acoustics Biological acoustics Acoustical engineering

Aeroacoustics

General linearacoustics

Nonlinear acoustics

Structural acousticsand vibration

Underwater sound

Bioacoustics

Musical acoustics

Physiological acoustics

Psychoacoustics

Speech communication(production;

perception; processingand communication

systems)

Acoustic

measurements and

instrumentation

Acoustic signalprocessing

Architectural acoustics

Environmentalacoustics

Transduction

Ultrasonics

Room acoustics

REFERENCES:-

Websites:-

http://en.wikipedia.org/w/index.php?title=Physical_acoustics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Biological_acoustics&action=edit&redlink=1http://en.wikipedia.org/wiki/Acoustical_engineeringhttp://en.wikipedia.org/wiki/Aeroacousticshttp://en.wikipedia.org/w/index.php?title=General_linear_acoustics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=General_linear_acoustics&action=edit&redlink=1http://en.wikipedia.org/wiki/Nonlinear_acousticshttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Underwater_soundhttp://en.wikipedia.org/wiki/Bioacousticshttp://en.wikipedia.org/wiki/Musical_acousticshttp://en.wikipedia.org/wiki/Auditory_systemhttp://en.wikipedia.org/wiki/Psychoacousticshttp://en.wikipedia.org/wiki/Speech_communicationhttp://en.wikipedia.org/w/index.php?title=Acoustic_measurements_and_instrumentation&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Acoustic_measurements_and_instrumentation&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Acoustic_measurements_and_instrumentation&action=edit&redlink=1http://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Architectural_acousticshttp://en.wikipedia.org/w/index.php?title=Environmental_acoustics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Environmental_acoustics&action=edit&redlink=1http://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Ultrasonicshttp://en.wikipedia.org/wiki/Room_acousticshttp://en.wikipedia.org/w/index.php?title=Physical_acoustics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Biological_acoustics&action=edit&redlink=1http://en.wikipedia.org/wiki/Acoustical_engineeringhttp://en.wikipedia.org/wiki/Aeroacousticshttp://en.wikipedia.org/w/index.php?title=General_linear_acoustics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=General_linear_acoustics&action=edit&redlink=1http://en.wikipedia.org/wiki/Nonlinear_acousticshttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Underwater_soundhttp://en.wikipedia.org/wiki/Bioacousticshttp://en.wikipedia.org/wiki/Musical_acousticshttp://en.wikipedia.org/wiki/Auditory_systemhttp://en.wikipedia.org/wiki/Psychoacousticshttp://en.wikipedia.org/wiki/Speech_communicationhttp://en.wikipedia.org/w/index.php?title=Acoustic_measurements_and_instrumentation&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Acoustic_measurements_and_instrumentation&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Acoustic_measurements_and_instrumentation&action=edit&redlink=1http://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Signal_processinghttp://en.wikipedia.org/wiki/Architectural_acousticshttp://en.wikipedia.org/w/index.php?title=Environmental_acoustics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Environmental_acoustics&action=edit&redlink=1http://en.wikipedia.org/wiki/Transducerhttp://en.wikipedia.org/wiki/Ultrasonicshttp://en.wikipedia.org/wiki/Room_acoustics

7/30/2019 Acoustic 97

16/16

1. http://wikipedia.org/wiki/acoustics

2. http://en.wikipedia.org/wiki/Musical_acoustics3. http://en.wikipedia.org/wiki/Acoustic_music

http://wikipedia.org/wiki/acousticshttp://en.wikipedia.org/wiki/Musical_acousticshttp://wikipedia.org/wiki/acousticshttp://en.wikipedia.org/wiki/Musical_acoustics