Acoustics

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The principles of acoustics were used in designing this sound tube in Melbourne, Australia. It was constructed to reduce roadway noise without detracting from the area's aesthetics.

Acoustics is a branch of physics that studies sound, or more precisely, mechanical waves in gases, liquids, and solids. It is concerned with the production, control, transmission, reception, and effects of sound. A scientist who works in the field of acoustics is called an acoustician. The application of acoustics in technology is called acoustical engineering. There is often much overlap and interaction between the interests of acousticians and acoustical engineers.

Knowledge gained through the field of acoustics has had great significance for applications related to artistic expression. The development of acoustic technology has also been important in the study of geologic, atmospheric, and underwater phenomena. In addition, ultrasound technology has led to important developments in medicine.

Contents

Background

The word acoustic is derived from the ancient Greek word ακουστός, meaning able to be heard [1]

The study of acoustics has been fundamental to many developments in the performing arts. Many of the principles of acoustics, especially in the area of musical scales and instruments, were explained theoretically by scientists only after long years of experimentation by artists. For example, much of what is now known about architectural acoustics was learned by trial and error over centuries of experience and only recently formalized into a science.

From a scientific viewpoint, sound waves are a form of mechanical vibrations (or mechanical waves). When the ear receives these waves, the signals are transmitted to the brain, which interprets them as sound. The study of sound waves led to the discovery of physical principles that can be applied to the behavior of all mechanical waves. Acoustics, therefore, involves the study of mechanical vibrations in general and the potential applications of the knowledge gained in modern life.

…[A]coustics is characterized by its reliance on combinations of physical principles drawn from other sources; and that the primary task of modern physical acoustics is to effect a fusion of the principles normally adhering to other sciences into a coherent basis for understanding, measuring, controlling, and using the whole gamut of vibrational phenomena in any material.

F. V. Hunt[2]

Divisions of acoustics

The following are the main sub-disciplines of acoustics:[3]

  • Acoustical measurements and instrumentation
  • Acoustic signal processing
  • Aeroacoustics: study of aerodynamic sound, generated when a fluid flow interacts with a solid surface or with another flow. It has particular application to aeronautics, examples being the study of sound made by flying jets and the physics of shock waves (sonic booms).
  • Architectural acoustics: study of sound waves distribution in variously shaped enclosed or partly enclosed spaces with effects of sound waves on objects of different shapes which are in their way. Mostly concentrated on how sound and buildings interact, including the behavior of sound in concert halls and auditoriums but also in office buildings, factories and homes.
  • Bioacoustics: study of the use of sound by animals such as whales, dolphins, bats etc.
  • Biomedical acoustics: study of the use of sound in medicine, for example the use of ultrasound for diagnostic and therapeutic purposes.
  • Environmental noise: study of the sound propagation in the human environment, noise health effects and noise mitigation analysis.
  • Psychoacoustics: study of subjective reaction of living beings to sound, hearing, perception, and localization.
  • Physiological acoustics: study of the mechanical, electrical and biochemical function of hearing in living organisms.
  • Physical acoustics: study of the detailed interaction of sound with materials and fluids and includes, for example, sonoluminescence (the emission of light by bubbles in a liquid excited by sound) and thermoacoustics (the interaction of sound and heat).
  • Speech communication: study of how speech is produced, the analysis of speech signals and the properties of speech transmission, storage, recognition and enhancement.
  • Structural acoustics and vibration: study of how sound and mechanical structures interact; for example, the transmission of sound through walls and the radiation of sound from vehicle panels.
  • Transduction: study of how sound is generated and measured by loudspeakers, microphones, sonar projectors, hydrophones, ultrasonic transducers and sensors.
  • Ultrasonics: study of high frequency sound, beyond the range of human hearing.
  • Musical acoustics: study of the physics of musical instruments.
  • Underwater acoustics: study of the propagation of sound in water.
  • Nonlinear Acoustics: study of large amplitude sound waves that propagate according to the Westervelt-Lighthill equation (in fluids) and analogous theories in other types of media (see parametric array).

Applications

As noted earlier, the study of acoustics has been of fundamental importance for developments in the arts. Other applications of acoustics technology are in the study of geologic, atmospheric, and underwater phenomena. Psychoacoustics, the study of the physical effects of sound on biological systems, has been of interest since Pythagoras first heard the sounds of vibrating strings and hammers hitting anvils in the sixth century B.C.E. However, the application of modern ultrasonic technology has only recently provided some of the most exciting developments in medicine.

Daniel Statnekov and others have recently been studying the effects of sound on the human brain. Harmonic frequencies in the form of binaural beats can effect the brainwave patterns of a person who plays an ancient Peruvian Whistling Pot to create a "trance state."[4]

See also

Notes

  1. S. C. Woodhouse, English-Greek Dictionary: (Abingdon, UK: Routledge. 1910), 392
  2. F. V. Hunt, Origins in Acoustics, (Yale University Press, 1978)
  3. Physics and Astronomy Classification Scheme: Acoustics. American Institute of Physics. Retrieved September 27, 2007.
  4. Daniel K. Statnekov Peruvian Whistling Vessels. Some public technical papers on this subject are given at this site. Retrieved September 27, 2007.

References

  • Beranek, Leo L. 1954. Acoustics. New York, NY: American Institute of Physics. ISBN 088318494X
  • Malcolm J. Crocker. 1997. Encyclopedia of Acoustics. Hoboken, NJ: Wiley. ISBN 0471804657
  • Hunt, Frederick V. 1978. Origins in Acoustics: The Science of Sound from Antiquity to the Age of Newton. New Haven CT: Yale University Press. ISBN 0300022204
  • Kent, Raymond D. 2001. Acoustic Analysis of Speech, 2nd Edition. San Diego, CA: Singular Publishing Group. ISBN 0769301126
  • Morfey, Christopher L. 2001. Dictionary of Acoustics. San Diego, CA: Academic Press. ISBN 0125069405
  • Morse, Philip M., and K. U. Ingard. 1968. Theoretical Acoustics. New York, NY: McGraw-Hill Education. ISBN 0070433305
  • Pickett, J. M. 1998. The Acoustics of Speech Communication: Fundamentals, Speech Perception Theory, and Technology. Upper Saddle River, NJ: Allyn & Bacon. ISBN 0205198872
  • Pierce, Allan D. 1989. Acoustics: An Introduction to its Physical Principles and Applications. New York, NY: American Institute of Physics. ISBN 0883186128
  • Stevens, Kenneth N. 1999. Acoustic Phonetics. Cambridge, MA: The MIT Press. ISBN 026219404X
  • Woodhouse, S. C. 1972. English-Greek Dictionary: With a Supplement of Proper Names Including Greek Equivalents for Famous Names in Roman History. (first published in 1910)Abingdon, UK: Routledge. ISBN 0415151546

External links

All links retrieved August 18, 2012.

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