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Acoustics

Acoustics is a branch of physics and is the study of sound, 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 of acousticians and acoustical engineers.

"... acoustics 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 medium." Origins in Acoustics. F.V. Hunt. Yale University Press, 1978

The main sub-disciplines of acoustics are

• Aeroacousticsis the 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 jets and the physics of shock waves (sonic booms).

• Architectural acousticsis the study of how sound and buildings interact including the behavior of sound in concert halls and auditoriums but also in office buildings, factories and homes.

• Bioacousticsis the study of the use of sound by animals such as whales, dolphins and bats.

• Biomedical acousticsis the study of the use of sound in medicine, for example the use of ultrasound for diagnostic and therapeutic purposes.

• Loudspeaker acousticsis an engineering discipline behind the design of the loudspeaker

• Psychoacousticsis the study of how people react to sound, hearing, perception, and localization.

• Physiological acousticsis the study of the mechanical, electrical and biochemical function of hearing in living organisms.

• Physical acousticsis the 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 communicationis the study of how speech is produced, the analysis of speech signals and the properties of speech transmission, storage, recognition and enhancement.

• Vibration acousticsStructural Acoustics and Vibration is the study of how sound and mechanical structures interact and includes the transmission of sound through walls and the radiation of sound from vehicle panels.

• Ultrasonicsis the study of high frequency sound, beyond the range of human hearing.

• Musical acousticsis the study of the physics of musical instruments

• Underwater acousticsis the study of the propagation of sound in the oceans. Closely associated with sonar research and development.

• Acoustic engineeringis the study of how sound is generated and measured by loudspeakers, microphones, sonar projectors, hydrophones, ultrasonic transducers, sensors, Electro Acoustics, and all other topics on this list. (see external links)

A sound wave is characterized by its speed, its wavelength and its amplitude. The speed of sound depends on the medium through which the sound travels and also depends on temperature and not on the air pressure. The speed of sound is about 340 m/s in air and 1500 m/s in water. The wavelength is the distance from one wave peak to the next. The wavelength, λ of a sound wave is related to the speed of sound c and its frequency f by

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