Acoustic Radiation Pressure


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Acoustic radiation pressure

The net pressure exerted on a surface or interface by an acoustic wave. One might presume that the back-and-forth oscillation of fluid caused by the passage of an acoustic wave will not exert any net force on an object, and this is true for sound waves normally encountered. Intense sound waves, however, can exert net forces in one direction of sufficient magnitude (proportional to the sound intensity) to balance gravitational forces and thus levitate an object in air.

Forces due to acoustic radiation pressure have been used to calibrate acoustic transmitters, to deform and break up liquids, to collect like objects or to separate particles (including biological cells) based on mechanical properties, and to position objects in a sound field, sometimes levitating the sample so that independent studies of the object's properties can be performed. Single bubble sonoluminescence phenomena depend on acoustic radiation forces to maintain a bubble in a zone while its substantial radial oscillations take place. See Acoustic levitation, Sound, Ultrasonics

Acoustic Radiation Pressure

 

(radiation pressure of sound), the constant pressure experienced by a body in a stationary sound field. Acoustic radiation pressure should not be confused with sound pressure, which is a periodically varying pressure in the medium in which a sound wave is propagating.

The acoustic radiation pressure is proportional to the density of the sound energy and hence to the square of the sound pressure. It is small compared to the sound pressure; for example, in a sound field in air in which the sound pressure is 102 newtons per sq m (N/m2), the acoustic radiation pressure for a sound wave that is normally incident on a surface that completely reflects the sound is approximately 0.1 N/m2. Acoustic radiation pressure is measured with a radiometer. When its value is known, the absolute value of the intensity of sound in a given medium can be found.

REFERENCES

Krasil’nikov, V. A. Zvukovye i ul’trazvukovye volny v vozdukhe, vode i tverdykh telakh, 3rd ed. Moscow, 1960.
Morse, F. Kolebaniia i zvuk. Moscow-Leningrad, 1949. (Translated from English.)

acoustic radiation pressure

[ə′küs·tik ‚rād·ē′ā·shən ‚presh·ər]
(acoustics)
A unidirectional, steady-state pressure exerted upon a surface exposed to a sound wave.