Transducer, Acoustic

an acoustic device for the perception and conversion of sound signals for purposes of measurement, transmission, playback, recording, or analysis.

Transducers that convert acoustic signals into electrical signals (electroacoustic transducers) are the most common. They include microphones, which are used in air; hydrophones, which are used under water; and Geophones, which are used underground. The most important characteristics of such transducers are sensitivity, which is the ratio between the electrical signal (voltage, current) and the acoustic signal (for example, sound pressure); frequency response; electrical self-impedance; and directivity pattern.

In addition to transducers that produce an electrical signal that reproduces the time variations of the corresponding acoustic signal (pressure, fluctuative particle velocity), transducers also exist that measure the averaged characteristics of a sound wave. They include, for example, the Rayleigh disk and radiometers. Thermocouples encapsulated in a sound-absorptive envelope are used in the ultrasonic range; their electromotive force is proportional to the ultrasound intensity.

The auditory organs of animals and humans may be treated as sound detectors that convert acoustic signals into nerve impulses that are transmitted to the brain centers.