Acontact microphone is a form ofmicrophone that senses audio vibrations through contact with solid objects.[1] Unlike normal air microphones, contact microphones are almost completely insensitive to airvibrations buttransduce only structure-borne sound. Often used asacoustic leakage probes, they also enjoy wide usage byelectroacoustic music artists experimenting with sound. Contact microphones can be used to amplify sound from acoustic musical instruments,[2] to sense drum hits, for triggering electronic samples, and to recordsound in challenging environments, such as underwater under high pressure.
Apiezoelectric sensor is the most commonly available contact microphone. It is made of a thinpiezoelectricceramic disc glued to a thinbrass or alloy metal disc (see image). Thevoltage produced from the sound vibrations can be measured across them.[3] Contact microphones based on piezoelectric materials are passive and high-impedance, and they soundtinny without a matchingpreamp.
Instead of being used as a microphone, they alternatively may be used to produce sound (typically used as thebuzzer in computermotherboards) by sending voltages to them.[citation needed]
Moving coil microphone contact microphones operate by suspending a coil of wire within a magnetic field or alternatively by suspending a magnet above a fixed coil, toinduce a signal directly from the object's vibrations.[4]