Contact microphone

A contact microphone, also known as a pickup or a piezo, is a form of microphone that senses audio vibrations through contact with solid objects. Unlike normal air microphones, contact mics are almost completely insensitive to air vibrations but transduce only structure-borne sound. Often used as acoustic leakage probes, they also enjoy wide usage by noise music artists experimenting with sound. Contact microphones based on piezo materials are passive and high-impedance, which can make them sound 'tinny' without a matching preamp.