a transducer that converts electrical to acoustic energy or vice versa

a small hidden microphone; for listening secretly

microphone consisting of a capacitor with one plate fixed and the other forming the diaphragm moved by sound waves

a microphone designed to be used in contact with a source of sound (or with a resonating surface)

a microphone in which sound waves vibrate a piezoelectric crystal that generates a varying voltage

a microphone that is designed to receive sound from a particular direction