A microphone, sometimes referred to as a mike or mic is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and broadcasting and in computers for recording voice, VoIP, and for non-acoustic purposes such as ultrasonic checking.

Speakers as microphones

In practical use, speakers are sometimes used as microphones in such applications as intercoms or walkie-talkies, where high quality and sensitivity are not needed. However, there is at least one other practical application of this principle: using a medium-size woofer placed closely in front of a "kick" (bass drum) in a drum set to act as a microphone. The use of relatively large speakers to transduce low frequency sound sources, especially in music production, is becoming fairly common. Since a relatively massive membrane is unable to transduce high frequencies, placing a speaker in front of a kick drum is often ideal for reducing cymbal and snare bleed into the kick drum sound.

Less commonly, microphones themselves can be used as speakers, almost always as tweeters. This is less common since microphones are very rarely designed for handling the power speaker components are routinely required to cope with.