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 transducers which detect sound waves and produce an electrical image of the sound; they produce a voltage or a current which is proportional to the sound signal. They were first used with early telephones and then radio transmitters and have evolved through a number of major changes to the high quality instruments of today.
Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice, VoIP, and for non-acoustic purposes such as ultrasonic checking.
The most common microphones for musical use are dynamic, ribbon, or condenser microphones. Most microphones in use today for audio use electromagnetic induction (dynamic microphone), capacitance change (condenser microphone, pictured right), piezoelectric generation, or light modulation to produce the signal from mechanical vibration.