Microphone

A microphone (colloquially called a mic or mike; both pronounced /ˈmaɪk/^[1]) is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1876, Emile Berliner invented the first microphone used as a telephone voice transmitter. Microphones are used in many applications such as telephones,tape recorders, karaoke systems, hearing aids, motion picture production, live and recorded audio engineering, FRS radios, megaphones, in radio and televisionbroadcasting and in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors.

Most microphones today use electromagnetic induction (dynamic microphone), capacitance change (condenser microphone), piezoelectric generation, or light modulation to produce an electrical voltage signal from mechanical vibration.

Types of microphone

Sound is an amazing thing. All of the different sounds that we hear are caused by minute pressure differences in the air around us. What's amazing about it is that the air transmits those pressure changes so well, and so accurately, over relatively long distances.

If you have read the HowStuffWorks article How CDs Work, you learned about the very first microphone. It was a metal diaphragm attached to a needle, and this needle scratched a pattern onto a piece of metal foil. The pressure differences in the air that occurred when you spoke toward the diaphragm moved the diaphragm, which moved the needle, which was recorded on the foil. When you later ran the needle back over the foil, the vibrations scratched on the foil would then move the diaphragm and recreate the sound. The fact that this purely mechanical system works shows how much energy the vibrations in the air can have!

All modern microphones are trying to accomplish the same thing as the original, but do it electronically rather than mechanically. A microphone wants to take varying pressure waves in the air and convert them into varying electrical signals. There are five different technologies commonly used to accomplish this conversion.  Take a look at the next page to see the first type.