Microphone

A Neumann U87 capacitor microphone.

A microphone, sometimes referred to as a mike or mic (both IPA pronunciation: [maɪk]), 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 television broadcasting and in computers for recording voice.

Kinds of Microphones

Sound passes through the air in waves, and as was said above, the microphone turns the sound wave into an electrical wave. Different kinds of microphones will turn the sound waves into electricity in different ways.

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  A Shure witness microphone
  Carbon button - This is the first kind to become commonplace, being used in most 20th century telephones. Sound waves, by compressing and decompressing a piece of carbon, change the amount of electric current flowing in the wire, thus creating electrical waves. This kind became rarer late in the century, due in part to lack of high fidelity.
• Dynamic - This uses a round plastic or rubber disk connected to a wire coil in order to turn sound into electricity. The sound wave hits the disk which vibrates as a result. This vibration moves the coil back and forth near a magnet very quickly in order to create an electrical current. The dynamic microphone is the exact opposite of a speaker which uses an electrical current to move the coil, which moves the disk. Then the disk makes sound.
  • 

    A simple dynamic microphone
    Ribbon - This is similar to a Dynamic microphone. A thin, small sheet of metal (tin or aluminum usually) hangs between two magnets. When sound hits the thin piece of metal, the metal vibrates. That vibration creates an electrical signal in the metal.
• Condenser - This uses two small metal plates to create an electrical current. Basically two small metal plates are placed very near to each other and electricity is run through the plates. This creates an electric field between the two plates. When sound hits these plates, the plates vibrate. The vibration makes small changes in the electric field. These changes create the electrical signal.
• Crystal or ceramic microphones use piezoelectricity.

Equipment

A pop filter (or pop shield) is often used in recording studios. It is an electronic filter that reduces or eliminates 'popping' sounds caused by fast moving air (such as air from the mouth).

History

The first microphones were invented as telephone transmitters. They included liquid and dynamic designs. Carbon transmitters were later used in this and other applications.

Electret microphone capsule.

Microphone Media

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  Shure Brothers microphone, model 55S, multi-impedance "Small Unidyne" dynamic from 1951

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  David Edward Hughes invented a carbon microphone in the 1870s.

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  Humphrey Bogart, Jack Brown, and Lauren Bacall with RCA Varacoustic MI-6203 ribbon microphones broadcast to troops overseas during World War II.

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  Inside the Oktava 319 condenser microphone

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  Audio-Technica AT3035 condenser microphone

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  Inner workings of the condenser microphone

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  AKG C451B small-diaphragm condenser microphone

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  First patent on foil electret microphone by G. M. Sessler et al. (pages 1 to 3)

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  Patti Smith singing into a Shure SM58 (dynamic cardioid type) microphone

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  Inner workings of a dynamic microphone

Related pages

• Loudspeaker — The inverse of a dynamic microphone

Other websites

• Info, Pictures and Soundbytes from vintage microphones
• Microphone construction and basic placement advice Archived 2009-10-16 at the Wayback Machine
• History of the Microphone Archived 2010-08-23 at the Wayback Machine
• Microphone sensitivity conversion — dB re 1 V/Pa and transfer factor mV/Pa
• Large vs. Small Diaphragms in Omnidirectional Microphones Archived 2008-05-10 at the Wayback Machine