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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.
- 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.
- 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.
- Ribbon - This is somewhat 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.
- Crystal or ceramic microphones use piezoelectricity.
- Loudspeaker — The inverse of a dynamic microphone
- Info, Pictures and Soundbytes from vintage microphones
- Microphone construction and basic placement advice
- History of the Microphone
- Microphone sensitivity conversion — dB re 1 V/Pa and transfer factor mV/Pa
- Large vs. Small Diaphragms in Omnidirectional Microphones