MICROPHONE
An ELECTROACOUSTIC TRANSDUCER which converts variations in SOUND PRESSURE into an equivalent electrical SIGNAL, which then may be fed to a TAPE RECORDER or other electronic equipment. Abbreviation: mic (pronounced 'mike').
The major types of microphones, each with its own type of DIAPHRAGM, are:
- dynamic microphones, of the moving coil or ribbon variety, operating on the basis of the motion of the coil or ribbon in a magnetic field inducing an electrical voltage in the coil or ribbon;
- condenser microphones, where the motion of one plate of a condenser changes its capacitance, which in turn produces voltage alternations when a constant charge is placed on the condenser;
- electret microphones, similar to condenser microphones in that they have a permanent electrostatic charge on the plates, but they are usually smaller in size;
- crystal or ceramic microphones, of poorer quality than dynamic or condenser microphones;
- carbon microphones, such as those used in telephones, very inexpensive but operating with a frequency response of about 300 to 3000 Hz. See: FUNDAMENTAL.
- contact microphones, which are attached to and receive the vibrations from the sounding object itself;
- boundary microphones, designed to be placed near a wall or floor such that there is minimal CANCELLATION between the direct and reflected sound.
Various types of microphones are designed with sensitivity characteristics that vary with the direction of the source. This pattern of sensitivity is called the DIRECTIVITY, directional characteristic or field pattern. See DIRECTIVITY for a list and diagrams and STEREOPHONIC for further discussion.
See also: ACOUSTIC FEEDBACK, BAFFLE, BINAURAL RECORDING, DIGITAL RECORDING, KUNSTKOPF, PARABOLIC REFLECTOR, SPILL, WIND SCREEN. Compare: LOUDSPEAKER.
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