A microphone is a device that converts sound waves into electrical signals of the same frequency and shape. The microphone may be classified into the following basic types depend upon their principle of operation :Crystal, Carbon , Dynamic, Ribbon and Condenser. Each types of microphones has different characteristics with respect to
1. Output level,
2. Frequency response, and
3. Output impedance.
The alternative of a specific microphone based upon the application, the frequency response desired and a number of other factors.
Generally the carbon microphone is utilized for telephone systems. The crystal microphone uses quartz crystals which have the property of producing emf when subjected to stress and strain. The moving coil type microphone is one of the most general microphones and the same principle is employed for both of the microphone and loudspeakers. This type of microphone works on generator principle. This device contains a diaphragm carrying coil of wire placed in magnetic field. The application of the sound pressure causes movement in the diaphragm and consequently, an emf is generated.
In the ribbon type microphone, the ribbon which may be regarded as a coil with single turn which is forced to move in powerful magnetic field, because of which, an output power is generated.
The condenser microphone depends for its operation on the variation of capacitance among a fixed plate and a strongly stretched metallic diaphragm.