Microphone and Types of Microphones

Microphones are conversion devices. Microphones are also known as transducers. as they convert mechanical waves to electrical waves. Once converted to electrical waves. these waves can be amplified.

Microphones are available in many different types and styles:

•  Carbon microphone A microphone using a flexible diaphragm, which moves in response to sound waves and applies a varying pressure to a container filled with carbon granules. causing the resistance of the microphone to vary correspondingly.

• Piezoelectric microphone A microphone in which deformation of a piezoelectric bar by the action of sound waves generates an output voltage between the faces of the bar; also known as crystal microphone.

• Magnetic microphone A microphone employing a diaphragm acted upon by sound waves and connected 10 an armature, which varies the reluctance in a magnetic field surrounded by a coil. Applications include miniature microphones for hearing aids and guitar pickups.

• Dynamic microphone A conductor (usually a coil attached to diaphragm or ribbon) flexible suspended in the field of a fixed magnet is vibrated by sound waves. This induces in the conductor an AC voltage that varies in step with the sound waves.

• Electrostatic microphone A flexible diaphragm and a fixed electrode together form a two-plate air capacitor whose capacitance varies in step with the sound waves that vibrate the diaphragm. This is also known as a capacitor microphone or condenser microphone. With electrostatic microphones, one of the electrodes caries a permanent charge.

 Microphones can also have directional or non-directional characteristics. Most microphones are simple non directional types. which pick up sounds from all directions equally. These microphones are called omnidirectional. 
Directional microphones are available in a few major classifications.

Cardiod microphones: are one type of directional microphone. This type of microphone has a heart shaped sound acceptance pattern. These microphones are used by entertainers to pick up their own voice. but to reduce sounds from other directions. 

Shot-gun microphones:are highly directional microphones. which are used by bird enthusiasts to listen to distant bird sounds and by private investigators to hear conversations from a distance.Movie studios often use shot-gun microphones with long booms to pick up conversations of two people talking on a movie set. 

Highly directional microphones are also known as parabolic microphones. Parabolic microphones are very sensitive and highly directional. They are designed to pick up sounds very far away and amplify them through an electronic amplifier. Parabolic microphones are very selective and the sound pickup pattern is very narrow (only a few degrees). Often when these microphones are used the" must scan an area until the desired sounds are heard