What is a Microphone ?

The microphone is a kind of transducer that converts sound energy into electrical energy. It is like a loudspeaker that works in reverse because a loudspeaker converts electrical energy into sound energy. Think of a microphone as a generator which generates electricity whenever it is struck by sound waves. We always see microphones being used by reporters, singers, tv host and film makers. Microphones have varying shape and sizes depending on its intended application. Some microphones are very small like the condenser mic and some microphones are very large as in the case of parabolic microphones which can detect sound waves from very long distances. Microphones are also constructed from different materials and they also operate on different mechanisms.

Microphones by Type

A. Condenser microphone - Condenser Micorphones are also known as Capacitor Microphones. These microphones operate on the principle that when you apply a fixed charge on a capacitor, and you change the capacitance, the voltage across its plate varies. The condenser microphone is made up of two plates separated by an insulator. The capacitance of the microphone varies as the plates move due to sound waves. The first condenser microphones use a small battery pack to supply a fixed charge on the capacitor. Today, condenser mics use "electrect", a material that has fixed charge built in it and does not require an external battery.

B. Dynamic microphone - The dynamic microphone or electrodynamic microphone uses a fixed magnet and a moving coil that moves in response to sound waves. To increase the chances of capturing sound waves propagating to the microphone, the moving coil is attached to a diapraghm. The movement of the coil in a magnetic field generates a small voltage on the end terminal of the coil.

C. Piezoelectric microphone - Certain crystals such as quartz and rochelle salt generates a small voltage whenever they are compressed or tensed. Sound waves can also compress or tense these crystals and thus they generate a small voltage on the crystal faces.

D. Ribbon microphone - These are similar in operation to the electro dynamic microphone. The only difference is that ribbon type microphones use a strip of metal shaped like a corrugated ribbon instead of a coil. Ribbon type microphones have lower voltage output than electro dynamic microphones but ribbong type mics impart a warm wellow sound to the voice of the user.

E. Carbon microphone - This microphone uses carbon granules packed in a capsule and was the first microphone to be used on telephone sets. The resistance of carbon granules varies with the sound wave that strikes the microphone capsule. Like the original capacitor microphone, this microphone needs an auxillary battery to operate.

Microphones by Function

Microphones can also be classified depending on its intended use. They may vary in design, appearance, size and shapes.

A. Recording microphone - Optimized for recording of music and voice.

B. Headset microphone - These are low cost, typically low fidelity microphones embedded on headsets.

C. Directional microphone - Microphones that can only "hear" sounds in one direction.

D. USB microphone - Microphone units that can be interfaced directly to a usb port.

E. Stereo microphone - These are two microphones packed as one unit. Sometimes they are attached to a dummy head. To simulate human hearing.

F. PC microphone / Computer microphone - Low cost microphones that are connected to the microphone input of a sound card or built in sound card on motherboards.

G. Cordless microphone/ Wireless microphone - Microphone set with built in FM transmitter. Oftentimes, they use electrect mic for this purpose. The electrect mic is then coupled to an amplifier and FM transmitter.

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