The World of Wired Microphones

By: Victor Epand

The Microphone is defined as an electric transducer or sensor that converts sound into an electrical signal. Microphones are used in many applications. They are used in various instruments like telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice, and also for non acoustic purposes such as ultrasonic checking. Loudspeakers can also function as microphones when in reverse use.

The basic function of a wired microphone is to capture waves from various surfaces and convert them into an electrical signal. A common signal flow is activated with the help of thin membranes producing a proportional electrical signal.

Most microphones in use today for audio, use electromagnetic generation (dynamic microphones), capacitance change (condenser microphones) or piezoelectric generation to produce the signal from mechanical vibrations.

In the world of wired microphones, there exists a large variety, with varied functions. The types of microphones are condensers or commonly also known as capacitor, dynamic, carbon and piezoelectric microphones.

Piezoelectric microphones produce signals from mechanical vibrations. The dynamic microphone is also known for the use of electromagnetic principles.

The condenser microphone, which is also known as a capacitor microphone, has a unique functionality. In this mic, the diaphragm acts as one plate of a capacitor, and the vibrations produce changes in the distance between the plates. The condenser microphone is further divided on two bases on the basis of audio output from the transducer. One division is called DC biased and the other is known as the RF or HF condenser microphone.

The condenser microphone's audio span ranges from cheap throwaways to high fidelity quality instruments. They generally produce a high quality audio signal. Condenser microphones are now the popular choice in laboratory and studio recording applications. They usually require a power source, which is provided either from microphone inputs as phantom power or from a small battery.

The dynamic microphone works in the same manner as the loudspeaker but only the principle is reversed. The function of the microphone is as follows. A small movable induction coil, positioned in the magnetic field of a permanent magnet, is attached to the diaphragm. The sound enters through the windscreen of the microphone and the sound waves move the diaphragm. As the diaphragm vibrates, the coil moves in the magnetic field, producing a varying current in the coil through electromagnetic induction.

Besides dynamic microphones, professional microphones generated using the principle of condenser often sport an external power supply for reasons of quality perception. Power is a necessity for the functioning of the capacitor. The capacitor plate can only function with power voltage. Power is also needed for internal amplification of the signal to a useful output level.

Condenser microphones are also available with two diaphragms, the signals from which can be electrically connected such as to provide a range of polar patterns such as cardioid, omnidirectional and figure-eight.

The world of microphones is not limited to just dynamic microphones and condenser microphones. Each day, a new innovation and invention takes place.

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