Today, all sound amplification and recording systems are electrical, therefore a microphone is needed to convert sound into an electrical signal. Unlike the human ear, there is no single microphone ideal for all tasks, therefore microphones come in all shapes and sizes, and the two main types of microphone are dynamic microphones and condensor (or capacitor) microphones.

Dynamic Microphones

Dynamic microphones have a light circular diaphragm, which is attached to a fine coil of wire, which fits into a magnetic gap, where it can move freely. When sound is produced, the diaphragm moves back and forth, which generates a small current, which can be amplified to a level suitable for a mixing desk, for example.

The dynamic microphone is inexpensive to produce, does not use electricty and is very rugged and can therefore be used in live situatuions as well as in the studio. The main disadvantage is that movement of the diaphragm is restricted and if it tries to move too fast, the high frequencies suffer and the sound quality of frequecies above 16 kHz gets worse.

Condenser (Or Capacitor) Microphones

Condenser microphones differ from dynamic microphones in the sense that condenser microphones can store an electrical charge. They have two metal plates seperated by an insulator and when the plates are charged, sound causes the diaphragm to move and the capacitor changes accordingly. This change can then be translated into a voltage and amplified, which creates an audio output. The charge needed can either be supplied by batteries or from a 48v phantom power supply from inside a mixing console.

Condenser microphones are expesive to produce, however they are very light, have brilliant sensitivity and performance and have a wider frequency response than the human ear.

Different microphones pick up sound in different ways and respond differently to sounds coming from a particular direction. This is known as directionality and there are three main types of directionality; omnidirectional, figure of eight and cardioid.

Omnidirectional

The pressure capsule of omnidirectional microphones has an omnidirectional pickup pattern, meaning that it picks up sound equally well from any direction, as the diagram below illustrates...


Omnidirectional Polar Pattern

Figure Of Eight

A figure of eight microphone has a diaphragm open to air on both sides, therefore it picks up sound most effectively at the two sides of the microphone, as the diagram below shows. This pattern would be particularly useful for two performers who want to record at the same time on one microphone.


Figure Of Eight Polar Pattern

Cardioid

As the name may suggest, a cardioid microphone has a polar pattern shaped like a heart and is most sensitive to sounds arriving from directly in front of it of the microphone and least sensitive to sounds behind it. Sounds from either side are picked up to a certain extent but less effectively than sounds in front, as the diagram below shows...


Cardioid Polar Pattern

There is also a hypercardioid pattern, which is even more directional than the cardioid pattern, but it is rarely used in the studio because there are inefficient at low frequencies. The diagram below shows the hypercardioid pattern...


Hypercardioid Polar Pattern