Microphones

A microphone is a piece of musical equipment that contains a transducer - a device that converts acoustic energy into electrical energy. The electrical signals that microphone produces are so small that a microphone pre-amp, or, preamplifier must be used. A pre-amp is a device that increases the voltage from microphone level to line level before it reaches the amplifier. Line level refers to the voltage level that travels through the cables. Microphones are separated into categories according to their transducer type.

The three most common microphones used by professionals today are the "moving coil microphone", "ribbon microphone", and "capacitor/ condenser microphone".

The Moving Coil Microphone

In a moving coil microphone a tiny metal coil is connected to a movable plate, or diaphragm, at the front of the microphone and suspended in a magnetic field. When sound waves hit the coil it moves within the magnetic field and creates a voltage. This voltage is proportional to the sound pressure from the sound waves acting on the diaphragm

The Ribbon Microphone

A ribbon microphone works in a similar way to the moving coil microphone. Instead of a coil, the ribbon microphone has a thin corrugated metal ribbon which is connected to a diaphragm and placed in a magnetic field. When sound waves move the diaphragm, a voltage is induced in the ribbon.

The Condenser Microphone

A condensor microphone, also known as the capacitor microphone, works differently than the ribbon or moving coil microphone. Instead of a magnetic field, voltage is stored in a space between the moving diaphragm and fixed back plate.

The term "capacitor" refers to a space that holds a voltage. As the diaphragm is moves, the voltage inside the capacitor changes at a proportional rate. This changing voltage then travels to the microphone's output. The capacitor microphone requires an outside voltage, which is provided either by the mixer or a battery inside of the microphone.

Pickup Patterns

The pickup pattern is the area from which the microphone gathers data. A microphone can have an omni directional, bidirectional, or unidirectional pickup pattern. A polar response diagram is a chart that shows the pickup pattern of the microphone.

Omni directional michrophones

Omni directional microphones pick up sound from all around. They pick up slightly better from the area in front of the microphone, but sound from the back is picked up as well.

Bidirectional microphones

Bidirectional microphones pick up sound located directly in front and behind the microphone. These microphones have a pickup pattern in the shape of a figure eight.

Unidirectional microphones

Unidirectional microphones, also called directional microphones, pick up sound from the front only.

Bidirectional and unidirectional microphones require ports which, by the process of phase cancellation, mute sound coming from unwanted directions.

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