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There are various types of microphone we can use, and various different ways of categorising them. Here we are going to examine the different technologies that are available, and polar patterns.

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Types of Microphone

All microphones are designed to convert acoustic energy into electrical energy, and all use a diaphragm as part of the process to achieve this. Having pointed out the common ground, we will now concentrate on the differences.

There are basically five different microphone technologies :

Carbon - The earliest microphones used carbon dust to interpret the audio signal. These microphones were commonly used in telephones and can still be found in some of todays telephones. A current is run through the carbon dust, the current fluctuates when the carbon is compressed by sound waves as they hit the diaphragm.

Crystal - The crystals used in this type of microphone change their electrical properties as they change shape. By attaching a diaphragm to a crystal, the crystal will create a signal when the diaphragm is vibrated by sound.

Ribbon - In a ribbon microphone, a thin metal wire is suspended in a strong magnetic field. Sound waves move the ribbon which changes the current flowing through it. This is a type of velocity microphone responding to air velocity rather than air pressure.

Dynamic - In a dynamic microphone, the diaphragm moves a coil between two magnets (positive and negative) when sound waves hit it, the movement creates a small current. more..

Condenser - The condenser microphone has been around for more than a century, and requires an external voltage (phantom power). A capacitor is created by the diaphragm and a backplate, they are electrically charged and the movement of the diaphragm in relation to the backplate causes a varying capacitance, in turn varying the voltage output. more..

Please note that comments on the microphone information pages are opinion gathered from a variety of different sources. We would urge you to do your own research before purchasing a microphone.

The next category we can use to distinguish between microphones is Polar Pattern, in other words the characteristics of the area around the microphone from which an audio signal can be picked up. And again there are five categories:

Cardoid - Strong sensitivity directly in front of the microphone, coupled with good sensitivity at the sides and rejection from behind. The pattern earns its name from the heart-shaped pickup area (as illustrated in Fig 1).

Supercardoid - Similar to the cardoid, but with slightly reduced sensitivity around the sides. The supercardoid pickup range includes a small area just behind the microphone (as illustrated in Fig 2).

Hypercardoid - This pattern is an even more exaggerated form of the Supercardoid, with a reduced sensitivity at the sides, and a larger area of sensitivity at the rear (as illustrated in Fig 3). More directional than the other two cardoid patterns, and thus used where maximum isolation between sound sources is required.

Omnidirectional - Indicating a microphone that picks up sound equally from all directions. This is the only microphone not prone to a proximity effect (undesirable low range interference when a sound source is too close to the microphone)

Bidirectional - A 'figure-8' pattern where sound is picked up equally well from two opposing directions, without sensitivity at the sides (as illustrated in Fig 5).This type of microphone may be useful in an interview situation.