Microphone directivity is a description of the sensitivity mode of sound from all directions in space, and it is an important attribute of a microphone. Most of the time, the first consideration in the selection of a microphone is its directivity, followed by other properties of the microphone. Except omnidirectional microphone, the other directivities is based on multi diaphragm technology. By changing the microphone’s cavity setting and mixing the sound signals received by multi diaphragm, the microphone can obtain the sensitivity to different direction of sound. Most microphones have a single directivity, but some of them can switch their directivity.
In microphone, there are three basic categories of directivity: omni-directivity, Bi directivity and uni-directivity.
Omnidirectional microphones (also known as non -directional microphones) pick up sound from all directions and are equally sensitive to sound from all direction. It’s best for picking up the sound effects of a room. Although this feature makes it more convenient to use when several people are standing or sitting around a single microphone, some directional microphones are often preferred in TV production. First of all, omnidirectional microphone can not effectively reduce or eliminate unwanted sound, such as camera noise, noise around the scene, etc., and can not maximize the voice of the main speaker.
二、Bi directional microphone
This kind of microphone is also called (8) type. It picks up sound from both sides, not from the front or behind. The typical use is to place between two instruments, or when two people standing face to face in front of the microphone, so that two kinds of sound can be recorded together, while preserving the independence of the two. Bi directional microphone is mainly sensitive to sound from two directions.
Unidirectional microphone is sensitive to sound from one direction. According to their sound characteristic curves, they can be divided into three types mainly: cardioid curve, super cardioid curve, special cardioid curve. Each has a slightly difference in directional curve.
This kind of microphone can directly sense the sound in front of it and has a small range of expansion on both sides. Cardioid microphones are sensitive to a wide range of sound in front of the microphone, but insensitive to sound coming from behind the microphone. When placed 2 m or more away from the speaker, it often picks up some unnecessary surrounding sound, including the reflected sound from the wall.
This kind of microphone can receive the sound far ahead, but the sound on both sides is very little can be received. Super cardioid is more directional than cardioid. When this kind of microphone points to a sound source, the interference sound (outside the axis) is often suppressed.
This kind of microphone can receive the sound far ahead, but the sound on both sides cannot be received. Because of its super directivity, it can shield the environmental noise to the maximum extent. Special microphones are more directional. This kind of microphone has a small angle to receive sound, and most of the sound outside the angle will be suppressed. However, when using the microphone, it must point to the sound source correctly and adjust the microphone pointing according to the speakers’ movement.