What is a Cardioid Microphone?

Microphone directivity is a description of the inspiration pattern of sound from all directions in space. It is an important attribute of microphones. In many cases, the first choice of microphone is its directivity, and the second is the other attributes of the microphone. Except for omnidirectional microphones, other directivity is based on multi-diaphragm technology. By changing the cavity setting of the microphone head and mixing and modulating the sound signals received by the multi-diaphragm, the microphone obtains sensitivity to sounds in different directions. Most microphones are single-directional, but some microphones can switch their directivity.

Microphone directivity

The directivity describes the sensitivity of the microphone to sound from different angles. The polar pattern above is usually used to indicate the specifications. In each diagram, the upper part of the dotted circle represents the front of the microphone, and the lower part represents the rear of the microphone.

The single directional microphone is mainly designed using the principle of Pressure Gradient. The diaphragm receives pressure from both the front and back through the small holes behind the microphone cavity. Therefore, the diaphragm is not under the same pressure in different directions, and the microphone has directivity. ^[2] And therefore, directional microphones have a close-talk effect. Single directional microphones fall into three categories:

Pressure Gradient

Cardioid

Heart-shaped pointing

The cardioid is best for sounds coming from the front of the microphone, while sounds from other directions are attenuated. Stereo recording systems such as XY, AB and ORTF usually use cardioid microphones. ^[1] Most handheld microphones are also cardioid, such as stage microphones and karaoke microphones.

Hypercardioid

Supercardioid

Compared to cardioid pointing, supercardioid pointing cancels out more sound coming from the side of the microphone. It is more commonly used in multitrack recordings of chamber music to reduce the sound from other nearby instruments. ^{[1] is} also often used in live sound reinforcement, reducing the risk of many feedback howling.

Gunpoint (Shotgun)

Gun type pointing

Gun-pointing microphones are a type of microphone that has the most extreme single-directional pointing. The best radio angle is a small cone area in front of it, which is mainly used for outdoor radio, such as outdoor news interviews and radio shooting of filming. Its better directivity makes the microphone can effectively reduce the income of the surrounding environmental noise.

Bi-directional (Figure 8)

Figure 8 Pointing

The two-point type accepts sound from the front and rear of the microphone, which cancels out most of the sound from the 90-degree side. This system is the directional characteristic of most early ribbon microphones. A bidirectional microphone is a component of many stereo and surround sound recording systems. For example, the side microphone in MS (middle-side) must be a bidirectional microphone. ^[1] ; required for the Hamasaki square system. Four bidirectional microphones are used; Ambisonics3D recording system also uses three bidirectional microphones. Due to the extremely low sensitivity of the bidirectional microphone on the side, it can also effectively reduce the sound from other nearby instruments when used in indoor multitrack recording.