1. Omnidirectional Microphone Head
Omnidirectional microphone heads are used when there is no fixed direction between the sound source and the microphone head. In this case, the microphone head is required to have the same sensitivity in all directions. This is achieved by opening a single hole in the outer shell of the microphone head in front of the microphone hole. Common applications include telephone handsets, mobile phones, and hands-free headsets.
2. Unidirectional Microphone Head
Unidirectional microphone heads are used when there is a fixed direction between the sound source and the microphone head. The microphone head is required to have different sensitivities in different directions. The sensitivity is highest when the sound source is at 0° relative to the microphone head and lowest at 180°. To achieve this, holes are opened in the front and back of the microphone head's outer shell. Applications include in-car telephones and other directional microphones.
3. Noise-Cancelling Microphone Head
Noise-cancelling microphone heads are used when there is a fixed direction between the sound source and the microphone head, with sensitivity varying depending on the direction. The sensitivity is highest at 0° and 180°, and lowest at 90° and 270°. This is achieved by opening holes in both the front and back of the microphone head's outer shell. Noise-cancelling microphones are commonly used in environments where background noise needs to be minimized, such as in-car telephones.
4. Sensitivity Comparison
Under the same conditions, omnidirectional microphones typically have the highest sensitivity. Unidirectional microphones are about 6–8 dB less sensitive than omnidirectional ones. Noise-cancelling microphones have the lowest sensitivity, approximately 10–12 dB lower than omnidirectional microphones.
