An electret microphone is a type of condenser microphone. The basic principle of a condenser microphone is to use a capacitor as an acoustic signal-electric signal converter. A plate of this capacitor can sense the change of sound pressure and play the role of sound signal intake. Usually, this pole is composed of a metallized polymer membrane, and the other pole constitutes a variable capacitor whose distance between the poles can be changed. When there is sound pressure, the diaphragm vibrates, and the vibration intensity and vibration frequency are determined by the instantaneous sound pressure, and the capacitance capacity also changes with the acoustic signal. If a constant voltage has been applied to the capacitor at this time, the change in capacitance will cause the amount of charge on the capacitor to change, thereby generating an electrical signal across the capacitor to achieve an acoustic-to-electrical signal conversion.
Some materials can hold these charges substantially permanently after the charge is added. This is known as electret material. Microphones using these materials are so-called electret condenser microphones. The condenser microphone pickup unit has two poles, one of which is a vibrating metallized diaphragm and the other pole is a metal plate. For an electret condenser microphone, one of the poles is made of electret material or an electret material is used, and the electret material itself can retain the charge characteristics, and the electret provides the normal work required. Constant voltage. This eliminates the part of the power supply voltage required for the operation of the microphone pole, and has a simple structure and a small volume.
According to the position of the electret material, it can be divided into diaphragm type and back pole type. In the early electret microphones, the diaphragm type was used, that is, the diaphragm was made of the electret material, and the process was relatively simple and the technical requirements were not high. However, the sound quality of the diaphragm made of electret material is not very good. Nowadays, the electret microphone is mostly back-type, that is, the electret material is attached to the other pole (back pole) of the capacitor. The charge is applied, and the diaphragm material can be selected from the viewpoint of pickup, and a diaphragm of a material having a better sound quality is selected. From the current technological development, the back-microphone is a trend of electret microphones.
Compared with the general condenser microphone, the electret microphone has a simple production process and low cost, and is suitable for mass production. At the same time, the volume is small, and it is convenient to use. It is widely used in various occasions, such as general meeting occasions, voice communication systems, such as telephones, cameras, mobile phones, repeaters, and the like. However, the sound quality of the electret microphone is relatively poor, and it is often used in situations where the sound quality is not high.
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