Specifications of electret condenser microphone
2025-04-14
Electret condenser microphones primarily consist of a fixed electrode plate (back electrode or back plate) and a moving electrode plate - diaphragm (a FEP film with a very thin metal layer deposited on one side and then bonded to a metal ring, with a charge on the other side), and a gasket, forming a variable parallel plate capacitor with air as the dielectric. According to electrostatics, the relationship of the parallel plate capacitor can be expressed by the following formula:
V=Q/C; C=ε·S/d (where V: voltage; Q: charge; C: capacitance; ε: dielectric constant; S: area of the electrode; d: distance between electrodes).
When the diaphragm is subjected to a sound signal, it vibrates, changing the distance between the diaphragm and the electrode plate, resulting in a change of △d. As the formula shows, the change in △d produces a change in △C. Because the charging charge is fixed, the change in △C produces a change in △V. This completes the initial conversion from a sound signal to an electrical signal.
Depending on the materials used for the diaphragm and the electret and their spatial arrangement, electret condenser microphones can be divided into several types in the field of acoustics, such as diaphragm type, back-electret type, front-electret type, and diaphragm type.
Electret condenser microphones contain a dielectric material capable of storing charge for a long time. This dielectric material is generally a polymer, such as polytetrafluoroethylene PTFE or polyfluoroethylene propylene copolymer FEP. In normal atmospheric pressure, the charging and polarization of the electret condenser microphone utilize a non-uniform electric field to cause local breakdown of the air, forming corona discharge. Then, the ion beam generated by the corona discharge bombards the dielectric, causing ionic charges to deposit on and near the surface of the dielectric, finally forming a space charge electret.
In the market, electret condenser microphones are the most widely used among all transducers, and their specifications cover almost the entire electroacoustic market. Below, we will explain several commonly used specifications of electret condenser microphones:
| Outer Diameter (mm) | Height (mm) | Applications |
| 3.0 | 1.2~3.0 | Bluetooth, digital products |
| 4.0 | 1.2~1.5 | Mobile phones, conferences, Bluetooth, headphones, digital products |
| 6.0 | 1.2~6.0 | Laptops, conferences, headphones, digital products |
| 9.7 | 4.5~6.5 | Conferences, toys, telephones |
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