A. Electret (Electret) : apermanent electric polarization state of the dielectric. The dielectric is usually polymers. Such as polypropylene, ptfe, etc.

2. The Microphone (Microphone) : the sound signal into electrical signal transducer. According to the principle of work can be divided into: moving coil, electromagnetic, piezoelectric, capacitance, capacitance and can be divided into audio capacitor microphone and two kinds of electret condenser microphone.

Three. Electret condenser microphone (ECM) : electret in the concrete application of electroacoustic transducer on microphone electret condenser microphone (ECM) classification: diaphragm type (Foil), Back pole (Back), the former pole (Front).

1. The diaphragm type ECM static principle diagram

Diaphragm type ECM static principle diagram

Diaphragm type characteristics of ECM: electret and diaphragm.

Metallized film and back plate forming air dielectric capacitor. Formation of electret charging electric field. E = Q/C sound waves make thin film vibration, change the capacitance and the electric field, produce electrical signals. Delta E = Q/delta C

Diaphragm type work dynamic principle diagram

Diaphragm type work dynamic principle diagram

2. The back pole ECM static principle diagram

Back pole ECM static principle diagram

Back pole type characteristics of ECM: electret with plate together.