ITWissen.info - Tech know how online

electret capacitor microphone (ECM)

In the condenser microphone, the speech electrode is biased with a DC voltage. In contrast to the condenser microphone, the electret capacitor microphone( ECM) works with a biased speaking electrode made of electret. This is the name of the permanently elastic substrate that is the electrostatic equivalent of a permanent magnet. Therefore, the electret microphone does not require any additional bias.

Electret is a permanently elastic material, like Teflon, that is permanently electrically charged by electron bombardment during manufacture. It is polarized and has a positive and negative electrical side. The electret is applied to the speech membrane and forms the counter-electrode on which the charge is virtually"frozen". When the sound hits it, the electrode vibrates, causing a capacitive change. This generates an electrical signal.

Miniature electret microphone as MEMS with integrated sigma-delta transducer, photo: Akustica

Miniature electret microphone as MEMS with integrated sigma-delta transducer, photo: Akustica

Microphone capsules of electret microphones are comparable to condenser microphones in their characteristics. They have a linear frequency response ranging from 50 Hz to 20 kHz, their impedance is 250 ohms, and their sensitivity ranges from a few mV/ Pa to about 40 mV/Pa. The field- noise transfer factor (FLÜ) depends on the directional characteristic and is about -40 dBV, the maximum sound pressure is 130 dB and the signal-to-noise ratio for A-weighting is about 80 dB(A).

Electret microphones are used in telephones, smartphones, desktops, tablets and headsets, among other things.

Informations:
Englisch: electret capacitor microphone - ECM
Updated at: 04.11.2021
#Words: 220
Links: indium (In), microphone (Mic), speech, electrode, distributed computing (DC)
Translations: DE
Sharing:    

All rights reserved DATACOM Buchverlag GmbH © 2022