Electret microphone is a type of capacitive microphone.
The electret microphone uses the principle of variable
capacitance to convert sound signals. Its working principle is
to use sound wave vibration to cause changes in the electric
field at both ends of the capacitor, thereby generating
alternating voltage that varies with the sound wave. The
capacitance between the diaphragm and the metal plate of this
type of microphone is usually relatively small, usually several
tens of picFaradas (pF), and it achieves sound electric
conversion by changing the distance between the diaphragm and
the metal plate.
Compared to traditional capacitive microphones, an important
feature of electret microphones is that they typically do not
require an external power source to provide a constant voltage,
as their membranes or backplates are permanently charged, making
them more portable and easy to use.
