The MEMS microphone stands for Microphone Electronics Mechanical System. As with other microphones, sound pressure is converted into electrical signals.
Depending on the design, the sound signal is converted into a corresponding analog output voltage or into a digital pulse-density-modulated (PDM) output signal.
The conversion of sound into electrical signals is effected by means of a change in the coupling capacitance between a fixed base plate and a movable base plate (membrane).
The sound hits the diaphragm and sets it in motion. This changes the air gap and thus the capacitance between the base plate and the diaphragm plate.
The air compressed in the rear chamber can escape through the pressure equalization opening so that the membrane can move. The electrical signals are then amplified by an ASIC chip.
A directional characteristic as omni or uni directional microphone is achieved by corresponding RF noise canceling filters.
There are microphones, whose design has the opening at the top of the housing or at the bottom in the circuit board.
The advantages of a MEMS microphone