Posted on January 20, 2014 at 19:15The basic acoustic parameters of a MEMS microphone are the Sensitivity, SNR, Frequency response and the Acoustic overload point. They are respectively defined as follow:
The sensitivity is the electrical signal at the microphone output to a given acoustic pressure as input. The reference of acoustic pressure is 1 Pa or 94 dBSPL@1kHz. The sound pressure level, expressed in decibel, dBSPL=20*Log(P/Po) where Po = 20μPa is the threshold of hearing. 20*Log(1Pa/20μPa) = 94 dBSPL
The signal-to-noise ratio specifies the ratio between a given reference signal to the amount of residual noise at the microphone output. The reference signal is the standard signal at the microphone output when the sound pressure is 1Pa @ 1 kHz (microphone sensitivity). The noise signal (residual noise) is the microphone electrical output at silence
The Acoustic overload point is the maximum audio signal is that which the microphone can generate without distortion. Actually, the specification allows up to 10% in terms of distortion at the acoustic overload point
The frequency response of a microphone in terms of magnitude indicates the sensitivity variation across the audio band. This parameter also describes the deviation of the output signal from the reference 0 dB. Typically, the reference for this measurement is exactly the sensitivity of the microphone @ 0 dB = 94 dBSPL @ 1 kHz.
Alessandro
