I need help with INMP441

[comeycalla]

Good afternoon,

I am making a sound level meter with the INMP441. I need help to translate the measurements that the INMP441 microphone module transmits me to dB SPL. The sensitivity of this microphone is -26 dBFS at 1KHz and 94dB SPL, but I don't understand very well what formula I have to apply to pass from a sensor measurement (from 0 to (2^23-1) to dB SPL.

Do I have to use the instantaneous or rms measurements ?

What is the relation between the INMP441 measurements and the dbSPL? (Assuming that the sound to be measured will always be at 1KHz so that the formula does not vary with the frequency.

Here is the sensor datasheet https://invensense.tdk.com/wp-content/u ... NMP441.pdf.

Greetings and thanks in advance.

[MicroController]

As I understand it, given a peak digital output value (amplitude) of X the corresponding SPL (rms) in dB should be

Code: Select all

SPL = 94 + 10 * log10( X / 420426 ) = 94 + 10 * ( log10( X ) - log10(420426) )

or equivalently

Code: Select all

SPL = (94+26) + 10 * log10( X / ((1<<23)-1))