After I read mic PDM data, how do I convert it to DB？

[Tomlee]

Hi，

   I am doing a micphone "sph0641lm4h-1",  and I use api of nrf_drv_pdm.c, 

   when I read mic data from sph0641lm4h-1,  they are just sets of 16 bit data, the following figure:

pdm_buffer[0], pdm_buffer[1], pdm_buffer[2], pdm_buffer[3], pdm_buffer[4]........

so my question:   when I read all the array data ,   how I convet them to db?

[Øyvind]

Hello, 

A quick google search gave me this result 
https://devzone.nordicsemi.com/f/nordic-q-a/28248/get-amplitude-db-from-pdm

Let me know how that works for you. 

Kind regards,
Øyvind

[Tomlee]

Hi  yvind,

    Thanks for your reply.

    Do you mean using "amplitude = 20 * log10(abs(sample) / 32767) dBFS"  ?

   but I don't understand what the parameter "sample" is ?

   is it pdm_buffer[1]?  or  is it the average of all pdm_buffers?