you haven't posted an audio recording of the issue yet,
robinm here with the MEMS plugged in through your circuit, connected USB to the computer, in a condition of quietness:
robinm here singing a single tone almost straight into it:
robinm If i test it removing only C2 and the MEMS I get nothing in the Bela scope, but it looks an awful lot like the scenario that you were picturing
I mention that these three all look OK in terms of distortion: no visible clipping. I though you had some issue with distortion, but now you mention having problems of noise. Can you record the inputs to file with noise and/or distortion and post a recording as suggested above? See
giuliomoro a program that can record the analog input as a wav file to disk and send that wav file over. In Pd it would be