We have to change the sample rate and AA filter for the mic channels before going too far with the circuit design.
PEM model is running at 64K now. It turned out to be tricky to increase the rate:
We should also increase cut off frequency of the low-pass filter in the microphone pre-amplifier from 2 kHz up to ~20-30 kHz.
Thank you for changing the sample rate!
Also we have to change the Anti-Aliasing filter, as Jamie said.
Now my question is, whether S/N ratio is enough at high frequencies or not. The quality of EM172 microphone is good according to the data sheet. But as you can see in previous picture, the S/N ratio around 1kHz is not so good, though we can see some peaks, e.g. the sound that a fan will make. I have to check it later.
And, is it possible to do online adaptive noise cancellation with a high sampling rate such that computationally expensive algorithms cannot be run?