ADC Question for Sampling With Electret
Math of sampling dictates two things:


You need to sample twice as fast (in the ideal, practically faster)
as the maximum frequency you'd like to capture
You need to remove frequencies above half the sample rate with a
low-pass filter, or they will corrupt your lower frequency content
through aliasing.


If you need 12 kHz, you need to sample at more than 24 kHz and provide an anti-aliasing filter before the sample is done.