FILTER
headman333
i belive a digital filter can help u much more
i know u r not going to use a dsp inside ur circuit , but i think u can do the required processing at PC side , better than that, is to use a dsp.
so, u just put a low pass filter on the signal comming out from the main microphone circuit. the resultants will be sampled by A/D and then the DSP task begins. there u can do very wide range of filterings. For example an elliptic IIR filter is so nice. it can do great job for u consuming very few of ur system resources
good luck