What exactly is this op amp being used to do? Bandpass filter?
Blue: Mic bias.
Orange: Amplifier, 10x if transistor is off, 100x if transistor is on. R7/C9 is a low pass filter, just to attenuate high-frequency noise. C6 is needed to block the DC in the feedback path, remember that the previous stage has biased the signal path to about 1/2 Vcc.
Green: Precision rectifier.
Purple: Peak detector &amp; Comparator (positive feedback).
General comment: this is a waste of computing power. A clever designer would move more of the functions into the MCU.