This circuit works quite well with low signal levels, but when the RMS ac signal is appr. 0.8 to 1.0 V (measured on pin #1 of the opamp), the negative half wave of sinusoidal signal is distorted so much that you can see it clearly on the oscilloscope. I am not asking, how to correct this circuit, but like to know the reason for this behavior. This is an existing circuit, and I know how it must be changed.
Added: Image from oscilloscope shows that the "negative" part of the signal is like wider quite much and has clearly different form. So it is not cutting, and if I add voice level to the microphone, cutting starts at the positive half wave first.