R5, R6, R7 and R8 should be selected to provide the desired dc gain of the microphone input.The gain should be such that the resultant output at the MICFB pin is within the microphone input signal range specified in 7.11.1. For optimum performance with low signal microphones, an additional external gain stage may be required. C6 and C7 should be chosen to maintain a flat low pass response up to 3kHz.If a single-ended microphone is used, then R6 should be connected to VBIAS and R5 deleted.R1 and C1 should be chosen to maintain a flat low pass response up to 3kHz.R9 and C8 should be chosen to maintain a flat low pass response up to 3kHz.