This microphone amplifier is based arond the TLC272 double opamp.
The first opamp is used as an amplifier. The voltage offset on the positive input is set to half Vcc with R2 and R3. The Closedloop gain is set at 100 by R5 and R4. There is an AC coupling/high pass filter to the 2nd opamp by C4 and R6. The second opamp is used as comparator: R7 and R8 determine a level sensitivity of 71 mV (with 5 Volt Vcc).
SPL is the sound pressure level. There is also an audio output for the amplified microphone signal. As the audio signal is DC coupled, the signal will swing around 1/2 Vcc
Note: In the picture you may see a TL072 chip rather than a TS272 (TLC272). That is because I briefly tried that one. The TL072 is a double opamp especially for audio purposes. My results with it however were not so convincing. Best use the TS272 (TLC272)