According to those papers:
- Pitch Analysis of Infant Crying
- Frequential Characterization of Healthy and Pathologic Newborns Cries
Values of C1 and C3 were calculated to create a band pass filter with a bandwidth of 250Hz-550Hz (capacitances are taken from E24 value series so the band is not 100% precise).
Voltage divider consisting of R1 and R2, outputs 1.65V threshold Voltage for NE5532. I want to output of amplifier to oscillate around this value (Vt). The output of the amplifier will be fed to MCP3008 - that's why voltage can't be higher than 3.3V.
R5 resistor is used to drive transistor inside the microphone.
R3 and R4 need to be changed (I don't think I will need a gain of 21 but I still did not get my microphone for testing).
I chose NE5532 because of its low-noise amplification, I think it will be better for this kind of task but, it might be an overkill and LM358 will do the job just fine.
Will this circuit work as described it?
As I mentioned before, the output is connected to ADC, which is connected to raspberry pi. Based on voltage level, raspberry pi will e.g. rise alarm.