How to safely determine which pins output a microphone signal?
If you have access to the microphone whilst it is active and can probe the output, you can make some acoustic sound and see which pins make a voltage that corresponds to this. Hopefully ground is easy to find so you can measure relative to that pin.

Analogue microphone signals are usually very small, so you may want an op-amp stage to boost it. This would be safe to connect to any output as it won't apply any voltage. The following stage has a gain of 100 and should boost the signal enough that your multimeter (which should be on an AC setting) will measure the difference when the mic picks up a signal.







simulate this circuit &ndash; Schematic created using CircuitLab

If you don't have an AC mode on your multimeter, you can add a diode, resistor and capacitor to the output which will detect the envelope (by rectifying) converting the signal closer to DC.







simulate this circuit