You cannot allow -V on any input pin nor allow more than +5.5V!
A Schottky diode can cut all V below +0.3V, a regular diode takes +0.7V to pass.
I got a voltage at the output of around 15 volt AC(rms)
That sounds like signal, more signal than you need. Are you sure it is AC?
Without the opamp, try feeding the low current microphone output directly to an NPN transistor base pin.
Connect 5V through a 1k resistor to the collector and a led + lead to the emitter, and ground the other leg of the led. Noise should cause the led to light. Worst case, you lose the transistor but those are cheap.
Any circuit that can make a led light up even dimly should be detectable.