florin:
I have a microphone conected to A0. If frequency is less than 1 HZ , a led is HIGH.If frequency is bigger than 1 HZ, another led is HIGH.
But a microphone generates rather random audio sounds comprised of many mixed frequencies and their harmonics, not a single frequency unless you have it pointing at a signal generating a single pure frequency through a speaker. Also audio is a AC voltages and an arduino analog input pin can only measure DC positive voltage values, negative voltages if large enough can damage the input pin. I think you need to rethink your application approach.
Lefty