Even if the amps were biased correctly which they are not (see my previous posts) the gain is so high you are relying on frequency variations as there will be no amplitude component (the amps are all saturated). Therefore anything from a mouse croak to a door slamming will trigger it.
R3? What's the point other than an attempt to make a comparator. With so much gain, it will be pointless.
You could achieve the same with a dual opamp. One for the gain, the other as a proper comparator.