Noise/Voice Surveillance System (unisens intercom)
For hear talks or watch the sound I use a simple audioamplifier like LM386, in this case is a special configuration – 74dB amplifier (see article How to get 74dB by LM386).
I redesigned the schematic with an old version of Autodesck Eagle PCB software
I made the schematic:
My application was to hear sounds of my daugter in apartament, at 10m distance..