This is not so much an invention I feel sure will work, as an interesting idea which might. In fact I did build it and test it. It is a room silencer. One places microphones in a room, which one directs at the source of some noise -- say the window, as I did -- and inverts the noise and amplifies it. In order to compensate for amplifier lag, one runs cables from the microphones to the amp. This is what I discovered. My room silencer, on early attempts, sufficiently silenced noise coming through the window for me to realise that noise was coming through the roof and ceiling, too. OBSERVATION: I should have guessed it. At that point, I realised that my project was more complex than I thought, and I moved on to inventions new.