[Ricardus]

The MUTE solution sounds interesting, and is certainly worth some research, but I see it having some problems. One obvious one is that the receiver might stay in that guy's window, and you might be in the apartment, say 15 feet away, so within that distance you can overcome the latency issue that was mentioned (because radio waves travel faster than sound waves) but the fact remains you're 15 feet away from the microphone in the receiver, and by the time the sound reaches you, it has changed dramatically. It has reflected off of 1000 surfaces by then and looks a lot less like it did at the receiver. So creating a waveform that's 180 degrees out of phase would be a gigantic challenge. I suppose you could do some work with Impulse Responses to solve this. You could take an IR of the room where the listener is and probably account for a lot of the changes and use some DSP to modify the waveform to make it more correct. But then if you move somewhere else in the room, everything changes and needs to be recalculated. Interesting idea though.

[randyt]

The solution is to use adaptive filtering.

[Ricardus]

The farther the microphone gets from your ears the harder the problem gets to solve. It's an interesting idea, but I suspect this won't see prime time in any meaningful way.