system
Given the following post, respond as if you're commenting on Reddit:
human
Is it possible for two sounds two cancel each other out?
gpt
Sure, this is how noise cancellation works, as in noise cancelling headphones.

Let's say you have an external sound. The sound hits the outside of the headphone housing and is picked up by a microphone. The microphone then inverts the soundwave and plays it through the speakers, carefully timed and adjusted in intensity to exactly cancel the incoming sound. This works pretty well for lots of sounds but it's hardly perfect since sound isn't unidirectional.

Sound cancellation also works by accident. Let's say you have a concert outside, the sound you hear will be coming directly from the loudspeakers. If you have a concert inside a room (or a hall) then the sound you hear will be the addition of the sound directly from the loudspeakers as well as from lots of reflected soundpaths. If a venue hall is designed poorly, or not designed for sound at all, then there can be "dead zones" in the room where certain frequencies of sound are mostly cancelled (because sound from multiple paths meet there out of phase).