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View submission: Ask Anything Wednesday - Engineering, Mathematics, Computer Science
The general phenomenon you're looking for is called interference, and it is a property of essentially all waves. This includes sound and other mechanical waves, but also light and even "quantum waves".
Interference arises from linearity but it is inherently nonlinear. This may seem contradictory, but it is not since the linearity and nonlinearity refer to different aspects. "Linearity" means that adding two waves gets you another wave. In the case of noise-cancelling, you add two "opposite" waves to get as close as possible to no sound. The nonlinearity appears because the intensity of a wave is proportional to the *square* of the wave. So when you add two waves and calculate the square, you get extra terms since (a+b)^2 is not a^2 + b^2 .
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