You’re on a flight, and the drone of the engines is getting on your nerves, so you pop on a pair of noise-canceling headphones, and sweet, blessed silence descends. But those headphones aren’t just muffling the sound -- they’re actually making it go away!

Bose designed a system that would use a microphone inside the headphones to pick up all the noise occurring in the atmosphere around the user. That noise would then be sent to electronics that generated an equal and opposite signal within a fraction of a millisecond that cancelled out the sound before it reached the eardrum of the listener. That was his theory, at least.

how noise canceling headphones work?

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Prof. Bose's Chat with MIT Acoustics Students - 1995

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