Eli5: How does active noise cancelling work on headphones?

Question

Eli5: How does active noise cancelling work on headphones?

In: 6

Answer 1

Sound moves in waves.

Say “Sound X” is what you’re trying to cancel.

Sound waves have two important characteristics when it comes to this: the amplitude and the phase.

(There’s more that goes into this, but think the “strength” and the “timing” of a given sound wave, respectively)

If you get “Sound Y” that has the same amplitude but opposite phase of “Sound X”, Sound Y will interfere with Sound X to form a new wave altogether, and effectively cancel both Sound Y and Sound X out.