How do noise cancelling headphones actually work?
In: Engineering
I’m not sure how familiar you are with how waves work, so let’s start with a fact: you can cancel a wave with another wave that’s equal but “opposite”, that is where the first one has peaks, the other has valleys of the same shape and height. Basically if you flip it around. When you combine them, they average out to zero, nothing. No wave. That’s destructive interference.
That’s what noise cancelling does. Microphones on the outside pick up sound and very rapidly produce a matching but opposite wave inside the headphones to destructively interfere with the original, cancelling it. That leaves only the other sounds purposely made by the headphones.
It’s of course not perfect, so some noise always makes it through, but still very effective.
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