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PokebannedGo t1_j2e4wan wrote

Reply to comment by theperfectmuse in Eli5 How exactly does Noise cancellation work? That too in such small airbuds by Professional-Ad3441

That's because the "opposite sound" doesn't make sense.

If a cat makes a happy meow, the noise canceling headphones does not make a sad meow noise.

The happy meow makes a sound wave

Think of these waves like waves in the ocean

If you were to send the exact same wave from the beach towards the ocean waves, imagine what's going to happen.

Both waves hit together at their peaks and you'll notice that after that point, the waves that would reach dry sand will be much lower in height.

So it's the same wave just coming at the opposite direction

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ShouldBeeStudying t1_j2f49sz wrote

If I blare huge sound at my ears it will ruin them. Like gunshots, jet engine or concert speakers. If I blare huge opposite sound at the same time are my ears fine?

Let's ignore the practicality of this please

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DragonFireCK t1_j2f6nlx wrote

If you managed a perfect inverse of the wave, the two waves will cancel enough other out and there will be no sound at all. This means that, with perfect noise cancelation, you could be sitting right on top of a jet engine and would hear nothing and have no damage occur.

Practically, getting a perfect inverse is impossible. You'd need a speaker perfectly aligned between the source of the sound and your ears, and the source will actually be a bunch of different points inside the engine, meaning you need roughly an infinite number of infinitely small speakers and microphones.

I did find a video that shows how the phasing works. Its worth noting that the antiphase (opposite) sound will sound the same as the original if heard on its own.

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