: could you use noise canceling on a speaker?

Question

Could you make a speaker “play” noice canceling to make a cafe, or other noisy enviroment quiet?
Also, could this be used in another interesting way?

In: 67

Answer 1

When you fill something with water, like a glass, and watch the edge where the water is along the glass it makes a line. If you cause ripples in the water, that line along the edge goes up and down. Sound going into your ear is kind of like that line, a single feed travelling into your ear canal.

Noise cancelling headphones take that single source of sound going into your ear, and for every high part of the wave, it counters with a low wave and vice-versa. This is how it cancels noise for your ear specially.

Move that noise cancelation device away from your ear, and it ceases to be a simple line of sound. Now it is the entire surface of the glass of water. Now you have multiple points of sound occurring in multiple locations.

Take three drops and drop it in the water. Each drop causes a ripple effect outward from where it entered the water’s surface. When the ripples of multiple drops meet, the highs become higher and the lows become lower while the highs and lows negate each other at each specific point on the surface. Across the entire surface, simultaneously, the interactions are happening in different ways.

It would be impossible for a single speaker to emit a single sound from, yet another point on that surface (another ripple), that would travel outward with the right pattern of highs and lows to negate every other ripple, because it is itself only a single ripple.

It would be like you dropping a single drop of water into the rippling surface and having that extra drop bring the entire surface to a flat standstill. It won’t happen.

The only option would be to create so much disruption on the surface that you can no longer isolate a single drop’s ripples. This is what white noise does, floods the sound you hear with other sound to disrupt your ear from hearing a particular one. But that single sound isn’t outright cancelled, just diffused in the other noise.