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Noise-canceling robots to 'mute' loud conversations in cafe | What if we told you that we can actually silence a noisy table right next to us in a café? (interestingengineering.com)

submitted 1 year ago by [email protected] to c/[email protected]

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Noise-canceling robots to 'mute' loud conversations in cafe | What if we told you that we can actually silence a noisy table right next to us in a café?::undefined

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[–] [email protected] 74 points 1 year ago* (last edited 1 year ago) (16 children)

I've always thought phase cancellation technology could potentially be crazy revolutionary. Seems these guys know what they're doing, but the real challenges come with high decibel levels if I remember right.

If you tried to phase cancel out the sound of a jet engine, it would work and you wouldn't hear it, but you could also have easily just burst your eardrums too, because the sound pressure level is still present, even if the actual sound is inaudible. It's a crazy phenomena.

Edit: the sound pressure level IS cancelled out by destructive wave interference, but if this is knocked even by a matter of milliseconds, the wave is doubled and that's not good for anyone.

Also, on retrospect, phenomena was poor word choice. It's physics.

[–] [email protected] 22 points 1 year ago (9 children)

Wait, what? Doesn’t phase cancellation actually cancel the waves? How can it be inaudible but still present?

[–] [email protected] 4 points 1 year ago (2 children)

Yes, sorry, I didn't phrase that well at all. The sound pressure is actually cancelled out, but with the hypothetical example of the jet engine, anything going wrong could double the dB level instead of cancelling, and because we're talking milliseconds difference, it would be quite easy to go wrong in this sense.

[–] [email protected] 5 points 1 year ago (1 children)

It can't double the dBs. It will only add 3 as dBs are a log scale and +/-3dBs is double/half.

[–] [email protected] 1 points 1 year ago

Oops, yes, this. A perceived doubling!

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