this post was submitted on 21 Sep 2023
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211
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] 22 points 1 year ago (2 children)

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

[–] [email protected] 24 points 1 year ago (2 children)

The waves are canceled (i.e. gone) until something goes wrong. You could end up accidentally causing constructive interference, in which case you my double the sound's amplitude.

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

Thankfully double would only be 3db, and 10db is about a doubling by our perception?

[–] [email protected] 14 points 1 year ago

Yes - but 3db is twice the energy, which is what matters when it comes to damaging your cochlea

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

I feel like this doesn't happen very often though. I mean I wear sound canceling headphones all the time and I've never noticed it accidentally making anything louder. Then again, I don't normally stand near jet engines.

[–] [email protected] 4 points 1 year ago

I wouldn't imagine noise cancelling headphones would have the ability to output high enough for serious damage. But some people do experience discomfort and pressure when using noise cancelling headphones for the first time, this could be due to a number of factors though.

[–] [email protected] 2 points 1 year ago

My noise cancelling headphones make wind noise much louder when it's really windy.

[–] [email protected] 4 points 1 year ago (1 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!