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

74 points
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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.

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9 points

We can start with cancelling my neighbor’s dog at 6AM and work our way up to jet tarmac zen garden.

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22 points

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

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24 points

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.

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3 points

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

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2 points

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.

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4 points

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.

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5 points

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

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18 points

Besides what you mention, I have my reservations about ‘crazy revolutionary’. If I remember correctly, noise cancelling only works in one very concentrated spot where the waves are measured and cancelled out. If you move a couple of inches, the cancellation isn’t perfect anymore and does practically nothing. That’s why ANC headphones work well (always right by your ear) but any other open application seems implausible to me.

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4 points

Absolutely, this is spot on, but if they can find ways to work around this like with these microphone swarms they’re proposing, then there could be a lot more applications for it. Some quite scary.

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2 points

You’re right. Without a demonstration I don’t believe it works. Could be a misunderstanding on the part of the author trying to interpret what the inventors are saying…

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3 points

Wouldn’t this system cause more noise for people on other tables around you?

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2 points

Yes when the path between the noise and the noise canceling is out of phase the sound will be lower when they are in phase it will be amplified. Their canceling speakers will need to be very directional to stop this from happening

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48 points
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What if we told you that we can actually silence a noisy table right next to us in a café?

I’d say we almost certainly have different definitions of what ‘silence’ means.

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11 points

I can already do that

waves gun

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11 points

*screaming intensifies*

“Whoops, turned it up instead of down, one sec.”

BANG

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15 points

They’re going to use that technology to spy us isn’t?

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17 points

Given that noise cancellation thus far as involved multiple microphones to identify background noise - yes

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5 points

Why does every cool innovation have to have an immediately applicable shitty implication 😭

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0 points

Eh, everything can be used shitty, but it’s often more work to use a cool thing shitty than it is to just be shitty.
Like you could do this, or you can put a cheap directional mic in the ceiling where it has free access to power.

Being able to beat someone to death with a defibrillator doesn’t undermine it’s value as a life saving tool.

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7 points

Why would they do this ? They already do it through your smartphone.

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1 point

They’re different people.

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6 points

This tech isn’t at all needed to spy on you.

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4 points

I was going to say, wouldn’t this require recording of literally every noise around you in order to cancel it out?

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0 points

They already do that in order to cancel everyone sounds, your conversation is the noise of the next table.

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24 points

Forbidden sushi

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5 points
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If only the PCB was white…

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22 points

As an autistic person this technology could actually allow me to access the community without being overwhelmed. This is revolutionary and would change my life.

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