[ed]

A low tech alternative mentioned in the paper is the Plenum Window. Imagine sliding glass shower doors, but with a bigger gap between panes for airflow. It also claims 10dB reduction, and doesn’t need a computer :)

Also from the paper: typical noise cancellation systems create local dead zones of radius ~1/10th the wavelength of blocked sound. E.g., you can block a 1KHz wave within 3.4cm of an error correcting microphone. Good enough for noise canceling headphones but not a whole room.

This work builds on an earlier finding that you can treat the window itself as a point source. Noise cancellation at its source is much more effective, so this way they’re able to create a dead zone the size of your apartment.

[the_pwner224]

The book Daemon by Daniel Suarez has a similar concept in it. The evil guys put a few cameras and ultrasonic speakers in the room. They can create a localized area of intense sound to really fuck up the good guy's head without any indication of what's going on, as well as beam voices directly into his head - silence on the walkie talkies and no physical indication of what's going on. If you limit yourself to one occupant, and can get good 3d tracking of their ears, then theoretically a few speakers on a pan/tilt mount should be able to do ANC over the entire room. Of course if you have to do it for multiple occupants then you would need a speaker every 6.8 cm.

[Animats]

The audio device mentioned in Daemon exists. It's been tried for advertising. You can buy one if you want.[1][2] The audio quality is not very good, but voice will get through. The main application is museums, where you have one next to each exhibit, pointing down from above.

The problem with creating nulls by cancellation is that you create peaks somewhere else. You could null out one person (maybe only one ear) somewhere in the room, but multiple targets will be really hard.

[1] https://ultrasonic-audio.com/products/

[2] https://www.soundlazer.com/shop/

[the_pwner224]

A conventional speaker creates a sphere of sound. A directional speaker like the one you linked creates a beam of sound. But an array of speakers could create a localized spot of sound by creating sound which would only add up to the target at that location. Of course there would be random fragments of parts of the sound (the unadded components) at other random places where the waves coincide, but for only one person in a room this is effectively the same as having a spot of sound with no other side effects.

I did forget to think that two ears would be like having two different people - there would be two target points where the sound would have to add up/subtract to the target.

[Animats]

That's not how directional ultrasonic speakers work. They exploit the fact that propagation in air is nonlinear. It's not just phase addition.

[hirundo]

So we'll start to see noise cancelling modules integrated with point sources like washing machines, air conditioners, ceiling fans, blenders, etc., will compete at a level >10db lower than now.

Or buy a box of standalone cancelers and stick them where you need them. Like the dog's collar.

Faster please.

[cheerlessbog]

That's with one microphone and presumably a single speaker. I wonder how well one could do with several microphones around the room and several speakers, with their relative positions known accurately and some computing power to generate the best possible reverse sound distribution.

[contravariant]

I reckon the attenuation you can get will be something like the cosine of the phase difference between the speakers. Basically you'd need to them to be much closer than a single wavelength, otherwise they'll amplify the sound, rather than attenuating it.

I reckon you could probably do some extremely local noise cancelling (which would only work for a few people at most), but then the speakers don't only need to balance out the external noise, but also each other, which could require extreme volumes if the distributions of speakers is a bad fit.

[ed]

You’d need a lot of speakers (one every 6.8cm) to get the same coverage with an array inside the room.

[TheOtherHobbes]

And it's a much harder problem, because antiphase sound from multiple sources will interfere with itself and probably also interact with room resonances, potentially making the problem worse in some locations.

[hwillis]

> Imagine sliding glass shower doors, but with a bigger gap between panes for airflow. It also claims 10dB reduction, and doesn’t need a computer :)

Note that this is ~50% reduction in volume, roughly the difference between a loud and normal conversation. Noise cancelling headphones are more like 75%-87%, the difference between a loud conversation and a whisper.

[qznc]

Noise cancelling tech only cancels certain sounds though. Traffic noise works. Voices are not cancelled at all by mine.

[hwillis]

Not all headphones are the same, and for higher frequency, quickly-changing sounds like voices, having some extra processing speed really helps. Better microphones and transducers also make a much larger difference than you'd think.

Acoustic cancellation is used at the room scale to remove vibrations from sensitive scientific experiments. Its not the tech that only works on certain sounds, its the implementations.