Scientists Say You Can Cancel the Noise But Keep Your Window Open (nytimes.com) 67
An anonymous reader quotes a report from The New York Times: Researchers in Singapore have developed an apparatus that can be placed in a window to reduce incoming sound by 10 decibels. The system was created by a team of scientists, including Masaharu Nishimura, who came up with the basic concept, and Bhan Lam, a researcher at Nanyang Technological University in Singapore. Their results were published on Thursday in Scientific Reports. The prototype is not yet the most practical device in real world conditions, but it points the way toward the development of technologies that may help ease the strain of noisy city living.
Borrowing from the same technological principles used in noise-canceling headphones, the team expanded the concept to fit an entire room by placing 24 small speakers in a window. The speakers emit sound waves that correspond to the incoming racket and neutralize it -- or, at least some of it. The system is based on the frequency of the sound waves and, for now, the optimal range is between 300 and 1,000 hertz. [...] The system uses a microphone outside the window to detect the repeating sound waves of the offending noise source, which is registered by a computer controller. That in turn deciphers the proper wave frequency needed to neutralize the sound, which is transmitted to the array of speakers on the inside of the window frame. The speakers then emit the proper "anti" waves, which cancel out the incoming waves, and there you have it: near blissful silence. Unfortunately, there are some limitations. The system works best from the types of steady noise sources found within the optimal frequency range and isn't great at neutralizing sporadic noises. Also, since human voices don't fit within most of that range, they won't be canceled out.
Borrowing from the same technological principles used in noise-canceling headphones, the team expanded the concept to fit an entire room by placing 24 small speakers in a window. The speakers emit sound waves that correspond to the incoming racket and neutralize it -- or, at least some of it. The system is based on the frequency of the sound waves and, for now, the optimal range is between 300 and 1,000 hertz. [...] The system uses a microphone outside the window to detect the repeating sound waves of the offending noise source, which is registered by a computer controller. That in turn deciphers the proper wave frequency needed to neutralize the sound, which is transmitted to the array of speakers on the inside of the window frame. The speakers then emit the proper "anti" waves, which cancel out the incoming waves, and there you have it: near blissful silence. Unfortunately, there are some limitations. The system works best from the types of steady noise sources found within the optimal frequency range and isn't great at neutralizing sporadic noises. Also, since human voices don't fit within most of that range, they won't be canceled out.
Maybe more distant microphones could help (Score:2)
It's interesting it only works in such a limited range...
I was wondering if it might work a lot better, if you had several microphones oriented well away from the window at different locations - so you could get directional information on sound, which might in turn use differently oriented speakers to help cancel out particular sounds better coming from different directions.
Or, maybe speakers located at these of the bed facing the window would have a more advantageous position to cancel out noise - then you
Wavelength is the problem for higher frequencies (Score:3)
The systems work by producing the same same sound wave, but in opposite phase.
For a low-frequency sound, the wave is over 10 meters, so the air pressure rises and falls in the entire room and the device can counteract that by doing the opposite.
For high frequency sounds, the wavelength is several millimeters, so the pressure is rising in one of your ears while it's falling in the other ear. There is really to way to counterbalance that with speakers a few meters away. Maybe if you had a million microphones
Re:Wavelength is the problem for higher frequencie (Score:4, Insightful)
Of course two layers of glass, say 6mm and 8 mm with a 50mm airspace between will do a lot more permanently. Now add in a duct, a filter and a small fan and suck in outside air past a filter and blow it in (use a solar panel to power the fan), cleaner and more reliable (when the winds do not blow). Fixed windows and ducted air is probably more sound in reality, health wise and environmentally.
Re:Wavelength is the problem for higher frequencie (Score:4, Funny)
Re: (Score:2)
I've got a double window, but it does not keep out sound, and I've used ear plugs most nights for over a decade. It's not loud noise, but a low rumbling that just keeps going on (strip mall nearby, the sound used to be due to a recycle plant that does all the noisy stuff at night, but sometimes it seems to be just large delivery trucks leaving the engines running). A sharp loud noise doesn't bother me, but the constant low frequency stuff once it wakes you up won't let you get back to sleep. I have at ti
Re: (Score:2)
Re:Wavelength is the problem for higher frequencie (Score:5, Interesting)
No, you can absolutely cancel the sound at an arbitrary location from the source of noise and the cancellation transducers. You just need to track the listener's position accurately. And then accept that everyone else in the room will have a significantly degraded (louder) experience. But you can cancel anywhere you want - it's just a matter of getting the phase correct at the receiver (listener) position.
And yes, I design audio products - including ANC headphones - for a living.
Re: (Score:1)
Re: (Score:2)
You can cancel noise for everyone too, it's just less effective and more limited in scope than headphone based cancellation.
Look up industrial noise cancelling for things like fans and motors. It only works with fairly low frequencies and where there is some constraint on the sound (e.g. a manifold that channels it) but it does work. Some car manufacturers also use it to reduce engine and road noise, again at low frequencies.
Both ears? (Two positions) (Score:2)
> No, you can absolutely cancel the sound at an arbitrary location from the source of noise and the cancellation transducers. You just need to track the listener's position accurately. And then accept that everyone else in the room will have a significantly degraded (louder) experience.
Can you cancel it at TWO positions I choose? That seems quite a bit more difficult because anything you do to cancel it at one position may very well make it louder at the other position.
That's important, because most peo
Re: (Score:2)
It depends. If the noise is coming from a single distant point, the wavefront through the window can be mostly cancelled.
More source points spread over wide angles, and shorter wavelengths, makes the job more difficult and impractical.
Re: (Score:2)
Two positions, like ears, where the spacing is fairly constant? Yes, yes I could. Two positions that constantly vary not just in relation to the source of the noise and cancellation signal, but to each other? Damn near impossible without a LOT of advanced tracking systems and highly networked processing (each cancellation network would need to know completely about the other network, and compensate for each other).
By the way, the ears are about 180mm apart, so about 2 kHz. You can absolutely cancel to f
Re: (Score:2)
> Two positions, like ears, where the spacing is fairly constant? Yes, yes I could. Two positions that constantly vary not just in relation to the source of the noise and cancellation signal, but to each other? Damn near impossible
That's interesting. Specifically, let me clarify that the difference in distances from ears to device changes. In other words, if the listener is looking at the device, both ears are 1 wavelength away. It's as if there's is no distance between the ears. If the listener turns
Re: (Score:2)
Re: (Score:3)
I don't know how you've ended up with that!
Velocity = Frequency * Wavelength.
Speed of sound is about 340 m/s in air at one atmosphere.
Hence wavelength = 340/20,000 = about 0.017m, (17mm).
My suspicion is that you've used the speed of light instead of the speed of sound here...
Re: (Score:2)
I was wondering if it might work a lot better, if you had several microphones ...
It works best if you simply roll your windows all the way up and use the A/C. :-) Besides, the Mythbusters already demonstrated that cars (theirs anyway) got better mileage with the windows up and A/C on.
Re: (Score:2)
Re: (Score:3)
Re: (Score:2)
I suspect that you could get a similar level of attenuation by building a section of S-shaped duct lined with sound baffling material and place that in the window opening. No active electronics and it can attenuate high frequencies pretty well.
If the duct reduces air flow too much, a few muffin fans can be added, which will provide an additional benefit of producing some white noise (sorry if that's not P.C.).
Could make for some chilling movie scenes (Score:3, Interesting)
It's also kind of a pretty apt metaphor for modern society: try to block out what is going on right outside your window as much as possible so that you can focus on more important things (like the latest twitter trends, etc.).
Sorry. That's enough cynicism for today.
Re: (Score:2)
Re: (Score:1)
Is this true? How? Please clarify, because I don't believe you and I fear I'm wasting effort trying to understand.
Re: Could make for some chilling movie scenes (Score:3, Informative)
Re: (Score:2)
High sound pressure levels displace oxygen within your body, and can cause a pulmonary embolism, which is something that has been actively researched in the realm of active sonar systems, link below.
No such claim is made by the article you cited. In spite of that article containing no valid scientific information (more on that below).
When one employs active noise cancellation, it does not take all of the energy out of the air, but rather causes constructive interference that redirects that energy.
That would be destructive interference. And it does in fact reduce the energy or intensity of the signal.
https://www.scientificamerican.com/article/does-military-sonar-kill/ [scientificamerican.com]
I'm afraid the Scientific American has really jumped the shark in terms of actual science. "235 decibels" 235 decibels WHAT? Decibels are a ratio between two values, one being a reference level. It could be dbV, dbm, or in the case of sound dBSPL. No legitimate scientis
Re: (Score:3)
I am imagining some apocalyptic event happening outside someone's window and they don't even notice because of something like this. Or a person's child screaming for help right outside while they casually make dinner.
Yeah, imagine such a movie scene, where the protagonist didn't notice because the window was closed.
Are you scared yet?
Re: (Score:2)
Re: (Score:2)
I am imagining some apocalyptic event happening outside someone's window and they don't even notice because of something like this. Or a person's child screaming for help right outside while they casually make dinner.
I'm sure the zombies will ring the doorbell, the child not so much. Why is it that every advance that is technology based is treated with cynicism. You've somehow jumped straight to bad scenarios ignoring that a typical double pane glass, closed window, and wall insulation will already have a far more sound deadening affect than this.
Re: (Score:2)
You've missed an important point: one can always close a window.
This is all about keeping windows open and avoiding too much noise. Their invention cancels about 10 dB. A double-pane window blocks about 30 dB of noise, some special ones block up to 40 dB.
Thus... (Score:2)
cheaper version (Score:5, Funny)
Re: (Score:2)
Re: (Score:2)
And that sets off the same box that three neighbours have which in turn causes your box, along with seven nearby, to play, etc, etc, until there are two alternating rings of "Shut the hell up" continuously playing throughout the city.
10 dB is not enough (Score:3)
A closed double-pane window will reduce noise levels by ~30 dB. The best window vents also provide that much reduction.
At only 10 dB, the reduction would be noticeable, but traffic noise would still be annoyingly loud.
Re: (Score:2)
It depends if a window vent is going to provide enough airflow for your needs.
It would help if buildings were properly designed to facilitate airflow. With the correct positioning of windows and vents you can set up passive air movement through the building, but it's rarely a consideration when copy/pasting standard designs onto a map.
Re: 10 dB is not enough (Score:3)
I'm pretty sure that bedrooms in converted lofts will always be hot and require either venting or active air circulation. Some might be surprised just how much heat even a well insulated roof holds on to even in the UK. I have planes on final approach to Heathrow going over at 500-600m, but it's actually the road a 100m away that bothers me more, so I sleep with the Windows closed even if it's the middle of summer and the room is above 30 degrees. They're going to have to do a lot more than 10dB before t
Re: (Score:2)
I could also add that my Velux skylights have a position for the handle that does some minor venting. it does make much difference to the heat, but it does allow a lot of external higher frequency noise it. I.e. any kind of external venting can quickly become a sound problem.
Re: (Score:2)
There are high-airflow solutions that have good sound reduction. Basically you have to build a labyrinth for the air to go through.
Forget the windows, we need such things near roads (Score:1)
Re: (Score:2)
My neighbourhood has changed over the time I've lived in it from a lot of white collar workers to more trades people. That has mean the quieter cars have gone and been replaced by noise pick-ups. Especially the larger pick-ups like the Ford F-250. There's one guy with a motorcycle that you can hear from blocks away. Annoying as heck.
One thing during this lockdown for COVID-19 is that the traffic has been much lighter and I haven't been hearing these vehicles as much. Or as many airplanes (I'm on the flightp
Finally! (Score:3)
So I won't hear it when the lady upstairs is on her balcony at 3am smoking a cigarette while arguing over the phone with her latest boyfriend.
Oh wait. Shrieking is normally above 1000Hz. Never mind.
Re: (Score:2, Funny)
Re: (Score:2)
It sounds like you need a wooden stake and garlic rather than noise reduction.
Alternatively... (Score:2)
You pricks who leave your dogs at home, barking in the backyard, while you go out to work or whatever you're doing (heck maybe you're at home?)
Maybe you could consider being thoughtful and considerate neighbours and not buy the damn things in the first place if you can't look after them?
Endless problem in suburbs and seemingly getting worse. Best part is to try talking to someone about it, literally 9 times out of 10 the owner takes it personally / aggressively, as if neighbours have no rights to peace an
Only cancells low frequencies (Score:2)
how about you can motorbikes? (Score:2)
Re: (Score:1)
Re: (Score:1)
The "loud pipes save lives" myth has been debunked many times. Hi-viz clothing and a modulating headlight (and in the case you present, not riding in a blindspot) will do a whole lot more to prevent accidents than making more noise.
Re: (Score:2)
Now New Yorkers can ignore murders with excuse (Score:1)
Now New Yorkers can truthfully say they did not hear a thing!
Of course, reality of the New York case in 1964 is that the 911 system had not been invented. So those that tried to call in the murder, may have had trouble finding the correct police precinct and duty officer. But we won't let the truth & insignificant details derail our rant about New Yorker
Ho hum. (Score:1)
A good quality window provides something 30-40dB of sound attenuation. That 10 dB is not going to seem like much if there's any kind of noise outside. The work was a nice school project, though.
Wrong Problem (Score:2)
Instead of trying to reduce the sound in the residence the solution should be to make the sources of mechanically generated sound to disappear or be reduced so that you don't need something like what this article is about in the first place.
In my city they had a bunch of hybrid public buses and they were great because the noise they generated were about half the volume, at least, of a regular diesel engine bus. However the management of the public transit company didn't like hybrid buses and got rid of them
Similar idea (Score:2)
I had a similar idea, I'm glad to see someone actually working on this! My idea was to set up an array of microphones and speakers around your bed so you can sleep more peacefully. I think the system would also need cameras so it could tell where your ears are.
What you actually need (Score:2)
is this [scitation.org].
The idea is your "window" is actually a tuned resonating cavity - it passively blocks sound around the tuned frequency, but lets air through.
The authors claim 30dB+ reduction of sound while allowing air flow. No speakers, no power source.
Hello (Score:1)