The article mentions using feno-like resonance to transform the frequency response (and phase). The effects of this are localized to a frequency-band around 440 Hz. Interestingly, this is a similar effect as mie-scattering.
Therefore, I am not sure the common knowledge of bass-traps and heavy materials for muffling sounds are actually applicable here.
I suggest reading the article and studying feno resonance.
It's not a question of pressure; a wave has whatever pressure it has. It's a question of frequency (wavelength). Just like a flute can't make tuba sounds, a small one of these can't attenuate large wavelengths. But they make larger flutes that can play lower tones. Could you not just make one of these arbitrarily large to handle an arbitrarily low frequency?
> The most effective material is high mass and flexible, like cork or hemp crete.
Those materials work by providing a physical barrier. This invention is not comparable because it appears to allow air to flow down the pipe but (somewhat) prevents the sound. I guess it should be compared to the performance of acoustic ducting or inline silencers (ie like in a car exhaust).
Thank you for posting about the bass trap, I had never heard of it before and am enjoying spending time learning about it (and the other sound-dampening materials you mentioned)
This makes me wish I could put some bass traps in the wall between one neighbour and me, and something like hemp crete to drown out the sound of the screaming kids from another neighbour!
The article mentions on one hand a high pitched note, but on another hand enough bass to see the subwoofers play it:
"Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away."
You might be being downvoted because you've confused frequency with amplitude. Bass means low frequency / long wavelength. It doesn't say anything about amplitude / pressure.
I am surprised to read that you were downvoted by some. Even if you are completely wrong (I have no idea, I am not a sound engineer), you are trying to provide an opinion and I would simply debate it with you, rather than downvoting.
And it's very unlikely to be a broadband attenuator. Attenuating a single frequency is a neat trick, but most acoustic applications require require something that works a wide frequency range.
Given the breathless tone and the curious turns of phrase, I strongly suspect the author has no background in sound, acoustics, science, or journalism.
I feel like a lot of the comments here are missing the point because this isn't a magic noise-cancelling material.
The neat thing about this is that it works while still allowing air to flow through. Even if it's not blocking broad spectrum sound, it's still useful to block specific narrow frequency ranges. One immediate application mentioned in the article is for drones, which are very loud. Maybe if you put these devices below the fans of a drone, you could make it run much quieter.
It also establishes acoustic metamaterials as a new field of study, so we could soon see significant improvements in this technology - imagine a dynamic version of these rings which can change the frequencies which they block.
Did... no one read the article before upvoting? This can reduce specific frequency sounds by -12db, NOT 94% of "sound". Can /u/dang or someone edit this clickbait title?
The wavelength of 100hz is 56.5 feet. While it may be possible that these rings can attenuate specific high frequencies, they don't [and cannot] reduce all sound in general. To say otherwise would be to defy physics. Assuming the rings aren't vaporware, they could work for specific, constant higher frequency sound sources, like machine hums as mentioned in the article. However, the rings' aesthetic would be useless inside of an MRI machine...
There is a reason existing sound barriers aren't open, because even regular walls block high frequencies. (And not just specific ones that match to a ring's size). The best way to kill frequencies are thick objects (like walls). For a room (like a editing studio or recording booth), it should have a non-symmetrical wall with various recessed spaces to function as sound baffles, at the least.
And lastly, these would be completely useless for low frequencies.
Minor pedantry: 10log(6/100) = -12.2, so you could sort of get the number stated if you assume they meant sound power.
These metamerial, interference based approaches, are not going to be broadband by the standards of physical acoustics.
This could be useful for helping cancel a particular harmonic of a helmholtz resonator.
The real question, to me, is does it still work at high transitional Reynolds numbers, or under full turbulent flow?
Source: End effects during transitional and turbulent flow for Helmholtz resonators (i.e. bass reflex ports) in high output pro-sound loudspeakers has been something I've played around with in the past.
10^(-1.2) = 0.063 so 12 dB down means intensity is reduced to 6.3%, or by 93.7%.
-12 dB is a worthwhile cut if it can be achieved with a barrier that has some good qualities: being unobtrusive, reasonably light-weight, thin, cost effective, perhaps transparent or translucent, etc.
If you double it up, -24 dB may be possible.
Stopping sounds in higher frequency ranges has applications. It won't block your neighbor's thumping bass, but there are other situations that benefit from noise blocking, like appliances with motors.
Like you said, it’s not wideband. This implementation is a notch filter about 50Hz wide. Interesting if you’re looking to reduce a specific source, which can happen. For example to cancel fan noise.
Because of these click-bait titles I am jumping to comments directly to see the validity of articles and I know I am not alone. This actually hurts submissions that are front page worthy.
Maybe. Probably. I'll upvote a headline so it ends up in my "upvoted submissions" list so that I can peruse that list and read things later that looked interesting. Then I'll unvote if I didn't like it.
No, I have not yet adapted to the 'favorite' link.
The article implies that the test stand was running at a fixed frequency. This makes me suspect that this has to be designed to interfere with transmission of sound at a specific frequency, and perhaps isn't capable of eliminating more complex sounds like voices or music.
As someone with disposable income working in an open office, I desperately want to know if this can be used to build something to cancel out human voices more completely than Bose QC-35s.
For voices you need passive sound isolation, not active noise cancelling. Try these: Howard Leight by Honeywell Sync Stereo MP3 Earmuff (1030110), Black https://www.amazon.com/dp/B004U4A5RU/
They also give off a very strong “I’m busy” vibe
If that’s still somehow not enough, wear these concurrently (this is great for planes too): Etymotic High-Fidelity Earplugs, ER20XS Standard Fit, 1 pair, Polybag Packaging https://www.amazon.com/dp/B00RM6Q9XW/
Also recommend the above with these foam tips for longer wear, I’ve done up to 16 hours with only a little discomfort: Shure EABKF1-10M Medium Foam Sleeves (10 Included/5 Pair) for E3c, E4c, E5c, E500PTH, i3c, i4c & SE Earphones (Black) https://www.amazon.com/dp/B0015PN3W6/
Not a fan of the QC-35. I find their ANC headache-inducing, and while the overall sound signature is very good, it's only because of built in DSP doing EQ. The distortion is unbearable.
Thus I use the audio-technica MSR7 at work. At home, I don't need isolation, so I enjoy sennheiser's HD600.
The trick with this material is that it pretty much reflects sound waves. On the way back, these reflected sound waves then crash into the upcoming soundwaves and they cancel each other out.
Headphones with active/acoustic noise cancelling use the same trick, except that they pick up the upcoming sound waves with a microphone and then use a speaker to generate those "reflected" soundwaves.
Actually-reflected soundwaves cannot be as strong as the upcoming soundwaves, so they're never going to fully cancel out the noise. Those generated soundwaves can.
One point is that there's most likely less latency for a soundwave to get reflected vs. picked up by a microphone and then generated by a speaker.
However, to my knowledge our human senses have even more latency than both of those, so I don't think that matters.
I've found that musician earplugs under ear defenders essentially cancels all sound, including human voice.
It's not something I would recommend. It makes me feel uneasy. A dozen people could walk up behind you and watch you work, and you'd never know until they tapped you on the shoulder. If you have any anxiety at all about this, true silence will make it far, far worse.
Noise isn't the only problem with open office layouts. It's just a convenient way to describe it to people who don't understand. If you think it's hard to talk to business people about the problems caused by excessive sound levels, imagine how difficult it is to talk to them about how you feel.
At some level, though, they do know this. Your CEO doesn't have his desk facing the door of his office because that position is the quietest. Try do-si-do'ing his desk one day and see how long that lasts.
Since you mention disposable income, if you can tolerate in-ear monitors I would suggest getting custom-fit silicone IEM. Used with even a very low level of music (or even some white noise generator) they dampen noise like nothing else in my experience. Successfully tested in a work environment with endless yammering, bleeping computer equipment, that mandatory 'shout-speaking' colleague, and even once a guy who let a 1U server running on his desk for a week for testing purposes (because why not).
The only down-side for me was that they are not as quick to pop on and off as regular headphones.
Like others here, I wonder how well this really works, but I applaud the effort nonetheless and I hope to see progress in this area in the coming years!
Better sound blocking tech would really improve people's lives and stress levels, especially people who can only afford to live on busy streets in old apartments without proper sound proofing. No to mention people who want to do music in their apartments without bothering their neighbors.
I'm not sure how you could use it for that. Well, you could put a couple of those things over your ears, but earmuffs already exist. More likely it would be useful for building better mufflers onto noisy equipment. A muffler on musical instruments? I could imagine it fitted to a trumpet perhaps.
Too bad sound perception is logarithmic. 94% is nowhere near as much as one would be led to believe if one did not know what a "decibel" is. Which is just as well I suppose: makes for a very nice, clickbaity headline.
_Many_ people don't get this. People are surprised to discover that a 10W guitar amp is not that much quieter than a 100W one, and even 1W amp can be pretty darn loud, even though it's just 1% of the power.
What does it mean to “cancel” or “block” “94% of sound”? From the paper’s abstract: “Finally, the proposed unit-cell performance is validated experimentally, demonstrating a reduction in the transmitted acoustic energy of up to 94%.”
Does this basically mean amplification by about −12 dB?
Just couple of points about the article.
1- the main focus of the study is to silence the sound while maintaining ventillation, i think comparison with the barrier is not relevant.
2- the structure is deep subwavelength compare to the mufflers size
3- low frequency can still be silenced with this design but need an stiffer material maybe metal
4- experiment is design considering both fabrication limitation ( 3D print size) and the tube material to be effectively work as a waveguide
In physics we are learning about sound waves, and how noise cancelling headphones detect noise and produce waves which are destructive to those incoming sound waves, by matching the amplitude and sending them out at a different time interval. I think future noise cancelling materials will make use of some kind of tech like this.
I don't think materials that simply absorb sound are very efficient.
As a side note, I know that I am old (and grumpy) but was it really necessary for the actual engineers to pose for the leading article picture?
I mean if it was a journalist's or editor's choice to mis-illustrate the invention creating a picture with models I would be fine with it, but the actual engineers/inventors posing for it?
[+] [-] tmikaeld|7 years ago|reply
The most effective material is high mass and flexible, like cork or hemp crete.
Bass-traps also exist, they eat up the energy of sound pressure and are usually large tubes and many of them are needed to make a difference.
So there's a reason that this test is on high-frequencies, not low ones.
EDIT: Fine, down-vote me if you want but it doesn't make it less true [1]
[1] https://www.acousticfields.com/how-do-you-stop-low-frequency...
[+] [-] edejong|7 years ago|reply
Therefore, I am not sure the common knowledge of bass-traps and heavy materials for muffling sounds are actually applicable here.
I suggest reading the article and studying feno resonance.
[+] [-] rdiddly|7 years ago|reply
[+] [-] abainbridge|7 years ago|reply
Those materials work by providing a physical barrier. This invention is not comparable because it appears to allow air to flow down the pipe but (somewhat) prevents the sound. I guess it should be compared to the performance of acoustic ducting or inline silencers (ie like in a car exhaust).
[+] [-] bloopernova|7 years ago|reply
This makes me wish I could put some bass traps in the wall between one neighbour and me, and something like hemp crete to drown out the sound of the screaming kids from another neighbour!
[+] [-] fulafel|7 years ago|reply
"Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away."
[+] [-] IshKebab|7 years ago|reply
[+] [-] simonebrunozzi|7 years ago|reply
[+] [-] ScottBurson|7 years ago|reply
[+] [-] TheOtherHobbes|7 years ago|reply
Given the breathless tone and the curious turns of phrase, I strongly suspect the author has no background in sound, acoustics, science, or journalism.
[+] [-] abainbridge|7 years ago|reply
[+] [-] Mizza|7 years ago|reply
The neat thing about this is that it works while still allowing air to flow through. Even if it's not blocking broad spectrum sound, it's still useful to block specific narrow frequency ranges. One immediate application mentioned in the article is for drones, which are very loud. Maybe if you put these devices below the fans of a drone, you could make it run much quieter.
It also establishes acoustic metamaterials as a new field of study, so we could soon see significant improvements in this technology - imagine a dynamic version of these rings which can change the frequencies which they block.
[+] [-] intertextuality|7 years ago|reply
The wavelength of 100hz is 56.5 feet. While it may be possible that these rings can attenuate specific high frequencies, they don't [and cannot] reduce all sound in general. To say otherwise would be to defy physics. Assuming the rings aren't vaporware, they could work for specific, constant higher frequency sound sources, like machine hums as mentioned in the article. However, the rings' aesthetic would be useless inside of an MRI machine...
There is a reason existing sound barriers aren't open, because even regular walls block high frequencies. (And not just specific ones that match to a ring's size). The best way to kill frequencies are thick objects (like walls). For a room (like a editing studio or recording booth), it should have a non-symmetrical wall with various recessed spaces to function as sound baffles, at the least.
And lastly, these would be completely useless for low frequencies.
[+] [-] phasetransition|7 years ago|reply
These metamerial, interference based approaches, are not going to be broadband by the standards of physical acoustics.
This could be useful for helping cancel a particular harmonic of a helmholtz resonator.
The real question, to me, is does it still work at high transitional Reynolds numbers, or under full turbulent flow?
Source: End effects during transitional and turbulent flow for Helmholtz resonators (i.e. bass reflex ports) in high output pro-sound loudspeakers has been something I've played around with in the past.
[+] [-] kazinator|7 years ago|reply
10^(-1.2) = 0.063 so 12 dB down means intensity is reduced to 6.3%, or by 93.7%.
-12 dB is a worthwhile cut if it can be achieved with a barrier that has some good qualities: being unobtrusive, reasonably light-weight, thin, cost effective, perhaps transparent or translucent, etc.
If you double it up, -24 dB may be possible.
Stopping sounds in higher frequency ranges has applications. It won't block your neighbor's thumping bass, but there are other situations that benefit from noise blocking, like appliances with motors.
[+] [-] atoav|7 years ago|reply
So this could be useful for attenuating small computer fans by 12 db without or adding meandering pipes filled with absorbing foam.
For general acoustics I'd stick to a accuratly calculated and well built diaphragmatic absorber or at least a helmholtz absorbers.
[+] [-] esmi|7 years ago|reply
Like you said, it’s not wideband. This implementation is a notch filter about 50Hz wide. Interesting if you’re looking to reduce a specific source, which can happen. For example to cancel fan noise.
[+] [-] rohan1024|7 years ago|reply
[+] [-] delinka|7 years ago|reply
Maybe. Probably. I'll upvote a headline so it ends up in my "upvoted submissions" list so that I can peruse that list and read things later that looked interesting. Then I'll unvote if I didn't like it.
No, I have not yet adapted to the 'favorite' link.
[+] [-] kebman|7 years ago|reply
[+] [-] lolc|7 years ago|reply
> An “acoustic metamaterial” that can cancel 94 percent of sound _at one frequency_.
I don't see how that could counter the turbulence generated by a jet engine. Maybe that was just the journalist getting ahead of themselves.
[+] [-] danjayh|7 years ago|reply
[+] [-] lolc|7 years ago|reply
[+] [-] IshKebab|7 years ago|reply
[+] [-] afarrell|7 years ago|reply
[+] [-] deegles|7 years ago|reply
They also give off a very strong “I’m busy” vibe
If that’s still somehow not enough, wear these concurrently (this is great for planes too): Etymotic High-Fidelity Earplugs, ER20XS Standard Fit, 1 pair, Polybag Packaging https://www.amazon.com/dp/B00RM6Q9XW/
Also recommend the above with these foam tips for longer wear, I’ve done up to 16 hours with only a little discomfort: Shure EABKF1-10M Medium Foam Sleeves (10 Included/5 Pair) for E3c, E4c, E5c, E500PTH, i3c, i4c & SE Earphones (Black) https://www.amazon.com/dp/B0015PN3W6/
[+] [-] snvzz|7 years ago|reply
Thus I use the audio-technica MSR7 at work. At home, I don't need isolation, so I enjoy sennheiser's HD600.
[+] [-] Sylos|7 years ago|reply
Headphones with active/acoustic noise cancelling use the same trick, except that they pick up the upcoming sound waves with a microphone and then use a speaker to generate those "reflected" soundwaves.
Actually-reflected soundwaves cannot be as strong as the upcoming soundwaves, so they're never going to fully cancel out the noise. Those generated soundwaves can.
One point is that there's most likely less latency for a soundwave to get reflected vs. picked up by a microphone and then generated by a speaker. However, to my knowledge our human senses have even more latency than both of those, so I don't think that matters.
[+] [-] ken|7 years ago|reply
It's not something I would recommend. It makes me feel uneasy. A dozen people could walk up behind you and watch you work, and you'd never know until they tapped you on the shoulder. If you have any anxiety at all about this, true silence will make it far, far worse.
Noise isn't the only problem with open office layouts. It's just a convenient way to describe it to people who don't understand. If you think it's hard to talk to business people about the problems caused by excessive sound levels, imagine how difficult it is to talk to them about how you feel.
At some level, though, they do know this. Your CEO doesn't have his desk facing the door of his office because that position is the quietest. Try do-si-do'ing his desk one day and see how long that lasts.
[+] [-] VanPossum|7 years ago|reply
The only down-side for me was that they are not as quick to pop on and off as regular headphones.
[+] [-] zaroth|7 years ago|reply
Recent studies are mixed as to which has a more deleterious effect on creativity, the coworkers yapping or the heavy metal.
[+] [-] eeZah7Ux|7 years ago|reply
[+] [-] imtringued|7 years ago|reply
[+] [-] jaggederest|7 years ago|reply
[+] [-] nicodjimenez|7 years ago|reply
Better sound blocking tech would really improve people's lives and stress levels, especially people who can only afford to live on busy streets in old apartments without proper sound proofing. No to mention people who want to do music in their apartments without bothering their neighbors.
[+] [-] incompatible|7 years ago|reply
[+] [-] mjmj|7 years ago|reply
[+] [-] m0zg|7 years ago|reply
_Many_ people don't get this. People are surprised to discover that a 10W guitar amp is not that much quieter than a 100W one, and even 1W amp can be pretty darn loud, even though it's just 1% of the power.
[+] [-] chrismorgan|7 years ago|reply
Does this basically mean amplification by about −12 dB?
[+] [-] rezreza|7 years ago|reply
[+] [-] rezreza|7 years ago|reply
[deleted]
[+] [-] WilliamEdward|7 years ago|reply
I don't think materials that simply absorb sound are very efficient.
[+] [-] saagarjha|7 years ago|reply
[+] [-] hatsunearu|7 years ago|reply
Anyone have access to this paper? This is driving me nuts and I want to know, damn it :P
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] tylerg|7 years ago|reply
[+] [-] petra|7 years ago|reply
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] deytempo|7 years ago|reply
[+] [-] jaclaz|7 years ago|reply
I mean if it was a journalist's or editor's choice to mis-illustrate the invention creating a picture with models I would be fine with it, but the actual engineers/inventors posing for it?