13 ms·

Engineers create synthetic, sound-silencing structure that blocks 94% of sounds

121 points by fezz 7y ago

rootsudo 7y ago
Now that is cool. I can see it being implemented in HVAC/Central Air. I don't understand how it'd be implemented, in say, an open office?
- Frost1x 7y ago
  Presume you can just tile these in a 2D grid or plane to make a wall you can see and let air flow through but sound is severely canceled. You'd have to cover the ceilings as well to avoid reflectance into other open spaces I'm assuming. As neat as this is, there are a lot of cases where sound is advantageous for us humans regardless of when it being annoying, it often can pass useful information buried in all the rest of the unuseful noise. This is already a problem in some cars where you can't tell if emergency vehicles are nearby/incoming or hear other drivers horn signals. Sometimes you want to ignore this but sometimes it's quite useful.
  - standyro 7y ago
    This article neglects to mention that scientists and architects in Silicon Valley have recently discovered an amazing new technology to improve productivity for workers in open office plans. It involves creating four directly connected acoustically designed walls made out of acoustic foam and eco friendly recycled wood with a fifth addition of a wall above the cubicle, with a removable door. Interior designers have coined a new term for this luxury: "private offices"
    - erentz 7y ago
      Don't forget that Silicon Valley and aspiring Silicon Valley companies in order to "be hip" and look like they rented the cheapest warehouse-esque startup space they could find, require all ceiling tiles be removed to ensure maximum possible sound reflection in their open plan offices.
    - amluto 7y ago
      Acoustic foam? As I understand it, plain old fiberglass or rock wool batts are considerably more effective as acoustic material in a stud bay.
hlieberman 7y ago
Reading the underlying paper (Ghaffarivardavagh, R., Nikolajczyk, J., Anderson, S., & Zhang, X. (2019). Ultra-open acoustic metamaterial silencer based on Fano-like interference. Physical Review B, 99(2)), this works on a particular frequency that you can design one of their mufflers for. A 10Hz change to either side of the target drops the effectiveness from 95%+ down to below 50%. Still very cool, and extremely useful for sources like turbines and HVAC systems that are primarily one or two frequencies, but it's hardly a cone of silence; it won't block out your co-workers anytime soon.
- tensor 7y ago
  I suppose you could stack several of these on a duct, each designed for a different range, to get more coverage?
  - hlieberman 7y ago
    Probably. Still, it's something to cure fan noise, maybe a couple of harmonics -- not the sort of thing that will work on speech.
  - ChuckMcM 7y ago
    Exactly right, just like stacking filters in a signal path. With a 10Hz 3dB point, the bandwidth is 20Hz. Your typical engine exhaust has an acoustic spectrum bandwidth of about 150Hz so a stack of 15 of these would allow you to overlap your filters by 5Hz on either side and notch the entire spectrum out. Depending on how much back pressure it put into the system that could pretty effectively quiet a generator or a turbine.
tsumnia 7y ago
More of an aside, but I really like the article they linked [1] because in addition to scientific explanation, it included a lesson plan and questions for practice. With the spark in "Nifty Assignments" in CS journals, this was a nice feature to include. [1] https://www.lencore.com/Portals/5/Lencore_Docs/Article_UnderstandingAcoustics.pdf https://www.lencore.com/Portals/5/Lencore_Docs/Article_Under...
tmikaeld 7y ago
Last time this was posted, I pointed out that it does not block low frequencies, aka. Bass. Only high mass can do that, the waves pass straight through everything else.
- amluto 7y ago
  I see no reason at all that a low-mass engineered structure, meta or otherwise, couldn’t absorb or reflect bass. Silly example: two sheets, with vacuum in between, held apart by an active structure that transmits constant force independently of displacement. This will reflect bass. It may not be practical, but that’s a separate issue.
  - tmikaeld 7y ago
    You'd basically need a vacuum box to contain it and wait until the waves (eventually) run out of energy.
    - AstralStorm 7y ago
      Why vacuum if you want to absorb maximum energy? You want liquid or gel instead. By the way we have these, they're called bass traps.
      - tmikaeld 7y ago
        Sound doesn't travel in a vacuum. Bass traps work by eating up the energy in pressure waves that hit them, there's a lot of waves that don't hit them. Which means that bass traps are only good for minimizing resonances inside an enclosed room, not to stop bass from reproducing through walls or materials.
michaelt 7y ago
Scientists: We've designed a muffler that can reduce 95% of the noise from a single-frequency point source aimed down a plastic pipe. Might be useful for fan noise in ducts. Journalists: Acoustic metamaterial blocks all sound. Soundproof yet transparent walls. Cubicles will never be the same.
- baxtr 7y ago
  Calling FastCompany journalism is like calling McDonald’s a restaurant (I enjoy both from time to time!)
- Angostura 7y ago
  Its fun beating up journalists, but the examples they give are exactly the ones that appear in the press release, which has direct quotes about them from the scientists. https://www.eurekalert.org/pub_releases/2019-03/bu-brd030619.php https://www.eurekalert.org/pub_releases/2019-03/bu-brd030619... So in this case, if you have a bone to pick, it's not with the journalist.
  - dang 7y ago
    > the examples they give are exactly the ones that appear in the press release, That's not true. For example, The Fast Company article says "they could be stacked to build soundproof yet transprent walls. Cubicles will never be the same." The press release doesn't include that. This makes sense because it ties in to the emotionally charged reference to "your coworkers" in the title, which is not a trick that the press release pulls. More significantly, the Fast Company article is written in a cloying hyperbolic style while the press release is pretty neutral. And the titles are beyond comparison, which is probably the most significant thing because titles have the greatest influence on discussion. Many readers have developed allergic reactions to titles like "Scientists have discovered a shape that blocks all sound–even your co-workers", which insult the intelligence so badly. What's interesting is how the journalistic outlet has to be so much more exaggerated and use so many more tricks even than a press release. Presumably this reflects the economics of media vs. that of universities.
alltakendamned 7y ago
While this research is more limited than the title makes it sound, I would very much be first in line if there ever was a technological breakthrough that could really block all sound, without requiring one to completely isolate themselves.
downrightmike 7y ago
This paper came out last year and was on HN https://www.researchgate.net/publication/327274462_A_Review_of_Tunable_Acoustic_Metamaterials https://www.researchgate.net/publication/327274462_A_Review_...
Havoc 7y ago
Soooo....better suppressors for the CIA then?
- BubRoss 7y ago
  Suppressors work by cooling down the exhaust gasses before they reach the air so that they don't create a burst of expansion.
seltzered_ 7y ago
Wonder if this could be applied for use on computers, partly for reducing noise on home machines but interesting if there would be any benefit in noise reduction in datacenters. Or at least an add-on it specialized rack case to quiet down hardware lab environments.
colsandurz 7y ago
94% loss is only 12.2 dB (10 * log10(1-0.94) == 12.2)... not that much. Also, where's the STL if I want to try this myself??
- corporatehobo 7y ago
  Here it is https://www.thingiverse.com/thing:3575092 https://www.thingiverse.com/thing:3575092 I'm going to try it myself.
dharma1 7y ago
Not broadband sound, right?
pentode 7y ago
The way this article is written, we are led to believe that "thrumming subwoofers" are producing an "irritatingly high pitched whine." Seriously? Who writes this stuff?
sinab 7y ago
I'm surprised no one has discussed the possibility of using this device for reducing snoring sound transmission. I need to read the paper [1] more carefully but on first glance it seems like the effectiveness is best around 450 Hz and snoring is about 150Hz [2]. [1] https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.024302 https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.02... [2] https://www.ncbi.nlm.nih.gov/pubmed/12071989 https://www.ncbi.nlm.nih.gov/pubmed/12071989
- AstralStorm 7y ago
  Snoring is too wideband either, and is impulse noise where this is even less effective.
njaremko 7y ago
Original discussion: https://news.ycombinator.com/item?id=19344682 https://news.ycombinator.com/item?id=19344682
ohiovr 7y ago
Could it be used to quiet a submarine turbine?
- AstralStorm 7y ago
  Yes, but not in the useful sense of making the submarine harder to detect with passive sonar, as most of the vibration is transferred directly into water via the transmission. The other modes are better dampened with the usual absorption.
revel 7y ago
Does this mean we're going to get silencers for leaf blowers? If so, how many nobel prizes can they be nominated for?
- AstralStorm 7y ago
  No, leaf blowers are way too wide spectrum for this to work. Most of the noise in them is air moving throw narrow ducts at high velocity.
wizardforhire 7y ago
From the image I’d hardly call that a metamaterial. It’s just a novel shape for a Helmholtz-resonator which if the name didn’t give it away has been known about for a very long time. I will give them credit for stream lining the design process. https://en.wikipedia.org/wiki/Helmholtz_resonance https://en.wikipedia.org/wiki/Helmholtz_resonance
RickJWagner 7y ago
Truly awesome. I hope we get a practical application soon, I'd like to sound-proof a room for musical instrument practice.
proc0 7y ago
We need over-ear headphones with this ASAP. Current noise dampening products are mostly targeted for high dB sounds. It would be nice to have pure silence anywhere with relatively small headphones.

121 points by fezz 7y ago

Now that is cool. I can see it being implemented in HVAC/Central Air. I don't understand how it'd be implemented, in say, an open office?

Frost1x 7y ago
Presume you can just tile these in a 2D grid or plane to make a wall you can see and let air flow through but sound is severely canceled. You'd have to cover the ceilings as well to avoid reflectance into other open spaces I'm assuming. As neat as this is, there are a lot of cases where sound is advantageous for us humans regardless of when it being annoying, it often can pass useful information buried in all the rest of the unuseful noise. This is already a problem in some cars where you can't tell if emergency vehicles are nearby/incoming or hear other drivers horn signals. Sometimes you want to ignore this but sometimes it's quite useful.
- standyro 7y ago
  This article neglects to mention that scientists and architects in Silicon Valley have recently discovered an amazing new technology to improve productivity for workers in open office plans. It involves creating four directly connected acoustically designed walls made out of acoustic foam and eco friendly recycled wood with a fifth addition of a wall above the cubicle, with a removable door. Interior designers have coined a new term for this luxury: "private offices"
  - erentz 7y ago
    Don't forget that Silicon Valley and aspiring Silicon Valley companies in order to "be hip" and look like they rented the cheapest warehouse-esque startup space they could find, require all ceiling tiles be removed to ensure maximum possible sound reflection in their open plan offices.
  - amluto 7y ago
    Acoustic foam? As I understand it, plain old fiberglass or rock wool batts are considerably more effective as acoustic material in a stud bay.

hlieberman 7y ago

Reading the underlying paper (Ghaffarivardavagh, R., Nikolajczyk, J., Anderson, S., & Zhang, X. (2019). Ultra-open acoustic metamaterial silencer based on Fano-like interference. Physical Review B, 99(2)), this works on a particular frequency that you can design one of their mufflers for. A 10Hz change to either side of the target drops the effectiveness from 95%+ down to below 50%. Still very cool, and extremely useful for sources like turbines and HVAC systems that are primarily one or two frequencies, but it's hardly a cone of silence; it won't block out your co-workers anytime soon.

tensor 7y ago
I suppose you could stack several of these on a duct, each designed for a different range, to get more coverage?
- hlieberman 7y ago
  Probably. Still, it's something to cure fan noise, maybe a couple of harmonics -- not the sort of thing that will work on speech.
- ChuckMcM 7y ago
  Exactly right, just like stacking filters in a signal path. With a 10Hz 3dB point, the bandwidth is 20Hz. Your typical engine exhaust has an acoustic spectrum bandwidth of about 150Hz so a stack of 15 of these would allow you to overlap your filters by 5Hz on either side and notch the entire spectrum out. Depending on how much back pressure it put into the system that could pretty effectively quiet a generator or a turbine.

tsumnia 7y ago

More of an aside, but I really like the article they linked [1] because in addition to scientific explanation, it included a lesson plan and questions for practice. With the spark in "Nifty Assignments" in CS journals, this was a nice feature to include. [1] https://www.lencore.com/Portals/5/Lencore_Docs/Article_UnderstandingAcoustics.pdf https://www.lencore.com/Portals/5/Lencore_Docs/Article_Under...

tmikaeld 7y ago

Last time this was posted, I pointed out that it does not block low frequencies, aka. Bass. Only high mass can do that, the waves pass straight through everything else.

amluto 7y ago
I see no reason at all that a low-mass engineered structure, meta or otherwise, couldn’t absorb or reflect bass. Silly example: two sheets, with vacuum in between, held apart by an active structure that transmits constant force independently of displacement. This will reflect bass. It may not be practical, but that’s a separate issue.
- tmikaeld 7y ago
  You'd basically need a vacuum box to contain it and wait until the waves (eventually) run out of energy.
  - AstralStorm 7y ago
    Why vacuum if you want to absorb maximum energy? You want liquid or gel instead. By the way we have these, they're called bass traps.
    - tmikaeld 7y ago
      Sound doesn't travel in a vacuum. Bass traps work by eating up the energy in pressure waves that hit them, there's a lot of waves that don't hit them. Which means that bass traps are only good for minimizing resonances inside an enclosed room, not to stop bass from reproducing through walls or materials.

michaelt 7y ago

Scientists: We've designed a muffler that can reduce 95% of the noise from a single-frequency point source aimed down a plastic pipe. Might be useful for fan noise in ducts. Journalists: Acoustic metamaterial blocks all sound. Soundproof yet transparent walls. Cubicles will never be the same.

baxtr 7y ago
Calling FastCompany journalism is like calling McDonald’s a restaurant (I enjoy both from time to time!)
Angostura 7y ago
Its fun beating up journalists, but the examples they give are exactly the ones that appear in the press release, which has direct quotes about them from the scientists. https://www.eurekalert.org/pub_releases/2019-03/bu-brd030619.php https://www.eurekalert.org/pub_releases/2019-03/bu-brd030619... So in this case, if you have a bone to pick, it's not with the journalist.
- dang 7y ago
  > the examples they give are exactly the ones that appear in the press release, That's not true. For example, The Fast Company article says "they could be stacked to build soundproof yet transprent walls. Cubicles will never be the same." The press release doesn't include that. This makes sense because it ties in to the emotionally charged reference to "your coworkers" in the title, which is not a trick that the press release pulls. More significantly, the Fast Company article is written in a cloying hyperbolic style while the press release is pretty neutral. And the titles are beyond comparison, which is probably the most significant thing because titles have the greatest influence on discussion. Many readers have developed allergic reactions to titles like "Scientists have discovered a shape that blocks all sound–even your co-workers", which insult the intelligence so badly. What's interesting is how the journalistic outlet has to be so much more exaggerated and use so many more tricks even than a press release. Presumably this reflects the economics of media vs. that of universities.

alltakendamned 7y ago

While this research is more limited than the title makes it sound, I would very much be first in line if there ever was a technological breakthrough that could really block all sound, without requiring one to completely isolate themselves.

downrightmike 7y ago

This paper came out last year and was on HN https://www.researchgate.net/publication/327274462_A_Review_of_Tunable_Acoustic_Metamaterials https://www.researchgate.net/publication/327274462_A_Review_...

Havoc 7y ago

Soooo....better suppressors for the CIA then?

BubRoss 7y ago
Suppressors work by cooling down the exhaust gasses before they reach the air so that they don't create a burst of expansion.

seltzered_ 7y ago

Wonder if this could be applied for use on computers, partly for reducing noise on home machines but interesting if there would be any benefit in noise reduction in datacenters. Or at least an add-on it specialized rack case to quiet down hardware lab environments.

colsandurz 7y ago

94% loss is only 12.2 dB (10 * log10(1-0.94) == 12.2)... not that much. Also, where's the STL if I want to try this myself??

corporatehobo 7y ago
Here it is https://www.thingiverse.com/thing:3575092 https://www.thingiverse.com/thing:3575092 I'm going to try it myself.

dharma1 7y ago

Not broadband sound, right?

pentode 7y ago

The way this article is written, we are led to believe that "thrumming subwoofers" are producing an "irritatingly high pitched whine." Seriously? Who writes this stuff?

sinab 7y ago

I'm surprised no one has discussed the possibility of using this device for reducing snoring sound transmission. I need to read the paper [1] more carefully but on first glance it seems like the effectiveness is best around 450 Hz and snoring is about 150Hz [2]. [1] https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.024302 https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.02... [2] https://www.ncbi.nlm.nih.gov/pubmed/12071989 https://www.ncbi.nlm.nih.gov/pubmed/12071989

AstralStorm 7y ago
Snoring is too wideband either, and is impulse noise where this is even less effective.

njaremko 7y ago

Original discussion: https://news.ycombinator.com/item?id=19344682 https://news.ycombinator.com/item?id=19344682

ohiovr 7y ago

Could it be used to quiet a submarine turbine?

AstralStorm 7y ago
Yes, but not in the useful sense of making the submarine harder to detect with passive sonar, as most of the vibration is transferred directly into water via the transmission. The other modes are better dampened with the usual absorption.

revel 7y ago

Does this mean we're going to get silencers for leaf blowers? If so, how many nobel prizes can they be nominated for?

AstralStorm 7y ago
No, leaf blowers are way too wide spectrum for this to work. Most of the noise in them is air moving throw narrow ducts at high velocity.

wizardforhire 7y ago

From the image I’d hardly call that a metamaterial. It’s just a novel shape for a Helmholtz-resonator which if the name didn’t give it away has been known about for a very long time. I will give them credit for stream lining the design process. https://en.wikipedia.org/wiki/Helmholtz_resonance https://en.wikipedia.org/wiki/Helmholtz_resonance

RickJWagner 7y ago

Truly awesome. I hope we get a practical application soon, I'd like to sound-proof a room for musical instrument practice.

proc0 7y ago

We need over-ear headphones with this ASAP. Current noise dampening products are mostly targeted for high dB sounds. It would be nice to have pure silence anywhere with relatively small headphones.