Scientists Have Discovered a Shape That Blocks All Sound (fastcompany.com) 179
Scientists have developed an "acoustic meta-material" that can catch certain frequencies passing through the air and reflect them back toward their source. When a loudspeaker was placed into one end of a PVC pipe with a 3D-printed ring of the metamaterial, the ring "cut 94% of the sound blasting from the speaker, enough to make it inaudible to the human ear," reports Fast Company. From the report: Typical acoustic paneling works differently, absorbing sound and turning the vibrations into heat. But what's particularly trippy is that this muffler is completely open. Air and light can travel through it -- just sound cannot. The implications for architecture and interior design are remarkable, because these metamaterials could be applied to the built environment in many different ways. For instance, they could be stacked to build soundproof yet transparent walls. Cubicles will never be the same.
The researchers also believe that HVAC systems could be fitted with these silencers, and drones could have their turbines muted with such rings. Even in MRI machines, which can be harrowingly loud for patients trapped in a small space, could be quieted. There's really no limit to the possibilities, but it does sound like these silencers will need to be tailored to circumstance. "The idea is that we can now mathematically design an object that can blocks the sounds of anything," says Boston University professor Xin Zhang, in a press release. You can see a demo of the noise cancellation device here.
The researchers also believe that HVAC systems could be fitted with these silencers, and drones could have their turbines muted with such rings. Even in MRI machines, which can be harrowingly loud for patients trapped in a small space, could be quieted. There's really no limit to the possibilities, but it does sound like these silencers will need to be tailored to circumstance. "The idea is that we can now mathematically design an object that can blocks the sounds of anything," says Boston University professor Xin Zhang, in a press release. You can see a demo of the noise cancellation device here.
What about flow restrictions? (Score:4, Interesting)
If it lets through normal air flow, can it be used for engine exhausts?
Re:What about flow restrictions? (Score:5, Informative)
rtfa: yes it allows air flow.
yay no more rap/crap/dance/disco/pop/edm (Score:1)
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It can also stop the cries of A/C.
Yes, they mentioned HVAC in the article.
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If it lets through normal air flow, can it be used for engine exhausts?
Not just exhausts, but intakes too. Intakes often have all kinds of stupid silencer junk. And I just replaced a turbo silencer with a straight pipe and now when I get on it the Sprinter sounds like it's in a field of crickets because of turbo noise. I replaced it because it came apart at the seam, but if it were round then it wouldn't need a seam.
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Honda fart cans!
Here is the actual information (Score:5, Informative)
*sigh*
Since the editor and submitter didn't do it,
here [eurekalert.org] is the BU research alert, which includes an image [eurekalert.org] of the new material, and
here [aps.org] is a link to the published paper, from which you can get a DOI number if you want to read about their work.
The acoustic suppressor looks like thick a 3-d printed bushing.
Looks self-contradicting. Anyone? (Score:1)
So they are cancelling sound... but not air flow. ... Even though that is literally the same thing.
I can only guess that it is a low-pass filter.
And the speakers emanated an "irritatingly high-pitched" "screching", but "you would see the loudspeaker's subwoofers thrumming away".
Which one is it?
A single driver, or a whole loudspeaker with a tweeter and a woofer?
I can only gues the author messed up.
And the articles are all way too vague. I wish I could imagine, how a ring would block a pressure wave going th
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So they are cancelling sound... but not air flow. ... Even though that is literally the same thing.
Not really, sound is vibration waves in the air not the flow of air. If it was you wouldn't be able to hear much down wind of you.
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You just have to get larger muffler bearings and tune the oscillating resonator...
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Align the deflector shields, I don't want any exhaust noise to get through!
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And don't forget to reverse the polarity!
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You must first bounce the graviton particle beam off the main deflector dish.
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Best muffler bearings. [kalecoauto.com]
That's a feature, not a bug. (Score:2)
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The sound is reflected, it doesn't just disappear. The echo chamber inside your engine could experience some undesirable effects from all the resonance if the sound does not find somewhere else to radiate out from.
So you didn't RTFA. If you did, you wouldn't post a comment like this.
The basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, they say.
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The sound is reflected, it doesn't just disappear. The echo chamber inside your engine could experience some undesirable effects from all the resonance if the sound does not find somewhere else to radiate out from.
So you didn't RTFA. If you did, you wouldn't post a comment like this.
The basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, they say.
Yeah, that's what reflected means. It's going to bounce off whatever it came from, maybe back the same way again and it will run out of energy after a few trips but it's probably not going to reflect directly back and could go off any way depending on what's producing the sound in the first place.
Sending it down a tube is one thing, there's only one way to go but try it in a complex machine and see what happens.
Re: What about flow restrictions? (Score:2)
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engine exhausts yeah and .. I guess there's some designs like that in some cars tail ends already.
what I'm more skeptical about is turbines and drones and such. as sound is generated on the airflow hitting the outside air anyways. and input side.
and surely if it worked for that well right now, they would have used that as a demo instead of a speaker. just silence a lawnmower or something.
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If it lets through normal air flow, can it be used for engine exhausts?
* looks at aftermarket muffler industry *
Uh, it doesn't look like people want to actually quiet that product...
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If it lets through normal air flow, can it be used for engine exhausts?
* looks at aftermarket muffler industry *
Uh, it doesn't look like people want to actually quiet that product...
One of the articles I read said it doesn't allow sound through- by reflecting the sound back. So if the muffler isn't making sound on the outside- and the sound is reflected back- that means the sound will likely be louder to the people inside the car.
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No. Not all the people in the car. Just the ones inside the exhaust pipe. But, who cares about them anyway?
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Or in those open-back headphones.
You are aware that we have these products that already resolve that problem, right?
Strangely enough, they're called closed-back headphones.
Also, in a word? Earbuds.
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I can easily get a conventional sound attenuator for ductwork that reduces noise by 13 dB or more in the frequencies of speech and higher (lower frequencies are harder), and I won't have to know the frequency ahead of time to tune it.
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According to the report, cubicle walls are the first considered target application. After that, HVAC, MRI and drones! I guess engines don't make much sound.
I have a better list:
the secretary's mouth in my dept harley motorcycles fat mufflers (should be illegal to begin with) juicers blenders coffee grinders factory machinery such as looms heavy equipment any worksite where there is a sign "hearing protection required past this point" squeeking wheel in dining hall food tray carts when I have a fever
It's not a magic thing you can put on something to make it quiet. If it was there would a huge market in childcare.
Re:Make sure to test it on... (Score:5, Funny)
...a bawling kid at night in an airplane at 35,000ft.
If you could blot _that_ out I'd be well impressed.
Ya, but stuffing a kid into a PVC pipe might be going a bit too far, unless, of course, you're on United.
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you just need a wall of these (Score:2)
you just need a wall of these around the kid and they'll reflect the sound back at the kid. I guess the size of the circles in the wall would need to depend on the frequency of the screeching. like, it's not an universal one size fits all(at least I don't see how it would be possible and they do speak about mathematically modelling for "any sound", needing different for different frequencies)
that's the theory anyways. still, it's fastcompany reporting. also it would need to be designed for the sound.
also I'
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Please can we have these installed in shopping centers, lifts, waiting rooms, ... where the owners think it good to blast people there with people cat-a-wailing. I don't like it, many others also do not call it music.
I am stuck in a hotel that had this racket assaulting me when I went down for breakfast. I was told ''Oh, we can't switch that off.''. I'm going to stay somewhere else the next time that I am in this area.
Noise pollution: a plague of our times.
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> If you could blot _that_ out I'd be well impressed.
Some airlines are proud to offer convenient, complimentary child muzzles.
And guns, a new and more effective siliencer? (Score:1)
That's the first application that come to mind.
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ATF here. Do you have a dog?
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I have 5 Great Danes, 2 Pit Bulls, 4 German Shepherds, 3 Rottweilers and 2 Cane Corsos
(In your best Australian accent) That's not a dog. This is a dog. [wfla.com]
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Expecting a dire wolf. Was not disappointed.
Re: And guns, a new and more effective siliencer? (Score:2)
Poor doggie is sick; I has a sad.
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I don't think that empties the magazine on a Glock 19, and especially not on a MP5 or an M4 rifle.
All dogs do is give the cops target practice.
That sounds like a two-stroke exhaust (Score:3)
They are tuned to reflect the exhaust back at the piston to increase the compression... At least in model airplane engines that used alcohol. Haven't seen one of those in a while though.
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They are tuned to reflect the exhaust back at the piston to increase the compression...
IME they're tuned to do the opposite, they produce vacuum so as to better scavenge the exhaust. But maybe they do both?
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See the description and animation on the relevant Wikipedia page.
Wikipedia is cool, but there's more under heaven and earth [cycleworld.com] than is imagined in their philosophy. The exhaust is tuned both to promote scavenging and to increase compression.
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Yeah I guess moving air doesn't create sound, which makes the use of a muffler on the exhaust kind of puzzling.
What is the purpose of the muffler on an exhaust?
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It stops the exhaust catching a cold
Re:That sounds like a two-stroke exhaust (Score:5, Informative)
I hope you aren't being snarky back to the AC (who deserves it) so I don't subsequently look like a moron in what follows, but on the off chance you aren't... The exhaust from a piston engine consists of high pressure, very hot bursts of gas at the exhaust ports. Hot, high pressure, and bursty going into relatively cool outside air -- perfect combination to create a lot of sound. Exhaust manifolds and mufflers combine and smooth out the exhaust bursts to create a smoother flowing, more uniform in time exhaust flow resulting in less noise. There are all kinds of pressure and flow reflections in a good exhaust system to help scavenge the exhaust gases during the exhaust stroke and reduce noise. Even a smooth flow is loud if it is fast and hot enough -- as exemplified by jet engine exhaust, which (I think) makes its noise from turbulent mixing in itself and with the outside air.
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Yes, it's the delta between the ambient air pressure and the pressure out of the nozzle that makes the noise, the drag is basically cavitation at a higher pitch due to medium. If tailwinded, the sound barrier speed goes up too.
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There are all kinds of pressure and flow reflections in a good exhaust system to help scavenge the exhaust gases during the exhaust stroke and reduce noise.
Mostly to reduce noise. Scavenging is generally facilitated in just two places, in the header and in the H/X cross pipe... And inline engines don't have the cross pipe.
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Oh I see. It must be another one of those unreliable wikipedia pages.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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Sorry, still don't see it. You must be the same guy who thinks the speed of the hammer has something to do with the glass breaking.
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Sorry, still don't see it. You must be the same guy who thinks the speed of the hammer has something to do with the glass breaking.
The sound is vibrations within the medium. You are talking about reflecting the medium itself. The sound involved is irrelevant in that regard.
BS article and summary (Score:5, Informative)
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Also, -94% (aka 6%, aka -12 dB by everyone that's not retarded) is not "enough to make it inaudible to the human ear" unless you started out as quiet as "Light leaf rustling, calm breathing" (10 dB).
If something wants to claim to make sound "inaudible to the human ear," it really needs to at least -120 dB (aka -99.9999999999% for dummies).
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6% is 16.6 times = 24.4 dB, but agree - nowhere makes anything inaudible.
120dB is a million times, only -99.9999% - but again, you are correct - you need this level of damping to acheive "inaudible"
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10^(dB/10) converts from dB to a multiplier of sound pressure.
10* log10(P1/P0) converts from a multiplier of sound pressure to dB.
-10 dB reduction results in 10% of the sound.
-20 dB reduction results in 1%.
Assuming a 94% reduction means a reduction to 6% of the original sound, we're talking around -12 dB, which is significant,
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their demo video uses "microphone voltage".
0.05 with their damper and 0.25 without.
also the article quite clearly speaks of needing modelling for different sounds so it's not "any sound" but that it can be tuned for "any frequency".
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Link to the paper (Score:5, Informative)
Re:Link to the paper (Score:4)
The third images from the preview [aps.org] indicates that there is only dampening by 14 dB. This doesn't seem like much.
If this works by reflection, is it even possible to stack more of these in several layers to achieve higher dampening (because the layers would themselves reflect the sound)?
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If this works by reflection, is it even possible to stack more of these in several layers to achieve higher dampening
Directly stack? Probably not. To put several in the same pipe? Probably, but there are likely practical limits on how close they can be to one another and still function.
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Yep, Put some pink noise on that speaker instead of a pure tone, and I bet you could barely hear the range that was notched out.
Re: BS article and summary (Score:2)
So only taking out one band does little, but cant mufflers be designed as a trumpet? You basically blow a mess of noise resembling a tone into one end, and it adds its energy to a single tone via standing wave in tube out the other end. It must direct all energy into that output, there is no way a trumpet is a bandpass filter, since the output tone sounds so much louder than the input, let alone the input muted through a bandpass filter.
Right?
Re: BS article and summary (Score:2)
Iâ(TM)ve played trumpet a little though, the tone is chosen by the keys you press with lip tension choosing something like fifth or octave, so to be clear, the trumpet enforces a tone. What youâ(TM)re saying though is the resonance enforces the lips to vibrate at said tone, so if you tried it with engine, the resonance would actually be screwing up and working against engine?
If so, I wonder if you could make a trombone muffler, that resonates with engine rpm.
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The shape is a little more convenient than a Helmholz resonator for making a ventilating barrier.
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Maybe, but it ain't going to help in an MRI scanner. Whoever said that simply does not understand where the noise in an MRI scanner comes from.
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According to the math it will work for harmonics, presumably the open area will represent an upper limit for that though.
The shape of a husband's ear? (Score:5, Funny)
Works for me.
NSFW (Score:3, Funny)
I'm not sure of the name of the shape, but when we were younger, my wife could sit on my face so that I couldn't breathe... nowadays, I can't hear the stereo.
With 3d printing, peer review should be easy (Score:2)
HVAC (Score:2)
Screw HVAC, can I please get this in the data center !?!?
Over what range of wavelengths? (Score:3)
That said, high pitched sounds are easy to block with (relatively) thin insulation. If this could be made to block the lower end of the spectrum, without the large amount of insulation which that normally requires, I could picture this as being a nice development. Or if you have a mono-toned source of noise, like in the demo. I don't think that's very common though.
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it reflects the soundwaves back though, so you'll still need insulation somewhere on the box...
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Helical tuned sound absorbers? (Score:3)
Sounds like a helical version of this: http://www.deicon.com/tuned-ac... [deicon.com]
Broken record (Score:2)
So, theoretically, if one were to wrap one's wife in this material, then he wouldn't be able to hear her insist that he take the garbage out during the 4th period of the Warrior-Rockets game?
Asking for a friend.
Comment removed (Score:4, Informative)
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The energy would go where most of the energy in fuel goes period, heat. It's not like a turbofan is short of cooling air flow.
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don't look for this to be on aircraft anytime soon... that's my prediction.
My understanding of the phenomenon - which may well be wrong - is that it is already being used in acoustic dampening around aircraft engines, at least according to Wikipedia [wikipedia.org] which says:
"Helmholtz resonators are also used to build acoustic liners for reducing the noise of aircraft engines, for example"
Not the HVAC... (Score:2)
The everpresent hum of central AC is very calming. As long as the outdoor temperature isn't expected to drop below 55, I turn it on in fan mode most nights as a white noise generator. At work it keeps stress low, whenever they turn it off for maintenance the silence throws everyone off.
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Hang on tight, I'm working tangential to your comment on AC sound...
Funny you mention that, I'm addicted to fans.
Living room, bedroom, cubicle; all have fans. Car, fan on high most of the time.
I believe I get 20+ hours of fan every day.
Unless it's terribly hot I camp without a fan (I camp a lot). Of course a chorus of crickets is quite similar to the drone of a fan. Winter is a test in silence, because:
I also have tinnitus (permanent ear ringing - stupid teenager, too many concerts, too little ear prote
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I wouldn't mind the Dyson fan for in the living room to move air but not have to increase entertainment volume to compensate for the noise. But, yes, they are stupid expensive.
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literally night and day (Score:2)
literally night and day
Science in 2019, ladies and gentlemen, they LITERALLY produced NIGHT AND DAY
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This is why a Chevy volt can be quiet on gas (Score:4, Interesting)
Biggest breakthrough (Score:2)
What? I'd say their biggest breakthrough is finding that 94% = 100%.
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In medicine, 94% is "excellent".
94% is 12 dB. Not a lot reduction. (Score:2)
If a talk to you, the sound is around 60 tot 70 dB. A reduction of 12 dB gives a sound of 48 to 58 dB. You can still understand me speaking.
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It would be 24 dB if you were measuring the amplitude of the sound wave, but we hear sound pressure, not amplitude. 12 dB is correct for a sound pressure reduction to around 6%.
And a reduction of 12 dB does take 70 dB to 58 dB (or 60 dB to 48 dB). It is a simple arithmetic subtraction when evaluating sound attenuators. It is not a simple addition when adding serveral sources together, but that's not what the sound attenuator number is.
How do I mount it on a bird? (Score:2)
What nonsense (Score:1)
Come on, everything about this thing has been known for centuries (theories go back to Newtons time) and the fact that it (logically) can only work for a single frequency means it is completely useless for blocking broad spectrum signals.
None of the proposed use cases are going to work with this thing since it only filters a single frequency and almost all noise sources have a bandwidth to them. The proposed applications are simply idiotic given what this thing does.
Moreover, the statement that it will "cut
Highway sound barriers (Score:1)
Maybe useful as a highway sound barrier? Either as a replacement for the current walls to allow airflow, or in addition to.
scraping the barrell (Score:2)
You just know this isn't go to take the world by storm (for some as yet undisclosed reason) when the first press release you encounter is blathering on about silencing MRI machines for the benefit of people who are allergic to synthetic earplugs, and who can't, unfortunately, use the ones made out of solid steel, either, because of the intense magnetic fields.
Marketing person grappling with harsh reality: Gee, the HVAC people have all the volume, whereas the MRI people have all the money.
Probable end result
94% != All (Score:2)
Jesus fuck, Slashdot editors. Did you fail basic elementary school math as well?
Will this work on: (Score:2)
Noise cancelling headphones? (Score:2)