Acoustic invisibility cloak
Researchers from Duke University think it may be possible to develop a composite material that would make objects acoustically "invisible." The idea is that sound waves approaching an object wrapped in the material would bend around the object and then keep going. The idea was inspired by the recently-developed "invisibility cloak" that bends microwaves. From National Geographic News:
Previously on BB:
• Invisibility cloak is one step closer after science demo Link
LinkThe most obvious use of an acoustic cloak would be hiding submarines from enemy sonar—sound waves that are used to locate underwater objects.
But the advance could also be used in architecture—in music halls and theaters, for instance.
"Right now . . . the acoustics are built into whatever you're doing structurally," (Duke professor Steve) Cummer said. "So you probably have a set of tradeoffs, structurally and acoustically."
But with acoustic cloaking technology, "a giant beam that might be important structurally and bad acoustically could be rendered acoustically invisible."
Previously on BB:
• Invisibility cloak is one step closer after science demo Link
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I wonder if it would work against all of those high-tech sonic weapons being developed by the military?
I want my cone of silence.
and i'm sure wave-bending has no effect on frequency...
Neon goatse.
and i'm sure researchers at one of the best schools in the country forgot all about frequency when theorizing about this material...
Well, since they're looking at using materials that transmit acoustic vibrations at different rates depending on angle of incidence, they're going to have some heavy math to do in order to account for the phase shift caused by modifying the time domain before retransmitting the vibrations. Also, it may very well fail when dealing with reverberant echoes if the directionality is too specific. I'd put my money on #2's spellbook over Duke's researchers.
Y'know, thinking about this from a practical/non-James Bond standpoint, soundproof stalls in public restrooms would be an ok thing. Not to be crass, but going into a movie theater bathroom to wash your hands and being subjected to a chorus of rattling farts ain't no pik-a-nik basket.
captain pedant writes:
Acoustic invisibility ?
what next, "Inaudible paint" ?
#7 - this isn't about making things soundproof - it's about making them maximally sound-permeable.
oh wow man, see how the graphic vibrates when ya scroll up and down fast!?.....
@#7
What they need is the Oto-Hime.
Or maybe just some music or white noise... though I'd prefer better ventilation.
All I can say, is if they manage to make a wide bandwidth material, absolutely brilliant.
[Warning, High Science content ahead!]
The idea is that you can use all of the nifty tricks that the Electrical and Optical engineers have been messing around with in making negative index metamaterials. The brillant bit is that in this application you are treating light as a wave, so why not use the same math for a different type of wave like a sound wave? You basically have a 3-d array of resonant units, so I imagine that an acoustic meta-material would resemble some sort of structure with a bunch of small tuning forks.
The current problem with negative index meta-materials, is that the "bandwith", or number of different frequencies, is pretty limited; also most meta-materials are pretty lossy. This means you might be able to make a column invisible to high notes or low notes, but not both. Still, this is really only an engineering gripe right now, there is nothing to say it won't be solved.
hmm,so apart from entire submarines, this technology (if developed) could conceal sea mines.
I can't imagine why not. the tricky part is concealing the mine/sub from an active ping. A ping is a close approximation to an impulse function, which is effectively an infinite series of discrete frequencies. To make a "perfect" cloak, you would need to be able to effect enough of these frequencies to fool the sensors of your opponent.
Though talking about the mines vs. sub, I have no idea how radiation within a meta-material volume would react, which is critical for an active system like a submarine. Would it reflect the acoustic energy back inward, shaking the sub apart? Or would the energy be refracted outward in some strange way that would be easily detectable? There is probably a PhD thesis in there somewhere.
an absorbed energy sink? Use it for drive.