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'Invisibility cloaks' could break sound barriers
Duke University ^ | January 9, 2008 | Unknown

Posted on 01/09/2008 2:03:11 PM PST by decimon

DURHAM, N.C. -- Contrary to earlier predictions, Duke University engineers have found that a three-dimensional sound cloak is possible, at least in theory.

Such an acoustic veil would do for sound what the "invisibility cloak" previously demonstrated by the research team does for microwaves--allowing sound waves to travel seamlessly around it and emerge on the other side without distortion (http://www.pratt.duke.edu/news/?id=792).

"We've devised a recipe for an acoustic material that would essentially open up a hole in space and make something inside that hole disappear from sound waves," said Steven Cummer, Jeffrey N. Vinik Associate Professor of Electrical and Computer Engineering at Duke's Pratt School of Engineering. Such a cloak might hide submarines in the ocean from detection by sonar, he said, or improve the acoustics of a concert hall by effectively flattening a structural beam.

As in the case of the microwave cloak, the properties required for a sound cloak are not found among materials in nature and would require the development of artificial, composite metamaterials (For more about metamaterials, see http://www.ee.duke.edu/~drsmith/neg_ref_home.htm).

The engineering of acoustic metamaterials lags behind those that interact with electromagnetic waves (i.e. microwaves or light), but "the same ideas should apply," Cummer said.

The report by Cummer's team is expected to appear in Physical Review Letters on Jan. 11.

In 2006, researchers at Duke and the Imperial College London used a new design theory to create a blueprint for an electromagnetic invisibility cloak (http://www.pratt.duke.edu/news/?id=433). Only a few months later, the team demonstrated the first such cloak, designed to operate at microwave frequencies (http://www.pratt.duke.edu/news/?id=792).

Cummer and David Schurig, a former research associate at Duke who is now at North Carolina State University, later reported in The New Journal of Physics a theory showing that an acoustic cloak could be built. But that theory relied on a "special equivalence" between electromagnetic and sound waves that is only true in two dimensions, Cummer said. A report by another team had also suggested that a 3-D acoustic cloak couldn't exist. It appeared they had reached a dead end.

Cummer wasn't convinced. "In my mind, waves are waves," he said. "It was hard for me to imagine that something you could do with electromagnetic waves would be completely undoable for sound waves."

This time, he started instead from a shell like the microwave cloak his team had already devised and attempted to derive the mathematical specifications required to prevent such a shell from reflecting sound waves, a key characteristic for achieving invisibility. On paper, at least, it worked.

"We’ve now shown that both 2-D and 3-D acoustic cloaks theoretically do exist," Cummer said. Although the theory used to design such acoustic devices so far isn't as general as the one used to devise the microwave cloak, the finding nonetheless paves the way for other acoustic devices, for instance, those meant to bend or concentrate sound. "It opens up the door to make the physical shape of an object different from its acoustic shape," he said.

The existence of an acoustic cloaking solution also indicates that cloaks might possibly be built for other wave systems, Cummer said, including seismic waves that travel through the earth and the waves at the surface of the ocean.

###

Collaborators on the study included Bogdan-Ioan Popa, David R. Smith and Marco Rahm of Duke; David Schurig of N.C. State University; John Pendry of Imperial College London; and Anthony Starr of SensorMetrix, Inc. in San Diego, Calif.


TOPICS: Culture/Society; Miscellaneous; News/Current Events; Technical
KEYWORDS:
See no evil, hear no evil.

The article doesn't mention sonic booms.

1 posted on 01/09/2008 2:03:12 PM PST by decimon
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To: decimon

BTTT


2 posted on 01/09/2008 2:06:43 PM PST by hattend
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To: decimon

This sounds like something a submariner could use.


3 posted on 01/09/2008 2:07:07 PM PST by numberonepal (Don't Even Think About Treading On Me)
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To: decimon
Cone of Silence
4 posted on 01/09/2008 2:08:38 PM PST by peyton randolph (tag line taking a siesta)
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To: peyton randolph
WHAT?
5 posted on 01/09/2008 2:12:26 PM PST by KarlInOhio (Rattenschadenfreude: joy at a Democrat's pain, especially Hillary's pain caused by Obama.)
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To: decimon

6 posted on 01/09/2008 2:13:42 PM PST by Hegemony Cricket (Although most dead people vote democrat, aborted babies, if given the choice, would vote Republican.)
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To: numberonepal
This sounds like something a submariner could use.

Yeah, they mentioned that. Good thing they didn't have this in WWII or we wouldn't have those cool submarine movies. ;-)

7 posted on 01/09/2008 2:15:16 PM PST by decimon
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To: Thud

fyi


8 posted on 01/09/2008 2:16:44 PM PST by Dark Wing
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To: decimon

Turn it inside out and mount it on a firearm....Hmm.


9 posted on 01/09/2008 2:17:30 PM PST by Smokin' Joe (How often God must weep at humans' folly.)
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To: KarlInOhio
From the show Get Smart - "Another of the show's recurring gags was the Cone of Silence. Smart would pedantically insist on following CONTROL's security protocols; when in the Chief's office he would insist on speaking under the Cone of Silence--two transparent plastic hemispheres which were electrically lowered on top of Smart and the Chief--which invariably malfunctioned, requiring the characters to shout loudly to even have a chance of being understood by each other, and even then, most of the time that failed. In one episode, the device worked so badly that an outside observer, who could hear everything spoken inside, had to relay messages to the people inside because they could not even hear each other. At other times, the Cone of Silence would malfunction while being lowered and fail to stop at the proper desk level; the device would then repeatedly crush down onto Agent 86 and the Chief, resulting in loud anguished screams. The Cone actually worked as intended once. However, at the end of the conversation, the Cone malfunctioned leaving the Chief trapped within, with silent screams of frustration as Agent 86 walked away."
10 posted on 01/09/2008 2:17:39 PM PST by peyton randolph (tag line taking a siesta)
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To: decimon

someone put one over Hillary and they’ll be granted sainthood.


11 posted on 01/09/2008 2:18:55 PM PST by WOBBLY BOB (I think I'll buy everyone a carbon credit for Christmas.)
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To: nnn0jeh

ping


12 posted on 01/09/2008 2:23:31 PM PST by kalee (The offenses we give, we write in the dust; Those we take, we write in marble. JHuett)
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To: Locomotive Breath

ping


13 posted on 01/09/2008 2:25:05 PM PST by krb (If you're not outraged, people probably like having you around.)
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To: decimon
The article doesn't mention sonic booms.

You're thinking of this technology in the wrong way.

Sonic booms are generated by aircraft moving faster than the speed of sound. If an aircraft is made of this new theoretic material, it would still be moving faster than the speed of sound and would still generate a 'sonic boom'.

However, any item made of this material that is in the path of the sound waves produced, would not disrupt the waves at all.
This is why the most exciting application would be in submarine stealth technology. No disruption of sonar (sound) waves, no way to detect the presence of the sub that is outfitted with this new material. Think of the possibilities.

14 posted on 01/09/2008 2:33:16 PM PST by Bloody Sam Roberts (Great spirits will always encounter violent opposition from mediocre minds.)
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To: Bloody Sam Roberts
"Such an acoustic veil would do for sound what the "invisibility cloak" previously demonstrated by the research team does for microwaves--allowing sound waves to travel seamlessly around it and emerge on the other side without distortion (http://www.pratt.duke.edu/news/?id=792)."

< >

"Cummer wasn't convinced. "In my mind, waves are waves," he said. "It was hard for me to imagine that something you could do with electromagnetic waves would be completely undoable for sound waves.""

Oil is oil.

I have no idea if this could apply to sonic booms. Just thought I'd raise the question.

15 posted on 01/09/2008 2:41:43 PM PST by decimon
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To: decimon
I have no idea if this could apply to sonic booms. Just thought I'd raise the question.

Electromagnetic radiation consists of photos, and travels through a medium. Sound waves are comprised of oscillations in the medium itself.
16 posted on 01/09/2008 2:52:22 PM PST by zencat (The universe is not what it appears, nor is it something else.)
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To: peyton randolph
Thus the "WHAT!" I always remember the Chief and Smart having a hard time hearing each other while using the Cone of Silence.
17 posted on 01/09/2008 3:01:23 PM PST by KarlInOhio (Rattenschadenfreude: joy at a Democrat's pain, especially Hillary's pain caused by Obama.)
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To: Hyzenthlay

ping


18 posted on 01/09/2008 3:06:45 PM PST by metmom (Welfare was never meant to be a career choice.)
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To: zencat

“Electromagnetic radiation consists of photos”

I have seen these photos.


19 posted on 01/09/2008 3:08:25 PM PST by UCANSEE2 (Just saying what 'they' won't.)
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To: decimon

Metamaterials.

Guess we are going to have to develop a bit more in the field of metaphysics.


20 posted on 01/09/2008 3:09:34 PM PST by UCANSEE2 (Just saying what 'they' won't.)
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To: zencat

“Electromagnetic radiation consists of photos, and travels through a medium. Sound waves are comprised of oscillations in the medium itself.”

Same difference.


21 posted on 01/09/2008 3:12:23 PM PST by UCANSEE2 (Just saying what 'they' won't.)
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Development and full-scale production of such a product can’t arrive soon enough ... and mandated for those cranium-pounding harmonic frequency generators installed in some vehicles today. I swear that being exposed to that shit while in my car drives me nauseously psycho.


22 posted on 01/09/2008 3:21:09 PM PST by Orbiter
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To: peyton randolph

well, there goes my transparent cape invention.


23 posted on 01/09/2008 3:55:52 PM PST by Para-Ord.45
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To: decimon; rdb3; Calvinist_Dark_Lord; GodGunsandGuts; CyberCowboy777; Salo; Bobsat; JosephW; ...

24 posted on 01/09/2008 3:57:36 PM PST by ShadowAce (Linux -- The Ultimate Windows Service Pack)
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To: Bloody Sam Roberts

bump for later read


25 posted on 01/09/2008 4:03:43 PM PST by Captain Beyond (The Hammer of the gods! (Just a cool line from a Led Zep song))
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To: WOBBLY BOB

especially when she laughs


26 posted on 01/09/2008 4:07:44 PM PST by TomasUSMC ( FIGHT LIKE WW2, FINISH LIKE WW2. FIGHT LIKE NAM, FINISH LIKE NAM)
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To: decimon
I have no idea if this could apply to sonic booms.

Oh, it was my first thought as well. But on further thought...sound waves passing harmlessly around an aircraft is different than the air that is displaced which creates a shockwave.

Now, if a material can be produced that does the same for radar energy. Whooppeee!

27 posted on 01/09/2008 4:08:12 PM PST by Bloody Sam Roberts (Great spirits will always encounter violent opposition from mediocre minds.)
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To: decimon
The article doesn't mention sonic booms.

Here's why: "Such an acoustic veil would do for sound what the "invisibility cloak" previously demonstrated by the research team does for microwaves--allowing sound waves to travel seamlessly around it and emerge on the other side without distortion."
28 posted on 01/09/2008 4:20:57 PM PST by aruanan
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