Print 10 comment(s) - last by HomerTNachoChe.. on Jan 21 at 3:35 PM

Nicholas Fang  (Source: L. Brian Stauffer)
The cloak is used to control sound waves underwater

University of Illinois researchers have developed a cloak that can be used underwater to hide objects from sonar and other ultrasound waves. 

Nicholas Fang, study leader and mechanical science and engineering professor at the University of Illinois, along with fellow researchers at the university, have created an acoustic, underwater cloak as a way of controlling sound waves. 

Up until this point, scientists have been trying to push the use of materials that wrap sound around objects instead of absorbing or reflecting it. But turning the concept into a reality has been difficult. 

Now, Fang and his team have made a prototype of a cloak that can make an object seem invisible to a variety of different sound waves. 

"We are not talking about science fiction," said Fang. "We are talking about controlling sound waves by bending and twisting them in a designer space. This is certainly not some trick Harry Potter is playing with."

To make this cloak, researchers used metamaterial, which is a class of artificial materials that are engineered to have altered properties. The cloak is two-dimensional and cylindrical, and has 16 concentric rings of acoustic circuits, where each ring has a different index of refraction. This allows the cloak to help guide sonar and other ultrasound waves. 

"Basically what you are looking at is an array of cavities that are connected by channels," said Fang. "The sound is going to propagate inside those channels, and the cavities are designed to slow the waves down. As you go further inside the rings, sound waves gain faster and faster speed."

Researchers tested the cloak on a steel cylinder, among other objects with different shapes and sizes. The cloaked object was submerged underwater, and when sound wavelengths were transmitted, the sound waves would propagate around the cloak's outer rings and the acoustic circuits actually bent the waves so that they'd wrap around the outside of the cloak. Tests showed that cloak provided "acoustic invisibility" to sound waves from 40 to 80 KHz. 

"This is not just a single wavelength effect," said Fang. "You don't have an invisible cloak that's showing up just by switching the frequencies slightly. The geometry is not theoretically scaled with wavelengths. The nice thing about the circuit element approach is that you can scale the channels down while maintaining the same wave propagation technology." 

Fang and his group would like to see this cloak used as an aid for military stealth, health care and soundproofing, but more research is needed to iron out a few kinks in the technology, such as formation and implosion of bubbles, called cavitation, in fast-moving underwater objects. 

The paper can be found here.

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health care?
By tastyratz on 1/7/2011 7:48:19 AM , Rating: 2
What purpose could this technology serve in healthcare?

RE: health care?
By meepstone on 1/7/2011 4:44:17 PM , Rating: 2
To trick pregnant women there isn't a baby inside them when they get an ultrasound.

RE: health care?
By kontorotsui on 1/10/2011 4:15:55 AM , Rating: 3
They can't admit they developed a technology useful mostly as a first (nuclear) strike, now can they?

By DEVGRU on 1/6/2011 5:39:06 PM , Rating: 5
I think Tom Clancy just got wood. :)

By vol7ron on 1/10/2011 9:57:54 AM , Rating: 2
I don't know enough about this, but the way SONAR works is to bounce soundwaves off an object and make sense of what is returned. If nothing is returned, then couldn't that be a problem in the in shallow coastal waters where something is expected.

I'm also curious what frequencies this applies to. If SONARs use a multi-spread spectrum, then its possible to not have a purpose.

I'd more like to see this applied to roads/highways to reduce noise pollution (if possible).

RE: Hmm
By AnnihilatorX on 1/10/2011 1:22:13 PM , Rating: 1
If nothing is returned, then couldn't that be a problem in the in shallow coastal waters where something is expected.

The sonar sound wave will pass straight through the cloak, hit the beach or sea floor, reflected back and pass straight through the cloak again as if nothing was there. This would therefore still work.

Noise pollution reduction you want sound absorbent material, not a cloak. The former is low tech and widely available. Even trees do the job.

RE: Hmm
By vol7ron on 1/12/2011 10:51:53 PM , Rating: 2
No we're talking about from the road. Trees kind of do the job, but there are many places where trees can't be planted. There was a show on history talking about super highways (like those in China) and this would be good for that.

As for the SONAR, I guess it could reflect the beach back, but I think that would depend on the angle of the material on the other side as well. Something might still be able to sense a disturbance. I don't know why I was down rated, I said then and I'll say it again - still don't know enough about it.

Can I use this to ...
By ekv on 1/8/2011 4:14:20 PM , Rating: 2
1) Cone of Silence

2) keep my computer quiet [the fans on CF Radeon 6970 get to the point of loud and obnoxious].

3) help Ralph Cramden ["... one of these days ... Pow! Right in the kisser! One of these days Alice, straight to the Moon!" 8]

If it doesn't reflect sound...
By sonoran on 1/15/2011 11:35:20 AM , Rating: 2
...won't the enemy sonar just have to look for the blank spot in the image, where no sound was returned? (To give a visual analogy, it'd be like being wrapped in a perfectly black material, that reflects no light. You'd see the big black spot easily.)

By HomerTNachoCheese on 1/21/2011 3:35:23 PM , Rating: 2
"Cloak of Silence" May Give Submarines Additional Layer of Stealth 6/18/09

Just more details than before, and some testing.

"Intel is investing heavily (think gazillions of dollars and bazillions of engineering man hours) in resources to create an Intel host controllers spec in order to speed time to market of the USB 3.0 technology." -- Intel blogger Nick Knupffer

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