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  (Source: MGM)
So is a flying pyramid/saucer in the works for the CIA and USAF?

Want to make an object indistinguishable from the background?  Well you'll have to develop multiple cloaking technologies to cover common detection modes.
I. Activate the Cloaking Shroud
In the past we've written about optical cloaks, which thus far have been largely confined to the nanoscopic regime.  Optical cloaks make light bend around an opaque object such that the observer seemingly "see through" it.
Duke University has published a new study in Nature Materials that offers another kind of cloaking technology -- acoustic cloaking.  Acoustic cloaks are particularly handy in deep ocean water, where light does not travel far and where sound waves are the primary means of "seeing" one's surroundings.
The device is a hood of sorts that goes over the object you wish to cloak.  It consists of a pyramid, of sorts, with multiple stacked plastic shrouds.  Each shroud has holes in it allowing for the unique routing of sound waves around the object being disguised.

Duke acoustic cloak
Duke's accoustic cloak from schematic to fabrication [Image Source: Nature Materials/Duke]

Mounted to a flying plane or undersea craft, it might resemble a flying saucer or Ra's spaceship from Stargate (the feature film).
II. Building an Acoustic Cloak
Duke Electrical and Computer Engineering (ECE) Professor Steven Cummer describes in a university press release:

The particular trick we’re performing is hiding an object from sound waves.  By placing this cloak around an object, the sound waves behave like there is nothing more than a flat surface in their path.

The structure that we built might look really simple.  But I promise you that it’s a lot more difficult and interesting than it looks. We put a lot of energy into calculating how sound waves would interact with it. We didn’t come up with this overnight.

Professor Cummer was the senior author of the paper and led the effort.  Lucian Zigoneanu, Ph.D, a postdoctoral research in Professor Cummer's lab, and Bogdan-Ioan Popa, Ph.D, a research scientist with the lab, handled the experimental work and fine-grain design.

Duke cloak
Duke research scientist Bogdan-Ioan Popa checks out the acoustic cloak. [Image Source: Duke]

A video of the shroud in action is seen below:

To test the device, the team put a ping pong ball within the unique cloaking shroud and pinged it with sound waves.  

Duke cloak
The object is almost disguised when cloaked, as seen in this sound wave study.
[Image Source: Duke/Nature Materials]

Compared to alternatives, the pyramid showed no trace of the ping pong ball and made the cloaked object and cloaking construct almost invisible.
III. Tuning and Future Applications
The cloak still needs a bit of tuning.  
It does not yet completely disguised the object, even if viewed along a face.  The research team believes that with a bit more tweaking it can be made to provide a near-perfect cloak.

Duke cloak
Duke's cloak needs a bit more tuning. [Image Source: Duke/Nature Materials]

Obviously, cloaking military structures or stealth submarines would be a prime application of the technology, but it may also come in handy in designing materials for better concert halls.  Comments Professor Cummer:

We conducted our tests in the air, but sound waves behave similarly underwater, so one obvious potential use is sonar avoidance.  But there’s also the design of auditoriums or concert halls—any space where you need to control the acoustics. If you had to put a beam somewhere for structural reasons that was going to mess up the sound, perhaps you could fix the acoustics by cloaking it.

The U.S. military is clearly interesting in this novel cloaking technology; the successful project received funding from both the Office of Naval Research (ONR) (N00014-13-1-0631) and the Army Research Office (ARO) (W911NF-09-1-00539). 

Sources: Duke University, Nature Materials, Duke on YouTube

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RE: Not very...
By michael2k on 3/17/2014 6:08:03 PM , Rating: 2
This could also be stowed away while in motion, but deployed when stationary!

Or erected around a very slow moving UUV, akin to a moving depth charge.

Another idea is to hide a microphone, part of an array, so that you can monitor an area without casting shadows.

It's also useful for UUVs that are merely used for recon to monitor an area. Move to an area, undetected, and then send back data without being detected.

RE: Not very...
By marvdmartian on 3/18/2014 8:12:50 AM , Rating: 2
Of course, a submarine is most silent when it's not moving, or moving very slowly, so that sort of takes away any advantage of having this "cloaking device". Not to mention the noise made while deploying it, or stowing it again.

Personally, I'd rather see these placed over top of the cars that have those huge bass speakers, and guys who like to blow their eardrums out. You know the ones. They're the obnoxious a-holes that drown out all other sounds while you're waiting at a red light.

RE: Not very...
By Donovan on 3/18/2014 11:59:49 AM , Rating: 2
You're thinking about passive sonar, but this is designed to avoid active sonar. Deploying it while the sub is stationary (or moving slowly) would still be useful for evasion or sneaking past a blockade.

RE: Not very...
By Reclaimer77 on 3/18/2014 4:15:29 PM , Rating: 2
What are you guys talking about? This isn't the Cold War and we're not out trying to find Captain Ramius of the Red freaking October.

The only nations anymore with a true first-rate nuclear blue water Navy is the United States and a handful of our allies.

RE: Not very...
By michael2k on 3/18/2014 5:22:39 PM , Rating: 2
And stealth depth charges/UUVs will keep it that way

"We’re Apple. We don’t wear suits. We don’t even own suits." -- Apple CEO Steve Jobs

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