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Researchers create invisibility cloak for sound

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December 22, 2011

Dr. Nicolas Stenger's microstructured polymer plate

Dr. Nicolas Stenger's microstructured polymer plate

Many of the current experimental "invisibility cloaks" are based around the same idea - light coming from behind an object is curved around it and then continues on forward to a viewer. That person is in turn only able to see what's behind the object, and not the object itself. Scientists from Germany's Karlsruhe Institute of Technology have applied that same principle to sound waves, and created what could perhaps be described as a "silence cloak."

For the experiments, Dr. Nicolas Stenger constructed a relatively small, millimeter-thin plate, made of both soft and hard microstructured polymers. Different rings of material within the plate resonated at different frequencies, over a range of 100 Hertz.

When viewed from above, it was observed that sound wave vibrations were guided around a central circular area in the plate, unable to either enter or leave that region. "Contrary to other known noise protection measures, the sound waves are neither absorbed nor reflected," said Stenger's colleague, Prof. Martin Wegener. "It is as if nothing was there."

While the plate is a small-scale proof-of-concept, the principles at play in it could perhaps ultimately be used to shield people in a "cloaked" area from loud background noises, or to keep eavesdroppers who aren't in that area from hearing those peoples' private conversations.

Hopefully, should the technology be developed to that point, it will work better than Maxwell Smart's Cone of Silence.

A paper on the Karlsruhe research was recently published in the journal Physical Review Letters.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
7 Comments

If this is developed further, it could be great for musicians that have to practice at home allot but don't want to disturb family, room mates or neighbors.

Or for people who want to sleep in silence in whilst living or staying in a busy and noisy city.

Oztechi
23rd December, 2011 @ 01:16 am PST

I bet the DoD would be interested in incorporating this technology in the stealth program. No more screaming loud jets/bombers. Can possibly eliminate/reduce sonic booms as well. Same goes for helicopters. Can easily imagine a fleet of choppers running more silent than a parked golf cart in the not so distant future.

ep1s0de
23rd December, 2011 @ 03:02 am PST

The real and best use of this technology will be instantly obvious to any parent....!

Mike Barnett
23rd December, 2011 @ 08:17 am PST

Sorry, all I can think of is Maxwell Smart's "Cone of Silence." http://www.wouldyoubelieve.com/cone.html

Charles G. Gage
23rd December, 2011 @ 10:21 am PST

Silence in specified areas is an often neglected area of research, and so is are harmful effetcs of noise pollution on human mind

I am writing this from india and its 12 at night, and my house is next to a mjaor road( like 5 m fom the back wall of my house ) I can still hear horrible vehiclar noise. It only stops for about 2 hrs every night, and starts at 4 in the morning again

We really need somethine like this, coz soon noise will the biggest cause of psychological problems in our cities.

atul292
23rd December, 2011 @ 10:35 am PST

Silence is golden and will literally make these inventors super wealthy when they get this to work in a consumer product.

Carlos Grados
23rd December, 2011 @ 02:24 pm PST

Few of us know what true silence is like, we are so psychologically adapted to it. If one experiences true silence, one can go mad, and has to hear noise, listen to music, talk to someone or make noise or talk to one self. This does not include people who do some kind of meditation or worship. This invention is for noise reduction, but we can explore the new world of true silence. If not adapted, dissociation occurs.

Dawar Saify
27th December, 2011 @ 11:13 am PST
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