3D Acoustic Cloak Can Hide Objects From Sound

Underwater invisible super lairs may be just around the corner!  Duke engineers have created the first 3D acoustic cloak.  This device can reroute sound waves which makes it seem as if the cloak, and whatever is beneath it, is not there. All it took to make was a few clear pieces of plastic, mathematics most of us will never understand and a lot of time.

No matter which direction sound comes from, the cloaking device works.  The future potential is a lot more impressive than the small pyramid shaped device lets on.  For instance, sonar avoidance and architectural acoustics are just the start.

“The particular trick we’re performing is hiding an object from sound waves,” said professor of electrical and computer engineering, Steven Cummer. “By placing this cloak around an object, the sound waves behave like there is nothing more than a flat surface in their path.”

Cummer and his colleagues investigated the field of metamaterials which are natural materials that have repeating patterns which achieve unnatural properties.  The new acoustic cloak manipulates the behaviour of sound using plastic and air. The device is shaped like a pyramid and looks like many plastic plates with a repeating pattern of holes which have been poked through them.

In order to achieve the illusion that nothing is there, the cloak must change the sound waves direction in order to match what the waves would look like had they been sent across a flat surface.  “The structure that we built might look really simple,” said Cummer. “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.”

In order to test to see if the device works, researchers put a small ball under the cloak then zapped it with sound waves at many different angles.  They followed how the waves responded using microphones, then videoed them travelling through the air.  The videos were then compared to videos that were made with a true flat surface as well as an uncloaked ball.  The result? The device made it seem as if the sound waves had been bounced off an empty surface.

So what is this technology good for?

“We conducted our tests in the air, but sound waves behave similarly underwater, so one obvious potential use is sonar avoidance,” said Cummer. “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.”

So there you have it, the potential is amazing!  Perhaps evil-geniuses have a future in secret lairs after all.  We shall have to wait and see!  As always, if you have any sensible comments regarding this story, please leave your comments in the section below.

[Image via huffingtonpost]

SOURCE: http://phys.org/news/2014-03-world-d-acoustic-cloaking-device.html#ajTabs