Acoustic Cloaking Device Hides Objects from Sound
Baku, March 13 (AZERTAC). Using little more than a few perforated sheets of plastic and a staggering amount of number crunching, Duke engineers have demonstrated the world’s first three-dimensional acoustic cloak. The new device reroutes sound waves to create the impression that both the cloak and anything beneath it are not there.
The acoustic cloaking device works in all three dimensions, no matter which direction the sound is coming from or where the observer is located, and holds potential for future applications such as sonar avoidance and architectural acoustics.
The study appears online in Nature Materials.
To achieve this new trick, Cummer and his colleagues turned to the developing field of metamaterials—the combination of natural materials in repeating patterns to achieve unnatural properties. In the case of the new acoustic cloak, the materials manipulating the behavior of sound waves are simply plastic and air. Once constructed, the device looks like several plastic plates with a repeating pattern of holes poked through them stacked on top of one another to form a sort of pyramid.
To give the illusion that it isn’t there, the cloak must alter the waves’ trajectory to match what they would look like had they had reflected off a flat surface. Because the sound is not reaching the surface beneath, it is traveling a shorter distance and its speed must be slowed to compensate.
Cummer and his team then compared the videos to those created with both an unobstructed flat surface and an uncloaked sphere blocking the way. The results clearly show that the cloaking device makes it appear as though the sound waves reflected off an empty surface.
Although the experiment is a simple demonstration showing that the technology is possible and concealing an evil super-genius’ underwater lair is a long ways away, Cummer believes that the technique has several potential commercial applications.
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