Photo: wikipedia commons
Photo: Physical Review of Letters
No longer a Tom Clancy plot twist, new technology promises to make objects invisible to sound waves.Detailed in the Physical Review of Letters, “The Experimental Acoustic Ground Cloak In Air” is no more than a layer of plastic sheets with a bunch of holes punched through them.
During tests, however, this meta-materials placed over a 10 centimeter block of wood bounced all incoming sound-waves off its surface. The testing worked in shallow water and immediate applications could be the cloaking of ships and submarines.
Meta-materials are man-made materials that don’t occur in nature. These in particular were created to force light waves to travel around an object as if it’s not there. If light waves pass by an object instead of bouncing off of it to a persons eye, or radar, the object is essentially “invisible”.
While testing the materials for visual cloaking, researchers found they worked on sound waves in the 1 to 4 kHz range.
Ortwin Hess, a director of Imperial College London’s Centre for Plasmonics and Metamaterials, called the work “a really remarkable experimental demonstration.” He told the BBC:
“It’s a bit more challenging for three dimensions. I don’t see any reason why it shouldn’t be possible but it won’t be just an afternoon’s work.
“The work shows that an object can be hidden from sonar, and protected from incoming sound, but the same principles could be applied in the other direction – that is, containing or directing the sound within a space, for instance in soundproofing a studio or fine-tuning the acoustics of a concert hall.”
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