Duke University researchers have developed the world's first 'invisibility' cloak that can hide anything from sonar, Live Science reported Friday.
The device, made out of perforated plastic, can hide ojects underneath it from sonar by altering the shape and speed of sound waves as they make contact with the device. The sound waves are then reflected off the device's surface, making whatever is underneath it seem invisible, Live Science reported.
News of the sound cloak was published in the journal Nature Materials earlier this month.
Researchers Lucian Zigoneanu, Bogdan-loan Popa and Steven Cummer first tested the device, shaped like a pyramid with holes, by putting a sphere underneath it.
They placed the pyramid inside a mostly empty room with a sound generator. The generator created a "ping" sound that bounced off the pyramid, which was recorded by a microphone from different locations, Live Science reported.
The key to the device is the holes- the sound waves would simply bounce off of it without them. The holes slowed down the sound waves, which were then reflected back as if they were hitting a flat surface, making it seem like the pyramid was not there.
The device could be useful for cloaking larger objects like submarines. However, the researchers said that would be tricky with the presence of water. The vibrations would pass through the cloak and the object inside because of the density of water, unlike air which is less dense.
"The real kicker in trying to transition to water is that there's so much contrast in the material," Cummer told Live Science. "With air and a solid, no sound wave energy gets into the solid."
But the device could be used to help with internal design, such as in auditoriums. The 'invisibility' cloak could be installed in such a way as to mask echoes heard by people who sit all the way in the back, Live Science reported.
