The invisibility cloak for SOUND: Plastic pyramid could hide objects from sonar

The invisibility cloak for SOUND: Plastic pyramid could hide objects from sonar Engineers from Duke University in North Carolina, claim the acoustic cloaking device works no matter which direction the sound is coming from The device reroutes sound waves to create the impression that both the cloak and anything beneath it are not there A refined version of the technology could one day be used for sonar avoidance and to refine noise in concert halls It might look like a quirky plastic model of an ancient Egyptian pyramid, but this model is in fact a 3D 'acoustic cloak', created using just a few perforated sheets of plastic. Engineers from Duke University in Durham, North Carolina such as Bogdan Popa who is pictured with the pyramid, claim that unlike other efforts, the acoustic cloaking device works in all three dimensions, no matter which direction the sound is coming from The materials manipulating the behaviour of sound waves in the plastic pyramid, which is constructed using plastic plates with a repeating pattern of holes that are stacked on top of one another, are simply plastic and air. The scientists conducted their tests in the air, but sound waves behave similarly underwater, so the device could one day be used for sonar avoidance. ‘We conducted our tests in the air, but sound waves behave similarly underwater, so one obvious potential use is sonar avoidance,’ he said.