3D sound cloaking device makes objects audibly invisible
A cage-like plastic shell composed of several different rings has successfully cloaked an object from soundwaves
A new device which looks like a 3D cage composed of rings of various sizes has successfully cloaked an object from sound waves. The technology could spell new possibilities for reducing noise pollution and allow ships, such as submarines, to successfully avoid sonar detection.
Recent efforts in cloaking have been largely focused on visually cloaking various objects (often subatomic particles). However, the same principles generally apply to sound cloaking as well. Objects are visible (or audible) because electromagnetic waves and sound waves scatter when they come in contact with the objects. The general approach to cloaking is to curve the waves around the object and thus prevent the scattering.
This futuristic ball of rings keeps the sound away
José Sánchez-Dehesa, an electrical engineer at the Polytechnic Institute of Valencia in Spain, has developed a cloak that works differently: Instead of curving the waves, the waves are simply prevented from scattering on contact. By using computer algorithms, a ring-based structure was created which according to simulations would interfere with the scattered waves, thus eliminating them. This is the same technique used by noise-cancelling headphones to eliminate outside noise.
Because the cloaking method employs a fairly simple physical phenomena, a model to test it could easily be produced by Sánchez and his team with a 3D printer. They hung the device from the ceiling of an echo-free chamber and pointed speakers at it. When the speakers played a tone of 8.55 KHz, the cloaked sphere became invisible to the audio sensors behind it.
This marks the first time a three-dimensional object has been cloaked from sound, and should be very promising news to the US Office of Naval Research, which partially funded the study. Despite the discovery though, we’re predictably a long way from sonar-proof submarines at this point.