Invisibility cloaks have been making headlines recently, whether underwater or in labs. They're great for keeping you out of sight, but what if you want to move silently too? There's the newly developed "silence cloak".
It works on the same principle as conventional invisibility systems, light — or in this case, sound — wraps around an object and continues on unimpeded. For his experiment, Dr Nicolas Stenger built a 1mm-thick plate of both hard and soft carbon polymers with each ring of the plate resonating on a different frequency in a 100Hz range. As sound waves were directed at the plate, they resonated through it, rather than being absorbed or deflected. "It is as if nothing was there", said Stenger's colleague, Prof Martin Wegener. [Gizmag]