It uses simple plastic sheets with arrays of holes, and could be put to use in making ships invisible to sonar or in acoustic design of concert halls.
Much research has been undertaken toward creating Harry Potter-style "invisibility cloaks" since the feasibility of the idea was first put forward in 2006.
Those approaches are mostly based on so-called metamaterials, man-made materials with properties that do not occur in nature. The metamaterials are designed such that they force light waves to travel around an object; to an observer, it is as if the object were not there.
But researchers quickly found out that the mathematics behind bending these light waves, called transformation optics, could also be applied to sound waves. (more)
