When Harry Potter slips underneath his visibility cloak, he can wander freely, undetected. But what about a cloak of silence, one that completely deadens sound? That's just what scientists from Spain's University of Valencia have designed, on a tiny scale. They wrote about their research in the New Journal of Physics. A paper published last year showed how such a cloak could be made in theory—researchers purpose using materials made up of what are called sonic crystals. These are solid cylinders that can scatter sound waves. The Spanish scientists wanted to figure out the specs to make a real acoustic cloak that could totally reroute sound around a given object. According to their models, it would take about 200 layers of the sound-silencing materials to make it completely impervious to sound waves. They also think that they'll eventually be able to get the same effect with a thinner rendered your ears cover. Among the first applications could be a silent coating for naval ships, so that they're invisible to sonar. But even more important could be wall coverings that would finally protect from those annoyingly noisy neighbors.