Sound has this habit of traveling in more than one direction -- useful in most circumstances, but not so welcome when a person in one room is looking for a little peace and quiet while someone in the next is blasting music. Sound-proofing is one solution to that problem, but some researchers at Caltech say they've now come up with a better one: an acoustic diode that can be tuned to allow sound to pass through in only one direction. As you might expect, however, that's all still very much in the early stages, but the researchers say the technology could eventually could eventually allow for "true soundproofing," or even be used for other purposes, like scavenging sound energy
