Why you might soon think you're hearing things: "A technology that beams sound directly into people's ears has advertisers salivating, but as Vito Pilieci writes, critics fear yet another invasion of privacy. After more than a decade of development, technology that directs a beam of sound straight into a person's eardrums is ready for primetime. The technology works by beaming waves of hypersonic sound at a pitch that is undetectable by the human ear. The waves continue until they smash into an object such as a person's body. The waves then slow, mix and re-create the original audio broadcast. If the person steps out of the waves, they are no longer obstructed and are rendered inaudible."