» Why you might soon think you're hearing things
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. … Using the technology, marketers can target an audio message at one person in a crowd of hundreds, leaving everyone around that person unaware.