Directional sound isn't new or classified (Score 1)

The idea of creating a focused beam of sound is not new. What the article refers to as "putting voices in people's heads" really is more like aiming an audio source at them that is so narrowly focused that only they can hear it. The science behind this has been around since the first attempts at sonar, though the technology to make practical use of it probably hasn't been around as long. I remember seeing some program on PBS about some audio company (Bose?) working on this to create speakers in cars that would direct sound to a specific seat.

Read here for a fairly simple explanation.