Imagine you want to look to your favorite program on television, but you don't want to disturb the other persons in the room. You could of course try a headphone, but holosonics now comes up with a way more pleasant solution.Researchers of the MIT (Massachusetts Institute of Technology) have managed to create a source that emits sound in a very narrow and directed band. When you are standing in the path of the wave, you can hear the noise and the person that is next to you won't hear it. This makes it possible for everyone in the car or airplane to listen to their own music, while not having to wear a headphone. The ultrasound, whose wavelengths are only a few millimeters long, are much smaller than the source, and consequently travel in an extremely narrow beam. Of course, the ultrasound, which contains frequencies far outside our range of hearing, is completely inaudible. But as the ultrasonic beam travels through the air, the inherent properties of the air cause the ultrasound to distort (change shape) in a predictable way. This distortion gives rise to frequency components in the audible bandwidth, which can be accurately predicted, and therefore precisely controlled. By generating the correct ultrasonic signal, we can create, within the air itself, essentially any sound desired.
Source: holosonics.comAdded: 22 February 2007