Uni-directional speakers. Yes, apparently it is actually possible! I recently came across this video of a guy in the States named Woody Norris. Woody is an professional inventor, with a huge portfolio from a single-seater helicopter to the hands-free kit for mobile phones. Fortunately for all us audio-addicts he seems to have a keen interest in all things sound related. In the video below Woody demonstrates one of his then most recent inventions, a uni-directional audio speaker to an impressed audience. (A shame he never quite points it at the camera)
In 2004 (when I believe this video was shot) this concept was an entirely new design, and branched out into the military to develop as a non-projectile, non-lethal weapon. It relies on hyper-sonic sound to transmit audio through the air with a very tiny amount of loss. Not only that, but it is capable of being incredibly directional. The directionality of the speaker can be adjusted to cover a wider spread, or focused like a spotlight to reach greater distances. USA today published this article in April 2005 about the new design, and for more information on the inventor himself go here. Superb inventing Woody! You could really imagine this being attached in some way to 3D tv’s to give the viewer binaural audio, as the picture and sound would be relatively similar processes.