I’m not quite sure I buy the physics behind these speakers entirely. The idea is that instead of simply vibrating a driver at the correct frequencies and projecting those vibrations out into the room, you use ultrasonic waves to vibrate only the air molecules along a path, and things outside of that path won’t hear the sound.
It’s my understanding, however, that if the air molecules are indeed being excited, that actually is producing the pressure waves we know as sound, and those waves will propagate normally, albeit in a less directed fashion.
That said, I know that focused sound using reflector dishes like these can certainly be created, but you really have to be in the sweet spot to hear it. Maybe these concept speakers manage to make it practical. But do you really want ultrasonic waves being fired at your head all day long?
[via Dvice]