I was project manager once at a science museum. We had a 6m...

I was project manager once at a science museum. We had a 6m diameter weather balloon filled with CO2 sitting in the middle of the hall. People around the outside could have a clear conversation with people directly on the other side of the balloon, but their conversation could only be heard within a space about 3-500mm wide. On either side of that you could hear nothing. The balloon and CO2 acted like a lens for sound. It was quite eerie, but shows that a sound beam can be focussed as easily as a light beam. If you can shape and direct a beam of sound you can do all sorts of tricks like those you imagine. From what I understand, the arrays can be used to produce more than one beam, so sound can be sent to people in different languages for instance without each hearing the others "beam" apart from a bit of reflection. Just imagine having kids in the back seat playing games and people in the front not being able to hear the crashes and bangs from their games. And yes I know they could be wearing headphones, but then they could not hear you telling them to stop yelling!