Directed sound projectors are freaky shit. Last year when Kinect hacks were still a hot thing I really wanted to pay someone to make a project where cameras picked a person out of the crowd and then shot secret messages directly into their ears, giving the impression of a ghostly whisper just above audible. Or perhaps more insidiously, projecting messages directly into their ear to lead them out of a crowd and into a special area where they’d win a prize. Yeah, win a prize. Definitely wouldn’t lead them into a dark alley and murder them. I’ve learned my lesson there.