| That's actually been done, although no lasers were involved. You can modulate an ultrasonic beam with an audible sound in such a way that someone hit by the beam will hear the audible sound. Ultrasonic beams can be focused into a fairly narrow region. See [1]. They used this in an ad in New York in 2007 for the TV series "Paranormal State", which was premiering soon on A&E. It was a paranormal themed reality show. They had a big billboard for the series on the side of a building, and Holosonic's "audio spotlight" technology on the roof that sent two beams of modulated ultrasound down to the sidewalk. Pedestrians who walked directly into the beams would hear a disembodied voice whispering creepy things like "Who's there? It's not your imagination", but someone next to them who didn't enter the beam would hear nothing. Here's a video [2]. Here's an article about that ad campaign, and it also mentions some other ad uses of the technology [3]. Interesting quote from it: > Joe Pompei, president and founder of Holosonics, said the creepy approach is key to drawing attention to A&E's show. But, he noted, the technology was designed to avoid adding to noise pollution. "If you really want to annoy a lot of people, a loudspeaker is the best way to do it," he said. "If you set up a loudspeaker on the top of a building, everybody's going to hear that noise. But if you're only directing that sound to a specific viewer, you're never going to hear a neighbor complaint from street vendors or pedestrians. The whole idea is to spare other people." [1] https://en.wikipedia.org/wiki/Sound_from_ultrasound [2] https://www.youtube.com/watch?v=qwAeb3RBZ1Y [3] https://adage.com/article/news/hear-voices-ad/122491/ |