by Steve Dent, Engadget
It can beam tones, music and speech to someone’s ear from a distance.
Researchers from MIT have discovered a way to send highly targeted audio signals directly to someone’s ear at a distance using laser beams. The system works using the “photoacoustic” effect, where water vapor in the air absorbs light, forming sound waves. The research may pave the way to systems that allow audible messages to be transmitted to spies or other agents, warning them of impending danger like an active shooter.
The team started with a laser beam that fired at wavelengths absorbed by water. By sweeping the beam at the speed of sound, they found that it could be used to generate sound that can only be heard at a specific distance from the transmitter. That would allow a message to be sent to an individual, rather than just anyone who crossed the path of the laser.