Photo credit: HOLGER LANGMAIER / MATT SEYMOUR / TAG HARTMAN-SIMKINS via Science Alert
MIT Lincoln Laboratory researchers have devised a way to send secret whispers directly into a person’s ear by simply pointing a laser at someone from a distance. That person then hears the transmitted audio but others in the same area do not. These special laser systems can transmit tones, music, and recorded speech at a conversational volume to specific people who don’t need to wear any special equipment. Read more for a video and additional information.
How does it work? In the study, published in the journal Optics Letters on Friday, the researchers described two different methods to transmit audio messages through a laser, with both using a photoacoustic effect, which occurs when soundwaves are formed as a result of a material (water vapor) absorbing light. The first involves sweeping a laser beam at the speed of sound and changing the length of the sweeps to encode different audible pitches, enabling you to transmit sound to a person more than 8.2 feet away at 60 decibels. The second method encodes audio message by adjusting the power of the laser beam. One caveat: it produces quieter but clearer results. “A laser transmits the message, which is encoded upon a modulated laser beam and sent directly to the receiver’s ear via the photoacoustic effect,” said the researchers.
