MIT: New Tech Uses Laser to Transmit Audible Messages into a Person’s Ear

January 30, 2019

Massachusetts Institute of Technology’s researchers have demonstrated that a laser can transmit an audible message to a person without requiring a receiving device.

Massachusetts Institute of Technology’s researchers have demonstrated that a laser can transmit an audible message to a person without requiring a receiving device. The ability to send highly targeted audio signals over the air could be used to communicate to people across noisy rooms such as an active “shooter”.

In a paper published on January 25, 2019 and entitled “Photoacoustic communications: delivering audible signals via absorption of light by atmospheric H2O” researchers from the MIT’s Lincoln Laboratory report using two different laser-based methods to transmit various tones, music and recorded speech at a “conversational volume” (i.e. at a volume of 60 decibels). Both techniques are based on the “photoacoustic effect”, which occurs when a material forms sound waves after absorbing light. In this case, the researchers used water vapor in the air to absorb light and create sound.

For the 1st technique, the MIT’s researchers “swept” a laser beam at the speed of sound, changing the length of the sweeps to encode different audible pitches. This technique allowed them to transmit sound to a person more than 2,5 meters away at a volume of 60 decibels (the loudness of a conversation in a restaurant, office or a background music) without anyone between the source of the sound and the “target” hearing it. For the 2nd one, researchers encoded an audio message by adjusting a laser beam’s power. They said this technique produced a quieter but clearer result.

“Our system can be used from some distance away to beam information directly to someone’s ear”, said MIT research team leader Charles M. Wynn. “It is the first system that uses lasers that are fully safe for the eyes and skin to localize an audible signal to a particular person in any setting. This can work even in relatively dry conditions because there is almost always a little water in the air, especially around people. We found that we don’t need a lot of water.”

In the lab, MIT researchers showed that commercially available equipment could transmit sound to a person more than 2.5 meters away at 60 decibels using the laser sweeping technique. They believe that the system could be easily scaled up to longer distances, and plan to demonstrate the method outdoors at longer ranges. “We hope that this will eventually become a commercial technology”, said Ryan M. Sullenberger, first author of the paper, “there are a lot of exciting possibilities”.

This voice-beam technology could be very useful for a variety of purposes, but that doesn’t mean it will be used for things that are “good” for the average person, since this kind of technology sets the stage for a number of unintended consequences: in the wrong hands, voice-beam technology can be used for a number of “wicked purposes”.

Full Article: “Photoacoustic communications: delivering audible signals via absorption of light by atmospheric H2O