MIT Researchers Use Laser to Transmit Sound into People’s Ears

Brian Taylor
January 30, 2019

Laser technology has been used for several decades and has a wide of applications, including bar code scanning, Lasix eye surgery, and industrial cutting and engraving. Now, laser might be used in hearing technology. Researchers from the Massachusetts Institute of Technology’s Lincoln Laboratory report using two different laser-based methods to transmit various tones, music and recorded speech at a conversational volume.

The MIT researchers demonstrated that a laser can transmit an audible message to a person without any type of receiver equipment in the ear canal. The findings, under the direction of lead author Charles Wynn, were published in The Optical Society journal, Optics Letters.

The new approach is 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 that was transmitted directly into someone’s ear.

“This can work even in relatively dry conditions because there is almost always a little water in the air, especially around people. 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”

–Charles Wynn, lead study author

In the lab, the researchers showed that commercially available equipment could transmit sound to a person more than 2.5 meters away at 60 decibels using a laser sweeping technique. The researchers believe that the system could be easily scaled up to longer distances.

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