Researchers at MIT’s Lincoln Laboratory, a United States Department of Defense research facility, developed laser systems that can “transmit various tones, music and recorded speech at a conversational volume” to specific people without the recipient wearing any special equipment. Basically, the operator points a laser at someone from a distance and that individual hears the transmitted audio even though others in the area don’t. Conspiracy theorists, start your engines.
Researchers have demonstrated that a laser can transmit an audible message to a person without any type of receiver equipment. The ability to send highly targeted audio signals over the air could be used to communicate across noisy rooms or warn individuals of a dangerous situation such as an active shooter.
The new approaches 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.
“This can work even in relatively dry conditions because there is almost always a little water in the air, especially around people,” said Wynn. “We found that we don’t need a lot of water if we use a laser wavelength that is very strongly absorbed by water. This was key because the stronger absorption leads to more sound.”
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