A researcher at the Lincoln Laboratory at MIT appears to have found a way for recipients to send secret messages directly to the human ear without the need to use specialized communications equipment.
The operator can point the laser at someone in the street. The person hears the transmitted audio, but not others in the same area.
They have developed a laser system that can transmit tone, music, and recorded conversations in an interactive volume to specific people who do not need to wear special equipment.
How it Works
In one study in the journal Optical letter The researchers described two ways to send audio messages via lasers on Friday.
Both use the so-called photoacoustic effect that occurs when sound waves are formed as a result of light absorbing materials. Researchers used water vapor in the air as a material.
"The laser transmits the encoded message to the modulated laser beam and is transmitted directly to the receiver's ear through the photoacoustic effect," the researchers wrote in the study.
One way to do this is to sweep the laser beam at the speed of the sound and change the length of the sweep to encode different audible pitches.
This technology allows you to send sound to people who are more than 8.2 feet away from 60 dB, and can communicate the volume of background music or conversations in the dining room. The person receiving the message can hear the sound without anyone else listening.
The researchers are working to improve the method so that it can work at longer distances.
Another way is to adjust the power of the laser beam to encode the audio message. The researcher said it is quieter but produces clearer results.
This technology can provide a new way for people to communicate in secret. Audio messages can be exchanged in crowded places without others listening.
As transmission distances expand, there may be military-critical applications that are technology-critical. It can help soldiers exchange secret messages on the battlefield. It can also. Use in certain situations, such as weapons of mass destruction, when certain people are secretly alerted to active shooters.
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