Scientists
have figured out how to use a laser to transmit audio, ranging from music
to speech, to a person across a room without any receiver equipment — a
potential breakthrough for the future of audio and communication.
“Our system can be used from some distance away to beam information directly to someone’s ear,” Massachusetts Institute of Technology research Charles M. Wynn said in a press release. “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.”
In
a paper published on Friday in the journal Optics
Letters, the MIT team describes how it developed two different methods to
transmit tones, music, and recorded speech via a laser.
Both
techniques take advantage of something called the photoacoustic effect,
which is the formation of sound waves as the result of a material absorbing
light. In the case of the MIT research, that material was water vapor in the
air.
For
one of their methods, the 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 8.2 feet away at
a volume of 60 decibels — about the loudness of background music or a
conversation in a restaurant — without anyone between the source of the sound
and the target hearing it.
For
the other method, they encoded an audio message by adjusting a laser beam’s
power. They said this technique produced a quieter but clearer result.