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. The system can be used from some distance
away to beam information directly to someone’s ear. 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. MIT 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.
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 beams power which produced a quieter but
clearer result. further research will allow them to scale up the transmission
distance, which could make the technique useful in dangerous situations, such
during a mass shooting.
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