Humans can 'speak' like bats and dolphins.
An ultrasonic microphone has been
developed to help humans communicate in the manner bats and dolphins do through
ultrasonic waves.
The microphone has been built by
scientists of University of California Berkeley physicists, who used graphene
to build lightweight ultrasonic loudspeakers and microphones, enabling people
to mimic and gauge the distance and speed of objects around them.
"Sea mammals and bats use
high-frequency sound for echolocation and communication, but humans just
haven't fully exploited that before, in my opinion, because the technology has
not been there," said researcher Alex Zettl.
The study appears online in the
Proceedings of the National Academy of Sciences. Speakers and microphones both
use diaphragms, typically made of paper or plastic, that vibrate to produce or
detect sound, respectively.
The diaphragms in the new devices are
graphene sheets a mere one atom thick that have the right combination of
stiffness, strength and light weight to respond to frequencies ranging from
subsonic (below 20 hertz) to ultrasonic (above 20 kilohertz).
Humans can hear from 20 hertz up to
20,000 hertz, whereas bats hear only in the kilohertz range, from nine to 200
kilohertz. The grapheme loudspeakers and microphones operate from well below 20
hertz to over 500 kilohertz.
More practically, the wireless
ultrasound devices complement standard radio transmission using electromagnetic
waves in areas where radio is impractical, such as underwater, but with far
more fidelity than current ultrasound or sonar devices.
They can also be used to communicate
through objects, such as steel, that electromagnetic waves can't penetrate.
"The microphone and loudspeaker
are some of the closest devices to commercial viability, because we've worked
out how to make the graphene and mount it, and it's easy to scale up,"
Zettl said.
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