While humans can only broadcast
about one percent of their vocal power through their speech, some animals and
mammals are able to broadcast 100 percent. The secret to their long-range
howls? A combination of high pitch, a wide-open mouth and a clever use of the
body's shape to direct sound—none of which are factors that humans can
replicate.
"Will humans ever be able to
call to each other over long distances in an emergency situation, as wild-life
has evolved to do well over millions of years?" asks Ingo Titze, director
of the National Center for Voice and Speech at the University of Utah.
The research is published in
the Journal of the Acoustical Society of America and was funded by
the National Institute on Deafness and Other Communications Disorders.
Moving air efficiently
Animals produce sound by moving air from the
lungs, through the throat, and out of the mouth. The slow-moving air has to be
converted to rapid back-and-forth movement to produce sound. At each stage,
some of that sound power is lost. Only about 10 percent of the aerodynamic
power produced in the lungs makes it to the throat. And the soft tissues in the
throat absorb sound further, Titze says. But then there's the radiation
efficiency—the amount of sound that is transmitted out of the mouth.
It's this calculation that Titze
and Anil Palaparthi, a doctoral student in biomedical engineering are
introducing in this study. "We went back to mathematics that were
available 100 years ago," Titze says. "We looked at a more modern way
of computing it and came up with an efficiency formula."
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