Re: Human Language. (long post)
John A. Halloran (seagoat@primenet.com)
14 Jan 1997 17:37:03 -0700
In article <5bde5s$fuq@news.cc.ucf.edu> clarke@acme.ucf.edu (Thomas Clarke) writes:
>For a hunter then the best frequency would be a tradeoff between
>the ear sensitivity (which I think can be shown has a maximum
>near the frequency at which the sound wavelength matches the hearing
>apparatus size), the absorption of sound by air and the difficulty
>of producing low frequency sound (this is also difficult if the sound
>producing apparatus is much smaller than the wavelength of sound to
>be generated).
>Possibly there is an explanation here for why men's voices tend to
>be lower than womoen's, but I don't think that descent of the larynx
>can be pegged to the need for long distance acoustic communication.
The vocal tract does appear to act as a resonating chamber that increases the
loudness of the voice (similar to the hollow, egg-shaped resonating chamber
that howler monkeys have evolved from the primate hyoid bone). Note the last
part of this quote from the 1997 Grolier Interactive Encyclopedia.
"The control of vocal pitch is performed by adjustments in the intrinsic
laryngeal muscles. These stretch the vocal folds, making them thinner and
causing them to vibrate at a higher frequency. As a result, the column of air
in the vocal tract is also excited at a higher frequency. In addition, the
entire vocal tract is typically shortened by raising the entire larynx. This
action amplifies higher frequencies. Control of vocal intensity is performed
by adjustments in the flow of air. By using the abdominal muscles to create a
more forceful flow past the vocal folds, the column of air in the vocal tract
is excited to a greater extent with each cycle of vibration. This increases
the perceived loudness of the voice."
Descent of the larynx appears to 1) increase the length/size of the vocal
tract; and 2) facilitate production of lower-pitched sounds.
Regards,
John Halloran
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