Re: Human Language. (long post)
Thomas Clarke (clarke@acme.ucf.edu)
13 Jan 1997 13:43:24 GMT
In article <seagoat.804.003B66AD@primenet.com> seagoat@primenet.com (John A. Halloran) writes:
>, low-pitched sounds require more energy to produce.
Not so. This is one area about which I have some expertise.
Producing a sound at a given sound pressure level (SPL) does not require
more or less energy (power really) as the frequency is varied.
Human hearing, however, has quite variable sensitivity. Being maximumum
in the midrange (about 3000 Hz) and dropping to zero at about 20 Hz,
and 20,000 Hz depending on age etc. Look for Fletcher-Muenson curves
in a book on human factors. THese are the standard curves used in
designing PA systems and the like.
Thus to produce the same apparent loudness at 30 Hz as at 3000 Hz in
the ear of the listener, a higher SPL, more power, is required.
To that extent you are correct.
On the other hand, in the hunting context of long distance sound
projection, the absorption of sound by air is much less at lower
frequencies than at higher frequencies. This is why distant
thunder is only a low rumble. The high frequencies that would make
the "crack" or nearby lightning have been absorbed.
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.
Tom Clarke
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