Re: My first posting/hearing

[boblong@xxxxxxxxxxx (Robert Long)]

On Wed, 16 Jul 1997 20:24:47 +1300, Colin McKie wrote:

|Mr645@xxxxxxx wrote:
|>=20
|> Most people don't hear beyond 16khz,  The whine of a home TV is around
|> 17.6khz.
|> *
|
|The upper limit of human perception of sound (note that I didn't say
|hearing!) can be more like 27kHz. The 16-20kHz limit is only valid for a
|headphone/signal generator type setup. Also note that European TVs run
|at 15kHz (50Hz frame rate).
|
|That is well off topic, but we shouldn't be too dogmatic about anything
|concerning human perception.=20

It is off-topic, and it's also the subject of a debate that has been
continuing for at least 30 years to my knowledge.  Fact: on average,
women can resolve higher frequencies than men can.  Fact: the ability
to hear high frequencies deteriorates with age.  Fact: exposure to
high sound levels can permanently damage the ability to hear high
frequencies.  Ergo, while 20 Hz to 20 kHz is widely accepted as the
band that needs to be addressed if most listeners are to be unable to
perceive any limitation, the actual range of perceptable frequencies
varies radically from individual to individual.  The debate centers
around just how many can hear higher frequencies, and how much higher
they go.  One informal (and uncorroborated, as far as I know) study
suggests that women under 30 can hear 37 kHz.  And on and on...

That said, the neuro-aural mechanism and the neuro-visual mechanism
are not all that similar, despite Isaac Newton's attempts to squeeze
them into a similar mold.  Based on the 2:1 frequency/wavelength ratio
of the octave (the primary unit, so to speak, of sound perception) and
of the limits of the spectrum to which the eye is sensitive, he
postulated but never proved a relationship between the two.

Back in 1959 Edwin Land (of Polaroid fame) published in Scientific
American a startling series of experiments that had been carried out
evidently in search of a means of color photography with the Land
cameras.  (Polaroid's stock went up as a result of that publication
even though the experiments were worthless in terms of delivering an
instant-print color medium.)  Essentially what they demonstrated was
that there is no direct relationship between the frequency of the
light stimulating the retina and the color perceived in the brain as a
result.  His tentative conclusion was that *in effect* (because no
attempt was made to study the actual neural mechanisms) the brain
wants to perceive a full ROYGBIV spectrum.  When presented only with
an oddball spectrum, it may "stretch" the available information to fit
the ideal paradigm and therefore "see" colors that demonstrably are
absent in terms of wavelength realities.  Fascinating article, which I
recommend to all.  But its implication for the present question is
that the bandwidth of sight is presumably much more fixed than that of
hearing--and that any conclusion based on the one sense is unlikely to
have a closely related analog in the other.

Bob Long
(boblong@xxxxxxxxxxx)
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