Fusion and the rainbow

Assuming there's some relavence in how other sense systems operate...

I see an anology between the fusion of partials into a fundamental
pitch, and why the sky looks blue.

From how I understand of 'Why is the sky blue?' (and it's always
been hard to get a strait answer on that! Like (I was actually told
this)...

"Hey Dad, why is the sky blue? Uhm..., son, that's because the
oxygen is blue, and it acts like a blue filter".)

...the eye acutally sees all the colors of the raimbow, but
*decides* to 'call it blue' since the wavelenth of that color is 200
times more energetic than the other colors -- essentially ignoring
them, even though it sees them. (Then why isn't the sky purple?)

So that reminds me of how the ear, even though it hears the soft
upper partials, ignores them, and presents the listener with just a
low fundamental.

I wonder if that's a common mechanism, like how both vision and
hearing record their stimuli logrythmically?

Hi traktus5!

on Sat, 18 Feb 2006 "traktus5" wrote:
>
> Assuming there's some relavence in how other sense systems operate...
>
> I see an anology between the fusion of partials into a fundamental
> pitch, and why the sky looks blue.
>
> From how I understand of 'Why is the sky blue?' (and it's always
> been hard to get a strait answer on that! Like (I was actually told
> this)...
>
> "Hey Dad, why is the sky blue? Uhm..., son, that's because the
> oxygen is blue, and it acts like a blue filter".)

Dispersion. The particles of the upper atmosphere disperse light
of all wavelengths longer than (a greenish) blue. Their energy is
scattered and lost in multiple collisions with air particles. But the
blue - AND the indigo, violet and ultraviolet - do get through.

> ...the eye acutally sees all the colors of the raimbow, but
> *decides* to 'call it blue' since the wavelenth of that color is 200
> times more energetic than the other colors -- essentially ignoring
> them, even though it sees them. (Then why isn't the sky purple?)

Because "purple" is any mixture of the colours at the blue end of the
spectrum with the colours at the red end of the spectrum (it is
inherently impure). Since there's no red coming through, there can
be no purple.

Perhaps you really meant "violet" and not "purple"? Well, the colour
receptors in our eyes that respond to red also have a smaller peak
in sensitivity down towards violet. Although the primary response of
our eyes to violet is by the blue colour receptors, this adds an
apparent reddish component, which is why we often perceive violet
as a purplish blue. Which in turn is why we can close the "colour
wheels" used by artists and interior designers by gradating from
blue through indigo and violet, through purples to red, thus
effectively joining two ends of the spectrum.

If we had a white sun, instead of the orange-yellow Sol, we'd surely
get more light down the blue-indigo-violet end of the spectrum.
Perhaps the increase in indigo and violet would alter the colour of
the mixture we perceive, towards (the apparently more purplish)
violet.

> So that reminds me of how the ear, even though it hears the soft
> upper partials, ignores them, and presents the listener with just a
> low fundamental.
>
> I wonder if that's a common mechanism, like how both vision and
> hearing record their stimuli logrythmically?

The same thing happens with colour perception. Asked to name the
colour of a car going past, you may immediately and unhesitatingly
say "yellow". Yet you recognise an astounding variety of colours as
different "yellows", some of which you may have names for:
"buttercup", "marigold", "lemon", "mustard", "gold", ... maybe even
"cream". There are even more "greens" than there are "yellows",
"reds" or "blues", since that's where our eyes are most responsive.
Yet most of use will immediately classify a colour that's almost
blue, and another that's almost yellow, as "green".

Apart from the underlying physiology, the fascinating thing about
colour perception categories is that they're very largely cultural
artefacts. A similar comment might apply to sound perception
categories, don't you think? Despite many years of hearing
Indonesion gamelan and anklung music, my impressions of it are
more timbral than tonal. Yet the similarly complex timbres of the
piano are usually, for me, just a colouring layered over a
fundamentally tonal experience. This surely reflects the ways in
which both cultures traditionally organise their tonal & timbral
material. (Despite my name, I grew up in Australia listening to
a lot of piano music, some classics and a little pop or rock.)

Regards,
Yahya

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