From: ras@athena.mit.edu (Richard A Shandross)
Subject: Re: Perfect pitch
Organization: Massachusetts Institute of Technology
Date: Thu, 1 Oct 1992 23:42:50 GMT

In article <aalz=bh@rpi.edu> petrop@vccsouth07.its.rpi.edu (Philip A. Petrocelli) writes:
>
>We DO know that both percepetions indeed ARE governed by two totally different
>mechanisms.  I know we are not all physicists, but for those of us who know 
>a little, have we forgotten that color is an ELECTROMAGNETIC WAVE, and it's 
>perception is a result of a chemical reaction that occurs in the rods and cones
>in our retinas????  And, that sound is a MECHANICAL WAVE that occurs as
>compressions and rarefactions of air molecules - and it is that transfer of 
>vibratory motion (thru our ear drums and the bones in our ear) that gets 
>translated into a form that our brain can process???
>The same mathematical methods that we apply to sound waves (ie overtones, etc)
>simply CANNOT be applied to electromacnetic waves.  Their properties are just
>apples and oranges.  Mechanical waves manifest themselves as vibrating
>molecules, whereas electromagnetic waves need no medium because they are a
>result of varying magnetic and electric fields.  True, the sines and cosines 
>are the same, but varying fields and vibrating molecules are two totally
>differnent animals.  That's what I never understood about David's ads...
>
>MORE INPUT???


	All true, but the textures/shades/colors are in the frequencies, not
the method of propagation.  So, for example, perhaps it's true for both sound
and light that an even distribution of frequencies over a fairly wide range
might be "warm," and a sharp distribution over a narrow range "cold."  I'm not
sure that those distributions means those things, but they would be percieved
as different, in the same way, for both sound and light.  For the sake of
argument, let's say they mean what I've put above.

	   |
 Intensity |                       _____ Texture 1  - "cold"
   axis	   |                      /
	   |                /^^\ /              ____ Texture 2 - "warm"  
	   |               |    |              /
	   |               |    |             /
	   |           ****|****|*************
	   |          *   /      \            *
	0  |_________*___/________\____________*__________________________

	   420nm       430nm      440nm     450nm     460nm      <-- LIGHT    
	   420Hz       430Hz      440Hz     450Hz     460Hz      <-- SOUND    


	It's not a hard stretch for me to extend this to "color" as well as
texture.  Light color and sound pitch are both "scales" for frequency... A =
some number of Hz _by definition_, and Red = some number of nanometers _by
definition_.  (For those of you who caught the fact that a nanometer is a
wavelength and not a frequency, remember that light frequency is just 
(speed of light)/wavelength.  That is, if you are talking about the 
wavelength of light you are really talking about frequency too, because there
is only one frequency for each wavelength.)  
	 Why shouldn't different frequencies feel unique for both the eye and
the ear?  I imagine one can be trained to recognize and identify mechanical
vibrations of 25, 50, 100 and 150 Hz placed on the skin.  I don't see any
difference between that and the eardrum.  It would take a lot of training to
distinguish 25 and 26, but I'd bet that it could be done.  If nothing else, by
the amount of energy transmitted for the same amplitude vibration.  There's
more energy per vibration in the 26 Hz wave than the 25 Hz. (See your college
physics book.)  Then there's the simple ability to sense a difference in how
many times the skin is moved per second. 

	Rich


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