Jeff, (01)
That is the point I was making: (02)
> For that matter, sound is used as a sort of picture frame
> at the beginning and end of a piece to delineate when the
> piece starts and ends. (03)
If you just have silence with no beginning or ending sounds,
there is no contrast to delineate the silence. (04)
> In a hall 120 feet deep, sounds would only need to be deflected
> a couple of feet (at 440Hz) when bouncing off the walls to hear
> a doppler shift of a quarter tone. (05)
That deflection would shift the phase, but it would not shift
the frequency. (06)
To get a Doppler shift, you would have to bounce the sound off
a reflector that was moving away. But if you just bounce it off
a stationary reflector at any angle, there would be no change
of frequency. (07)
The same principle applies to light: there is no way that you
can change the color (shift in light frequency) by any kind of
reflection (although you could absorb some colors while reflecting
others, if the original light happened to be white). (08)
If you pass light through glass, it will slow down while going
through the glass. That shifts its wavelength while in the glass,
but it doesn't change the frequency. When the light emerges after
passing through the glass, it has the same frequency (and wavelength
as it had before. Chromatic aberration in lenses is actually caused
by bending different frequencies at different angles. (09)
> In fact, they do. So does "echo point" in the mountains, where
> the sender often hears the reflected sound a bit lower. (010)
I can believe that the sender "hears" it lower -- perhaps because
some of the higher frequencies are not reflected as much, but I
don't believe that a suitable instrument would detect a different
frequency of the fundamental tone from the original. (011)
John (012)
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