[sdiy] Stupid Sheppard Generator Question

[KA4HJH]

>Could one of you guys explain to me what exactly a Sheppard Generator does?
>I know, I know...I'm the big know it all ....but this one I must of missed.
>They SOUND great (samples on Grant's Page)....but I am not sure what I am
>hearing.

The "sonic barberpole" illusion invented by psychologist Roger Shepard at
Bell Labs. The illusion consists of a seemingly endlessly rising or falling
set of tones. The trick is done by simultaneously sweeping eight (or so)
pure tones (i.e., sine waves) tuned exactly one octave apart. The human
ear/brain has a really hard time figuring out which pure tone is the
fundamental, so it "slips" periodically, just like an eye watching a
barberpole (or looking at an Escher staircase). To conceal the tones'
appearing and disappearing they fade in at one end of the cycle and fade
out at the other.

http://www.crowncity.net/ratcave/Audio/Audio.html
-- 

Terry Bowman, KA4HJH
"The Mac Doctor"

"You'd PAY to know what you REALLY think"--Dobbs