carl@DISTANCE (Carl Tollander) (12/04/87)
>Plus, there is an audio illusion I've been looking for, for quite >a while now. Basically it is an ever increasing tone. It (they) are called Shepherd's Tones. I forget where I saw this first or why they're called that. Basically, you take several oscillators (voices), let's say, four. Number them 1-4. Each voice can vary equally in frequency and amplitude. Start with all voices at low frequency, low amplitude. Slowly raise the frequency and amplitude of the first voice. At about its mid-range, slowly decrease the amplitude of the first voice. At the same time, start slowly raising the frequency and amplitude of the second voice. At about the mid-range, slowly decrease the amplitude. Repeat for however many voices you have. When a voice becomes sub-audible, change the frequency back to low again and begin to raise the frequency and amplitude. The first voice should go sub-audible at the same time as the fourth is starting to become audible. Wrap the process from the last voice to the first. The effect is something like a circular bucket brigade, with the "bucket" being the perceived rise in tone. The method works for descending tones as well. ---------------------------------------------------------------------------- Carl Tollander ARPANet: carl@ads.com