[sdiy] roto-pan

[Paul Perry]

At 12:05 AM 19/02/01 -0500, matti at devo wrote:
>All right, how's it done? I tried feeding two demuxes with an LFO...and
>the stereo image seems to go _through_ my head, not around it. Anyone can
>help? Perhaps a scematic?
>
It cant possibly go around your head, because there are no appropriate
psycoacoustic cues present.
A sound source moving around yur head creates a varying phase shift at
different frequencies because the absolute distance from object to ear1 and ear2
is changing. The ear uses this info to get a handle on what is happening, as
well as the absolute levels. So it is possible to make a system (using 
pjase modulation, possibly constructed by varying delays) to fake this up.
In the real world, the outer ear shape provides further info regarding 
direction.
Using a dummy head microphone system and actually recording a moving source,
you will get an idea of what is going on.
I have a friend who does this sort of research professionally.
There are (expensive) convolution dsp systems that do this for video 
game applications.

paul perry melbourne australia (Frostwave analog fx)