I was rather thinking about transmitting small-band noise to combine motion-sensing with position-sensing.
yes, that should do it, too. one thing I noticed though is that US receivers can be confused by loud audio signals. Just clap your hands, and it might take it for a returned US pulse. Has wrecked many performances that worked perfectly at home, but couldn't handle the louder stage conditions.
my biggest problem with reflective US was always the amount of energy I got back from soft objects (like dancers or people in general...) which was never enough to make it work reliably for larger distances
Try calculating differences between successive echoes.
I don't see how this helps when the signal is burried in noise.
I would be interested over what distance you receive information from moving people. And are you using the Polaroid transducers, the smaller stuff from RS/Farnell, or something else ?
Sukandar
__--__--__-___-_--_-_-___-_-_--___-_-___ sukandar kartadinata the glui performance hardware http://www.glui.de/proj/gluiph.html _--__---_--_--___---_-_-_--_-__-