I don't think they have one distinct sound. i have heard a few different ones, and some whine, some howl, and I've heard some are real quite. Are you looking at getting one and worried about the sound?
They sound like a super charger on a car or truck. It also depends on who makes it and the width of the belt. I have the Baker with a 2.5 belt and you can not hear it that much especially with the Loud ass exhaust (Street Walker R P Gees 2-1)
I actually know what they sound like. That cogged belt gives off that distinct supercharger sound. I was trying to find an example to show the GF and couldn't find one. I was hoping someone here would have a clip or a link to a good clip.