Off boost at idle the old v1 s trim or t trim for that matter are loud as all get out, the newer ones are not quite as loud, I think pro charger's have a pretty good whitsle to them for new blowers......as far as on boost, Id say kb's or "h"eaton's
Here's a funny story. I'm sitting at a stop light with my window down when some girl yells out at me "EXCUSE ME!!!". So I turn and blink. She continues, "I had a mustang JUST like that and it was making that SAME exact noise! You need a new clutch!" I just grinned and yelled back "No, it's my supercharger."