You can barely here a KB 1.7 with 9#. The only time i can here it is when it is coming down from rpm. it makes a little whislting sound. Not loud at all. Especially with LT's and exhaust you will never here it.
the whine gets louder as more psi is made so if a 9# kit is kinda quiet a 14# pulley swap will make it whine more..........oh and that snake bite vid WHOA!!!!!! even though i have seen it before