I had not even considered it might be the mounts or the case rattling against the mounts as you suggested. So i took the fan off the case and tried the controller just holding the fan in my hand and it still made the noise. After doing some reading around, I see that some fans don't actually under-volt well. Too bad since they are actually pretty good fans that move a decent amount of air. Just so much air that it is a little annoying when my PC is just idling or I'm just surfing the web. Supposedly Noctua's under-volt well so I may pick up a couple of those (dispite their ugliness).
Anyway, thanks for the reply Ubrales.