I am trying to find a way to operate a 200cfm+ 120mm fan at a couple of speeds, so say full power, medium and low. With the low intended to be inaudible. I have used PWM to operate the different fan speeds, however the fans are very noisey at the low rpm, they give out a buzz, a high pitched whine and vibrate heavily.
Does anybody know if it is possible to make the fans smooth and also to reduce the electrical noises?
P.S. The reason the post is in the WC section is that it is being fitted to a WC rad