Noisy CPU fan 365

On Tue, 17 Jan 2006 03:02:24 +0100, "sbb78247"

A thin fan moves far less air an a given RPM. MUCH less when not in free air, even mounted in a case (on a case wall) there is almost always a pressure differential between intake and exhaust.

What do you mean by "not move enough"? The goal is the largest fan the case can reasonably accomodate, so if the case only accepts (for example) 80mm fan and the parts inside need more flow than an 80mm fan at very low RPM can provide, then the case was not suited for running those parts quietly.

A case with rear 92mm fan and median parts (plus the PSU exhaust) can cool a modern mid-grade system quietly at low RPM providing front intake area isn't too small. A rear 120mm can cool a very high-end system at very low RPM, again buttuming front intake area is sufficient. The front intake area can easily double the exhaust rate from same fan at a given voltage.

Providing optimal fans of each type (thin vs thick) are chosen and all else remains equal (like bearing type), a thick fan will always be quieter moving same amount of air.

What the resistor does over other control methods is to limit current rather than only dropping voltage. When a fan is ran at very low RPM, it is rapidly energizing the motor windings sequentially. If there is no current limit, the current surge with each winding energization causes a sudden "jolt", torque instead that can sound a bit like clicking or pulsating.

I was speaking of quality, longevity and imbalance-induced vibration, but yes if they're going to implement a thermal control then the temp vs RPM response would have to be complimentary to the targeted use.