Micro Cooling Fan noise and friction

"Micro Cooling Fan" noise and friction, about the air flow. Fan speed, the greater the amount of wind noise will be greater due to another fan's own shock factor can not be ignored. Of course, high-quality fans will shake itself is small, but the first two were, but it is difficult to overcome. To solve this problem, we can try to use a larger size "Micro Cooling Fan". Should be at the same air volume, a large fan operating noise at a lower speed is less than the operating noise small fan at high speed. Another factor is that we tend to ignore the "Micro Cooling Fan" bearings. Due to the high-speed rotation of the fan to be friction between the shaft and bearing a collision, it is also a major source of fan noise.