"Micro Cooling Fan" noise and friction, air flow related. Fan speed, the greater the amount of wind noise caused by the greater will be another fan's own shock factor can not be ignored. Of course, high-quality "Micro Cooling Fan" of their shock will be very small, but the front two who is difficult to overcome. To solve this problem, we can try to use larger size fan. Should be in the same amount of wind, the large "Micro Cooling Fan" operating noise at a lower speed to the operating noise is less than a small fan at high speed. Another factor is that we tend to ignore the fan bearings. Since the fan rotates at high speed friction between the shaft and the bearing to the collision, it is also a major source of fan noise.