"220V AC Cooling Fan" noise and friction, air flow related. Fan speed, the greater the amount of wind noise caused will be greater, in addition to the fan's own shock factor can not be ignored. Of course, high-quality cooling fan will shake itself is small, but the first two were but it is difficult to overcome. To solve the "220V AC Cooling Fan" problem, we can try to use larger size power cooling fan. Should be at the same air volume, a large operating noise at a lower fan rotational speed must be less than the operating noise of small fan at high speed. Another factor is that we tend to ignore the fan bearings. Since the "220V AC Cooling Fan" To friction between the shaft and the bearing to rotate at a high speed collision, it is also a major source of cooling fan noise.