"220V AC Cooling Fan" noise and friction, air flow related. 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 "220V AC Cooling Fan" shake itself will be very small, but the first two were, but it is difficult to overcome. To solve this problem, we can try to use larger size fan. Should be at the same air volume, a large "220V AC Cooling Fan" operating noise at a lower speed is less than the small fan operation noise at high speed. Another factor is that we tend to ignore the 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.