"220V 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 "220V 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 in the same amount of wind, the big fan operating noise at low speed is less than the work of a small fan noise at high speed. Another factor is that we tend to ignore "220V 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.