"220V Cooling Fan" noise and friction, air flow related. DC fan speed, the greater the amount of wind noise caused by the greater will be the other DC fan vibration itself also can not be ignored. Of course, high-quality DC fan vibration itself will be small, but the first two were is difficult to overcome. To solve this problem, we can try to use larger size "220V Cooling Fan". In the case of the same amount of wind, big DC fan operating noise at low speed to less than a small DC fan operating noise at high speed. Another factor is that we tend to ignore the DC fan bearings. Because "220V Cooling Fan" to friction between the shaft and the bearing is rotated at a high speed collision, it is also a major source of DC fan noise.