Of course, high-quality "DC Fan" of the shock itself will be small, but it is the first two were difficult to overcome. To solve this problem, we can try to use larger size fan. Should be in the same amount of wind, the noise is a big fan of working at low speed is less than the small fan operating noise at high speed. Another factor is that we tend to ignore the fan bearings. Due to the high-speed fan rotation between the shaft and the bearing to friction and collision, it is also a major source of fan noise.