Air-flow resistance will cause the air flow noise generation. Due to poor design of air flow channel turbulent high-frequency noise will occur if the runner does not improve very difficult to have a qualitative improvement. Cooling fan speed sooner the better, the greater the greater the "220V AC Cooling Fan" the size of the air volume, the better the cooling effect. The larger the fan speed, the higher the noise, the greater the larger the size of the noise.