"220V Cooling Fan" process in order to reduce the use of low-noise must note the following: System Impedance: Air flow resistance will cause air flow noise generation. Airflow turbulence: due to poor design of the flow channel of air turbulence caused by high-frequency noise will appear, if it does not improve the flow channel is difficult to have a qualitative improvement. Fan speed and size: the cooling fan speed sooner the better, the greater the "220V Cooling Fan" the larger the size of the wind, the heat, the better. The larger the fan speed, the higher the noise, the greater the larger the size of the noise. Temperature rise: after reducing the temperature difference between the temperature rise, the cooling effect is reduced. Vibration: vibration will cause the fan noise increased, reducing life expectancy as well as the speed is reduced. Voltage fluctuation: The voltage fluctuation will cause the fan speed changes, "220V Cooling Fan" make job insecurity and will generate additional noise.