"220V AC Cooling Fan" noise is the most concern to the user, to meet the cooling subject to the conditions, the general level of noise as possible. Fan noise and friction, about the air flow. Fan speed, the greater the amount of wind noise will be greater due to the other "220V AC Cooling Fan" their shock factor can not be ignored. 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 "220V AC Cooling Fan" noise. Microphone Noise testing standards to Fan1M distance to income test, special requirements will shorten the distance between.