"220V AC Cooling Fan" in addition to the cooling effect, cooling fan operating noise is also widespread concern. Fan noise is the size of the generated noise when the fan work, influenced by many factors, in decibels (dB). When measuring "220V AC Cooling Fan" noise in the noise is less than the need for a muffler chamber for 17dB, one meter from the fan and the fan air intake port is aligned along the axis direction of the radiator fan, the use of measurement of the A-weighted manner. Spectral characteristics "220V AC Cooling Fan" noise is also very important, so we must also use a spectrum analyzer records the fan noise frequency distribution, the general requirements of the fan noise to be as small as possible, but can not exist different tone.