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