"220V 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, one meter away from the fan, and the fan shaft is aligned along the direction of the fan air intake port, the use of A-weighted measurements manner. Spectral characteristics "220V 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. Fan noise and friction, about the air flow. Fan speed, the greater the amount of wind noise will be greater due to another fan's own shock factor can not be ignored. Of course, high-quality fans will shake itself is small, but the first two were, but it is difficult to overcome. To solve this problem, we can try to use a larger size "220V Cooling Fan". Should be in the same amount of wind, the big fan operating noise at low speed is less than the work of a small fan noise at high speed.