"24V DC Cooling Fan" in addition to the cooling effect of the fan noise at work is widespread concern. Fan noise is the size of the generated noise when the fan work, influenced by many factors, in decibels (dB). When measuring "24V DC Cooling Fan" noise less than 17dB noise needs muffler chamber for the distance of one meter the fan and the fan shaft are aligned in the direction of the fan air intake port, using measured A-weighted manner. Spectral characteristics "24V DC 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.