"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 the noise of the cooling fan needs sun noise is less than 17dB for a muffler chamber, one meter from the cooling fan sun, and aligned along the axis of rotation of the fan the fan air intake port, using measured A-weighted manner. The spectral characteristics of the cooling fan noise sun 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. "24V DC Cooling Fan" sun and friction, air flow related. Fan speed, the greater the amount of wind noise caused by the greater will be another fan's own shock factor can not be ignored. Of course, fans of high-quality shock itself will be very small, but the front two who is difficult to overcome. To solve this problem, we can try to use larger size fan. Should be under the same amount of wind, the large fan working noise at low speed is less than a small fan operating noise at high speed. Another factor is that we tend to ignore the fan bearings. Since the "24V DC Cooling Fan" to the friction between the shaft and the bearing to rotate at a high speed collision, it is also a major source of sun cooling fan noise.