"Micro Cooling Fan" main function is cooling, exhaust, humidity, but no matter what kind of function, there will be noise, DC fan operating noise problem is widespread concern. DC Fan noise is noise generated when the size of the DC fan work, influenced by many factors, in decibels (dB). When measuring "Micro Cooling Fan" noise requires noise is less than 17dB muffler chambers were a meter from the DC fans, and along the axis of rotation is aligned DC fan DC fan inlet, using A-weighted approach to measurement. Spectral characteristics "Micro Cooling Fan" Noise is also very important, so we must also use a spectrum analyzer record DC fan noise frequency distribution, generally require a DC fan noise to be as small as possible, but can not exist different tone.