Analytical suffering 220V Cooling Fan noise in my heart

"220V Cooling Fan" in addition to the cooling effect of noise, fan noise is the job we pay attention to the title throughout. Fan noise is noise that occurs when the size of the fan operation, affected by various factors that influence when measured "220V Cooling Fan" noise requires noise is less than the muffler chamber carried out a meter from the fan, and the fan is aligned along the axis of rotation fan The intake port, the measurement method selection weighting. The spectral characteristics of the fan noise is also very important, so we must also use a spectrum analyzer documentary "220V Cooling Fan" noise frequency dispersal, usually require noise fans should be small, and can not exist different tone.