Distinguish Powerful and silent type "Small Cooling Fan" is not too strict, but the same size, the same voltage for computer fans, air pressure and noise will always be two irreconcilable contradictions. Fan speed is the number of "Small Cooling Fan" fan page revolutions per minute, the unit is rpm. Motor speed is determined by the number of turns in the coil, voltage, fan fan page number, inclination, height, diameter and fan bearing system. At a fixed "Small Cooling Fan" structure, the DC fan (i.e., a DC-powered fan) of the speed of change of the operating voltage changes in synchronization.