"220V Cooling Fan" of the blades is carefully calculated, deliberately so that the distance between the blades disorganized, presenting a "not equidistant" situation: this is very simple, it is hard to make the rotation of "220V Cooling Fan" Wind audio wheel and air generated by "irregular" and become "a" wind, rather than focusing on a band of wind. Noise has two narrowband and broadband noise, narrowband noise regular easy to attract people's attention, annoying; and "220V Cooling Fan" broadband noise closer to the nature of the noise situation, though not eliminate, but relatively "Naiting "a little, people are not so upset.