"220V Cooling Fan" blades "eccentric": the quality of the fan, its blades in the axial center of gravity, when the job is very smooth, very little noise, and poor fan, there will be a positive error, the focus of blades does not constitute "the eccentric" in the axis, so that after the "220V Cooling Fan" change up, is equivalent to a vibrator (vibrator motor shaft is pain plus a partial round), followed by the use of time becomes longer , "220V Cooling Fan" gradually bearing wear, or fan heat sink device is not robust, loose, etc., will cause increased noise fibrillation increases. Fans also may be due to poor quality, lubrication is not good, just initiate turn very astringent, and so turn to live, there was a softening lubricants, movement smaller.