Because "Cooling Fan Manufacturer" blade periodically suffer uneven pulse power outlet airflow effect, noise; on the other hand, due to the uneven distribution of pressure on the blade itself and the blade of the surrounding gas and parts of disturbance also rotates constitute the rotation noise; in addition the gas flowing through the "Cooling Fan Manufacturer" blade attached tear generate turbulence level, vortex and vortex detachment, causing pulsating pressure distribution on the blades and vortex noise. The same series of fan air flow pressure is greater, the noise is large, therefore, to a reasonable choice "Cooling Fan Manufacturer" form, I not only excessive waste of energy, but also increase the noise. The same type of fan, should try to use low-speed operation of the fan; for different models fan, you should choose a low-noise, and not only consider the speed.