The technical index of the cooling fan: noise

In addition to the heat dissipation effect, fan noise is also a widely concerned problem. The size of the fan noise is generated when the fan noise, affected by various factors, the unit is decibels ( dB) 。 When measuring the noise of the fan needs in the sound attenuation of noise is less than 17 db and fan, one meter distance along the direction of the fan rotor on the fan inlet port, was measured using A weighted way. The fan noise spectrum characteristics is also very important, so you also need to use spectrometer to record the noise of the fan frequency distribution, generally requires little as far as possible, the noise of the fan and cannot exist different sounds.
related fan, air flow noise and friction. Fan speed is higher, the air volume, the greater the noise caused by will also be more big, the other factors of the vibration of the fan itself is also cannot be ignored. Of course the high quality of fan vibration will be small, but the two in front of the person is difficult to overcome. To solve this problem, we can try to use the size bigger fan. Should be under the condition of the same volume, big fan work at low speed when the noise is smaller than small fan noise at high speed work. Another we easy to overlook the factor is the fan bearing. Because of the high-speed fan rotates to the friction between shaft and shaft bearing collision, so also is one of the main fan noise source. Vibration
if the physical fan rotor rotates the rotor center of mass and rotation inertia center is not in the same axis, will cause the imbalance of the rotor. Physical center of mass and the center of the rotor inertia rotor closest known as eccentricity, cause partial pitch rotor no scale, when the rotor rotation due to the effect of centrifugal force produces a force on the rotating shaft bracket and form of vibration, and vibration through the path to the mechanical parts. Wind
the fan is working, due to the blade periodically export under the pulse power of uneven air, noise; On the other hand, due to the blade itself and uneven distribution of blade pressure on, turns on the surrounding gas and noise disturbance also constitute parts of rotation; In addition because the gas flowing through the blade when turbulence level, vortex and vortex from attached, cause the pulsation of the pressure distribution on blade and vortex noise generation. These three reasons caused by noise can be integrated as & other; Cut the wind noise throughout the &; , generally air volume air pressure big fan, the wind noise is larger. Different sound
sounds only pure wind wind noise, and the sound is different, the fan operation, in addition to the wind, if there are other sound, can judge the fan appeared different sounds. Different sound may be due to the deformation of bearing or foreign body in it, and improper assembly and a collision, or uneven motor winding coil, create loose, is likely to produce different notes.