An experimental study on router cooling fan noise reduction by inflow screens

In this paper, the characteristic of the router cooling fan noise is studied by an experimental method through measuring the flow field and sound field. The interaction of inflow turbulence with the cooling fan is firstly identified as one of the main noise generation components. Based on such understanding, different layers of screens are proposed to suppress the inflow turbulence intensity and therefore reduce the noise. The flow and sound fields of the fan with different layers of screens are measured to estimate the suppression effect of the inflow turbulence. Experimental results show that three-layer screens have better performance than that of the single-layer screen in controlling turbulence intensity. With the layers of the screens increasing, the area of high turbulence intensity region becomes smaller significantly which leads to noise reduction with more wider frequency range. The noise level of the fan can be reduced up to 10 decibel at some peak frequencies when three-layer screens are used. It is also shown that the screens have little effect on the mean velocity field.