The effect of varying heat sink fin distances from cooling fan blade tip on noise emissions

The challenge to deliver performance improvements in computer graphic cards has surpassed the ability of finned, passive, cooling devices to dissipate the heat generated by next generation graphics processing units (GPU). The dissipation rates required by these latest GPU designs can only be delivered by more complicated thermal management systems which often require forced air cooling of finned heat sinks. The concurrent challenge to the industry is to provide this cooling while minimizing the noise generated by these cooling fans. One of the fundamental mechanisms for the generation of fan noise is the dynamic force fluctuations on the fan blade and how these fluctuations interact with fixed irregularities such as adjacent cooling fins. This study investigates the effect on the acoustic emissions resulting from the variation of the distance between the fan blade tips and the heat sink fins. A discussion and comparison of the measured results was presented using both traditional analysis techniques as well as psychoacoustic or sound quality metrics. It was found that a minimum distance between the blade and adjacent obstructions is desired in order to minimize excessive noise levels. The minimization of the noise emissions also had a desirable effect on the sound quality analysis