Towards a new era in fan design - RotoSub the active fan

摘要

Noise pollution from fans has always been a problem. Due to its high tonal content it is especially annoying even at low levels. The noise is created by a complex system of flow interactions. The steady forces on fan blades generate the thrust, but because of rotation, also create a steady-loading noise component. Eliminating noise from a flow perspective has proven to be difficult largely due to insufficient control of the target environment. Previous work has shown that active noise control is a feasible solution to attenuate noise radiated by axial cooling fans. Miniaturization of electronics create size constraints making it difficult deploying anti noise speaker around the fan itself. The situation is further worsened by the fact that both upstream and downstream sources are needed. The novel approach developed at RotoSub labs to solve this problem is to use the blades of the fan as sound generators. The solution integrates within the fan's infrastructure and creates a dual sided anti noise source with a position and phase match suitable to attack targeted noise. The solution shows simultaneous dual sided noise reduction. This report describes the integration of the RotoSub technology into an 80 mm cpu cooling fan. Up and downstream noise reduction measurements are presented. Future applications of this technology are also presented.