Spectral Optimization of Fan Rotation Noise Based on Vector Composition Method

In order to optimize the rotation noise spectrum of vehicle alternator cooling fan, a Vector Composition Method was proposed. Based on this method, the relative sound pressure level (RSPL) variations were calculated, which were then used as parameters in the optimization of spectral structure. In this article, the sound pressure level (SPL) variations of the 12th and 18th order (of rotation frequency) who had the most prominent fan rotation noises were set as optimization targets, the blade distribution angles were optimized to ameliorate the spectral structure and the distribution of spectral energy. Calculations showed that, the RSPL in orders 12 and 18 were decreased by 9.3dBA and 10.5dBA respectively, comparing with experiment results, the errors were 3.9% and 4.11% respectively. Results suggested that the rotation noise of target orders had been significantly diminished, so the objective of optimizing spectral structure was reached. This method has a guiding significance to the design of blade distribution angles.