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Supercharger gear whine noise has been a NVH concern for many years, especially around idle rpm. The engine masking noise is very low at idle and the supercharger is sensitive to transmitted gear whine noise from the timing gears. The low loads and desire to use spur gears for ease in timing the rotors have caused the need to make very accurate profiles for minimizing gear whine noise. Over the past several years there has been an effort to better understand gear whine noise source and transmission path. Based on understanding the shaft bending mode frequencies and better gear design optimization tools, the gear design was modified to increase the number of teeth in order to move out of the frequency range of the shaft bending modes at idle speed and to lower the transmission error of the gear design through optimization using the RMC (Run Many Cases) software from the OSU gear laboratory.

Extensive experimental and numerical investigations were done to improve the vibration and acoustic performance due to excitation at the timing gears of automotive supercharger. Gear excitation, system response, and covers have been studied to find the most cost efficient method for reducing gear whine noise. Initially, gear excitation was studied where it was found that transmission error due to profile quality was the dominant source parameter for gear whine noise. To investigate the system effects on gear noise, a parametric study was carried using FEM model of the supercharger, with special interests in optimizing dynamic characteristics of internal components and the coupling to supercharger housing. The BEM model of the corresponding supercharger was built to predict the noise improvement after dynamic optimization of the system. Good correlations were observed between experimental and numerical results in both dynamic and acoustic parameters.