NVH Optimization of Mounts for Reduction of Structure borne motor and road noise in Electric vehicle

Due to stringent emission norms, all OEMs are shifting focus from Internal combustion engine(ICE) to Electric vehicle (EV). NVH refinement of EVs are challenging due to less background noise in EVs in comparison with ICE vehicle. Motor whine noise is perceived in cabin when driven at the speed of 20 kmph. Vehicle is powered by electric powertrain(EPT). Electric powertrain is connected to the subframe with the help of three powertrain mount. Subframe is connected to the body with the help of four mounts. With the help of Transfer Path Analysis (TPA), it is identified that the noise is structure borne and the dominant path is identified. By optimizing the dynamic stiffness of the EPT mount and subframe mount, the structure borne noise levels are reduced. But reducing the dynamic stiffness of EPT mount and subframe mount deteriorated the road noise levels. The reason behind deterioration of road noise is investigated. The performance of double isolation of EPT is compared with single isolation of EPT with respect to both road and motor noise is discussed. Modal criteria which needs to be considered for EPT and subframe mount development in design stage with respect to road noise and structure borne motor noise is also discussed.