Noise Reduction on Electric Two-Wheeler by Structural Modification and Gear Design Optimization

The low running cost of electric two wheelers is resulting in high popularity and growing market share. The electric two wheelers are generally considered silent. However, the tonal nature of radiated noise is annoying for both driver and pedestrians in electric vehicles. This study focuses on electric two-wheeler with annoyance issue. The customer complained about non-linear noise with respect to speed and also whining during loading and coasting. The detailed Noise Source Identification (NSI) revealed that the noise is due to motor and transmission whine and structural resonances of chassis excited by this motor excitation during runup and gear whine orders during coasting when excitation by motor is absent. The motor mounting and chassis are structurally modified with suitable stiffeners and damping based on the results of modal analysis. The transmission gear geometry and contact pattern are optimized for transmission error reduction. The modification resulted in 6-8 dB overall noise reduction with complete elimination of whine noise in loading as well as coasting operation.