Challenges in Noise Refinement of a Pure Electric Passenger Vehicle

Currently, the governments are encouraging automotive vehicle manufacturers to produce electric vehicles (EVs) as these vehicles have a zero-emission footprint. Generally, the EVs are expected to be quieter compared to internal combustion engine (ICE) vehicles. But the absence of engine noise in EVs brings more challenges for noise, vibration, and harshness (NVH) as the other noise sources become more audible. Most of these noise sources are tonal in nature and, hence, cause discomfort to the passengers. The present work is related to the noise refinement in a pure EV. The dominant noise sources observed in this vehicle are the electric powertrain, cooling fan, and air compressor. The powertrain consists of a traction motor and a gearbox (GB) with a planetary gear system. The root cause identification of electric powertrain noise has been investigated with masking trials and with the acoustic camera. Experimental modal analysis (EMA) of the traction motor is carried out to understand its dynamic behavior, and the orders of traction motor and planetary GB are calculated to correlate with the vehicle interior noise data. A passive noise reduction method is implemented to reduce the powertrain noise and to improve the interior sound quality. A parallel baffle silencer (PBS) is developed for cooling fan noise reduction. The development of various types of silencers including a new innovative micro-perforated panel (MPP) silencer for the reduction of suction noise from an air compressor is also shown.