Optimization of electric vehicle exterior noise for pedestrian safety and sound quality

Without the noise of a running combustion engine, electrically driven vehicles are very quiet, sometimes even too silent to be noticed by other road users, especially pedestrians, putting their health and lives at risk. Therefore, authorities recommended the introduction of artificial exterior noise signatures to be emitted by vehicles with electric powertrains to ensure detectability and pedestrian safety. In response, many manufactures have already introduced synthesized noise generation systems using exterior loudspeakers.The paper at hand, discusses a systematic approach using exterior and interior simulations to optimize the system sound design. Within the scope of development of the exterior noise signals, the goal is to achieve the minimum required sound levels and transient pitch requirements, while ensuring the sound is both pleasant from the outside of the vehicle and at the same time non-intrusive to the vehicle interior. Utilizing an exterior transfer path approach for potential speaker locations, the sensitivity of variables such as speaker location, noise source routing, exterior noise transfer functions and sound source design can be evaluated to achieve the required sound levels and directivity while minimizing the noise intrusion into the vehicle cabin. A transfer path analysis to the vehicle interior is utilized to assess the influence of the exterior noise sources on the sound quality inside the vehicle.