Sound Character of Electric Vehicles

The electrification of vehicle propulsion has caused a significant change in many areas including the world of vehicle acoustics. Comments from the media currently range from “silently hums the future” to “electric car roars with V8 sound”. Decades of experience in designing brand-specific vehicle sound based on noise and vibration generated by combustion engines cannot be simply transferred to the upcoming vehicles driven purely by electric powertrains. Although electric vehicles are almost always considerably quieter than those powered by internal combustion engines, the interior noise is characterized by high-frequency noise components which can be subjectively perceived as annoying and unpleasant. Moreover, such disturbing noise is no longer masked by combustion engine noise. Fundamental questions regarding the sound design of electric vehicles have yet to be answered: it remains unclear what exactly the interior noise of an electric vehicle should sound like. Also questions regarding the approach to achieving a particular interior sound (e.g., use of artificially generated noise for desired sound) are still open. There is also an ongoing debate on the need for electric vehicles to emit additional noise in order to prevent the endangerment of pedestrians. The use of additional noise sources could work against the hope for noise reduction. This paper is intended as a contribution to the current discussion on what the target noise of electric vehicles could sound like and what possibilities currently exist for NVH engineers to design the sound of electric cars.