Vehicles with electric powertrains emit less noise than internal combustion engine vehicles. These quiet cars have raised concerns about pedestrian safety, especially among the visually impaired community. The primary concern is related to when electric vehicles are travelling at low speeds where tire noise and aerodynamic noise is minimal. In these situations, the EV might not provide an adequate auditory cue for visually impaired pedestrians who need auditory information for navigation and decision making.
A system called Approaching Vehicle Sound for Pedestrians (VSP) has been developed for the 2011 Nissan Leaf EV to help address the potential quiet car concern. This system emits a digitally generated signal from an onboard speaker to provide auditory cues to pedestrians during low speed forward movement and reverse. The auditory cues are designed to help achieve the same detectablity performance as internal combustion engine sound. In addition to achieving good detectability performance for pedestrians, the low speed forward movement signal is also designed to help maintain a quiet cabin for the driver and is not intrusive to neighboring communities.
This paper explains the methodology for developing the VSP system, focusing on the forward movement signal. It discusses how the frequency content and temporal structure of the signal are intended for achieving ICE level performance in pedestrian listening tasks, along with good quiet cabin performance and low noise intrusion for neighboring communities. It also presents the results from research laboratory and real world tests that validate the signal performance as compared to ICE sound. Finally, NVH pass-by and cabin isolation testing results will be discussed.
