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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 a traditional NVH development process, the realization of the targeted vehicle acceleration sound quality can be a highly laborious and costly process involving the creation and evaluation of multiple iterations of prototype parts. Consequently, development engineers are limited by long prototype part fabrication times while key product decision makers have to often accept the “in-process” sound quality due to aggressive program timing milestones and escalating program costs. The NVH simulator provides an alternative approach that is potentially more efficient in terms of reducing program timing, reducing development and prototype costs and improving the end-product sound quality. This paper presents the case of a V6 vehicle under development whose acceleration sound quality needed improvement. The NVH simulator was used to determine the key contributors that lead to the sound quality of the targeted vehicle.

An overview of the analytical noise, vibration, and harshness (NVH) simulations performed to support the design and development of the Nissan Quest mini-van is presented. The use of analytical techniques on this project was unique in that analytical results were used to drive the pre-prototype design efforts, as well as to assist in the prototype development phase. Analytical models were developed, and simulations performed, prior to the release of prototype drawings. The simulation results identified necessary changes which were incorporated into the design. Once prototype vehicles became available, analytical simulations and development testing were used hand-in-hand to minimize development time as well as to optimize the cost, weight, and performance of NVH countermeasures. The extensive use of analytical simulations in the design and development process was critical in achieving the aggressive NVH performance objectives set for the vehicle.