Many electric (EV) and hybrid-electric (HEV) vehicles are designed to operate using only electric propulsion at low road speeds. This has resulted in significantly reduced vehicle noise levels in urban situations. Although this may be viewed by many as a benefit, a risk to safety exists for those who rely on the engine noise to help detect the presence, location and behaviour of a vehicle in their vicinity. In recognition of this, legislation is being introduced globally which will require automotive manufacturers to implement external warning sound systems.
A key challenge for premium vehicle manufacturers is the development of a suitable warning sound signature which also conveys the appropriate brand aspirations for the product.
A further major difficulty exists when trying to robustly evaluate potential exterior sounds by running large-scale trials in the real world. Practical factors such as poor repeatability of the test condition (traffic, weather, etc.), the logistics of moving large groups of assessors around the physical scenario, and the time necessary to evaluate many sounds can all contribute to unreliable findings.
This paper describes an exterior sound simulator which has been developed to address these concerns. It accurately creates the sound which would be experienced by a pedestrian as vehicles are driven around a virtual urban scenario and enables the controlled subjective evaluation of many potential warning sounds in a wide variety of realistic scenarios. The technical approach is explained through a recent case study in which the exterior sound simulator was used to develop, and obtain management direction for, appropriate warning sounds for a new luxury electric vehicle.