Optimising the value of sound quality evaluations by observing assessors' driving strategies

Traditionally vehicle sound evaluations have been conducted either whilst driving a car or by auditioning fixed test conditions in a listening room. On‐road testing provides the right context but the results are often inconsistent and unrepeatable. Furthermore it is not possible to evaluate prototype sounds or carry out back‐to‐back comparisons. In‐room evaluations improve the statistical confidence, but the context of the assessments is unrepresentative. Interactive NVH vehicle simulators enable assessments to be performed in a setting representative of real appraisals. Accurate sounds can now be generated in real‐time, and assessors can adopt a driving strategy that allows their own interpretation of the attributes. The benefits include the opportunity to understand how preferences are formed by assessors, albeit with added complexities. Different assessors may be associating their preferences on different operating conditions which have different acoustical properties. Therefore for engineers to identify the key features that influence perception they need to be able to relate the driving strategies with the subjective preferences. This paper reports on new observational methods which capture assessors' decision making strategies. It demonstrates how these help in relating subjective preferences to vehicle operating conditions and how to design a structured evaluation to reduce sources of experimental error.