Sound Quality Assessment of Internal Automotive Road Noise Using Sensory Science

This paper presents a technique to describe the perception of internal automotive road noise. As the acoustic sources on a car reach lower sound levels, special attention is granted to acoustical comfort. While the knowledge of mechanisms behind road noise is growing, its perception by the driver remains relatively unexplored. In this study, a sensory science technique - the classical sensory profile - is applied to obtain a description of the internal road noise by quantitative perceptual criteria. Seven consumer cars (from Renault, Fiat, Peugeot, and Toyota) were driven under four well-defined conditions varying in speed and road surface. Twenty-one typical road noise recordings were presented to a panel of five experts in acoustics. Twelve listening sessions of three hours, individually and in group, led to a list of 15 relevant perceptual descriptors, such as rough aspect. The performance of the listeners was tested statistically: their repeatability, their ability to discriminate the sounds and the inter-subject agreement. Sufficient agreement was observed across the listeners for 10 of the 15 descriptors, which would constitute the perceptual basis for internal automotive road noise. Through multiple linear regression, strong correlations were found between the associated perceptual dimensions and psychoacoustic properties of the sound samples. The findings from this study are summarized in a sensory grid to assist the test drivers in the evaluation of road noise sound character, and a predictive tool for sound quality evaluation based on correlations between perceptual dimensions and calculated sound metrics.