Perception of tones below 1 kHz in electric vehicles

The perception of tonal sounds is one of the most important psychoacoustic sensations of NVH sound engineering. Much work has been done in the past to quantify tonal sound events. Previous studies resulted in several metrics for quantifying tonality, such as Prominence Ratio, Tonality DIN 45681 and the recently standardized Psychoacoustic Tonality (ECMA-74). Although these metrics are designed to assess the tonality of a sound, they do not explain how the pleasantness of a sound is affected by tonal events. This article describes an experiment aimed at evaluating the relationship between tonality and pleasantness of electric vehicle interior sound at different speeds with tonal components between 200 Hz and 900 Hz. It also explores how the established metrics for tonality calculation can be used to predict the pleasantness of these sounds. The results of the listening test are analyzed and compared with the calculated tonality values of the various metrics. The detectability of the tones was also analyzed and could be linked to the pleasantness observations. Furthermore, a hierarchical cluster analysis was performed to further examine the subjective results. Two main groups were categorized from this analysis where one cluster had higher detectability.