Influence parameters on the perceived magnitude of tonal content of electric vehicle interior sounds

Abstract

The interior sound is a key criterion for the purchase decision of a vehicle. Especially audible tonal components in the interior of electric vehicles significantly lower the pleasantness and possibly the acceptance of electric powertrains. These tonal components are commonly audible within the electric vehicle interior during transient driving conditions. The present study investigates the influence of different parameters of these tonal components, which are typically observed in recordings of interior sounds, on the perceived magnitude of tonal content (MOTC). Instead of recordings, artificial sounds were used to allow for controlled and systematic variations of these parameters. Parameters are the level and number of tonal components. In addition, the influence of temporal amplitude modulations, which, in the case of interior sounds, result from structural resonances, were investigated. Psychoacoustic experiments with normal-hearing listeners indicate that all these parameters have an impact on the perceived MOTC of the sounds: the perceived MOTC increases as the level of the tonal components increases and when an overtone was added. An increase in modulation frequency or modulation depth also yields to an increase in perceived MOTC. The experimental results are compared to predictions of a model of tonalness in a musical context and to the current version of the ECMA-74 standard. It is shown that those models predict basic trends that were observed in the data.