Pleasantness and magnitude of tonal content of electric vehicle interior sounds containing subharmonics

Abstract

The level of the interior sound of electric vehicles is substantially lower than that of combustion vehicles. Due to this low sound pressure level, the tonal components originating from the electric powertrain are often audible within the vehicle interior. The perception of tonal components can be characterized by the psychoacoustic perceived magnitude of tonal content (MOTC). The tonal components usually have high frequencies and have a negative impact on the perceived sound quality. For different driving conditions, the present study investigates the impact of stimulus alterations on the pleasantness and perceived MOTC of synthesized electric vehicle interior sounds. All synthesized sounds contained frequency sweeps mimicking electric motor orders and a background noise simulating the tire-road and wind-noise components. An amplitude modulation was applied to the synthetic orders to simulate the structural resonances within the vehicle. It is investigated how adding subharmonics of the electric motor orders and changing the background noise level alter the perceived MOTC and pleasantness of the sound. The addition of subharmonics tends to increase both the pleasantness and the MOTC. In contrast, the increase of the background noise level has a negative effect on both parameters, presumably due to the increase of loudness and the partial masking of low-frequency subharmonics.