Contribution of sound and vibration level to comfort in cars

Abstract

The goal of the study was to evaluate the contribution of sound and whole-body vibration levels on comfort for passengers of a running car. A full factorial experimental plan was designed: in four cars running on a rough surface, the sound at the ears of the front passengers and the vertical vibrations at the seat's slide were measured. The levels of sound and vibration stimuli were independently modified by 3-dB steps, giving a total number of 25 stimuli for each car. These stimuli were reproduced on a test bench (vertically vibrating seat and loudspeakers) and evaluated by 68 subjects. Each stimulus was rated on a scale ranging from "not at all comfortable" to "very comfortable". A good agreement between subjects was noticed. An ANOVA shown that the effects of the two factors as well as their interaction were significant. A linear model including the factors and their interaction proved to accurately reproduce the results. This model was checked using data from a previous experiment, confirming results from Howarth et al. or Paulsen et al., though the effect of vibration level was more important in this study, which may be due to a higher level of vibration stimuli.