Sound and Vibration Contributions to the Perception of Impact Harshness

Transient road disturbances excite complex vehicle responses involving the interaction of suspension/chassis, powertrain, and body systems. Typical ones are due to the interactions between tires and road expansion joints, railway crossings and other road discontinuities. Such transient disturbances are generally perceived as “impact harshness” due to the harshness perception as sensed by drivers through both sound and vibration. This paper presents a study of quantifying the effects of sound, steering wheel and seat/floorpan vibrations on the overall perception of the “impact harshness” during impact transient events. The Vehicle Vibration Simulator (VVS) of the Ford Research Laboratory was used to conduct this study. The results of the study show that sound and vibration have approximately equal impact on the overall perception of impact harshness. There is no evidence of interaction between sound and vibration. In terms of the individual vibration contribution to the overall vibration, the results indicate that vibration from the steering wheel has twice the contribution to the overall impact harshness vibration perception as does the vibration from the seat/floorpan. There is no evidence of interaction between these two individual vibration sources.