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When driving or riding in a vehicle, the customer is bombarded with sensory stimuli. These include tactile, auditory, olfactory and visual. In addition, the customer may be asked to perform various routine driving tasks that can have an influence on the perception of each of the aforementioned senses. Or perhaps, the influence of one sense may affect the perception of another. Since sound rarely occurs void of felt vibration and vice-versa, there is reason to believe one may influence the perception of the other, or that the two may interact in some way when the customer is exposed to a particular NVH (Noise Vibration and Harshness) event in a vehicle. The NVH engineer wishes to gage a sound or vibration's impact on the customer and make a determination as to whether corrective actions on the vehicle are necessary. NVH issues routinely show up as top warranty and customer satisfaction concerns.

A quiet passenger compartment is highly desired by today's customers. Vehicle design teams spend significant time and resources to minimize the vehicle's interior noise due to different exterior noise sources. Drive-by vehicles on the highways generate one of these noise sources. The objective of this study is to establish a correlation between customer's on-road experience due to drive-by noise and Noise Reduction Level (body transparency) tests conducted in a reverberation room. The average Noise Reduction Level (NRL) obtained in the reverberation room tests correlates (R2=0.89) with the peak loudness of on road tests. A sound quality listening study was also conducted to determine the most preferred NRL spectral distribution and its frequency range sensitivity.

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.