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The performance of structure-borne road NVH can be cascaded down to three major systems: 1) vehicle body structure, 2) chassis/suspension, 3) tire/wheel. The forces at the body attachment points are controlled by the isolation efficiency of the chassis/suspension system and the excitation at the spindle/knuckle due to the tire/road interaction. The chassis force transmissibility is a metric to quantify the isolation efficiency. This paper presents a new experimental methodology to estimate the chassis force transmissibility from a fully assembled vehicle. For the calculation of the transmissibility, the spindle force/moment estimation and the conventional Noise Path Analysis (NPA) methodologies are utilized. A merit of the methodology provides not only spindle force to body force transmissibility but also spindle moment to body force transmissibility. Hence it enables us to understand the effectiveness of the spindle moments on the body forces.

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.

This paper presents an innovative method of simulating tire non-uniformity forces for vehicle vibration sensitivity tests. The method utilizes a patented mechanical device to produce a vertical or tangential force independently at a vehicle wheel spindle to simulate the excitation generated by tire non-uniformity forces. Using this device in vehicle vibration sensitivity tests, the amplitude of a vertical force can be set at a desired level without inducing a tangential force; and vice versa for a tangential force. Therefore, the vehicle vibration sensitivity to the vertical or tangential forces can be tested respectively without the confounded effect of other direction excitation. This method eliminates the time and cost associated with tire sorting and provides an effective and reliable testing approach to measure vehicle vibration sensitivity due to tire non-uniformity forces.

During the pure electric vehicle high speed cruise driving condition, the unsteady air flow in the chassis cavity is susceptible to self-sustaining oscillations phenomenon. And the aerodynamic oscillation excitation could be coupled with the cabin interior acoustic mode through the body pressure relief vent, the low frequency booming noise may occur and seriously reduces the driving comfort. This paper systematically introduces the characteristics identification and the troubleshooting process of the low frequency aerodynamic noise case. Firstly, combined with the characteristics of the subjective jury evaluation and objective measurement, the acoustic wind tunnel test restores the cabin booming phenomenon. The specific test procedure is proposed to separate the noise excitation source.

The steering wheel is one of the primary sensory inputs for vehicle vibration while driving. Past research on hand-arm vibration has focused on a hand gripping a rod or a hand on a flat plate. Little work has focused on the perception of vibration felt through an automotive steering wheel. This paper discusses the investigation conducted at Ford's Vehicle Vibration Simulator Lab to develop equal annoyance contours for hand-arm vibration. These contours were developed for four different degrees-of-freedom: vertical, lateral, longitudinal and rotation about the steering wheel center. Rotation about the steering wheel is commonly induced by a 1st order tire non-uniformity force and imbalance of the wheel/tire. These 1st order excitation forces generate vibration in the frequency range of 8-20 Hz.

Tire cavity noise refers to the excitation of the acoustic mode of a tire cavity. The noise exhibits itself as sharp resonance-like peaks with frequencies typically in the range of 190-250Hz. For a rolling tire, the tire contact with the road moves relative to the tire. Furthermore, the load on the tire breaks the circular symmetry of the tire. Consequently, the peak frequency of the cavity noise shows dependence on the tire load and the vehicle speed. There are no models that simultaneously take these two factors into consideration. In this paper, we propose an analytical model and present experimental verifications of predictions on the noise peak frequency and its dependence on the tire load and vehicle speed. A wireless experimental measurement system is also presented which enables the measurement of tire cavity frequency for both non-rolling and rolling conditions.

A new experimental methodology has been developed to quantify spindle loads of a vehicle under actual operational conditions. The methodology applies an indirect six degree-of-freedom (6 DOF) frequency response function (FRF) measurement technique to obtain three translation/force and three rotation/moment FRFs of the suspension system of the vehicle. The Inverse Frequency Response Function (IFRF) method estimates the spindle loads under operational conditions. The feasibility and applicability of the developed methodology for vehicle road NVH applications was experimentally demonstrated. The results show that the methodology provides accurate spindle load estimation over a broad frequency range. This methodology can be used for benchmarking and target setting of spindle loads to achieve desired road NVH performance as well as for diagnosing root causes in problem solving applications.

Impact harshness characterizes interior sound and vibration resulting from tire interactions with discrete road disturbances. Typical interactions are expansion joints, railroad crossings, and other road discontinuities at low-to-medium vehicle speeds. One goal of the current study was to validate for light trucks and SUVs the metric that was developed for cars: a weighted combination of peak loudness values from the front and rear impacts after lowpass filtering at 1 kHz. Another goal was to see if other sound characteristics of impact harshness needed to be captured with a metric. A listening study was conducted with participants evaluating several different trucks and SUVs for impact harshness. Results show that the existing metric correlates well with subjective preferences for most of the vehicles.

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.