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This paper describes the application of the modal compliance method to a complex structure such as a vehicle body in white, and the extension of the method from normal modes to the complex modes of a complete vehicle. In addition to the usual bending and torsion calculations, the paper also describes the application of the method to less usual tests such as second torsion, match-boxing and breathing. We also show how the method can be used to investigate the distribution of compliance throughout the structure.

During the development of a new vehicle, the vehicle is usually tested to determine both its static torsional and bending stiffness, and its dynamic torsional and bending modes. This paper discusses a method for determining both static and dynamic properties from the modal analysis test. Such a connection between static stiffness and dynamic modes would be useful for three reasons: (1) the relative importance of apparent bending and torsion modes could be determined by their contribution to stiffness, (2) the stiffening effect of structural modifications could be determined from experimental modal tests (the modal frequency shift is also affected by any change in mass), (3) the total static compliance could easily be split on a modal basis into compliance due to the overall structure and local compliance due to local structural deflections.

This paper describes experimental methods for simulating and analyzing road noise using an artificial road surface mounted to a chassis dynamometer. The nature of the relationship of road noise to road surface is discussed, including the nature of sound produced by the artificial surface mounted to the dynamometer. A method is described for converting the harmonics usually produced in a chassis rolls test into a continuous spectrum. This method also smoothes statistical fluctuations which arise due to the short length of road simulated. Dynamometer techniques are shown to be particularly effective in separating sound contributions from the front and rear suspension, and in separating contributions due to road surface and the tire tread.

Since many automobile NVH issues involve the analysis of order spectra it is highly important that the methods used should be accurate and consistent. A review of the literature shows little discussion of several key issues which could cause problems and possibly invalidate test results. Also, experience indicates that different methods may yield different results unless these key issues are dealt with. This paper compares four different approaches to order tracking as applied to typical engine sweep data: order analysis of conventional fixed frequency waterfall plots, synchronous sampling order tracking, computed digital order tracking, and Kalman filtering. It is shown that unless the analysis parameters are carefully chosen the results of the analysis may be in error. The major issues for the conventional fixed sampling rate waterfall method arise because sweeping the orders causes a frequency smearing effect.

Vehicle interior noise due to powerplant radiation is a product of two factors, the noise level radiated by the powerplant and the effectiveness of the vehicle body and sound package in reducing this noise. Effective noise reduction strategies require that the appropriate target levels be set for these factors. This paper reviews studies performed at Ford to establish such targets and the theoretical basis of these studies. To set sound package targets engine noise simulators have been used to study the sound package noise reduction capabilities of various vehicles. These studies include the effect of noise source location on attenuation, the effect of powerplant location and dimensions, and the effect of interior microphone location. Engine noise targets are being established by testing powerplants in the hemi-anechoic dynamometer test cells of the new AEC Building. Studies include the effect of engine rpm, load, and microphone location.