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Three different acoustic finite element models of an automobile passenger compartment are developed and experimentally assessed. The three different models are a traditional model, an improved model, and an optimized model. The traditional model represents the passenger and trunk compartment cavities and the coupling between them through the rear seat cavity. The improved model includes traditional acoustic models of the passenger and trunk compartments, as well as equivalent-acoustic finite element models of the front and rear seats, parcel shelf, door volumes, instrument panel, and trunk wheel well volume. An optimized version of the improved acoustic model is developed by modifying the equivalent-acoustic properties. Modal analysis tests of a vehicle were conducted using loudspeaker excitation to identify the compartment cavity modes and sound pressure response to 500 Hz to assess the accuracy of the acoustic models.

A structural-acoustic finite element model of an automotive vehicle is developed and applied to evaluate the effect of structural and acoustic modifications to reduce low-frequency ‘boom’ noise in the passenger compartment. The structural-acoustic model is developed from a trimmed body structural model that is coupled with an acoustic model of the passenger compartment and trunk cavities. The interior noise response is computed for shaker excitation loads at the powertrain mount attachment locations on the body. The body panel and modal participation diagrams at the peak response frequencies are evaluated. A polar diagram identifies the dominant body panel contributions to the ‘boom’ noise. A modal participation diagram determines the body modes that contribute to the ‘boom’ noise. Finally, structural and acoustic modifications are evaluated to determine their effect on reducing the ‘boom’ noise and on the overall lower-frequency sound pressure level response.

A capability is developed to rapidly estimate in the early vehicle design stage the effect of different vehicle architecture types and specifications on the vehicle interior road and engine noise performance. Regression analyses from the database of vehicle on-road, wind tunnel, and chassis dynamometer tests are used to identify the sound energy transferred by various vehicle subsystem architectures. Energy excitation from tire-road interaction, aerodynamic loads, and powertrain loads are used to predict the interior noise (dBA) and Articulation Index (AI) responses. Comparisons of the estimated versus measured dBA and AI responses show reasonable agreement of the vehicle interior noise.

A traditional beam-type finite-element model of the automobile exhaust system is shown to only be accurate in predicting the low-frequency rigid-body motion of the exhaust system on the support hangers. The beam-element model is then modified to account for the cross-sectional deformation of the exhaust pipes and is shown to accurately predict the bending vibration up to 300 Hz. The theoretical modification of the beam element model to account for the cross-sectional deformation is described in this paper. Experimental modal analysis tests of an exhaust system installed on a vehicle are conducted to obtain the measured vibration response for experimentally evaluating the accuracy of the model.

A vehicle concept finite-element model is experimentally assessed for predicting structural vibration to 50 Hz. The vehicle concept model represents the body structure with a coarse mesh of plate and beam elements, while the suspension and powertrain are modeled with a coarse mesh of rigid-links, beams, and lumped mass, damping, and stiffness elements. Comparisons are made between the predicted and measured frequency-response-functions (FRFs) and modes of (a) the body-in-white, (b) the trimmed body, and (c) the full vehicle. For the full vehicle, the comparisons are with a comprehensive set of measured FRFs from 63 tests of nominally identical vehicles that demonstrate the vehicle-to-vehicle variability of the measured FRF response.

A structural-acoustic finite-element model of an automobile trimmed-body is developed and experimentally evaluated for predicting body vibration and interior noise for frequencies up to 200 Hz. The structural-acoustic model is developed by coupling finite element models of trimmed-body structure and the passenger-compartment acoustic cavity. Frequency-response-function measurements of the structural vibration and interior acoustic response for shaker excitation of a trimmed body are used to assess the accuracy of the structural-acoustic model.