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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 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 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 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.

An engine system finite-element model is developed and experimentally evaluated for predicting the structural vibration and radiated noise of the running engine. Combustion and inertial loads from a rigid-body dynamic analysis of the crank-piston motion are applied as operating loads in the model. Comparisons are made with measurements of the structural vibration and radiated noise of a running engine. The comparisons show that the accuracy of the model in predicting structural vibration and radiated noise is generally adequate.

Low-frequency interior noise in the automobile passenger compartment can be significantly affected by the vibration behavior of the body panels which surround the enclosed cavity. This paper reviews a finite element method for computing panel-excited interior noise and outlines an approach for identifying potentially noisy panels adjacent to the passenger compartment. To illustrate the potential of the analytical method, it is applied to a production automobile. A structural modification suggested by the procedure is shown to significantly reduce the low-frequency interior noise to which the occupant is exposed. Experimental verification of the method is presented.

This paper describes the capabilities of the finite element method for vehicle interior acoustic analysis. Structural and acoustic finite element models of a van-type vehicle are employed to illustrate the implementation of the method in the design stage. Included as representative examples are studies of the acoustic resonances and forced acoustic response of the compartment cavity, which provide preliminary guidelines for initial compartment acoustic design. At a later stage, when the vehicle structural model has been developed, the finite element models of the structure and the passenger compartment cavity can be coupled for a total vehicle system evaluation. The paper illustrates the accuracy of the coupled model by comparison with the measured response in the van. Finally, the systematic application of this finite element methodology in a computer-aided procedure for the acoustic design of the passenger compartment is discussed.

A coupled engine-block and crankshaft model is developed and applied to predict the engine block vibration and radiated noise. Block surface vibration which is excited by combustion pulses and inertia loads is investigated as the source of radiated noise. The predicted response shows the dominant engine harmonics, resonant frequencies, global modes and local surfaces which participate to produce the radiated noise. A structural modification is evaluated which reduces the transmission of the loads through the bulkheads, and significant vibration and noise reduction is predicted.

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.