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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 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.

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.

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.