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A computational design study, performed in conjunction with experiments, to reduce the howl noise caused by the roof rack crossbars of a production automobile is presented. This goals were to obtain insight into the flow phenomenon causing the noise, and to do a design iteration study that would lead to a small number of cross-section recommendations for crossbars that would be tested in the wind tunnel. The flow condition for this study is 0 yaw at 30 mph inlet speed, which experimentally gives the strongest roof rack howl for the vehicle considered for this study. The numerical results have been obtained using the commercial CFD/CAA software PowerFLOW. The simulation kernel of this software is based on the numerical scheme known as the Lattice Boltzmann Method (LBM), combined with a two-equation RNG turbulence model.

Modern product design cycles are requiring faster turnaround of design changes and the accompanying noise, vibration and harshness analyses. Design sensitivity analysis (DSA) guides the designer in making changes by indicating the model variables that cause the greatest benefit in noise or weight reduction. The use of analytical models based on statistical energy analysis (SEA) is attractive for predicting noise and vibration environments because of their simplicity and solution speed compared with deterministic models. This paper describes the implementation of DSA in an SEA computer code. Examples of SEA/DSA for controlling airborne and structureborne noise problems are described.

Airborne sound transmission through vehicle panels with penetrations and sound insulation is a major component of high frequency interior noise in cars and trucks. Accurate analytical models of interior noise require high fidelity simulation of these paths in order to perform upfront design of the sound package. This paper describes a modeling approach based on Statistical Energy Analysis (SEA) that provides a general and flexible capability for incorporating sound package parameters within an analytical model of high frequency interior noise. Validation of the model for sound transmission through panels with holes and with typical sound insulation material is achieved through innovative testing methods that reveal dynamics of the decoupler and barrier layers. Refinements of the general approach that consider more deterministic features of the specific decoupler material are also suggested.