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A CAE procedure for modeling the aerodynamic excitation of greenhouse surface vibration and its reradiation as noise is described. The procedure begins with a description of the steady flow over the surfaces. This is used as a basis for estimating the spatially varying unsteady pressure loading. The approach is semi-empirical, utilizing normalized pressure data collected through wind tunnel testing of production vehicles. The unsteady pressures are utilized within a normal mode analysis to predict vibration of the greenhouse panels. Interior noise associated with the panel vibration is estimated from a statistical energy analysis model. We show that contributions of multiple surfaces can be significant.

Power train noise reaches the interior through structureborne paths and through airborne transmission of engine casing noise. To determine transfer functions from vibration to interior noise a shaker was attached at the engine attachment points, with the engine removed. A simple engine noise simulator, with loudspeaker cones on its faces, was placed in the engine compartment to measure airborne transfer functions to interior noise. Empirical noise estimates, based on the incoherent sum of contributions for individual source terms times the appropriate transfer function, compared remarkably well with measured levels obtained from dynomometer tests. Airborne transmission dominates above 1.5kHz. At lower frequencies engine casing radiation and vibration contributions are comparable.