Boundary element formulation using modified Green's functions for media with random distribution of scattering objects

Paper in proceeding, 2009

The engine bay of an automotive vehicle is a partly open enclosure that is densely filled with numerous objects such as accessory parts, pipes, tubes, and cables. These objects cause scattering of the sound waves inside the engine bay, which leads to an increased absorption of sound power compared to an enclosure without objects. However, it is time-consuming to include all the details of the geometry and acoustical properties of the objects in numerical simulations, predicting the sound power radiated to the exterior. This paper presents how a deterministic boundary element model and a statistical intensity/power model can be combined to give an approximate description of the sound field for cases with randomly distributed scatterers. The boundary element formulation describes the coherent part of the wave field by using modified Green's functions that include the average effect of the scattering objects. The waves scattered at the objects are assumed to result in an incoherent field that is described by an intensity model. The modelling approach is evaluated by calculating the power radiated from a partly open enclosure in a two-dimensional geometry. The results are convincing and it is concluded that the approach is suitable.