Search Results

This paper addresses the numerical simulation of motorcycle exhaust system noise using a transfer matrix method (TMM) supporting high order analytical acoustic modes representation combined with finite element method (FEM) included in the Actran software, R15. In the state-of-the-art of hybrid TMM/FEM approach the main assumption consists in a 1D plane wave acoustic propagation in the components connections which is intrinsically limiting the maximum frequency of the analysis. In motorcycle exhaust systems this limitation is even stronger because typical geometries exhibit strong curvatures and bends causing the scattering of the acoustic wave into higher order modes. Therefore, results might be erroneous even at frequencies at which only the plane wave is expected to be propagating. The improved transfer matrix method presented in this paper overcomes this limitation allowing to increase the range of applicability of this method.

This paper describes a new approach for performing indirect vibration measurements using acoustic measurements and an inverse calculation procedure based on a finite element model and a new type of hierarchical basis (so-called pellicular modes) for representing the unknown vibration field. The paper first presents the theory of the method. A parametric study on a simple test case then highlights the effect of the number of microphones and of the background noise level on the quality of the reconstruction of the vibration pattern. The application to a real set of acoustic data on a section of an ATR regional aircraft is then provided.