A SEGMENTED RAYLEIGH-RITZ METHOD FOR PREDICTING SOUND-TRANSMISSION INA DISSIPATIVE EXHAUST SILENCER OF ARBITRARY CROSS-SECTION

Dissipative vehicle exhaust silencers often have cross-sectional geome tries that defy straightforward analytical solution of the acoustic ei genproblem; some kind of solution is, however, required as a part of t he basis for computational silencer design methods. As a useful altern ative to some of the more widely used numerical schemes such as finite element methods, a ''segmented Rayleigh-Ritz'' formulation is describ ed here. It has the advantages of being simple in concept and implemen tation, and making very modest computational demands. It has obvious d rawbacks in terms of a loss of accuracy in computing the eigenvalues a nd eigenfunctions, though these can be minimized by an appropriate cho ice of trial functions, segmentation geometry and number of segments. A trial function is proposed here, for the fundamental mode in an oval -section silencer. Favourable-comparisons are made between the predict ed and measured axial attenuation rate and phase speed. (C) 1995 Acade mic Press Limited