Noise transmission and radiation through the muffler shell are not usually negligible in terms of overall radiated sound power from a muffler. This is especially true in mid- and high-frequency ranges. For the identification of noise radiation from the muffler jacket, a simplified BEM is adopted for the band analysis of mid- to high-frequency sound radiated from a muffler jacket having an irregular shape. The boundary integral equation is modified into a quadratic form to enable the prediction of sound level in a band. Monopole and dipole source terms in the conventional BEM are transformed into the auto- and cross-spectra of two vibrating sources, in which the cross-spectra are eventually neglected by assuming that the involved correlation coefficients are negligible. The radiated noise from an actual rear muffler jacket is predicted using the proposed method. Predicted sound pressure levels at several field points show small deviations in comparison with the measured data.
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