In this study, TL characteristics of muffler shells are simulated using analytical and numerical model. Noise generated by engines, is radiated out into the atmosphere at the radiation end of the muffler and also from the shell of the muffler. So, accurate prediction of sound radiation characteristics from muffler shells is of significant importance in automotive exhaust system design. In analytical method, an exact solution is obtained by solving the vibration equation of the shell and acoustic wave equations simultaneously. Then, in numerical model, with the aid of SYSNOISE, commonly used commercial boundary element software, the coupled structural FEM-BEM model is applied to predict the TL of muffler shell. The predicted results agreed reasonably well with the experimental results. The effects of important design parameters likes thickness and geometrical shape are studied to provide design guidelines.