This paper is concerned with the use of the boundary element method for the analysis of acoustic characteristics of several resonator-type muffler elements. The transfer matrix approach is used to calculate the transmission loss of the muffler element. In the calculation of transmission loss of a closed tube or a resonator as a side branch, the impedance of the branch can be modeled by the impedance boundary condition in the boundary element model. This simplifies the modeling of the entire geometry and reduces the computational effort required. The boundary element solutions are compared with analytical solutions (plane-wave theory) and measured values; they show good agreement, in general, at all frequencies. The results demonstrate that the boundary element method gives reliable estimates of transmission loss of muffler elements in practical applications.