Exhaust noise of IC engines is the main component of noise pollution of the urban environment. To attenuate the exhaust noise, expansion chambers with different configuration has become an important area of research and development. The present study considers acoustic characteristics of circular fully-filled perforated dissipative mufflers with extended inlet/outlet. In addition to the finite element method, an experimental work is considered. Fiber material with different radii is presented and discussed. Perforation ratios of the pipes are also discussed in this study. All parameters validated with experimental work with a practical designed muffler for obtaining the transmission loss. Comparison with the results obtained via experimental measurements justifies the approaches used here.