In a large-scale problem which needs to be calculated in wide band of frequencies, an analysis of acoustic system via a finite element method usually requires significant computation time since it solves only one target frequency at once. To shorten such a long computation time, two numerical methods can be used. The one is a pade approximation and the other one is a model order reduction scheme based on Quasi-Static Ritz Vector. Pade approximants is the best approximation of a function by a rational function of given order. In this reason, pade approximants outperform the Taylor expansion and give a good approximation over a wide frequency ranges. Model order reduction scheme based on QSRV also shows good approximation in engineering systems. In this paper, analysis of acoustic system such as muffler was carried out by those two numerical methods. After calculating transmission loss of muffler by using pade approximants and model order reduction scheme, we compare the accuracy and error of transmission loss in each case. Furthermore analysis was also carried out in a large scale system such as 3D muffler and we compare the efficiency, accuracy and CPU time.