Abstract Some of the most harmful sources of noise pollution to humans are the exhaust gases of internal combustion engines and factory equipment such as compressors and turbines. An environment contaminated by these sounds can also cause brain cancer. These noise issues can be addressed by installing expansion chambers in the exhaust path. Although numerous studies have been conducted on mufflers, three-dimensional mufflers with non-coaxial inlet and outlet dimensions have not been emphasized in previous studies. To improve the acoustic attenuation performance of the reactive muffler, the effects of different parameters on transmission loss need to be investigated, which is performed in the present paper. The geometry of the muffler was considered one of the noise control parameters. The muffler was modeled using the Helmholtz equation and simulated in COMSOL for analysis. The results demonstrate that the noise level drops with an increase in length, width, and height. The optimal values for the length, width, and height of the muffler are calculated to be 700, 320, and 170 mm, respectively. In addition, the optimum size of the non-coaxial muffler is found 60 mm. Compared to existing mufflers, the proposed muffler reduces noise by 13% to 34%. These research findings will assist the automotive or other related industries to reduce the noise produced by vehicles and other industrial devices.