Examining the role of the hole and the orientation of the baffle on the loss of sound transmission in reactive mufflers using COMSOL software simulation

Introduction: Nowadays, noise pollution in the environment has become as a worldwide health concern. A large share of this noise comes from vehicles, where mufflers in their exhaust systems are essential for lowering engine noise levels. Proper muffler design and modifications to its geometric parameters, including adding holes in the baffle and changing their orientation, can significantly influence the acoustic performance of mufflers and contribute effective in enhanced noise reduction. Materials and Methods: The finite element numerical method was utilized to examine the acoustic effectiveness of the analyzed mufflers. At first, the mufflers were designed and modeled using COMSOL software. Subsequently, by modifying the desired geometric parameters, specifically by adding perforations to the baffle and changing the baffle orientations, their effect on sound transmission loss was examined. Results: The results of this study indicated that the sound transmission loss across the examined frequency range did not exhibit a consistent pattern with changes in geometric parameters. Specifically, at certain frequencies, the changes led to an increase in sound transmission loss, whereas at others, they resulted a decrease. However, in general, positioning the baffle's apex towards the muffler outlet increased the average transmission loss, while orienting the baffles’s peak towards the muffler outlet enhanced the average transmission loss, whereas adding perforations to the baffle reduced the average transmission loss. Conclusion: Creating perforations on the baffle and changing its orientation in reactive mufflers can affect sound transmission loss and, more broadly, its acoustic performance.