Objectives: Muffler with extended inlet has an additional dimension of variable compared to normal mufflers, that is the diameter. Understanding the effect of change in this diameter value affects Transmission Loss. Muffler used for experimentation is a reactive muffler, which cancels the noise waves using reflection phenomenon. Comparison of Computer Aided Engineering (CAE) in experiments to signify the technology advancement. Methods: MATLAB program is created for running the data and analytical solution. Finite element analysis with COMSOL Multiphysics using 3D model of muffler and computer aided engineering is done considering boundary conditions. The real experiment is carried out to evaluate confidence in simulated results where two load method is applied. Findings: Experimental setup results are showing results close to Numerical analysis. Analysis of the study suggest increase in diameter leads to rise in transmission loss. The experimental results of selected dimensions setup also prove same. Various geometric variation in muffler have effect of 10 to 30% on TL, while changing diameter from 10 to 20 mm of extended inlet raise the peak of TL to almost double and increase the average TL by 28%. Novelty: A diameter variation in extended inlet is an empty space in literature till now. This research combines analytical and experimental setups and comparison of results leads to a strong conclusion toward better muffler design.