•There are several significant contributions associated with the proposed approach.•From the experimental results, we have found out that the modified muffler is more effective than the others without modifications in terms of transmission loss reduction of around 10%.•The baffle plate in the muffler plays a major role in the reduction of transmission loss.•The numerical results in MATLAB shows that the redesigned muffler offers a lesser amplitude of noise.•The new muffler design would help in reducing the exhaust noise of the automobile. In many technical applications in the present era, acoustics noise is the most difficult issue for humans. Although reactive and absorptive types of mufflers are currently available for noise reduction, their performance is limited for a variety of reasons. This study involves measuring transmission loss in an automotive exhaust muffler and then adopting new design parameters to reduce transmission loss, which is important for a greener environment. The automotive mufflers chosen for this study are investigated and employed in a numerical study to compare with an experimental investigation of passive noise control for transmission loss in automobiles. The transmission losses are compared to the original muffler chamber specifications to find the change in transmission losses, and the muffler chambers are modified by integrating a baffle plate to minimise the automotive exhaust noise. The transmission loss in a muffler is experimentally controlled by a passive noise, and a numerical analysis is performed for comparison using commercial software MATLAB. The installation of the baffle plate reduces the transmission loss, both in the narrow band and octave band region, according to the experimental, numerical and theoretical data, with more reduction happening in the narrow band region than the octave band region in this passive noise control experimental work.