The effect of muffler design on reducing the noise pollution of a small two-stroke engine

Designing an efficient muffler for single-cylinder IC engines is not an easy task due to the limitation in designing a large muffler and the possibility of engine suffocation. In this regard, this research aims to experimentally investigate the feasibility of inexpensive muffler modification of a small portable two-stroke engine to reduce noise pollution. In experiments, the default muffler as a control treatment and a modified muffler together with a redesigned muffler have been examined to investigate the effect of muffler internal geometry and muffler design on sound emission characteristics. Based on the obtained results, the sound pressure level (SPL) of the modified and redesigned mufflers decreased by 5.31 and 6.86 percent compared to the default muffler, respectively. Meanwhile, installing the modified and redesigned mufflers increased the transmission loss (TL) equal to 8.62% and 10.08% compared to the default muffler, respectively. Also, the outcome of Discrete Fourier Transform (DFT) revealed that the intensity and amplitude of output frequencies from the redesigned muffler was significantly reduced in the frequency range of 2-6 kHz. As a general conclusion of this study, by installing the redesigned muffler, the maximum working times of the operator increased by 12.1 hours at 5000 rpm.