IC engines are a major source of noise pollution. Mufflers require specific design and construction. Considering various noise parameters produced by the engine,the conventional design does not include much of a parametric noise analysis or other engine characteristics. In this study, a muffler for internal combustion engine has been designed and manufactured. The performance characteristic and the effect on transmission losses are investigated for different types of orifice plates (circle and Square rectangle, triangle) with different bore areas and frequency. Agood agreement with other works is obtained where the triangular bore shape orifice with minimum bore area is found to be the most effective.