Muffler Design by Noise Transmission Loss Maximization

ABSTRACT: The reduction of the emitted noise pollution from the exhaust system of engines is a real challenge for various industries. At this regard, mufflers have been used to reduce the transmitted noise from the engine of vehicles into the surrounding environment. Mufflers are designed to reflect the sound waves produced by the engine in such a way that they partially cancel themselves out. Noise transmission loss performance in muffler depends on its geometry. Therefore, maximization of noise transmission loss in mufflers using shape modification concept is an important research area. In this research, three approaches have been followed for the maximization of noise transmission loss in mufflers by using of shape modification concept. To begin, Three-point method is used to calculate the transmission noise loss for a muffler. The effect of geometry of muffler on the maximization of noise transmission loss over the 1/3 octave band and the hole frequency range, are investigated. The same procedure is repeated by using of Transfer-Matrix Method for the calculation of noise transmission loss. The diameters and lengths of in-, out-takes and silencer are considered as the design variables. Finally, the optimum shape of muffler based on the considered design variables for having maximum noise transmission loss is searched by genetic algorithm method. Keywords: Noise Transmission Loss, Geometry Modification Concept, Narrow Band Frequency, Design, Muffler, Silencer, Transfer Matrix Method, Genetic Algorithm. …………………………………………………………………………………………………………………………