Acoustic attenuation of a circular expansion chamber including fiber material and extended inlet/outlet tubes

Exhaust noise of IC engines is the main component of noise pollution of the urban environment. With the ever increasing population density of vehicles on the road, this has become an important area of research and development. Most of the advances in the theory of acoustic filters and exhaust mufflers have come about in the last four decades. Due to their desirable broadband noise attenuation characteristics expansion chambers with different configurations are widely used in the exhaust systems. The present study addresses essentially to the investigation of the acoustic attenuation performance of a circular expansion chamber including fiber material and extended inlet/outlet tubes, in which a theoretical analysis has been made in order to determine the transmission loss of the system as the acoustic performance parameter. First, a two dimensional analytical solution for the transmission loss is established via boundary value formulation for the concentric configuration of the circular expansion chamber having fiber material and extended tubes. It is important to note that the solutions obtained are expressed in terms of parameters characterizing the physical properties of the system under consideration. In order to compare the solutions, transmission loss of the system is also computed by using the finite element method model. All equations are then numerically solved for various combinations of physical parameters and the results are represented in figures. The comparison of the numerical results obtained via analytical formulations justifies the finite element method approach used here.