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A simulative program named as MAP (Muffler Analysis Program) is developed for the rapid calculation and analysis of acoustic characteristics of duct muffling systems. The program is based on the plane wave theory and uses the Visual Basic 6.0 to create a friendly GUI (Graphic User Interface) for input of the geometrical and physical parameters to build and modify the duct muffling systems quickly. The relations among the acoustic elements are established by using the transfer matrix method, the transmission loss (TL) and insertion loss (IL) may be calculated, and then the results are plotted in terms of curves. Map allows designer to change parameters of the duct muffling systems expediently, in order to examine the effects of design changes on the acoustic attenuation characteristics and finally to get an acceptable solution.

The one-dimensional analytical approach, three-dimensional finite element method (FEM) and boundary element method (BEM) are developed to predict and analyze the acoustic attenuation performance of three-pass perforated tube muffler with end-resonator. For an elliptical muffler, the predictions of transmission loss from the FEM and BEM agree well each other throughout the frequency range of interest, while the one-dimensional analytical solution shows a reasonable agreement with the numerical predictions at lower frequencies and deviates at higher frequencies. The FEM is then used to investigate the effects of geometrical parameters and internal structure on the acoustic attenuation performance of three-pass perforated tube muffler with end-resonator.

The one-dimensional (1-D) time-domain approach and the three-dimensional finite element method (FEM) are used to predict and analyze the acoustic attenuation performance of three-pass perforated tube mufflers with and without end-resonator. For the given muffler configurations, the transmission loss results obtained from the 1-D time-domain approach agree reasonably well with the FEM predictions within the plane wave region, while the 1-D results derive the FEM predictions at higher frequencies. The FEM is then used to investigate the effects of internal structure on the acoustic attenuation performance of the mufflers, while the 1-D time-domain approach is employed to examine the influence of high temperature gas flow on the acoustic attenuation performance of the mufflers within the plane wave region.

Combining the acoustic attenuation behaviors of reactive and dissipative mufflers, a hybrid muffler design may be expected to provide broadband high noise attenuation and low pressure drop. In the present study, a multi-chamber muffler with selective sound-absorbing material placement proposed by Sterrett et al [1] is considered. The one-dimensional analytical approach based on the plane wave propagation theory and three-dimensional substructure boundary element method are developed to predict the acoustic attenuation characteristics of the multi-chamber muffler. The effects of flow-resistivity of sound absorbing material, porosity of perforation and geometrical parameters on the acoustic attenuation performance of the multi-chamber hybrid muffler are investigated in detail.