Simulation Analysis of Acoustic Attenuation Performance for Different Shape of an Expansion Chamber Silencer

This paper studied the internal laws of silencers´ acoustic attenuation performance, when the cross-sectional shape, length and diameter of the expansion chamber changed. Based on the BEM-FEM coupled model and to combine with the improved Four-pole Parameters Method, the transmission loss (TL) was calculated. It is pointed that the flatter the expansion chamber is, the worse the performance is. When the length decreases, the domes of the TL become broader, and the number of domes decreases. When the diameter increases, the TL increases, but the growth rate and the inactive frequency decrease. The results indicate that by using computer modeling analysis, it is sensible to optimize the shape to meet the needs of the eliminating frequency band and the applied circumstance.