The Impact of Fiber Filling Density Variation on the Acoustic Performance of Silencers

Fibrous materials are often used to fill chambers in automotive silencers to achieve acoustic attenuation of air borne noise (especially above 200 Hz) in exhaust systems. It is clear that one of the major determinants of the acoustic performance of an absorptive silencer is the amount of fibrous material in the silencer [1]. However, there is little published data as to the impact upon acoustic performance of fiber packing density variations [2] within a silencer chamber In this study, cylindrical silencers with a straight through perforated tube have been used to experimentally study the impact of large density variations and voids, in both the radial and axial directions, upon the acoustic performance of a silencer. The acoustic transmission loss in a no-flow apparatus was the test measurement employed to determine acoustic performance.