Multiple layer fiber filled sound absorber and a method of manufacturing the same

Abstract

A multiple layer fiber filled sound absorber and method of manufacturing the absorber are disclosed. The sound absorber includes an outer housing, a porous or perforated inner tube or housing defining a passageway through which a gas may flow, and two layers of sound absorbing material, such as fiberglass wool, is positioned between the housings. The sound absorbing material adjacent the inner housing is selected to be more heat resistant than the material farther away from the inner housing. The sound absorber is filled with the sound absorbing materials using a direct fill process in which continuous fibers are injected into the sound absorber. In preparation for filling, a partition is positioned between the housings to define two chambers. Each chamber is filled with one of the sound absorbing materials. The partition may then be removed from the sound absorber, or may be left in place (in which case the partition is preferably porous or perforated). The two sound absorbing materials may be filled to different densities. If the partition is removed, the densities will tend to equalize. The direct fill process simplifies and reduces the cost of filling the container and provides a muffler that is uniformly filled and has an improved sound absorbing quality.