This SAE Recommended Practice describes a laboratory test procedure for measuring the acoustical performance of a system consisting of a body cavity filler material formed into a rectangular cross-section channel. Materials for this test may include both heat reactive and chemically reactive products, with or without a shelf to simulate a baffle in an application, or a combination of body cavity filler and aluminum foil to enhance the performance. These materials are commonly installed in transportation systems such as ground vehicles, and thus reduce the noise propagation through the rails, rockers, and pillar/posts.