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Sound absorption for multiple materials was measured in a small reverberation room using different sample sizes. The largest samples were cut to progressively smaller sizes to study the effect of sample size on sound absorption. The materials tested included three different recycled fibers, two PET fibers with facers, and one open-cell foam. These materials spanned low, medium, and high sound absorption over the range of test frequencies. The results for each material and each sample size are reported and compared. Comments are provided on sample size for labs with small reverberation chambers. These results will be considered in the development of an SAE test method for sound absorption using small reverberation rooms.

Flat, constant thickness composites that consisted of a microperforated top layer plus a fibrous decoupler layer were tested for random absorption and transmission loss (TL) performance. The top, microperforated layer consisted of a relatively thick film that contained small, precise micro-perforations. For reference, top layers that consisted of a resistive scrim and an impervious film were also included in this study. Two fibrous materials of constant thickness were used for the decoupler layer between a steel panel and the top microperforated film. The composites' absorption and TL performance were also modeled using the well-known transfer matrix method. This method has been implemented in a commercially available statistical energy analysis (SEA) software package. A comparison of testing and modeling results showed reasonable agreement for absorption results and even better agreement for transmission loss and insertion loss results.

The sound absorption coefficient and transmission loss of automotive floor systems with several different fiber decoupler materials are presented. Flooring materials included tufted carpet with and without mass layers and non woven carpet without mass layers. Decouplers included die cut and molded fiber under pads in a range of fiber types and weight. Mass backed floors as well as lightweight dissipative floor systems are compared. The results show a range of performance for sound absorption and transmission loss that allows an NVH engineer to select material combinations to achieve targeted noise reduction in a vehicle.