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This paper focuses on the development of treatments to control airborne noise through the dash panel. For a noise control material supplier, these treatments can be the most challenging to design because of the number of pass-throughs and design constraints. The dash panel development process includes extensive in-truck testing and analysis to identify sound paths (location and magnitude) and establish design criteria, laboratory material testing to aid in the selection of appropriate materials, laboratory component testing to select areas requiring treatment and to design the shape of the treatments, and in-truck testing to verify the performance of the new treatments.

The new Blachford Acoustics Laboratory was designed specifically for acoustical testing of large vehicles, such as off-highway machines, recreational vehicles, and heavy trucks. While there are many automotive and architectural test laboratories for which a new laboratory can be based, there are very few acoustics laboratories capable of testing these larger vehicles. However, by drawing on the experience with the previous Blachford Laboratory, several off-highway manufacturers' test facilities, and the newer automotive manufacturer and supplier laboratories, a functional and cost effective design was developed. This design features indoor and outdoor test areas, including a large hemi-anechoic chamber equipped with a chassis dynamometer, a reverberation room with several transmission loss openings, work rooms, office areas, and a 10 meter radius outdoor drive-by pad.

Class 8 truck manufacturers use a wide variety of materials for cab floor construction. These include traditional steel and aluminum plate as well as aluminum honey-comb and balsa wood core composites. Each of these materials has unique transmission loss properties. The acoustical performance of the floor system, (cab floor, decoupler, and barrier) depends not only on the acoustical performance of the decoupler and barrier, but also on the cab floor material. This paper outlines an experimental technique for selecting an acoustical floormat system utilizing vehicle and laboratory tests that takes these factors into account.