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As part of the update process to SAE J1637, “Laboratory Measurement of the Composite Vibration Damping Properties of Materials on a Supporting Steel Bar”, the Acoustical Materials Committee commissioned a round robin study to determine the current laboratory-to-laboratory variation, and to better understand best practices for composite loss factor measurements. Guidance within the current standard from a previous round robin study indicates a coefficient of variation of 35% for laboratory-to-laboratory measurements. It was hoped that current instrumentation and test practices would yield lower variability. Over the course of 5 years, 10 separate laboratories tested 4 bars: three damped steel bars and one bare steel bar. The bars were tested at -20°C, -5°C, 10°C, 25°C, 40°C, and 55°C. The damping materials were intentionally selected to provide low damping, moderate damping, and high damping to illustrate difficulties in determining the composite loss factor with increased damping.

As part of the update process to SAE J1637, Laboratory Measurement of the Composite Vibration Damping Properties of Materials on a Supporting Steel Bar, the Acoustical Materials Committee commissioned a round robin study to determine the current laboratory-to-laboratory variation, and to better understand best practices for composite loss factor measurements. Guidance within the current standard from a previous round robin study indicates a coefficient of variation of 35% for laboratory-to-laboratory measurements. It was hoped that current instrumentation and test practices would yield lower variability. Over the course of 2 years, 8 laboratories tested 4 bars, three damped steel bars and one bare steel bar. These bars were tested at -20°C, -5°C, 10°C, 25°C, 40°C, and 55°C. The damping materials were intentionally selected to provide low damping, moderate damping, and high damping as difficulties in determining the composite loss increase with increased damping.

Test standards are essential for evaluating the performance of a product properly and for developing a data base for the product. This paper discusses various standards that are available for determining the acoustical performance of sound package materials. The paper emphasizes various SAE standards that are available in this area, the reasons why these standards are important to the researchers working in the mobility industry, the history behind the development of these standards, and how they are different from standards that are available from other standards organization on similar topics.

The new Blachford Acoustics Laboratory was designed and constructed to bring resources typically available only in the automotive industry to the non-passenger car markets. Prior to the opening of this laboratory, engineering tools common in the automotive industry, such as a hemi-anechoic chamber with chassis dynamometer or a reverberation room with a front of dash transmission loss suite were difficult or impossible to find for Class 8 truck, transit bus, or Class A motor home acoustical analysis. This was primarily due to vehicle size and weight, but also due to cooling air and engine exhaust extraction requirements. In a previous paper1 the author described the design of the laboratory and the acoustical goals for the various test spaces. Challenges included construction cost, sizes and weights of the test vehicles, the variety of potential products to undergo testing, and the selected laboratory site.

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.

Motorhomes or recreational vehicles (RV's) are unique vehicles in that they pose many interesting design challenges to acoustical engineers. This type of vehicle has many of the typical NVH (Noise Vibration and Harshness) issues seen in passenger cars and heavy trucks; however, there is an entire arena of NVH issues that are not seen in these other products. The issues are not present in these other markets; because a motorhome, not only serves as a means of transportation, it also serves in a secondary role as a home. The dual role of the coach creates many residential noise concerns. Some of these issues include managing generator sound levels while the coach is either parked in a campsite or on road, controlling engine noise levels for designs where the bed serves as the engine cover, and controlling wind noise to improve speech communication between the driver and passengers. Complicating these issues is the fact that each unit is semi-customized.

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.

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.