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Technical Paper

Optimal Sound Package Design Using Statistical Energy Analysis

In the early stages of a vehicle program, sound package design is significantly complicated by numerous competing requirements including cost, weight, acoustical targets and packaging space. The problem is further convoluted due to a limited definition of the vehicle at this time. In this article, a Statistical Energy Analysis (SEA) model of the vehicle is created based on a gross description of the vehicle architecture. A large material database of commonly used sound package configurations is then linked to the SEA model. Genetic Algorithms (GA) are finally applied to optimize the sound package design to satisfy cost, weight, acoustical targets and packaging requirements in the vehicle design.
Technical Paper

A Dissipative Approach to Vehicle Sound Abatement

This paper explores the performance of light weight attenuators, which take a dissipative approach to sound abatement in the motor vehicle. An analytical model is used to predict the sound transmission loss and random incidence sound absorption of attenuators, absorbers and sandwich insulation systems. Then, a mathematical expression is developed which combines the dissipative and sound transmission loss performance to determine the total noise reduction provided in the vehicle. Using this equation, the performance of multi-layered attenuators is shown to be comparable to, or better than that of sandwich insulators. Finally, test results from various studies in vehicles show that significant weight savings can be realized by using these multi-layered attenuators, which take a dissipative approach to vehicle sound insulation, rather than the traditional sandwich insulation system.
Technical Paper

Reclaimed Fiber Acoustical Composites - Addressing Today's Recycling Challenges

Recycling of resinated and non-resinated reclaimed fiber pad, used in automotive applications as sound absorbers and insulators for headliners, package trays, floor insulators etc., has been ongoing for over thirty years. The feedstock for the fiber is a source reduction of textile industry waste, as compared to alternate first use material products. The fibers are actually reclaimed from apparel trim scrap (approx. 700MM pounds of apparel scrap produced annually). The acoustical trim product uses 60 to 100% of the available reclaim apparel scrap - material originally intended for basic necessities such as clothing, and in the case of resinated pad, blends this fibrous material with a binder resin (this only is a first use material.) During pad production, “pre-use” processing and trim scrap are reclaimed and re-introduced into production, up to 70% loading for resinated pad and up to 100% loading for non-resinated fiber pad.
Technical Paper

New Low-Odor Phenolic-Resin Molded Insulators: Product and Process Technology

Fiber-bonded insulators are reclaimed textile fibers bonded with phenolic resins. These have been used in automobile interiors and under-hood applications for a considerable time. Odor issues can result with the conventional phenolic-resin bonded molded insulators under improper process conditions. Under improper process conditions conventional phenolic resins can result in the formation of trimethylamine and other amines, which can form objectionable odor in the automobile interior. This paper highlights the process and product development for new low-odor phenolic-resin molded insulator. The materials are characterized by odor performance, mechanical properties and acoustical behavior. The odor issues associated with the phenolic-resin molded insulators have been shown to be eliminated.