Title: Use of Layered Media for Noise Abatement in Automotive Interiors: A Balanced Approach
text: Concepts for dual density materials for usage as absorbers and decouplers are based on well-established layered media principles and have been applied for many years in non-automotive applications. Balancing the mass, air flow resistance, and thickness allows for improved noise attenuation in the low to mid frequency range which is of particular interest for automotive NVH management. Using these principles, products were tuned via mass and airflow resistance to reduce noise levels while also significantly reducing mass. Validation in various vehicles confirmed that up to a 55% reduction of a sound package's mass is possible. The considerable weight reductions of dash insulators and carpet systems are possible at the same times as the sound level in the vehicle interior is at least maintained and frequently improved. Product designs utilize non-woven fabrics and vertically and or horizontally lapped fibers to provide excellent fit and finish at low weight in an all-thermoplastic, recyclable product. Here, product development is described, which utilized computer modeling to provide a balance between transmission loss and absorption properties. Test results showing the effects of various properties on sound transmission loss and normal incidence absorption as well as in vehicle performance are given.