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The continuous improvement of powertrain structure and airborne NVH characteristics has brought both higher expectation of customer acceptability and an increasing challenge to solution innovation. Emergence of “unique” vibro-acoustic power train signatures has been driven by three basic factors; 1) material and manufacturing technologies of power train subsystems and components with new material and structural properties 2) expanded diversity in base power train system concepts (e.g. hybrids, CVT's, Alternative /PEM/SI/common rail fuel delivery, diesel proliferation, “power on demand” combustion strategies etc.) and 3) Acoustic “unmasking” effects with respect to detectable sources of noise as overall sound pressure levels decrease.

This paper discusses the approach and application of controlling material and manufacturing parameters in development of lightweight acoustic interior systems. First addressed is the theoretical premise of noise control mechanisms and their relationship to material property/process sensitivity through poroelastic model simulation. The optimal balance of sound transmission loss and absorption in achieving optimally tuned acoustic performance is then presented along with material sample and in-vehicle experimental results. The ability to acoustically tune the vehicle interior to a desired sound level and frequency content through proper design & control of the elastic porous properties achieved by unique acoustic material/process flexibility & capability is demonstrated.

This paper describes a method which combines state of the art NVH measurement methods for structure and airborne noise characterization integrated with a manufacturing process which utilizes results of these measurements to spatially vary the construction of dash insulators based on specific automotive vehicle requirements. An integrated technique for measuring structure and airborne based noise sources are discussed and demonstrate the capability to measure accurately higher frequency phenomena and the associated short acoustic wavelength and high spatial mode complexities often encountered in the development of vehicle sound packages. Based on these results the variable mass barrier process is explained specific to incorporation into the manufactured product using a robotic spray technology that varies distribution of material across the dash insulator surface. Overall benefits are discussed.