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The approaches used to develop an NVH package for a vehicle have changed dramatically over the last several years. New noise and vibration control strategies have been introduced, new materials have been developed, advanced testing techniques have been implemented, and sophisticated computer modeling has been applied. These approaches help design NVH solutions that are optimized for cost, performance, and weight. This paper explains the NVH practices available for use in designing vehicles for the new millennium.

Most of NVH related issues start from the vibration of structures where often the vibration near resonance frequencies radiates the energy in terms of sound. This phenomenon is more problematic at lower frequencies by structureborne excitation from powertrain or related components. This paper discusses a laboratory based case study where different visco-elastic materials were evaluated on a bench study and then carried on to a system level evaluation. A body panel with a glazing system was used to study both airborne and structureborne noise radiation. System level studies were carried out using experimental modal analysis to shift and tune the mode shapes of the structure using visco-elastic materials with appropriate damping properties to increase the sound transmission loss. This paper discusses the findings of the study where the mode shapes of the panel were shifted and resulted in an increase in sound transmission loss.

Body cavity fillers are used to inhibit noise propagation/amplification through body cavities such as sills, pillars, and posts' to improve vehicle NVH performance. Cavity fillers should be optimized by matching their performance with the global NVH objectives of the vehicle. A standard test method must be defined to acquire acoustical profiles and facilitate in the proper selection of materials based on performance. This paper discusses test results of 38 cavity filler samples which represent all currently used materials by the “Big Three” automotive OEMs. The samples were grouped into 4 categories based on their weight and fill configurations. Data was obtained utilizing an established, laboratory based, acoustical test method for fillers (SAE paper 930336). The laboratory results were analyzed to generalize the performance of cavity filler materials and to set acoustical goals for vehicle applications.

Liquid spray applied damping materials have potential advantages over conventional sheet damping materials in automotive body panel vibration applications. In order to understand the acoustical impact, a laboratory based NVH study was conducted to compare the damping and stiffness performance characteristics of various sprayable damping materials versus the production damping treatment. Based on this comparison, a criteria was developed to select potentially viable sprayable damping materials for vehicle testing. In-vehicle tests were also performed and compared to the laboratory findings to understand how well the results correlate. This paper discusses a criteria for selecting sprayable damping materials based on bench-top tests for vehicle applications, and the potential benefits of sprayable materials.