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Finite element analysis (FEA) is commonly used in the automotive industry to predict low frequency NVH behavior (<150 Hz) of structures. Also, statistical energy analysis (SEA) framework is used to predict high frequency (>400 Hz) noise transmission from the source space to the receiver space. A comprehensive approach addressing the entire spectrum (>20 Hz) by taking into account structure-borne and air-borne paths is not commonplace. In the works leading up to this paper a hybrid methodology was employed to predict structure-borne and air-borne transfer functions up to 1000 Hz by combining FEA and SEA. The dash panel was represented by FE structural subsystems and the noise control treatments (NCTs) and the pass-throughs were characterized via testing to limit uncertainty in modeling. The rest of the structure and the fluid spaces were characterized as SEA subsystems.

Tuned mass dampers (TMDs) or vibration absorbers are widely used in the industry to address various NVH issues, wherein, tactile-vibration or noise mitigation is desired. TMDs can be classified into two categories, namely, tuned-to-resonance and tuned-to-discrete-excitation. An overwhelming majority of TMD applications found in the industry belong to the tuned-to-resonance category, so much of information is available on design considerations of such dampers; however, little is published regarding design considerations of dampers tuned-to-discrete-excitation. During this study, a problem was solved that occurred at a discrete excitation frequency away from the primary resonance frequency of a steering column-wheel assembly. A solution was developed in multiple stages. First the effects of various factors such as mass and damping were analyzed by using a closed-form solution.

Recently introduced “Stow-'n-Go” feature in minivans provides the option of folding the 2nd and 3rd row seats flat into a special compartment. These special storage compartments, or “tubs”, are designed under many challenging and competing design requirements, one of which is noise and vibration. In this study, both experimental and analytical tools are used to study the NVH performance of seat tubs considering different materials, constructions and damping treatments. The challenge of balancing stiffness and damping in a tight packaging space is augmented by the minimum weight and cost requirements. The details of material selection process for the minivan tubs are presented considering different materials and damping treatments. Various design alternatives considered during the optimization of weight, packaging space, and NVH performance are discussed. Results of the component and the vehicle testing are complemented with SEA modeling.

In industrial applications, both constrained and unconstrained damping treatments are used frequently for noise and vibration control. The additional Damping Loss Factor (DLF) and stiffness gained from these damping treatments are quantified by a standard test procedure, as detailed in ASTM and SAE standards. In this test procedure, which is commonly referred to as Oberst beam testing, the uniform isotropic behavior of traditional damping material is evaluated by measuring one-dimensional flexural vibration response of a simple beam. The recent advances in damping technology have led to emergence of robotic Liquid Applied Spray-on Damping (LASD) treatments. The application of LASD can result in non-uniform thickness, uneven distribution, and orthotropic behaviors.

Acoustical performance of many NVH systems is evaluated by computing the radiated noise of such systems. Although the computation of relevant acoustical quantities such as the radiation efficiency and sound power can be performed by using approximate method such as the Rayleigh integral method, in most instances rigorous methods such as the boundary element method is preferred. Unfortunately the boundary element method for radiation problems fails at the eigenfrequencies associated with the interior cavity. Additionally, in most instances the acoustical performance is needed to be evaluated over a range of frequencies and in a traditional boundary element system this evaluation is performed independently at each discrete frequency. In this presentation, issues associated with the accuracy and efficiency of these solutions are addressed by investigating the solution of progressively more complex industrial problems.