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A verified computational model of a complex structure is crucial for reliable vibro-acoustic simulations. Mass and stiffness matrices of such a computational model may be constructed correctly, provided all the design information is available. Since it is an unknown, the damping matrix is usually populated through mathematical models based on some assumptions. In the current study, it is proposed to use the identified non-proportional structural damping matrix in the computational model. Structural damping matrix can be identified using the complex frequency response functions obtained from experimental modal analysis data. No matter what type of a damping mechanism a structure has; proportional or non-proportional, the frequency response functions of the system can be measured. First, the calculation procedure for the non-proportional structural damping matrix is explained. The damping matrix of an analytical model is identified successfully using the proposed procedure. The same procedure is then applied through a case study. Computational model of a test vehicle is constructed. Next, the test vehicle is subjected to a modal test to measure the frequency response functions of the structure. Incompleteness of the measured data and the requirements of the procedure are discussed, as well. The described procedure can be used in any model updating framework.

The coupled vibro-acoustic response of a sedan is analysed, and the effect of the folding rear-seat aperture is studied. First, a simplified model of an acoustic cavity that consists of two adjacent boxes connected by an aperture is modelled. An analytical solution is proposed to calculate the acoustic eigenfrequencies of the simplified model. Then, the uncoupled acoustic eigenfrequencies of the actual cavity (where the trunk cavity and the cabin cavity are connected through an aperture) are computed. It is shown that the planar acoustic eigenfrequencies of the sedan can be calculated approximately using the analytical solution proposed. To clarify the effect of the folding rear-seat aperture further, the coupled vibro-acoustic response of the sedan is analysed using different case studies. It is observed that the booming noise is highly correlated with the calculated uncoupled planar acoustic eigenfrequencies.

In this work, vehicle noise variability and dominant paths that cause low frequency booms are investigated. Five identically produced vehicles are subjected to road tests to acquire engine and exhaust mounts' acceleration and cabin sound pressure level (SPL) data. When the acquired data are processed, significant variability is observed among SPLs of vehicles. Low frequency booms are also diagnosed and two of the tested vehicles are selected to be further analysed. Structural transfer path analysis (TPA) is carried out, in which several parameters such as test conditions and frequency response function estimation procedures are highlighted. Dominant paths that contribute to booms are identified. To diagnose the cause of variability, a systematic approach is proposed, where all steps consist of experimental studies only. Finally, it is deduced that predominant paths, which are found to be main contributors of diagnosed booms, are also the root causes of variability observed.