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In this work the acoustic behavior of silencers with absorbent material is analyzed through the transmission loss. The numerical models are validated through the approximation of numerical and experimental data. The main steps for the development of this work includes: (i) obtaining the analytical model, (ii) obtaining the experimental data for acoustic characterization of the material, (iii) solution of the mathematical model using the transfer matrix techniques.

The strategy for optimizing the shape design of automotive mufflers is presented. The main goal is to obtain the basic dimensions of the acoustic muffler with the TL been maximized in the interest band frequency. The Finite Element Method with quadratic elements and the method of the four modified parameters are used to calculate the necessary parameters to evaluate the TL's numeric value. The minimizing (or maximizing) problem is solved using the method of the viable directions of Zoutendijk due to its robustness. Numerical experiments performed with asymmetric expansion chambers with extended inlet/outlet show results for the shape optimization with and without constraints.

The dynamical behaviour of an automotive vehicle is analysed by use of a model with seven degrees of freedom for two load situations of the vehicle, loaded and unloaded, and for two different types of road, asphalt and paved. The vehicle velocity is varied between 5 and 30m/s. The passive linear suspension system is firstly optimized. Afterwards a system with passive elements in parallel with active elements with full and limited state feedback is optimized. To find the suspension elements characteristics it is used the stochastic optimal linear control theory through the minimization of the performance index whose constituent parts are: vehicle acceleration (comfort), suspension working space (structural limitation), road holding (safety) and control force.