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With stricter pass-by norms, reducing engine noise radiation is becoming more important. Adding ribs to improve stiffness is one efficient approach to achieve this goal. This paper performs the optimization of ribs which are added on the surface of an inline six-cylinder engine block. The ribs are placed orthogonally. For the optimization, optimization variables are set up to update the dimensions of the ribs in each iteration. The limits of the size changes are defined by the optimization constraints. The overall sound power radiated from the engine block surface between 500Hz and 1450Hz is chosen as the optimization objective. In each iteration, the radiated sound power is obtained by numerical analysis of a fully coupled structural-acoustic model, while the FEM (finite element method) is adopted for calculating the structural response and BEM (boundary element method) is used to compute the noise radiation from the engine block surface.

Sound propagation through noise control treatment is governed by fluid, mechanical and geometric properties of the materials. The knowledge of material properties is important to improve the acoustical performance of the resulting noise control products. A method based on optimization together with genetic algorithm is used to estimate material properties of multi-layered treatments. Unlike previous inverse characterization approaches based on normal incidence performance metrics measured using standing wave impedance tubes, the current approach is based on random incidence performance metrics. Specially, the insertion loss ‘measured’ from two room transmission loss suite is utilized. To validate the applicability of the proposed method, numerically synthesized insertion loss computed from known material properties are used. In order to properly represent the ‘measured’ values, noise is added to the numerically synthesized insertion loss values.