Nishino H., Honda I.

Regarding the prediction of structure-borne sound in a structure consisting of thick elements, there are some difficulties in application of the conventional SEA based on thin plate bending and in-plane waves. The vibration energy transmission phenomena between thick elements are more complicated than that of thin plates, - for instance, the adjacent walls, ceiling and supporting walls, and beams in structural frame. This paper examines the applicability of WIA (wave intensity analysis) to the prediction of the vibration energy level in an L-shaped structure assembled by thick plates. The bending wave in plates is thus expressed by Mindlin�fs theory, taking the shear deformation and rotary inertia into consideration. The new model is introduced to improve the accuracy of wave transmission coefficients for line junctions between thick plates by considering a beam element at the junction. As an example for adoption of the present method, the vibration energy level of L-shaped assembly with an elastic rib at the junction is calculated by injecting the input power into one side of elements. The results are compared with ones calculated by the conventional SEA and FEM. In the analysis by FEM, the thick plate elements are divided into extremely fine meshes to express an appropriate wave field in the high frequency of interest. The vibration energy level by the present method is in good agreement with one by FEM, approximately within 3dB up to 2kHz. This concludes that the present method using Mindlin�fs bending and assuming the junction inserted an elastic beam brings forth an improved prediction of structure-borne sound in a structure consisting of thick elements.