Application Of The Modal Expansion Technique To Improve The Results OfFEM/BEM Acoustic Radiation

Abstract

The use of FEMIBEM models in the prediction of sound radiation by vibrating structures is a well-known method already available in different software packages. There are many papers dealing with the numerical precision of the acoustic BEM methods, but it is clear that the accuracy of their predictions is mainly affected by the correct description of the problem boundary conditions, especially the surface normal velocities. In this work, a simple test case consisting of a vibrating thin metal plate is solved using different methods to describe the normal velocities. FE structural model, measured data assigned to different surfaces and a hybrid technique called modal expansion are used. The aim of this paper is to evaluate the differences in the prediction using the different models and to check the possible errors coming from usual mistakes in real application (modelling errors and measuring errors). Finally an experimental work is carried out to enlighten the previous conclusions.