4pSA8. A normal decomposition technique for fully coupled problems in structural acoustics.

Session: Thursday Afternoon, June 19

Author: Debashis Basu
Location: State Univ. of New York at Buffalo, 212 Ketter Hall, Amherst, NY 14260
Author: Suresh Kumar S.
Location: State Univ. of New York at Buffalo, 212 Ketter Hall, Amherst, NY 14260


Problems in structural acoustics are inherently coupled. Whenever a structure vibrates, there is a noise associated to it. Similarly, any noise would induce vibrations in the structure, however small, depending on how thin it is. The indirect boundary element technique has been used for quite some time now to model the acoustic domain. Again, plate/shell formulations for thin structures using finite elements are well known. Usually, for a coupled structural acoustic problem, the associated eigenvalue problem of the structure is solved first, and then the acoustic system is coupled using a predetermined number of modal participation. For weak coupling, this technique gives accurate results considering a few modes, while a greater number of modes are necessary for problems with strong coupling. An alternate technique is presented in this paper, where the structural degrees of freedom are condensed to couple directly with the acoustic system. For the frequency under consideration, there are absolutely no assumptions involved and the coupling is exact. Several examples illustrate the validity of the method. For problems where the level of coupling (weak or strong) and the number of modes to be included are difficult to ascertain, the current technique provides an excellent alternative. With noise control playing a major role in developed and developing countries, a better simulation of the field problem clearly identifies areas for noise reduction measures.

ASA 133rd meeting - Penn State, June 1997