### ASA 127th Meeting M.I.T. 1994 June 6-10

## 4pSAb5. Response of a nonbaffled sandwich panel submitted to a reverberant
chamber acoustic environment.

**Hugues Nelisse
**

**
Olivier Beslin
**

**
Jean Nicolas
**

**
**
*G.A.U.S., Mech. Eng. Dept., Univ. de Sherbrooke, Sherbrooke, PQ J1K 2R1,
Canada
*

*
*
A method has been developed to obtain the structural response of a
sandwich panel placed in a large reverberant chamber excited by a so-called
diffuse field. The approach is based on an integral equation method for the
pressure response in the chamber. The Helmotz--Kirchoff theorem is expressed
using a pressure jump function across the surface of the panel [see for
instance D. Ouellet et al., J. Acoust. Soc. Am. 89, 2131--2139 (1991)]. A modal
expansion over modes of rigid cavity and in vacuo modes of the panel leads to a
set of linear coupled equations reflecting the existence of fluid--structure
interaction. Numerical resolution of the set of equations allows us to obtain
physical quantities of interest, such as the deflection of the plate and the
jump of sound pressure across the panel. It is found that the modal behavior of
the acoustic excitation is of a major importance for the response of the panel.
Results for large panels with added masses, used for instance in aerospace
industry, will be discussed. Convergence of the solution, as well as its
frequency range of validity will also be analyzed.