## 4aAA7. Sound transmission through a thin baffled plate: Comparison of a light fluid approximation with the numerical solution of the exact equations and with experimental results.

### Session: Thursday Morning, December 5

### Time: 9:40

**Author: Paul J. T. Filippi**

**Location: CNRS, Lab. de Mecanique et Acoustique, 13402 Marseille Cedex 20, France**

**Author: Pierre-Olivier Mattei**

**Location: CNRS, Lab. de Mecanique et Acoustique, 13402 Marseille Cedex 20, France**

**Author: Adriaan H. P. van der Burgh**

**Location: TU Delft, 2600 Delft, The Netherlands**

**Author: Koen de Jong**

**Location: TU Delft, 2600 Delft, The Netherlands**

**Abstract:**

A thin elastic rectangular plate, with clamped boundaries, extended by an
infinite perfectly rigid plane baffle is considered. Both half-spaces are
occupied by a gas. A sound source is located on one side of the plate. One is
interested by the sound field transmitted through the plate. The boundary value
problem governing the system is solved by two methods: A boundary element
method, which gives a numerical solution of the exact equations; and a series
representation of the solution in terms of the fluid-loaded plate resonance
modes, an analytical approximation which is obtained by a perturbation technique
(the ratio of the gas density to the surface mass of the plate being the small
parameter). The discrepency between the two methods does exceed 1 dB or so: This
shows that the perturbation method, which is much less time consuming than the
BEM, is a very powerful prediction tool. The Laboratoire de Mecanique et
d'Acoustique in Marseille has two anechoic rooms, which are connected by an
aperture. A steel plate has been built inside the aperture. The measured
acoustic pressure transfer function between points located on both sides of the
plate is well predicted by the numerical methods. [This research has been partly
sponsored by the Ministere de l'Environnement and by the Programme International
de Cooperation Scientifique Vibro-Acoustique dans le Domaine des Transports
initiated by the CNRS.]

ASA 132nd meeting - Hawaii, December 1996