## 4pNS7. Sound diffraction effects by screens in a room.

### Session: Thursday Afternoon, December 5

### Time: 3:45

**Author: Dominique M. Habault**

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

**Author: Ulf R. Kristiansen**

**Location: N. T. N. U., Acoust. Group, N-7034 Trondheim, Norway**

**Abstract:**

Several numerical methods are used to describe the effects of diffraction
by two kinds of screens in a room: a perfectly rigid screen and a vibrating
screen. This study has two main applications in acoustics: In room acoustics,
the aim is to describe the influence of a vibrating screen on the acoustical
characteristics of a room in which screens made of light materials are suspended
from the ceiling; in structural acoustics, it is to describe the effect of a
vibrating structure in a cavity. An application in active noise control is also
presented. First, the sound pressure in the room is computed by using a boundary
element method. Then, a perturbation method is used in the case of the vibrating
screen. Comparisons are made between the two methods and a finite-element method
for two typical geometries. The numerical examples presented correspond to a 2-D
problem and a rectangular room. From the acoustics point of view, it is shown
that the effect of a vibrating screen compared with a rigid screen is bigger at
low frequencies and for light materials. This difference also depends on the
acoustical properties of the room (i.e., the reflection coefficients on the
walls).

ASA 132nd meeting - Hawaii, December 1996