"Image source method for simulating wave motion in rectangular enclosures"

Supervised by G.Brown

Abstract

In designing rooms, architects are faced with the problem of evaluating the room's acoustics. A good understanding of the sound field within a room would assist in this work. This project determines the sound field in a closed rectangular enclosure using the image source method. In addition, the visual presentation of the results is explored. The project divides into two parts; the first is the determination of the sound field, the second the presentation of the results.

In the first part, the different approaches of determining theoretically the sound field in the room are discussed, with the emphasis on the image source method. This method is then used to determine the sound field in the room. The method is based on a single frequency source placed in the room, with the reflections from the walls being described in terms of amplitude attenuations and phase changes of image sources. An extension to allow for a number of sources is included. The results are determined at a three-dimensional rectangular array of receivers. These results need to be displayed in a way that is easily interpreted.

The second part describes the three different basic techniques used to create the visual displays; they are the colour-plane, the contour plane and the iso-surface. The details of these techniques are given and the way they are used for the three-dimensional displays presented.

In addition an aural presentation technique is described.

The programs, developed in the project, give a method of determining the sound field in a closed rectangular enclosure together with a variety of ways of displaying the results.