Analytic expression to derive the image source point between two symmetrical sloping planes

The sound field in open cavities with sloping walls can be represented by image sources and edge diffraction components. Sloping walls will generate a systematic structure to the positions of the image source, and explicit expressions for those positions are presented here. Using such explicit expressions, rather than the general image source method, makes it straightforward to study arbitrarily high orders. When two opposite walls form parts of an infinite wedge, then their image sources will be positioned on a cylindrical surface. The addition of a floor is easy, while adding more walls requires an iterative procedure, with explicit visibility tests. First-order diffraction components can then be generated for each image source. Simulation results are compared with experimental measurements in a three dimensional open cavity with sloping walls.