Edge absorbers are known for their high effectiveness in absorbing low-frequency sound energy and reducing low-frequency reverberation. The influence of edge absorbers on the decay behaviour of the sound field has been extensively proven empirically. Nevertheless, no suitable model for sound absorption by edge absorbers exists to date. In order to be able to develop such a model, it is essential to know the sound field in the edge of a room precisely.This paper attempts to develop a more precise understanding of the sound field in one edge of a cuboid reverberation chamber. It is verified by measuring potential and kinetic energy. For this purpose, initially the interference patterns for diffuse sound incidence in a rectangular edge according to R. V. Waterhouse are presented. Subsequently, these interference patterns are verified by means of sound pressure and particle velocity measurements in the reverberation chamber. In a further step, the influence of porous absorber material in one edge of the reverberation chamber on these interference patterns is measured. By comparing the calculated and measured interference patterns, the accuracy of the Waterhouse model is investigated. Finally, a range of validity for this model is specified as function of a sound diffuseness measure.