For many years the question of appropriate scattering treatments in concert halls has vexed acousticians and it remains largely unresolved. Whilst subjective surveys indicate that the degree of surface relief in a concert hall is of great importance to the aural experience, there has been little research to inform contemporary designs. A new International Standard provides methods to quantify the sound dispersion by different surfaces in terms of diffusion and scattering coefficients. This paper reviews potential applications for these different coefficients and presents the first systematic research of how varying surface relief influences the sound field in concert halls. Details are given for an acoustic physical scale model of a concert hall, with modular panels to allow changes to the surface relief. Four different types of scattering surface used in the model are described. Measurements are analysed for various configurations of the scattering surfaces. The location of scattering treatments is shown to strongly influence the sound field diffusivity and degree of back_scattering in the model.