Modal model prediction of surface waves and resonant characteristics of rectangular grooved gratings

A modal model formulation explains many aspects of sound propagation over complex grooved surfaces. Insights that such a formulation offers about the intrinsic resonant properties of rectangular grooved surfaces shall be explored and applied to predict phenomenon such as surface waves and non-specular energy redistribution (blazing). Furthermore, the effects of filling the grooves with a porous material are investigated. A brief summary is made of the modal method and the mechanisms involved with sound propagation over rough surfaces to provide the context before exploring, in detail, how the modal method may be applied to predict various resonant behaviours of rectangularly grooved gratings. As well as their general predictive capabilities, the modal methods also provide significant insight into the wave modes diffracted by grooved surfaces under incident excitation at a low computational cost.