Modeling (non-)uniform scattering distributions in geometrical acoustics

In most cases, a surface is not ideally smooth. It rather contains regular and irregular dents, bumps, and other textures that influence the reflection of the incident wave. A reflection on such a corrugated surface causes a frequency-dependent redirection of the incident sound energy outside the specular direction, called scattering. While the computation of the specular part is well elaborated today, a model that thoroughly captures the wave phenomenon of scattering is still under discussion. Here, the most common assumption is that scattered energy follows a uniform Lambert distribution, which has proven to be a good approximation, especially in room acoustical applications. In this contribution, we will discuss Lambert-based scattering models (specular/diffuse sound field decomposition and vector mixing) and their implementations in methods of Geometrical Acoustics. We will analyze benefits and flaws of the respective models and investigate possibilities to introduce angle-dependent scattering for use cases where the uniform Lambertian distribution becomes invalid.