A Diffraction Model for Acoustical Ray-Tracing Based on the Energy Flow Lines Concept

Geometrical acoustics models are currently the most popular prediction tools in room-acoustics due to their low computing load. However, they seldom take into account the diffraction occurring at free edges. Moreover, the existing diffraction models implemented in geometrical acoustics algorithms are either limited to specularly reflected paths or either present excessive computation load. Recently, a diffraction model based on an approximation of the far-field direction of the Poynting’s vector around half-planes has been introduced for computing
the scattering due to faceted dielectric objects. In this article, this model is developed to handle obliquely incident waves and is implemented within an acoustic ray-tracing software using the analogy between the Poynting’s and the acoustic intensity vectors. The proposed model can handle both diffuse and specular reflections and sets no limit in terms of reflection or diffraction order. The first results obtained by ray-tracing agree well with the uniform theory of diffraction and the boundary elements method for single and double diffraction problems even if
the interference effects are neglected and as long as the number of emitted rays is sufficient. Moreover, the additional computation load to handle diffraction is shown to be low compared to the one from a classical ray-tracing algorithm.