The differences and though the equivalence in the detection methods of particle, ray, and beam tracing

Within the numerical methods used in room acoustics, the geometrical and energetic methods of sound particle, ray and beam tracing are often confused. This rather tutorial paper does not treat the tracing algorithms but rather aims to explain the differences in the physical models and the corresponding detection and evaluation methods. While ray tracing needs spherical detectors as receivers to count rays, the particle model is based on a weighting of the energies of the particles with their inner crossing distances to compute the local sound energy densities. For beam tracing, receiver points are sufficient. In its core, this paper shows the convergence of the evaluated intensities computed from immitted sound particle energies to those predicted by the well-known 1/R<+>2<+>-distance law for the free field—as applied with the mirror image source method and beam tracing as its efficient implementation. Finally, the geometrical methods are classified depending on their efficiency with higher orders of reflection and their extensibility by scattering and diffraction.