Hybridization (GA)

When integrating ISM with the stochastic energy particle model of RR, two key considerations must be addressed. First, to avoid double counting of reflections, specular reflections already accounted for by ISM must be excluded from RR to ensure a correct energy balance. Consequently, RR should only track energy particles that have undergone scattering, as purely specular reflections are fully handled by ISM. However, beyond the maximum reflection order of ISM, no further restrictions apply, allowing all possible combinations of reflection types (e.g., diffuse, specular, scatter) to be considered in the RR process.

The Geometrical Solver computes two separate impulse responses: the ISM impulse response (ISM-IR), which represents the direct sound and specular reflections up to the defined ISM reflection order, and the RR impulse response (RR-IR), which includes all reflections that have undergone scattering up to the ISM reflection order, as well as all other possible types of reflections for higher orders. Since geometrical acoustics (GA) methods rely on the superposition of sound pressure signals from individual reflections at the receiver, the final impulse response is obtained by summing both ISM-IR and RR-IR.

The figure below presents an example of ISM-IR and RR-IR in a room where surface scattering is applied.