Interaction of absorption and scattering coefficients in room simulations based on geometrical acoustics

Lukas Aspöck, Michael Vorländer
Fig. 2 and Fig. 3 show the effect of different scattering coefficient on the simulated energy histogram and the reverberation time (T 30 ). For T 30 the role of the scattering coefficient decreases with increasing absorption. Other parameters, such as EDT and C 80 (cf. Fig. 4 and Fig. 5 ), are less affected by a change of the scattering coefficient. To understand the relationship of scattering and the energy decay, the mean free path of the room is considered, which is defined as [5]: with V
more » ... d as [5]: with V being the volume and S the surface area of the room. This equation states that the mean free path does not change when different scattering coefficient are applied in a simulation. It does, however, change when a more detailed room model used, as more details in the model increase the surface area S of the room. Fig. 6 shows the mean free path of a ray tracing (50,000 particles, time limit: 2 s, maximum energy loss: 60 dB) for two different rooms, the seminar room and a corresponding shoebox room with the same volume and the same ratio of height, width and length. In addition to the room geometry, room acoustic simulations based on geometrical acoustics (GA) typically use absorption and scattering coefficients to model the physical behavior of the boundary conditions. The scattering coefficient is often considered to be less relevant, however, it can also have a substantial impact on parameters such as the reverberation time. If a simulated energy decay is matched to a measured energy decay of a room, it is thus important to adjust absorption coefficients as well as the scattering coefficients. This work investigates the effect of the scattering coefficient on the results of room acoustic simulation with respect to the application for calibrating room simulations.
doi:10.18154/rwth-2019-11491 fatcat:fw6asw65qzewpduaqsbhbsx5ua