A dodecahedron inside a room acoustic simulation: Are the results compatible with the typical ideal omnidirectional source?

The general acoustical characteristics of a room are described by a set of acoustic parameters that can be measured or simulated. The ISO 3382-1 standardizes these parameters and specifies that the directivity of the acoustic source shall be as close to omnidirectional as possible. A commonly used acoustic source that satisfies the ISO 3382-1 omnidirectionality criteria is the dodecahedron. These sources typically are omnidirectional at low frequencies becoming more directional as the frequency increases. In room acoustic simulations, on the other hand, the source is typically modeled as an ideal omnidirectional source across all frequencies. This paper describes the directivity measurement of a dodecahedron source and evaluates the use of a measured dodecahedron against an ideal omnidirectional source in room acoustic simulations. The results show that when averaging all receivers in a room, both sources produce compatible reverberation time estimations. Other parameters, such as C80, present larger differences in frequencies above 2000 Hz. Finally, for specific receivers, the differences in acoustic parameters are significantly above JND. This is especially important when calibrating simulations to match a measurement or producing realistic auralizations.