Analytic Model Based Analysis of Modal Sound Field Decay (en)
* Presenting author
The estimation of reverberation times from measurements of sound field decay and Sabine's theory of reverberation are two of the most fundamental concepts for room acoustic analysis and modeling. However, Sabine's theory is only valid above the Schroeder frequency and requires a diffuse sound field, as well as a similar damping of the modes of radiation constituting the sound field in a room. These requirements are typically not fulfilled at low frequencies, in small rooms, and in the case of non uniform distribution of absorbing materials. Specifically the latter is problematic during the measurement of absorption in reverberation rooms. The concept of modal decay times has been discussed to overcome aforementioned limitations. Multiple authors proposed modified versions of Sabine's equation for modal sound field decay modeling based on geometrical considerations or in combination of the latter with wave based approaches using FEM simulations. In this contribution we use a wave-number approach based on analytic modeling to investigate the damping of modes, as well as their direction of propagation. Intensity distributions inside the room volume as well as on its boundaries are analyzed and linked to modal decay parameters.