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Description
The measurement of Sabine's random incidence absorption coefficient as obtained from reverberation room measurements is well known to suffer from poor inter-laboratory reproducibility. This issue is often attributed to an insufficiently diffuse and distinctly non-uniformly dampened sound field within the laboratory, which are most prominent when the absorbing test specimen is mounted. Characteristic multi-exponential energy decay curves and corresponding multi-modal damping distributions are extensively reported already in the early literature on the topic. In recent years, multiple methods have been investigated to consider non-uniform damping either through explicit or implicit numeric modeling or when inferring the reverberation time of the empty and occupied laboratory.In this contribution we analyze the uniformity of damping using an energy based stochastic modal damping model originally introduced by Kuttruff. Discrete damping distributions are computed for a rectangular reverberation room with non-uniform damping based on the closed form solution for rectangular rooms. Finally, we investigate the suitability of the damping distributions of the occupied and empty reverberation room for the estimation of Sabine's random incidence absorption coefficient.