On the Directional Distribution of Decay Constants in a Reverberation Room
The measurement of absorption coefficients in a reverberation chamber according to ISO 354 requires a uniform damping of the modes of vibration composing the sound field. This requirement is violated when an absorbing specimen is mounted inside the room, resulting in decay curves with characteristic multi-exponential slopes when measured with an omni-directional microphone. In this contribution we investigate the directional distribution of decay times of corresponding modes with respect to their direction of propagation. The sound field is decomposed into its two-dimensional wave number spectrum implicitly approximating the modes of vibrations as superposition of plane waves, followed by Schroederintegration for each direction. Decay times are estimated from the respective directionally dependent Schroeder integral and their distribution is compared to individual reverberation times of the multi-exponential decay process extracted from the omni-directional decay curve using a Bayesian framework.