Effects of Different Diffusor Types on the Diffusivity in Reverberation Chambers

Regular paper

Mélanie Nolan

Acoustic Technology Group, Technical University of Denmark

Monday 1 june, 2015, 15:40 - 16:00

0.9 Athens (118)

Knowledge of sound absorption properties of typical building materials is essential for all tasks related to room acoustic design. The absorption coefficient is measured in a reverberation chamber according to the international standard ISO 354. It is known that inter-laboratory reproducibility of these results is poor, which leads uncertainties in prediction and compliance with building contracts. It is assumed that differences in the diffuse field conditions between laboratories are the main cause of the poor reproducibility. Achieving a diffuse sound field is one of the most important requirements for the reverberation chamber. Diffusing elements such as hanging panels are typically installed in reverberation chambers. In this study, the effects of hanging panel diffusors, boundary diffusors and hanging volume diffusors on the diffusivity of the sound field in two reverberation chambers are systematically compared. The sound field diffusivity is characterized based on the diffuse field factor, which compares the measured standard variation of the reverberation time with the theoretical standard variation under diffuse field conditions. This sound field is determined both with a highly sound absorptive sample in the room and without. The results will be presented, showing the possibilities and limitations of the use of the diffuse field factor.

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