Effects of Different Diffusor Types on the Diffusivity in Reverberation Chambers
Regular paper
Acoustic Technology Group, Technical University of Denmark
Monday 1 june, 2015, 15:40 - 16:00
0.9 Athens (118)
Abstract:
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.