Final Thesis

The Directional Energy Decay Curve in Reverberation Rooms

Bachelor Thesis of Imort, Johannes

In order to describe the acoustical absorption properties of arbitrary materials, usually, the random incidence absorption coefficient is determined. Measuring the absorption coefficient in a reverberation room requires the sound field to be diffuse. Previous studies showed poor results in reproducibility of these measurements among laboratories. There is reason to suspect the uncertainties result from a violation of the diffuse sound field requirement. A standardized method to characterize sound field diffuseness is lacking. This thesis evaluates the concept of directional energy decay curves in order to draw new conclusions on systematic defects in the isotropy of sound fields. Two room acoustic simulation studies were conducted, each consisting of a hypothetical absorption coefficient measurement scenario. While focusing on the dependency of room volume and absorber size, the results are evaluated and finally contextualized with the absorption coefficient calculation according to the international standard ISO-354. The results indicate a correlation between the spatial variation of the directional energy decay curve and the relative error in the absorption calculation procedure. Based on the findings of this thesis, a new single value diffuseness estimator is proposed. Deutsch