The dynamic of sound fields in enclosed spaces
A basic assumption in room acoustics is that the sound field above the Schröder frequency in an enclosed surface is highly diffuse. But how diffuse can a sound field get? The international standard ISO 354 suggests a measurement procedure to increase the diffusivity of a sound field inside a laboratory environment by adding panel diffusers. Although the standard does not give an absolute measure for diffusivity, it defines the quality of the sound field by measuring the reverberation time and calculating the absorption coefficient of a sample. This procedure is highly questionable because it is not possible to achieve comparable accuracy between different laboratories and the absorption coefficient reaches values > 1 which is physically not possible. In this work, the hypothesis is set up that panel diffusers create coupled spaced and therefore reduce the effective volume of the chamber.