The DENORMS Round Robin Test (RRT) is intended for studying and improving the techniques used for the determination of the sound absorption coefficient of materials especially in reverberation rooms. It is well known that the main reason why the frequency range of interest cannot be extended below 100 Hz is that the modal behavior of the room dominates below such frequency. This behavior is obviously dependent on the geometry of the room and this is one of the reasons why a discrepancy of the results coming from different laboratories can be found even if the same material is tested. This paper describes the measurement protocol used for the RRT, developed with particular focus on gathering data on the acoustic response of each room with and without absorbing materials inside. The types of tests carried out and of post-processing operations performed on the resulting data are also discussed in the paper.
