NUMERICAL ANALYSIS FOR THE IMPROVEMENT OF A SPECIAL REVERBERATION TEST ROOM

A cuboid-shaped special reverberation test room, based on the requirements defined by ISO 3743-2:2009 standard and usually utilized as the termination of an experimental apparatus for insertion-loss measurements, was tested in terms of reverberating time and sound energy density. Tests were made in accordance with the EN ISO 3382 standard and showed that the behavior of the room, albeit being an acceptable terminal for the insertion-loss measurements mentioned above, is below the standard. Various actions were then analyzed to the aim of improving the acoustical behavior of the room. To predict the effects on sound reverberation of these actions a numerical model of the room was implemented by means of a simulation software based on pyramid-tracing algo-rithm, which is able to solve the three-dimensional sound propagation in enclosures under the assumptions of geometrical acoustics. Tested improvements were based both on the addition of elements inside the room (wall diffusion panels, suspended diffusion panels, semi-cylindrical diffusers) as well as on the change of the shape of the room itself. The numerical model was calibrated and then used to analyze and compare the effects of each action. Numerical simulations showed that, due also to the small size of the room, a really effective solution does not exist: interventions which increase the reverberation time usually have a bad impact on the sound energy density distribution, and vice-versa. The least unsatisfactory, also considering the economical point of view, would be using suspended diffusion panels, since they give a little increment of the reverberating time at the highest frequencies and they make the sound field more evenly distributed.