Influence of diffusive surface position and extension on the acoustics of a small performance space

The research on diffusive surfaces has been the object of many studies. The investigation on their influence on the acoustical conditions in different performance spaces has not always been possible in real scale halls since the production and experiment design of such research requires a lot of effort, time and economical funds. The potential of a real scale variable-acoustic concert hall, such as the Espace de Projection, a small performance space at the Institut de Recherche et Coordination Acoustique/Musique in Paris, made it possible to further investigate the influence of diffusive surface on the hall’s acoustic behavior through measurements, simulations and perception listening tests. Twenty-four configurations of the hall have been tested by modifying the wall’s panels in three conditions: absorptive, reflective and diffusive. In this way different positions of the diffusive surfaces and different amount of surface covering have been investigated. Measurements have been carried out using an artificial head and an array of omnidirectional microphones. The objective acoustic variables, such as EDT, T30, C80, D50 and IACC, have been used for comparison of different conditions. Eight configurations have been also simulated using a ray-based software (Odeon 12.0), where the diffusive surfaces have been modeled in two different ways. The simulated objective parameters have been compared with measurement results. Listening tests, which aimed on determination of the audibility of the diffusive surface position and extention changes at audience ares, have been performed by headphones, using the ABX testing method. Two different music passages have been convolved with the measured binaural room impulse responses for a listening set-up of one listening position and two source positions.