Experimental evaluation of the accuracy of the Sabine and Eyring theories in the case of non‐low surface absorption

The Sabine and Eyring diffuse‐field theories are often used to predict the sound decay/reverberation time and steady‐state sound‐pressure levels in rooms. The Sabine theory can be considered to be an approximate version, valid for low surface absorption, of the Eyring theory, in principle valid for any surface absorption values. However, some practitioners believe that the Sabine theory is accurate for any absorption value. Further, there is some debate as to whether or not a 1−α factor should be included in the reverberant sound‐pressure term of these theories. Experiments were done, in a 1:2.5 scale model reverberation room with surfaces of varying absorption. The results were compared with predictions by various versions of the Sabine and Eyring theories in order to evaluate their accuracies in the case of non‐low surface absorption. It is concluded that the 1−α factor must be included to obtain accuracy. Eyring, but not Sabine, predictions were found to agree well with experiment, suggesting that only the Eyring theory can be accurate in the case of non‐low absorption.