Abstract
It is discussed in this paper from the results of acoustic experiments made with three models of halls whether or not a diffusor fixed to the side wall of each model is useful for the uniform decay of a sound. The usefulness of the diffusor is judged on the basis of statistical significance by making an analysis of variation of a two-way layout regarding the standard devitation of reverberation time on two assumptions that the decay of a sound will be exponential in all places in the hall and the diffusor will be useful for the uniform distribution of a proper tone, if the sound field is in a satisfactory diffusive state. It may be fairly said from these results that a side wall diffusor is useful for the uniform decay of a sound at a level of significance of 1%, especially contributing to sounds in the low frequency range when a sound source is generally in the position where a lecturere stands in any hall.
