We conducted seven subjective experiments in order to clarify the effects of the direction of arrival, spatial distribution, temporal distribution and listening level of reflections on listener envelopment (LEV). As a results, it became clear that the contribution of a reflection on LEV depends on the direction of arrival of other reflections and that it is not possible to make independent evaluations. LEV cannot be adequately evaluated with a physical index that weights and integrates individual reflection by the direction of arrival like the lateral energy ratio. It is necessary to consider the mutual effects of reflections by some means and to quantify the spatial distribution of reflections. Accordingly, we proposed SBTs quantifying the spatial distribution of reflections using point of gravity time Ts for each direction and demonstrated that it is possible to obtain a good correlation with the psychological scores of LEV.
