Psychological experiments on listener envelopment when both the early-to-late sound level and directional late energy ratios are varied, and consideration of calculated LEV in actual halls

The purposes of this paper are to clarify the relation between listener envelopment (LEV) and two physical factors, namely, early-to-late sound level C80 and directional late energy ratios (DLRs), and to demonstrate the significance of evaluating LEV using C80 and DLRs. Firstly, two psychological experiments are performed. In the first experiment, the results show that the previous findings about the effects of late reflections from lateral, overhead, and behind the listener on LEV are valid when they also consist of plural directional energy components, as are found in real sound fields. In the second experiment, the relational equation among LEV, C80, and DLRs is derived from results when the physical factors are simultaneously varied. Secondly, psychological scores for LEV are calculated in actual halls by applying measured values for C80 and DLRs to the equation. The results show that the differences in LEV among different seating positions and in the spatial uniformity of LEV among different halls are expected to be significantly large depending on the values of C80 and DLRs. This suggests the significance of evaluating LEV by means of C80 and DLRs.