A new physical measure for psychological evaluation of a sound field: Front/back energy ratio as a measure for envelopment

Broadening is one of the important characteristics for the psychological evaluation of a sound field. Several investigations indicated that broadening was comprised of two elemental senses, i.e., auditory source width (spaciousness) and envelopment [M. Morimoto etal., Proc. 13th ICA, Belgrade 2, 215–218 (1989); J. Acoust Soc. Jpn. 46, 449–457 (1990); and Hidaka etal., J. Acoust. Soc. Am. 92, 2469 (A) (1992)]. They inferred that the degree of interaural cross correlation of late reflections correlated with envelopment. This paper, however, shows the results of psychological experiments that envelopment is affected by the energy ratio of reflections coming from the front of the listener to those coming from the back of the listener, even if the degree of interaural cross correlation of the late reflections are equal. Namely, envelopment grows as the energy of the reflection coming from the back of the listener increases. This result suggests the need to measure the ratio which has never been measured.