A comparison between shoebox and non-shoebox halls based on objective measurements in actual halls

Abstract

In recent papers, the sound absorption by chairs and audiences were determined for shoebox (SB) and non-shoebox (NSB) types of concert halls (Beranek, JASA 120, 1399 (2006); Hidaka, Proc. ICA2007). The purpose of this paper is to examine objective differences in the sound fields in these two hall types. This investigation follows reports of music goers that the average subjective sound quality in NSB and SB halls differs appreciably and that there are greater subjective differences in sound quality from one seating location to another in NSB halls. Special attention is given to the temporal and amplitude structure in the early part (before 80 msec) of the impulse responses measured at various seat positions in six well-known halls (three SB and three NSB). To the extent the data permit, the usual objective parameters are also analyzed, both averaged and at various seat locations, in a total of 12 halls: reverberation time, early decay time, C80 (3-band), interaural cross-correlation coefficient (3-band middle frequency early before 80 ms), initial-time-delay-gap, bass ratio, and strength factors at low- and mid-frequencies. The differences found are discussed with reference to the subjective reports.