Evaluation of Results

Abstract

Mono and stereo ESS recordings were performed in three music performance halls: the Eckhardt-Gramatté Chamber Music Hall, the Husky Oil Great Hall, and the Rehearsal Hall, all located in the Rozsa Centre at the University of Calgary. The unedited mono-recorded sweeps are illustrated in Figure 6.1. Readily apparent are the differences in the low-frequency responses (below 100Hz) of the 15-second, 22 Hz-22 kHz ESS. In particular, the response of the Great Hall in Figure 6.1(b) has a gradually rising, more controlled low-frequency response, free of unwanted resonant peaks. In comparison, the low-frequency response of the Eckhardt-Gramatté Hall in Figure 6.1(a) has a 51-Hz resonant peak appearing just after the 2-s mark. This low-frequency resonance is not unexpected as the audience seating area in the Eckhardt-Gramatté Hall is built on a suspended floor in order to accommodate the air conditioning system under it. Consequently, it was observed that this cavity-like structure acts as a low-frequency resonant chamber. Furthermore, through spectral analysis of the hall, the low-frequency band of 40-60 Hz was measured to be naturally excessive. It is interesting to note that these features in the low-frequency responses of the different halls are confirmed through their final derived AIRF aural representations. That is, upon post-production listening to the convolution reverb of each hall, it was the Great Hall (illustrated in Figure 6.1(b)) that possessed the most pleasing and uniform low-frequency response.