ERATO Proceedings Istanbul 2006.pdf - Odeon

Though the structure of the impulse response is the same in the two theatres, the Schroeder integral
(Tab. 1) shows how the decay of energy is clearly more moderate in the Aspendos theatre. This is
confirmed in Figure 3 reporting the plots of the average values of the reverberation time (T30) in the
two spaces.
The measured values in the Aspendos theatre (1.7 s at middle frequencies) are much higher that
those of Jerash (1.2 s at mid frequencies), and are similar to those to be expected in a roofed theatre.
The discrepancy is primarily due to the presence of the gallery in the upper cavea and secondly to
the bigger overall dimension of this theatre. In particular the columned aisle keeps the space more
compact regarding the circulation of reflections which are impinging on the side walls. The trend of
the reverberation time is fairly regular in the two theatres.
T30 [s]
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Aspendos
Jerash
125 250 500 1000 2000 4000 8000 Lin A
[Hz]
Figure 3. Averaged reverberation time (T30) measured in the two theatres
By analysis of the measured impulse responses a set of parameters listed in the ISO3382 standard
was calculated. In Figure 4 the average values of clarity C50 is shown. In the mid frequency range
the values are similar for the two spaces and rather high if one considers that reverberation times are
also rather high.
C50 [dB]
14
12
10
8
6
4
2
0
-2
-4
-6
Aspendos
Jerash
125 250 500 1000 2000 4000 8000 Lin A
[Hz]
Figure 4. Averaged Clarity for speech (C50) measured in the two theatres
30