ERATO Proceedings Istanbul 2006.pdf - Odeon

trend of the G parameter, which, though similar in the three cases, shows some biases at a fixed
distance according primarily to the stage characteristics.
On the contrary the tail is very important for the reverberation time and therefore the visible
differences are given by the dimension of the cavea and the presence or absence of architectural
features like the upper colonnade.
Finally a compensation for the air absorption in the IR was experienced but later dropped. Its
effectiveness in the present case is surely not as important as in closed spaces; in fact the absorption
of the missing ceiling is far larger then any possible correction for the air absorption.
7 CONCLUDING REMARKS
As it is evident from the acoustical measurement results, the sound field in the ancient theatres has a
unique character. The contributions of the specific architectural parts can be traced back in the
impulse response. In particular the orchestra floor and the stage building provide very strong early
reflections and the cavea contributes with the scattered sound that makes up the reverberant tail.
Even if the theatres have no ceiling, which is replaced by an ideal surface of unit absorption, the
reverberation time in Roman theatres is similar to closed theatres: but in this case the clarity it is
higher and the sound level is very low.
The above set of scale model measurements can be compared with the measured data taken in
several real scale well preserved ancient theatres [3], [4].
2.0
1.8
Columns and stage
building
Different stage buildings
No columns
No stage building
No columns
1.6
1.4
T30 [s] (mid freq)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Aspendos
Roman
Hellenistic
Jerash
Roman w/o
columns
Greek
Taormina
Delphi
Greek w/o stage
Figure 8. Comparison between RTs measured in real theatres and different configurations of the scale model
By doing so, the effect of the architectural elements can be further tested through examination of the
measured RT at middle frequencies. The results of such procedure are shown in Figure 8.
The Aspendos theatre (Turkey) it is a very well preserved Roman theatre with the colonnade and the
complete stage wall. Despite the differences in tiers slope and overall dimensions, the measured RT
almost matches with RO and HE scale models.
Moreover the Jerash theatre (Jordan) is a Roman theatre without the colonnade and with a stage wall
where just one storey is preserved, and Taormina theatre (Italy) is a Roman theatre without
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