# Measurements of Acoustical Parameters in the Ancient Open-Air Theatre of Tymdaris (Sicily, Italy) +
## 5 Discussion
### General Results and Comparison with Other Ancient Theatres
Figure 10 shows the fine structure of the typical IRs measured in the theatre with the two source typologies, i.e., the dodecahedron and the firecrackers, obtained for S1-R6 and S2-R6 paths with MATLAB version 2015b. The IRs clearly show that the main contribution to the direct sound is coming from the first reflection from the orchestra, that is between 2.4 and 2.6 ms after the direct sound. Then, the first reflection is followed by minor scattered reflections from the cavea steps, distinguishable in the latter part. The absence of a scenic building is responsible for the absence of the third main reflection. In Figure 10, the IRs obtained with the dodecahedral source show the direct sound with a lower level than the first reflection. This could happen in the case of acoustical focusing, that is, as already mentioned, an effect quite common in ancient theatres [2]. The effect is shown along the R4-R5-R6 and R7-R8-R9 lines for both S1 and S2 only for the dodecahedral source, and it is not observed along the R1-R2-R3 line. It could be due to the lack of omnidirectionality of the dodecahedral source at the highest frequencies [26; 36] that determines selected focusing effects due to the loudspeakers position. Considering firecrackers, it does not exhibit directional characteristics or a very good repeatability [36; 48]. Moreover, IR with the dodecahedral source results to be less sharp than those obtained with firecrackers. This indicates the firecracker source as more suitable than the dodecahedron to obtain defined IRs, at least to investigate the fine structure of the reflection pattern. Figure 11 reports the frequency trend of the direct sounds extrapolated from the firecracker and dodecahedral sources and compared (measurement path: S1 and R6). The firecrackers direct sound is quite stable and flat until almost 10 kHz. However, the firecracker is more subject to problem of repeatability, as shown by the higher level of standard deviations obtained during measurements. A further comparison with other case studies measurements is proposed. The cases considered are the in situ measurements realized on six theatres: Syracusae, Aspendos, Jerash, Taormina, Delphi and Segesta [6; 25]. Regarding the in situ measurements, results for Syracusae (Italy, V cent. BCE; Greek-Roman theatre) in this study come from a measurement campaign conducted by the Acoustics Group at Politecnico di Torino in 2015 [25]. Aspendos (Turkey, I cent. CE; Roman theatre) and Jerash (Jordan, I cent. CE; Roman theatre) were the object of measurements during the aforementioned ERATO project. In particular, Aspendos is considered one of the best conserved ancient theatres in the world, as it still preserves architectural elements such as a complete scaenae froms and porticus; Jerash does not have any more a porticus, but it has a partially conserved scaenae froms. Instead, Taormina (Italy, 265-215 BCE, then modified in arena II-III cent. CE; Greek-Roman theatre), Delphi (Greece, II-I cent. BCE, Greek theatre) and Segesta (Italy, IV-I cent. BCE; Greek theatre) were object of another measurement campaign, performed by the University of Ferrara in collaboration with Kobe University [5]. Taormina has a partially conserved scenae froms, while Delphi and Segesta do not have any stage building. This further comparison allows understanding if the performed measurements in Tyndaris are comparable to those realized in previous experiences. Figure 11: Frequency trend of the direct sound, from firecracker measurements (red line) and dodecahedral source (black line). The results are presented in terms of RTmid, that is the average value between reverberation time in the octave bands 0.5, 1 and 2 kHz, together with the architectural characteristics of the aforementioned theatres as reported in [7], in the following Table 7. It is evident that the complete absence of scaenae frons corresponds to a drastic reduction of the reverberation inside the theatre.