# Echo Analysis in Iberian Bullfighting Arenas Through Objective Parameters and Acoustic Simulation 1
## 4 Results and Discussion
### Echo Criterion EK in the Study Cases  
Figure 12 shows the statistical data for the results of the echo criterion parameter (EK) for speech and music in the cases studied. For these calculations, the voice-source positions indicated in Section 3 and receivers in the audience area (segments of stalls, grandstands, boxes, etc.) are considered, as are those for the sound source of a musical nature and receivers in the audience area. From this figure it can be observed that, in the Ronda and Lisbon P (partially open oculus) configurations, all the sample data lie below the critical threshold, and for Seville, Madrid, and Lisbon C (closed oculus), the upper limit of 99% confidence interval is below or near the critical threshold. Only in the Italica amphitheatre do the data exceed this limit. Figure 12a also shows the similarity of the results in the Lisbon bullring in the two roof configurations. As for the EK for music, all the results, even for the Italica amphitheatre, are below the echo risk threshold, and, in the case of the bullrings, the results are far below this echo risk threshold. While these data indicate how these spaces behave with respect to echo problems in the spectator area, it remains necessary to analyse the timing of these strong reflections and their connection to impulse responses; this is carried out in the following sections.  
Henceforward, explanations will be given for those receivers where EK exceeds or coincides with the values of 1 and 1.8 for speech and music, respectively, in accordance with Table 1. The tables below show these values for each space studied and the time in ms of the reflection of the impulse response that gives rise to that EK value. The LASERA software provides the EK speech and EK music values, as well as the timings at which these values occur relative to the sound-source emission time, and therefore, LASERA does not correct the time of flight of direct sound. In the following tables, the times of flight of direct sound are corrected. Likewise, regarding the results of the sound source where musical sources are located in the bullrings (music band, bugle calls and timpani, and trumpets), if, at the corresponding reception points, there is no risk of a disturbing echo for music, then these receivers are not subsequently analysed in depth. In all the tables below, the numerical data for EK\({}_{\text{speech}}\) and \(T_{\text{speech}}\) of the strong reflection that is interpreted as echo after the analysis are shown in bold. Furthermore, the source-receiver distance \(d_{\text{S-r}}\), and the  
Figure 12: EK parameters in the venues studied: (**a**) EK for speech, and (**b**) EK for music. The box plot shows the median, the 99% confidence interval, and the min and max values of the parameter in the sample. The values of the echo thresholds for each EK provided by [PERSON] and [PERSON] are also shown.  
intelligibility parameters \(D_{\rm 50m}\), \(T_{\rm Sm}\) (averaged at 500 and 1000 Hz), and STI in the receptor are shown, together with the parameter ratings based on the work by [PERSON] and [PERSON] [28].