# Echo Analysis in Iberian Bullfighting Arenas Through Objective Parameters and Acoustic Simulation 1
## 4 Results and Discussion
### Echo Criterion EK in the Study Cases
#### 4.2.1 Results in the Bullring of Ronda  
The discussion is limited to the reception points where, for speech and music, EK exceeds or coincides with the values of 1 and 1.8, respectively, in accordance with Table 1. It can be observed that of the 39 source-receiver combinations in the Ronda bullring, there are only 4 combinations where, in a first approximation, there is a risk of echo for speech: for the sound source S3 in receivers R5 and R8; and for the sound source S4 in receivers R3 and R5, all located in the audience area. Table 5 summarises this information and describes their source-receiver distance and other speech intelligibility parameters for these receivers. In all four combinations, the EK values for speech are on the threshold level, and there is no risk of echo for music in any thereof. However, an inspection of the impulse responses of S3-R5, S4-R3, and S4-R5 and the times at which these strong reflections occur indicate that they are heavily delayed disturbances due to background noise and do not correspond to real echoes. Furthermore, since the S3 sound source is designed for musical use, it can be stated that no echoes are detected at the measurement points. According to the intelligibility parameters, intelligibility is considered Fair at various distances in the bullring, and Good at shorter distances. Discrepancies arise between the \(D_{\rm 50m}\) and STI results, since, according to [PERSON] et al. [29], the STI does not distinguish useful early energy from non-early energy, which does not contribute to intelligibility. In the digital acoustic model implemented in this bullring [22], using the room acoustics software ODEON [30], none of the 39 source-receiver combinations in the spectator area show echoes for speech when there is no audience present, in agreement with the findings in the in situ measurements. However, with the audience area 100% full of people, there is a risk of echo according to the \(\rm EK_{\rm speech}\) parameter for the sound source in S1 of the 11 combinations studied (see Table 2) in 6 receivers (R3, R4, R6, R7, R8, and R10) and the values are very close to the \(\rm EK_{\rm speech}\) value threshold of 1 in the remaining 5 receivers. For sound sources S2 and S3, there is no risk of echo in any of the associated receivers, while for S4, for the nine associated receivers (Table 2), there is a risk of echo for speech in two (R7 and R8). Furthermore, in this model, the acoustic simulation via ODEON has allowed the creation of the \(\rm EK_{\rm speech}\) colour maps of the Ronda bullring shown in Figure 12 for three sound-source positions (S3 music sound-source excluded) without spectators (left-hand side) and with spectators (right-hand side). Although in all cases the colour pattern without spectators is similar to that with a full capacity of spectators in the galleries, it is observed that, with the source in the centre of the bullring S1, and due to the focusing of the sound from the barrier and grandstands, a distribution of high values of the \(\rm EK_{\rm speech}\)\(>\) 1 is observed in the bullring, with even greater \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline  & \(\rm EK_{\rm speech}\) & \(\rm EK_{\rm music}\) & \(\rm T_{\rm speech}\) (ms) & \(\rm T_{\rm music}\) (ms) & \(d_{\rm 8+}\) (m) & \(D_{\rm 50m}\) & STI & & \(\rm T_{\rm Sm}\) (ms) & \\ \hline S3 Music Band & & & & & & & & & & \\ \hline R5 & 1.05 & 0.93 & 2804 & 2814 & 42.8 & 0.54 & Fair & 0.54 & Fair & 100 & Fair \\ R8 & **1.03** & 1.26 & **66** & 69 & 62.3 & 0.30 & Fair & 0.53 & Fair & 99 & Fair \\ \hline S4 Lower Grandstand & & & & & & & & & & \\ R3 & 1.01 & 0.94 & 3402 & 46 & 57.9 & 0.46 & Fair & 0.58 & Good & 114 & Fair \\ R5 & 1 & 0.64 & 3349 & 3359 & 17.3 & 0.78 & Good & 0.42 & Poor & 49 & Good \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Echo and other acoustic parameters in the Ronda bullring in the audience area. In bold interpreted as an echo. values of the parameter observed with 100% capacity in the galleries.