# Echo Analysis in Iberian Bullfighting Arenas Through Objective Parameters and Acoustic Simulation 1
## 5 Conclusions  
Roadless buildings are more likely to experience echoes than are closed venues. To study this acoustic phenomenon, this paper presents the results of the Dietsch-Kraak echo criterion parameter for speech and music in four bullrings on the Iberian Peninsula, each with a unique feature (Ronda without open-air grandstands, Seville with an ovoid-shaped arena, Las Ventas as the largest bullring in Spain, and Campo Pequeno with a movable roof), and a Roman amphitheatre from the time of the Hadrianic Hispania as a precursor to bullrings. The experimental results of the parameter and the association of the times and signals of strong reflections have been obtained from the impulse responses measured in the venues. In addition to processing the echo parameter calculations, those reflections with sufficient acoustic energy and delay relative to the direct sound to be interpreted as echoes are identified. This delay has also been analysed by using energy-time decay curves, which allow the determination of whether the delay is either a true echo or is so large and \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline  & \(\text{EK}_{\text{speech}}\) & \(\text{EK}_{\text{music}}\) & \(\dfrac{\text{\emph{T}}_{\text{speech}}}{\text{(ms)}}\) & \(\dfrac{\text{\emph{T}}_{\text{music}}}{\text{(ms)}}\) & \(\dfrac{\text{\emph{d}}_{\text{+r}}\text{(m)}}{\text{D}_{\text{50m}}}\) & \multicolumn{2}{c}{**STI**} & \multicolumn{2}{c}{\(\dfrac{\text{\emph{T}}_{\text{sm}}}{\text{(ms)}}\)} \\ \hline S2 Arena & & & & & & & & & & \\ South Zone & & & & & & & & & & \\ \hline R1 & 1.45 & 1.45 & 36 & 40 & 33.7 & 0.91 & Exc. & 0.76 & Exc. & 37 & Exc. \\ R5 & 1.2 & 1.34 & 47 & 52 & 30.9 & 0.71 & Good & 0.53 & Fair & 57 & Good \\ \hline S3 Arena & & & & & & & & & & \\ West Zone & & & & & & & & & & \\ R1 & 1.03 & 0.99 & 41 & 46 & 12.8 & 0.94 & Exc. & 0.79 & Exc. & 24 & Exc. \\ R5 & 1.03 & 0.99 & 37 & 42 & 34.7 & 0.58 & Good & 0.56 & Fair & 66 & Good \\ R16 & 1.05 & 0.91 & 41 & 41 & 20.9 & 0.74 & Good & 0.67 & Good & 39 & Exc \\ R17 & 1.04 & 1.70 & 3.5 & 99 & 29.8 & 0.55 & Good & 0.65 & Good & 55 & Good \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Echo and other acoustic parameters in the Italica amphitheatre with source and receiver both in the arena. In bold interpreted as an echo. delayed that it can be associated with background noise. The results show that in neither the bullrings nor the amphitheatre is there a risk of echo for music in any of the public areas: the grandstands, covered galleries, and the cavea. Echoes for music have only been experimentally detected in two receivers in the bullring when the sound source is located in the centre of Las Ventas bullring. Likewise, there are few cases of echo in the public area for speech (of the 307 experimental recordings in the spectator area, only 11 recordings show a risk of echo for speech, see above), particularly in the grandstands of Las Ventas when the sound source is in the centre of the ring, due to the focusing of the sound from the great height of this bullring. In many cases when the echo parameter indicated the possibility of echo problems, these problems were merely very late noise reflections rather than actual echoes, while in other cases, they were early reflections that reinforced the direct sound. Furthermore, in several cases, although echoes exist for the spoken word signal, they are from sound-source positions of a musical nature that occur in the bullrings: a music band, bugles and timpani, or trumpets. In cases where both the sound source and the receiving microphone were located in the arena (Las Ventas, Campo Pequeno, and the Roman Amphitheatre according to experimental data, and Ronda and Las Ventas according to simulation data with the bullring empty), the results indicate that the arenas of the performing venues have large areas where echoes occur for speech and even for music, including when the ring is covered with a movable roof (Campo Pequeno, for example).