# Impact of Audio Delay and Quality in Network Music Performance +
## 5 Evaluation Results
### Scenario A: Audio Delay  
The study of the effects of audio delay was the main focus of our work; therefore, the musicians responded to an extended questionnaire (see Section 4)--the results from which are presented below. Figure 4 shows the answers to the Perception of Synchronization Degree (PoSD) question against the M2E delay; higher values indicate better synchronization. The regression line shows a clear negative relation to delay, starting at 4.3 and ending at 3, confirming that higher delays cause more synchronization problems. These results indicate a loss of synchronization when the M2E delay exceeded 40 ms, as opposed to the 25-30 ms previously reported, as the average PoSD only drops slightly between 30 and 40 ms (from 3.75 to 3.5) and the variance at 30 and 40 ms is quite similar. Figure 5 shows the results for the Perception of Audio Delay (PoAD) variable; higher values indicate more delay. The regression line now has a slightly increasing slope, starting at 1.4 and ending at 2.4. We again see a small change between the results for M2E delays of 30 and 40 ms (both very close to 2), which implies that a one-way delay of 40 ms is nearly as acceptable as 30 ms. Note that the confidence intervals around the fitted line are wider than for the PoSD variable but still quite narrow for most M2E delay values. Focusing specifically on the sessions that involved pianists (duets 1, 2, and 5), the responses from both the pianists and their partners (a total of six participants), presented in Figure 6, reveal a steeper increase in perceived delay, from 1.5 to 3.4. The corresponding confidence intervals are broader, reflecting the smaller sample size and greater variability in responses. This finding suggests that the perception of delay is context-dependent;  
Figure 4: Perception of synchronization degree (N = 22), 95% confidence, Adj. R\({}^{2}\) = 0.89. \begin{table}
\begin{tabular}{l l l l l l l l l l l} \hline \hline
**Duet** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** & **11** \\ \hline Genre & Folk & Folk & Rock & Rock & Funk & Funk & Rock & Rock & Classic & Folk & Folk \\ \hline Instr.1 & Piano & Piano & El Gtr & Bass & Organ & Bass & Bass & El Gtr & Flute & Ac Gtr & Lute \\ \hline Instr.2 & Santouri & Oud & El Gtr & El Gtr & El Gtr & Perc & Ac Gtr & Violin & Violin & Bouz & Violin \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Performance details for each duet. in particular, the presence of a pianist in the ensemble appears to heighten performers' sensitivity to audio delay. Arguably, the most critical variable in our study is the Perception of Satisfaction (PoSat), which effectively corresponds to the widely used MOS metric. As illustrated in Figure 7, the regression line exhibits a gentle downward trend, decreasing from an initial score of 4 to approximately 3.4. The difference in perceived satisfaction between 30 ms and 40 ms one-way delays is minimal, suggesting that musicians generally tolerate delays up to 40 ms without significant discomfort. While the decline from 40 ms to 60 ms is also modest, the contrast between 30 ms and 60 ms is more pronounced. These results indicate that, rather than a sharp threshold at 30 or 40 ms, satisfaction decreases progressively with increasing delay. Nonetheless, 40 ms emerges as a practical upper bound for maintaining synchronous performance in rhythmically demanding musical contexts. When we focus again on pianists and their partners for the PoSat variable, Figure 8 shows a regression line with a steeper slope, starting at 4.7 and ending at slightly less than 2.9, again with wider confidence intervals, confirming the lower tolerance to delay that was also indicated by the responses to the PoAD variable. Figure 5: Perception of Audio Delay (N = 22), 95% confidence, Adj. R\({}^{2}\) = 0.85. Figure 6: Perception of audio delay (pianists and partners, N = 6), 95% confidence, Adj. R\({}^{2}\) = 0.79. Figure 7: Perception of satisfaction (N = 22), 95% confidence, Adj. R\({}^{2}\) = 0.86.