# Impact of Audio Delay and Quality in Network Music Performance +
## 5 Evaluation Results
### Scenario B: Audio Quality  
The investigation of audio quality effects was a secondary objective in our study. Our primary aim was to determine the extent to which musicians can tolerate audio quality degradation in NMP scenarios, thereby avoiding the additional delays introduced by audio compression and decompression. Consequently, the audio quality experiments were conducted after the audio delay tests and employed a shorter questionnaire (see Section 4); the corresponding results are presented in this section.  
Figure 13 illustrates the results for the Perception of Audio Quality (PoAQ) in relation to the sampling rate. It is important to note that, in this case, the experimental conditions improve towards the right side of the figure (i.e., higher sampling rates). The regression line displays a very slight positive slope, with ratings remaining close to three across all sampling rates. This suggests that the perceived improvements in audio quality were minimal for most participants. However, when examining only the pianists and their partners, Figure 14 reveals a more noticeable upward trend, indicating that this subgroup was more sensitive to variations in audio quality.  
Similarly, Figure 15 presents the results for the Perception of Satisfaction (PoSat), our MOS indicator, as a function of the sampling rate. The regression line also shows a modest positive trend, with scores ranging from 3.2 to 3.5. Interestingly, when focusing on pianists and their partners, the trend becomes almost flat, as shown in Figure 16, suggesting that audio quality had little influence on their overall satisfaction. This further supports the observation that changes in audio quality had a limited impact, even though the sampling rate varied by an order of magnitude.  
Figure 14: Perception of audio quality (pianists and partners, N = 6), 95% confidence, Adj. R\({}^{2}\) = 0.03.  
Figure 13: Perception of audio quality (N = 22), 95% confidence, Adj. R\({}^{2}\) = 0.17.  
To ensure that musicians were not negatively affected by the experimental setup itself, we also measured their perceived levels of anxiety (Figure 17) and irritation (Figure 18) throughout the sessions. Both regression curves exhibit a slight negative slope, and average scores remain consistently close to 1, indicating little to no anxiety or irritation. This strengthens the reliability of the reported findings by confirming that participant discomfort did not influence the results.  
Finally, we assessed the statistical significance of these results by performing an ANOVA study for repeated measures; the independent variable was audio quality (i.e., sampling rate,) and the dependent variable was PoAQ or PoSat. As in the audio delay tests, we did not run the variables that were clearly uncorrelated with audio quality. We show the results for these variables (including all 22 participants) in Table 5. We can see that both \(p\) values are greater than 0.05, which is what we would expect from the very slight slopes in the regression lines shown in the graphs above. This implies that we can reduce the sampling rate in NMP without significantly reducing the QoE of the musicians. This is a very interesting observation, as reducing the audio bitrate without the delays induced by compression makes NMP more practical in limited bandwidth scenarios.  
Figure 16: Perception of satisfaction (pianists and partners, N = 6), 95% confidence, Adj. R\({}^{2}\) = 0.03.  
Figure 17: Perception of anxiety (N = 22), 95% confidence, Adj. R\({}^{2}\) = 0.47.  
Figure 15: Perception of satisfaction (N = 22), 95% confidence, Adj. R\({}^{2}\) = 0.17.