## 3 Results
### Results Analysis for Each Parameter Type  
The thresholds with outliers removed in each parameter type are analysed as percentages. Figures 8 and 9 provide the percentage of each impact threshold range of RER and FER removal on perceptual reverberation, respectively. The data in Figure 8 show that for BRIRs with 0.31 s, 0.91 s or 1.51 s reverberation time, most thresholds that influence participants' perceptual reverberation distribute between 0 and 30 ms, and about half of the thresholds are concentrated in 10-20 ms. Further, 26.3% of the thresholds are concentrated between 0-10 ms with 0.31 s reverberation time. These illustrate that when the RER is only removed a little, the reverberation difference can be clearly perceived, so people are sensitive to the RER of BRIRs.  
Figure 9 shows that the threshold distribution of FER removal is concentrated in 20-50 ms. These prove that the effect of FER removal on perceptual reverberation is weaker than RER removal. When the change of FER is within 20 ms, the effect of FER removal on perceptual reverberation is negligible.  
As shown in Figure 10, even though the thresholds of ITDG extension almost evenly distribute between 0 and 50 ms, when ITDG is extended for a few milliseconds, participants can clearly perceive the reverberation difference. Overall people are easy to distinguish the impact of ITDG extension on perceptual reverberation.  
Finally, reverberation time of BRIRs can influence the time of LR removal, so the ranges of parameter change are relatively large. As Figure 11 shows, for short reverberation time, the threshold distribution concentrates in 400-500 ms, at 0.91 s reverberation time, most resolution thresholds distribute 750-850 ms, and most thresholds concentrate in 1250-1350 ms. As shown in Figures A1-A3 in Appendix B, the grey impulse responses are the original impulse responses and the red impulse responses are the impulse responses with LR removed. Through calculation, the time length of the LR is 465 ms for the BRIR with 0.31 s reverberation time, 1329 ms for the BRIR with 0.91 s reverberation time and 1920 ms for the BRIR with 1.51 s reverberation time. A distinction is made here between the length of the LR and the reverb time to avoid confusion as to why the length of the LR is greater than the reverb time. This means that only when a large amount of LR is removed, the perceptual reverberation can be affected clearly, so it is hard for people to distinguish the difference of perceptual reverberation caused by LR removal and the impact of LR removal on perceptual reverberation is not serious.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**DF = 2** & **RER** & **FER** & **ITDG** & **LR** \\
**Significance Level = 0.05** & **Removal** & **Removal** & **Extension** & **Removal** \\ \hline \(p\) value & & & & \\ (ANOVA) & & 0.1093 & 0.1692 & \\ \hline Significant difference & & & & \\ (ANOVA) & & N & N & \\ \hline \(p\) value & & & & \\ (Kruskal-Wallis ANOVA) & 0.3901 & & & \({}^{*}\) 3.84768 \(\times\) 10\({}^{-12}\) \\ \hline Significant difference & & & & \\ (Kruskal-Wallis ANOVA & N & & Y \\ \hline \end{tabular}
\end{table}
Table 2: The ANOVA test results of RER removal, ITDG extension, FER removal and LR removal (Values marked with * indicate significant differences).  
Figure 8: Impact thresholds of RE removal on perceptual reverberation shown as a percentage of threshold ranges for BRIRs with three different reverberation times.  
Figure 9: Impact thresholds of FER removal on perceptual reverberation shown as a percentage of threshold ranges for BRIRs with three different reverberation times.