## Human-Performed Classification
### Listening Test Results
The histogram discussed above showed the listeners' scores lumped for all the BRIR sets, hence obscuring any inter-BRIR effects. To investigate how the accuracy scores varied between the stimuli synthesized using individual BRIR sets, they were also plotted in the form of boxplots across all BRIR sets, as illustrated in Figure 4a. The outcomes confirmed the previous observations. Namely, for almost all BRIR sets, the scores barely exceeded the no-information rate of 33.3%. Due to a large number of observations, the deviation from the no-information rate was statistically significant, except for BRIR sets 3, 7, 8, and 12, according to a double-sided _t_-test performed at 0.05 significance level. Interestingly, for a BRIR set 13, the accuracy scores were statistically different from the no-information rate but in the opposite direction. In this case, the mean accuracy score was statistically significantly less than 33.3%, confirming the above observation about the consistent misclassification of the scenes, as illustrated earlier in Figure 2e. Figure 3: Histogram of the accuracy scores calculated for each listener. Figure 2: Examples of confusion matrices obtained from human listeners: (**a**) All data; (**b**) BRIR set 1; (**c**) BRIR set 2; (**d**) BRIR set 5; (**e**) BRIR set 13; (**f**) BRIR sets 1-11 (data after post-screening). Vertical axis represents the classification results obtained from the listeners whereas the vertical axis denotes the scenes as intended during the procedure of the binaural synthesis of the audio recordings. Analysis of variance (ANOVA) test was carried out in order to formally investigate the inter-BRIR effects formerly seen in Figure 4a. The assumptions underlying the ANOVA model were positively verified using the omnibus test of homogeneity of variance and Jarque-Bera test of the assumption of normality. The obtained ANOVA model was statistically significant, \(F(12,199)=3.28\), \(p=2.39\times 10^{-4}\). However, according to the results of the post hoc Tukey HSD test, no statistical differences between the mean accuracy scores across the BRIR sets were detected, with the exception of a BRIR set 13, which was statistically different from the other ones. This outcome further supports the observation about the outlying nature of the data obtained for BRIR 13. The exact reason for the outlying characteristics of the data obtained using a BRIR set 13 is unknown. The above BRIR set was acquired in the Audio Laboratory at the University of Rostock, which was also the case for a BRIR set 12 (see Table 2). However, in the latter case, the results are not as outlying as the ones obtained using BRIR 13. Nevertheless, after excluding the outlying BRIR set 13, the results obtained using a BRIR set 12 are the worst of all the BRIR sets, with the mean accuracy of 33.96%, being almost equal to the no-information rate. In contrast to the stimuli synthesized using BRIR sets 1-11, the stimuli synthesized with BRIR sets 12 and 13 were generated employing a simulated wave-field synthesis model [13]. The outlying or poor results gathered for BRIR sets 12 and 13 could have resulted from signal processing artifacts pertinent to a wave-field synthesis (e.g., spatial aliasing). Hence, considering their commonalities in terms of the origin and the signal processing algorithm used, it was decided to remove (post-screen) the data obtained both for BRIR set 12 and 13.