## 4 Discussion  
This work aims to give more insight into the design aspects of concert halls related to the effects of diffusive surfaces location. Based on the results presented above, a few practically relevant comments can be made in order to achieve a more mindful design of concert halls and intervene in those areas that could lead to the required objective and perceived acoustic quality. The objective analyses presented in Figures 5-9 and Appendix A showed that the objective parameters are not significantly influenced by the diffusive surface location. These results confirm the findings of previous investigations [PERSON] et al. [18] and [PERSON] et al. [12], i.e., the diffusers installation on lateral walls do not have any significant effect on the overall acoustic parameters. However, a few significant differences could be observed at single receiver positions. Generally, no clear trend can be observed for \(T_{30}\), \(C_{80}\), \(D_{50}\), and \(T_{s}\) variations in the different configurations in both the absorptive (-A) and reflective (-R) conditions. _EDT_ was shown to be the most affected parameter. The differences over the configurations show that this is more evident for source location S2 and occurs at a larger number of receivers in the absorptive (-A) conditions. However, no significant trend  
Figure 11: Listening test results. The listeners’ subjective evaluations on the perceived differences between front and rear location of the diffusive surfaces in the absorptive and reflective conditions (Df-A vs. Dr-A and Df-R vs. Dr-R). The \(y\)-axis depicts the occurrences of each attribute given in the correct answers. The \(x\)-axis reports the attributes Co—coloration, Sp—spaciousness, Cl—clarity, Re—reverbearance, Lo—loudness. Figure 10: Listening test results. The dashed horizontal line indicates the minimum number of correct answers necessary to indicate a significant perceptual difference between configurations compared in one pair. \(x\)-axis indicates the pairs compared in each trial. could be observed with respect to the source-to-receiver distance and the statistical analysis did not show a statistically significant difference between the different diffusers locations. Generally, when the different configurations have been compared to the reference conditions (Table 3), no significant differences resulted in the reflective condition while in the absorptive conditions \(EDT\) and \(T_{30}\) resulted in the most affected. It was shown that in the absorptive conditions (-A), the combination of the listening position head 1 and source location S1 presented a greater number of parameters (\(EDT\), \(D_{50}\), and \(IACC_{\text{L}}\)) that reveal differences above 1 JND in comparison to Df-A with Dr-A (Table 4). Conversely, the listening position head 2 and source location S2 presented significant differences (>1 JND) for \(EDT\) only in both the reflective (-R) and absorptive (-A) conditions. Given these differences, as in previous studies [7; 12], it was not possible to correlate the objective parameters differences in these two positions to the perceived differences. The subjective test did not show significant perceived differences between the configurations Df-A and Dr-A or Df-R and Dr-R, i.e., front-rear asymmetric conditions of the diffusive surface location with respect to the listener position. Some of the listeners could still indicate a few differences by relying on different attributes as presented in Figure 10, which shows the occurrences of each attribute given in the correct answers. However, it was not possible to identify the preferred location of the diffusers due to the small perceived differences. It was observed that for each signal (trumpet, orchestra, pink noise), more than 75% of the correct answers were given relying on two or more attributes (reverberance, coloration, and spaciousness). These attributes have been also highlighted as the most affected in previous studies [4; 7; 20; 21; 23].