## 3 Analysis of Results
### 3D Sound Maps and Volumetric Behavior of the Sound Energy Inside the National Theatre of Zagreb  
Some selected positions of the multichannel spherical microphone have been considered for the realization of the acoustic maps, as indicated in Figure 2. It should be noted that the description and the technical details are already covered in Section 2 of this manuscript.  
By analyzing the IRs recorded by the multichannel spherical array microphone, it is possible to detect the direct sound coming from the position of the sound source placed on the stage, followed by the early and late reflections [41]. Figure 5 shows the direct sound energy at the four representative positions across the audience where the time frame goes from 40 ms to 300 ms, as shown at the bottom of every image.  
Based on the maps shown in Figure 5, the direct sound energy can be detected in the red color. Specifically, in the boxes of the first and second balconies, the sound energy easily hits the floor and ceiling of the boxes as well since the sound energy arrives on both surfaces simultaneously [42]. In the open spaces, such as the stalls and the upper gallery, the sound energy is more detectable, because there are no surfaces nearby other than the floor that reflects the soundwaves. The relationship between the soundwave amplitude of the time frame is visible with the color graphics; the higher the amplitude, the redder the contour levels.  
Similarly, the snapshots of the early and late reflections of the overlay videos are summarized in Figure 6, where the time frame goes from 40 ms to 300 ms, as shown at the bottom of every image.  
Figure 5: Panoramic view of the acoustic maps at the time of direct sound energy. Microphone positions in the stalls (**A**), first balcony (**D**), second balcony (**F**), and upper gallery (**I**). Time frame goes from 40 ms to 300 ms. Omnidirectional source on stage.  
Figure 6 illustrates the early reflections bouncing off towards the microphone. In particular, the two following scenarios can be observed: at position 1 and 4, the early reflections are weak, highlighted by yellow contour levels, while at position 2 and 3, corresponding to the boxes, the early reflections are stronger, highlighted by orange-red tonalities. As expected, this result can be explained by the presence of side walls and other bounding surfaces near the microphone, whereas in positions 1 and 4, the sound energy propagates throughout the open space.  
It is possible to analyze the late reflections, as summarized in Figure 7, where the time frame is always included between 40 ms and 300 ms, as shown at the bottom of every image.  
Figure 7 highlights the later energy reflections hitting the bounding surfaces farther from the sound source. Since the reflections are still within the 80 ms, they cannot be classified as late reflections, but they have been taken into consideration for their strong energy to be detectable from the contour levels. In position 1, the selected reflection clearly comes from the left side wall. In position 3, the detected reflection comes from the part of the ceiling closer to the proscenium arch, while in position 4 it comes from the ceiling but at a different angle. Inside the box of the first balcony, represented by position 2, strong reflections come from different directions, including the head of the right-side wall, the floor, and the ceiling of the box, as well as the architectural decoration that separates the first from the second order of balconies.  
Figure 6: Panoramic view of the acoustic maps at the time of the early reflections. Microphone positions in the stalls (**A**), on the first balcony (**D**), on the second balcony (**F**), and in the upper gallery (**I**). Time frame goes from 40 ms to 300 ms. Omnidirectional source on stage.