## 3 Results and Discussion
### Attributions Analysis to Airborne Sound Insulation  
Figure 6 describes feature attributions of the chosen building materials to the prediction of sound isolation. It shows the effect size of thickness and density of building materials and the importance of their presence. At low frequencies, results highlight the density effects of the CLT (cross-laminated timber) panel, OSB (oriented strand board) and lightweight concrete panels on the predictions. However, the sensitivity effect of the latter increases in middle and high frequencies, except for the OSB panel. In addition, the density of a gypsum board has an important attribution, the higher the frequency bands. For gypsum fiberboard, the effect of its density increases significantly compared to normal gypsum board, especially in low frequency bands. The latter can be explained due to stiffer material of gypsum fiberboard where the stiffness is dominant at low frequencies. Density of the insulation materials shows a non-negligible attribution across all frequencies, but more pronounced for wood fiber insulation at high frequencies. A previous study [66] emphasizes the effectiveness of rockwood density in improving the isolation below 1.25 kHz, which is in accordance with findings in Figure 6. Moreover, the density of coating material (mineral plaster) is also essential at low and high frequencies. Regarding the attribution of material thickness, it is noticeable that thickness of the CLT panel is essential in all frequencies. The same observation was also found for the thickness of insulation materials, air gap and coating material. However, the attribution of some materials' thickness tends to increase at middle and high frequency, such as OSB panel and gypsum board, where the mass control region starts to dominate [17]. Furthermore, the existence of certain building components (material effect) has a bigger effect than the densities or thicknesses on airborne sound insulation, such as air gap and glass fiber. Figure 7 shows the attributions of additional parameters to airborne sound estimations. It reveals a small influence of surface area \(S\) of a facade structure in very low and high frequencies. The importance of the structure area on prediction of airborne sound in low frequency bands is also reported in [67]. In addition, the receiving room volume \(V\) is vital at all frequencies, particularly at higher ranges, where energy of short sound waves can be easily damped out due to relaxation phenomena. This is more evident at high frequencies and/or in larger rooms, where the energy is exchanged between the sound  
Figure 8: Feature attributions of interior, main and exterior parts facade structures to predictions of airborne sound insulation. wave and air particles; the particles extract energy from the propagating waves and release it after a delay. This action leads to hysteretic energy losses, which contributes to sound attenuation [17]. The latter agrees with [45] and contrasts with another study [67] that showed the unimportance of \(V\) in the low frequency range. Contrary to the thickness of exterior study in a facade wall, the thickness of interior studs is a factor of higher weight on prediction across all frequencies. Moreover, the spacing between interior studs affects the predictions at low and middle frequencies, while the importance of spacing between exterior studs is only revealed at high frequencies. This finding emphasizes the role of mechanical connections, also known as sound bridges, in creating transmission paths and thus reducing insulation improvements [17; 68]. No remarkable attributions have been revealed for the depth of the resilient channels, except at very high frequencies. However, the spacing between the resilient channels has a noticeable effect in middle and high frequency bands. The total thickness of a facade structure influences the predictions at all frequencies, which is also concluded in [67]. Additionally, the total density affects the prediction the most across all frequencies, as also reported in [45].