## 2 Materials and Methods
### Acoustic Measurements  
The developed database contains 100 standardized laboratory measurements received from Lund University in Sweden and The National Research Council (NRC-CNRC) [57] in Canada. The measured data consists of airborne insulation measurements of 100 various facade walls in one-third-octave bands (50 Hz to 5 kHz). They were performed according to ISO 10140-2 (2010) [12] and ASTM E90-09 (2016) [15].  
To have a total agreement between insulation data, measurements that are performed in compliance with ASTM standards have been converted to follow ISO 717-1 (2013) [58] descriptor (the weighted airborne sound R\({}_{w}\)). This conversion is essential to unify the acoustic descriptors in the measurements.  
Figure 1a,b illustrate the 100 insulation curves of facades and mean with standard deviations, respectively. The database contains curves of airborne sound reduction index \(R(f)\) in frequency range from 50 Hz to 5 kHz. Hence, for every facade structure there are technical parameters and full-spectrum insulation curve. Table 1 summarizes the division of measurement numbers that are used to develop the network model.  
test the accuracy of the model (Figure A1 in the Appendix A). Measurement curves that are selected for testing are part from the total number of measurements. They include the average tendency of isolation curves and extreme values as well, at all frequencies, as illustrated in test facades #4, #9 and #1 in Figure 1a.  
In the database, each facade configuration is clustered in three parts: interior, main and exterior parts, respecting the installation order of each facade component. The dominant component or material is represented by the main part. Therefore, The interior and exterior sections present components clustered and located alongside the main facade material (Figure 2).  
MySQL software [59] is used to organize the database using 10 variables of structural parameters of each facade wall (Table 2). Those parameters present the input that are used to train the network model. They are arranged considering type of each facade component, their installation position, thickness and density of each layer, depth of study and spacing between them, area of a facade (\(S\)), volume of a receiving room (\(V\)), group and total thickness and mass of a structure, resilient metal channel depth and spacing between them. Values of airborne sound reduction index in one-third-octave bands are used as outputs or targets of the ANN model. Despite the fundamental role of certain elastic properties on the sound transmission, such as dynamic stiffeners and the modulus of elasticity of each material, they are not taken into account in the input parameters due to the lake of information in acoustic measurement reports.  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Parameter** & **Unit** & **Class** \\ \hline – type of material & — & i.e., CLT panel, insulation materials, etc. \\ – Material installation order & — & first/second/... \\ – Material thickness & mm & — \\ – Group thickness & mm & interior, main and exterior parts \\ – Total thickness of a facade & mm & — \\ – Material density & kg/m\({}^{3}\) & — \\ – Group density & kg/m\({}^{3}\) & interior, main and exterior parts \\ – Total density of a facade & kg/m\({}^{3}\) & — \\ – Facade area \(S\) & m\({}^{2}\) & — \\ – Volume of the receiving room \(V\) & m\({}^{3}\) & — \\ – Studs depth & mm & — \\ – Spacing between studs & mm & — \\ – Resilient channels depth & mm & — \\ – Spacing between Resilient channels & mm & — \\ \hline \hline \end{tabular}
\end{table}
Table 2: Structural variables used to organize the database and employed as inputs for the network model.  
Figure 2: An explanation schematic presenting how facade components are clustered in the database using an example of the test facade #6.