# Cross-Laminated Timber Floor: Analysis of the Acoustic Properties and Radiation Efficiency
## 4 Comparison between Measured and Calculated Values  
It is now possible to use the sound radiation and velocity level, experimentally determined, together with the geometrical features, to predict the impact noise by means of the literature and proposed methods (equations presented in Sections 2.1 and 2.2), in order to compare them with the measured one. In Figure 17, the normalized impact sound pressure level measured in the laboratory (\(L_{\text{n,meas}}\)), the expected level according to the reference curve (\(L_{\text{n,ref.curve}}\)) [13], the level derived from the velocity levels (\(L_{\text{n,Lv}}\)) according to Equation (5) and the expected level using the model in ISO 12354-2 (\(L_{\text{n,12354-2}}\)), using Equation (6), and the expected level (\(L_{\text{n,pr}}\)), using the proposed Equation (7) are shown. Table 4 shows the weighted normalized impact sound pressure levels for the measurements and models used. It can be noted that for all the models, the calculated values fall within a range of 2 dB. The result obtained using the velocity levels is more accurate, as it is derived from an actual  
Figure 16: Simulated normalized sound reduction index (Equation (7)) and energy average maximum impact sound pressure level (Equation (9)). Figure 17: Measured and predicted normalized impact sound pressure level. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \(L_{\text{n,w\_meas}}\) [dB] & \(L_{\text{n,w\_ref. curve}}\) [dB] & \(L_{\text{n,w\_LV}}\) [dB] & \(L_{\text{n,w\_12354-2}}\) [dB] & \(L_{\text{n,w\_pr}}\) [dB] \\ \hline
88 & 86 & 89 & 90 & 88 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Weighted normalized impact sound pressure level, \(L_{\text{n,w}}\). measurement made on the floor. It can be noted that the shape of the measured spectrum is similar to the reference curve [13], while the measured values are 2 dB higher than the reference curve. Figure 18 shows the sound reduction index measured in the laboratory \((R_{\text{meas}})\), according to the reference curve (\(R_{\text{ref.curve}}\)), derived from the velocity levels and the levels measured in the transmitting room (\(R_{\text{LV}}\)), in which A ed L1 are the measured values, while L2 is evaluated according to Equation (4), and the predicted level using the model in ISO 12354-1 annex B (\(R_{12354-1}\)) and predicted with proposed equations \(R=17.5\text{lg}(\textit{mf})-50\), between 315 Hz and 5000 Hz and \(R=17.5\text{lg}(\textit{m}^{\prime})-6.3\), between 50 Hz and 315 Hz. Table 5 shows the weighted sound reduction indices for the measurements and models used. The prediction made by velocity level and sound pressure level measurements in the transmitting room is quite accurate, because actual measurements are used on the floor. The reference curve overestimates the performance by 4 dB, while the ISO 12354-1 model (as from the equations in paragraph 2.1) overestimates (above 1600 Hz) and underestimates (between 80 and 1000 Hz) the performance of the floor, significantly. The proposed equations lead to the same index \(R_{\text{w}}\) and spectrum adaptation terms \(C\) and \(C_{\text{tr}}\). Figure 19 shows the maximum sound pressure level measured in the laboratory (\(L_{\text{i, Fmax\_meas}}\)), the level derived from the velocity levels (\(L_{\text{i,Fmax\_Lv}}\)) according to Equation (4) and the predicted level using the model in ISO 12354-2 (\(L_{\text{i,Fmax\_12354-2}}\)), using Equation (8) and the expected level (\(L_{\text{i,Fmax\_pr}}\)), using the proposed Equation (7). Table 6 shows the A-weighted sound pressure levels for the measurements and models used. The results show that looking at the weighted indices, the prediction made with the model derived from ISO 12354-2 gives a better value (+1 dB difference) than the model based on measured velocity levels (\(-2\) dB difference). This results from the fact that the A-weighting gives an increasing weighting, as the frequency increases from 50 Hz to 630 Hz.