## 3 Results
### Acoustic Properties  
The results of the acoustic properties are presented in Table 2. The acoustic properties were calculated in the L direction, both with the ultrasonic direct transmission (_USL_) and the transitory excitation method (_FREQL_). Then, the acoustic properties of the cross section \begin{table}
\begin{tabular}{l l l l l} \hline \hline  & **Parameter** & **Mean** & **st. dev.** & **CV(\%)** \\ \cline{2-5}  & \(\rho\) (kg m\({}^{-3}\)) & 463 & 48 & 10 \\  & _AWAR_ (mm) & 2.16 & 0.63 & 29 \\  & \%_LW_ (\%) & 20.96 & 5.19 & 25 \\  & \(\alpha\) (\({}^{\circ}\)) & 0.85 & 0.93 & 110 \\  & \(\beta\)(\({}^{\circ}\)) & 26.82 & 16.24 & 61 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Data of main parameters showing the average, standard deviation, and coefficient of variation (CV). The moisture content is 7%, as provided by the Petrof Ltd. company. \(\rho\) = density, _AWAR_ = average widths of annual ring, %_LW_ = percentage latewood component, \(\alpha\) angle = slope of grain, and \(\beta\) angle = the orientation of the annual rings in the orthogonal section. were measured through the ultrasonic method (_USRT_). Eventually, the flexural _MOE_ and \(R\) were calculated using the transitory excitation method (_FREQ_). Table 3 presents the range of results of the acoustic properties in the L direction distinguished by the two methods. The value of the sound velocity along the L direction (\(V_{LL}\)) for Norway spruce is around 5350 m s\({}^{-1}\)[35; 36; 37; 38]. This is also confirmed by [PERSON] [15], with a similar value: 5300 m s\({}^{-1}\). [PERSON] [14] recommends that the value of L velocity for soundboard wood should reside between 3900 and 6700 m s\({}^{-1}\). [PERSON] [9] experimented on Norway spruce that the V\({}_{\rm LL}\) value varied from a minimum of 4906 m s\({}^{-1}\) to a maximum of 6897 m s\({}^{-1}\), with an average of 6183 m s\({}^{-1}\). The L velocity achieved by the ultrasonic direct transmission method was 5833 m s\({}^{-1}\) and 5833 m s\({}^{-1}\) by the resonance method. The results were very close, and both acceptable according to the literature data. Furthermore, the values of radial sound velocity must lie between 1042 and 2194 m s\({}^{-1}\) and average 1889 m s\({}^{-1}\); the average of the radial-transversal velocity measured by this research was 1165 m s\({}^{-1}\), in agreement with the literature of [PERSON] [9]. The _MOE_ in the L direction (\(MOE_{L}\)) of a material used for piano soundboards should mostly lie between 6 and 20 GPa [14]. [PERSON] and [PERSON] [35] define the \(MOE_{L}\) of spruce of 13.5 GPa. Despite this, [PERSON] [32] identifies a 15.9 GPa of the \(MOE_{L}\) in Norway spruce. The ultrasonic direct transmission method found an \(MOE_{L}\) of 15.901 GPa, and the transitory excitation produced a value of 15.857 GPa. These results were closer to [PERSON]'s values than those of [PERSON] and [PERSON]. Moreover, the values of \(MOE_{B}\) of Norway spruce varied from 9 to 14 GPa [31]. Similar values were found by [PERSON] [9]: \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method:**_US_ & **Range of Values** & **Method:**_FREQ_ & **Range of Values** \\ \hline \(V_{L}\) (m s\({}^{-1}\)) & 4891.30 & 6818.18 & \(V_{L}\) (m s\({}^{-1}\)) & 4635.00 & 6367.50 \\ \(\text{MOE}_{L}\) (GPa) & 9865.53 & 22,369.25 & \(\text{MOE}_{L}\) (GPa) & 9854.53 & 22,607.64 \\ \(Z_{L}\) (MPa s m\({}^{-1}\)) & 1.93 & 3.63 & \(Z_{L}\) (MPa s m\({}^{-1}\)) & 1.95 & 3.63 \\ \(R_{L}\) (m\({}^{4}\) kg\({}^{-1}\) s\({}^{-1}\)) & 9.82 & 17.77 & \(R_{L}\) (m\({}^{4}\) kg\({}^{-1}\) s\({}^{-1}\)) & 9.34 & 15.77 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Data of acoustic parameters showing the average, standard deviation, and coefficient of variation (CV). The moisture content is 7%, as provided by the Petrof Ltd. company. \(v\), _MOE_, Z, and \(R\) are, respectively, velocity, dynamic Young’s modulus, impedance, and acoustic constant. Subscript _US_ = ultrasonic method, and _FREQ_ = frequency method.