## 3 Illustrative Example for Structure-Acoustic Analysis
### Field Measurements  
With respect to the wall-type structure specimen, a field measurement of vibration and noise was performed using the bang machine and impact ball, and a numerical analysis was conducted. For storage of the measurement data, a laptop and sensor signal acquisition device (Front-End SIEMENS SCADAS Mobile) (SIEMENS, Plano, TX, USA), microphone (4188, Bruel and Kjaer, Narum, Denmark), and preamplifier (2671, Bruel and Kjaer, Narum, Denmark) were used. In general, the noise measurement was performed using the bang machine and impact ball in accordance with the provision that says, \"the impact locations of the standard heavy weight impact source shall be 3 to 5 points, including 1 point around the central point, which are averagely distributed in the bottom plane over 0.5 m away from the wall around the room\" presented in KS as shown in Figure 11. However, since this study aims not to evaluate the noise of the target structure, but to develop an analytical impact force model through a comparison between experimental measurement values and numerical analysis results of the artificially produced analytical impact force model, only the measurement result of one location in the central point of the upper part of the specimen (location 3 in Figure 11a) was considered based on the noise measurement standards presented in KS.  
In relation to the microphone installation locations for indoor noise measurements, the provision which says, \"the measurement points of more than 4 points which are more than 0.7 m away from each other within the space over 0.5 m away from the ceiling, surrounding wall and bottom plane shall be evenly distributed in space\" presented in KS was adhered to. Accordingly, five microphones for noise  
Figure 11: Details of experimental testing: (**a**) impact source locations; (**b**) bang machine; and (**c**) impact ball.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Name** & **Concte** & **Expanded Polystyrene (EPS)** \\ \hline Modulus of Elasticity (GPa) & 24.834 & 0.005 \\ Density (\(\rho\), kg/m\({}^{3}\)) & 2400.0 & 15.0 \\ Poisson’s Ratio (v) & 0.167 & 0.05 \\ Acoustic Impedance (Z, MRayl) & 8.0 & 2.5 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Material property of the test specimen.  
measurements were installed in accordance with KS, and indoor noises were measured as shown in Figure 12.  
Figure 13 shows field measurement results (excitation at central point) of the bang machine and impact ball with respect to a 1/3 octave band and a 1/1 octave band, respectively. As shown in Figure 13, the response of the microphone at the central point was somewhat lower in the region prior to 100 Hz based on 100 Hz but found to be slightly higher than that of other microphones in the region after 100 Hz. With respect to the mean value for each case, a single number quantity (SNQ) was calculated, and the results were 57 dB and 59 dB, respectively.  
Figure 12: Microphone locations for noise measurements: (**a**) microphone locations in KS (Korean industrial standards); and (**b**) microphone setting for experimental testing.  
Figure 13: Acoustic response of experimental test for five microphones and its mean value: (**a**) bang machine; and (**b**) impact ball.  
As represented in Figure 13, the SNQ for the impact ball was slightly higher than that of the bang machine at 250 Hz and, therefore, the impact ball was found to be rather higher than the bang machine in the SNQ (See Table 9). It should be noted that KS F 2863 [32] is adopted to compute a SNQ for the standard heavy weight impact sources, _i.e._, bang machine and impact ball. The method of KS F 2863 is the same as that of ISO 717 [33], that is for the standard light weight impact source, such as a tapping machine, except the difference in the considered frequency range for calculation. Detailed information related to the computation can be found in KS F 2863 and ISO 717.