## 5 Full-Frequency Test-Simulation Comparison  
The FEM-BEM and SEA results are combined together to obtain full-frequency simulation results. The boundary between the two methods has to be set strictly beyond the validity criterion of the SEA model (\(>\)1600 Hz) and strictly below the limit of the modal truncation of the FEM model (2500 Hz). This boundary was set at 2200 Hz in order to include the second bottom resonance (around 2100 Hz) in the low-frequency range. FEM-BEM simulation provides the response acceleration PSD for every mesh point, with a fine frequency resolution, whereas SEA simulation provides a mean acceleration level per frequency band.  
From an industrial perspective, the first expected output of a full-frequency simulation tool is the overall root mean square acceleration level at every point of the structure. For this purpose, for every point studied, the RMS level computed below 2200 Hz using FEM-BEM can be summed with the mean RMS level beyond 2200 Hz of the SEA subsystem to which the point belongs (using a quadratic sum). The second level of analysis is the frequency content of the simulated response.  
For this analysis, the one-twelfth-octave band representation is chosen. The acceleration PSD measured is integrated in every one-twelfth-octave band to obtain the proper representation, and the FEM-BEM results are processed in the same way. The SEA simulation shown in Section 4 is carried out again choosing the one-twelfth-octave band discretization. When working in one-twelfth-octave band, the SEA criteria (at least three modes per frequency band) is validated above 1600 Hz for the envelope subsystems and above 2000 Hz for the bottom.  
Yet, in this last simulation, the DLF that were defined based on one-third-octave band measurement remain the same so that they are constant along each one-third-octave band. The results obtained are shown at three points located in the three SEA subsystems:  
* point (a) at the center of the envelope, located in SEA 2D 2, see Figure 20,
* point (b) located on the envelope, in SEA 2D 1 subsystem, see Figure 21, and
* point (c) on the bottom, located in SEA 2D 3, see Figure 22.  
A very good test-simulation agreement is observed in the full-frequency range, which proves the complementarity between the FEM-BEM and SEA methods. The corresponding RMS levels are presented in Table 3.  
Figure 20: Full-frequency test–simulation comparison at point (a), one-twelfth-octave frequency band representation. The experimental response (black curve with stars) is compared with the combination of the FE-BEM results (red curve with +) and SEA results (blue curve with +).  
Figure 21: Full-frequency test–simulation comparison at point (b), one-twelfth-octave frequency band representation. The experimental response (black curve with stars) is compared with the combination of the FE-BEM results (red curve with +) and SEA results (blue curve with +).  
Figure 22: Full-frequency test–simulation comparison at point (c) on the bottom, one-twelfth-octave frequency band representation. The experimental response (black curve with stars) is compared with the combination of the FE-BEM results (red curve with +) and SEA results (blue curve with +).