‚+ 
15 
Combined Uncertainty (All Runs Combined) 
F. Basan et al. 
= =BSH Sylence 
—— ‚AU ST600HF 
—- FO ST300HF 
— FO| Sylence 
— TUT Sylence 
25 
N 
A 
Dr 
Ss 
A 
© 
S 
3 
1.5 
Fr 
2.5 
d'— _ 
2000 3000 4000 
5000 6000 7000 8000 
Frequency [Hz] 
3000 
10000 
Fig. 6 Total combined uncertainty of free-field calibrations for recorders that were calibrated in 
FOTI’s tank and at FOI’s pontoon 
Overall, the deviations between tank and pontoon calibrations span a range from 
approximately +6 dB to —8 dB across the frequency band, showing a trend of 
decreasing difference with frequency. All recorders show a broadly similar spectral 
shape: positive offsets at lower frequencies that gradually transition into negative 
deviations. Device-specific features remain visible. For example, AU’s ST600HF 
exhibits two distinct peaks around 3.5 kHz and 6 kHz that are absent in the pontoon 
data and thus likely reflect tank-related artifacts. The BSH Sylence LP shows a 
pronounced drop above 8 kHz, consistent with the mounting effect described earlier. 
These tank-pontoon deviations are similar or even larger than the pontoon—- 
pistonphone differences shown in Fig. 4, supporting the view that both reflect a mix 
of system response and setup-related variability. 
A combined uncertainty was computed for each recorder that was calibrated at 
both facilities. This total combined uncertainty Uio1(f) was obtained by propagat- 
ing the terms: the within-run variability of the three repeated pulses per calibration 
run, the standard deviation across all calibration runs at both facilities, and the 
systematic uncertainty of the acoustic source. 
The resulting curves show consistent patterns across recorders (Fig. 6), with broad 
peaks between 5 and 8 kHz, probably reflecting the resonance regions of the projector 
system. The BSH Sylence again exhibits a slightly elevated and irregular curve, 
consistent with the mounting-related deviations discussed above. Overall, the