00C 
300 
BOO 
700 
N 
= 600 
* 500 
3 
400 
300 
3PA: 0.069868 km ; CTV 
AudioCPAPaak 
https:/doi.org/10.1121/10.0043324 
JASA 
TABLE II. Overview of identified CTV passages 
Parameter 
No. of identified CTVs 13 
CTV length range 22-32 m 
CTV draught range 1.1-2.3m 
Assumed source depth range 0.8-1.6 m 
No. of passages per CTV 4-94 
Speed range during passages (kn) 10-25 kn 
Value 
200 
00 
1-56 
14:36 
43 
14:38 14739 
ME 
14:40 14:41 14:42 
‚Jul 09, 2024 
FIG. 2. Example of the user interface that was used to manually select and 
verify the TCPAs in the acoustic data. The red line indicates TCPA from 
AIS data, and the dotted green line indicates TCPAs from the interference 
pattern analysis. 
regression for the clock drift was calculated, and all pas- 
zages with A 'TCPAs greater than 1 standard deviation were 
discarded from further analysis. These passages were 
sxcluded due to potential uncertainties in their data, such as 
inaccuracies in the AIS timestamps. Clock drift is a well 
known phenomenon in autonomous recorders and has been 
reported in previous studies using SoundTrap devices 
‘Ocean Instruments NZ, Auckland, New Zealand). For 
example, Malinka et al. (2020) observed a drift of approxi- 
mately 2 s/day for a SoundTrap ST300 recorder deployed in 
deep water, while Macaulay et al. (2020) reported a drift of 
72 ms/h (equivalent to ca. 1.72 s/day) for a SoundTrap 
Re: jar1 
on 
30 
75 
ST500 recorder. In contrast, the recorders used in this study 
exhibit a significantly lower drift, with values of 0.5 s/day 
(0.021 s/h) for recorder 1 and 0.47 s/day (0.0197 s/h) for 
recorder 2. This suggests that either newer device models 
have improved internal clock stability, or different deploy- 
ment conditions (e.g., shallower depth or higher tempera- 
tures) contributed to the reduced drift. The remaining 750 
CTV passages were used for subsequent analysis. 
All identified CTVs were measured during transit. 
Table II summarizes the number of vessels, their length 
range, the number of passages per vessel, and the observed 
speed range during the passages. 
D. Acoustical analysis 
There are well-established standards on how to measure 
radiated noise of cooperating vessels in deep water and for 
deriving SLs (ISO, 2016, 2019). The newly published ISO 
17208-3 builds upon these standards and describes proce- 
dures for ship noise measurements in shallow water, includ- 
ing the use of the SSCI approach for propagation loss 
Recorder 2 
+ all ATCPAs ı 
<  outlier 
——regression line 
„+10 
D 
30 
‚ 45 
N 
5 
30 
L 
A 
9 15 
Jun Jul 
Aug 
Time 
Sep 
Jul 
Aug Sep Oct 
Time 
FIG. 3. Difference of TCPAs (A TCPA) between the TCPA in AIS data and manually identified TCPAs in audio data; the red line in each panel indicates 
he trend line, i.e., time drift of each recorder. Only TCPAs within 1 standard deviation of the fitted trend were included in the analysis. 
3408 J. Acoust. Soc. Am. 159 (4), April 2026 
Basan et al.