as the best transmission loss model in
shallow water (Richardson et al., 1995), the source level of TF noise
can be estimated 160 dB re 1 μPa at 1 m. It is however possible that
this SPL value is much higher if recorded closer to the ferry boat, due
to several variables affecting the sound propagation in coastal area
(i.e. bottom morphology, absorption, shadow zones due to refraction,
salinity, thermal clines, etc). Both noise spectra had the main energy
content below 1.5 kHz, with a peak at 1033 Hz and 602 Hz for TF and
FB, respectively. Below 1.5 kHz, the spectral energies of TF and FB
noises were 13 and 33 dB re 1 μPa higher than Sea Ambient Noise
(SAN). The LLeq, 25 s of the recorded SAN was 132.3 dB re 1 μPa. The 1/3
octave band noise pressure spectra of the two boats and of SAN are
shown in Fig. 2.