The third-octave levels were found to be highly variable.
The 24-h centred means of the 63-Hz band within Falmouth Bay exhibit greater variation (approx. 38 dB) than the 20 dB measured at four deep ocean sites
Sound levels in shallow waters are known to be more variable than at deep ocean sites. This is due to the sea surface, water column and seabed properties varying considerably, temporally and spatially, all of which are important in determining acoustic propagation characteristics in shallow coastal environments
Consequently, this may also have implications for sampling as the duration required to determine a statistically significant
trend, outside the general variability, may be longer in comparison to deep ocean sites. Different management schemes, including differing GES thresholds, may therefore be required for deep and shallow marine sites, especially as the trends in anthropogenic noise may vary with the types of vessels commonly using each area , as well as other sources such as construction and renewable energy sites