Long-term underwater sound measurements in the shipping noise indicator bands 63 Hz and 125 Hz from the port of Falmouth Bay, UK

Authors: J. K. Garrett, Ph. Blondel, B. J. Godley, S. K. Pikesley, M. J. Witt, L. Johanning

Abstract

Chronic low-frequency anthropogenic sound, such as shipping noise, may be negatively affecting marine life. The EU’s Marine Strategy Framework Directive (MSFD) includes a specific indicator focused on this noise. This indicator is the yearly average sound level in third-octave bands with centre frequencies at 63 Hz and 125 Hz. These levels are described for Falmouth Bay, UK, an active port at the entrance to the English Channel. Underwater sound was recorded for 30 min h− 1 over the period June 2012 to November 2013 for a total of 435 days. Mean third-octave levels were louder in the 125-Hz band (annual mean level of 96.0 dB re 1 μPa) than in the 63-Hz band (92.6 dB re 1 μPa). These levels and variations are assessed as a function of seasons, shipping activity and wave height, providing comparison points for future monitoring activities, including the MSFD and emerging international regulation.