Operational noise associated with underwater sound emitting vessels and potential effect of oceanographic conditions: a Dublin Bay port area study

Abstract

This study presents analysis of acoustic data of underwater sound emitting vessels (USEV) recorded during operation in the Dublin Bay port area. Investigations were carried out to assess the magnitudes of these underwater sounds, and also the potential effect of changes in tidal states on these sound signals and their propagation. Power spectral densities (PSD) and 1/3 octave band sound pressure levels (SPL) were computed for frequencies between 50–500 and 50–1000 Hz, respectively. During the presence of these vessels in the study site, broadband SPL values for a range of frequency components were calculated to be between 94 and 121 dB (re 1 µPa) at a distance of 200 m from the vessels. These values decreased by 5–21 dB during their absence. The strongest sound level recorded at this site was during the departure of vessels from the dock at 200 m from the recording system. The SPL value calculated during this operational period at 315 Hz frequency was 121 dB re 1 µPa2/Hz. Associated components’ spectral of the vessels were identified, and the effect of difference in heights of tidal ranges (Neap/Spring) on this site was investigated.