Underwater sound measurements from fishing vessel "Brennholm"
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A methodology for measuring underwater sound from free running vessels was implemented inside IMR, following American National Standard ANSI/ASA S12.64-2009 grade B. An array of 3 calibrated NEXUS hydrophones was mounted in a drifting buoy provided with DGPS and radio communication. The sound measurement was recorded at different speed and engine settings (rpm and pitch) inside Osterfjørd on December 8, 2010. Optimal weather conditions and almost absent marine traffic prevailed during the data collection. Analysis of the data was done at 1/3 and 1/24 octave band filter, and sound pressure levels were normalized for distance from the hydrophones to the centre of the vessel. Sound pressure spectrum of radiated underwater sound from “Brennholm” showed a higher (ca. 30 dB) than recommended levels by the ICES CRR 209, at vessel speeds of 9, 11 and 12 knots.