A 50 Year comparison of ambient ocean noise near San Clemente Island: A bathymetrically complex coastal region off Southern California

摘要

Repeated ocean ambient noise measurements at a shallow water (110 m) site near San ClementeIsland reveal little increase in noise levels in the absence of local ships. Navy reports documentambient noise levels at this site in 1958-1959 and 1963-1964 and a seafloor recorder documentsnoise during 2005-2006. When noise from local ships was excluded from the 2005-2006recordings, median sound levels were essentially the same as were observed in 1958 and 1963.Local ship noise, however, was present in 31% of the recordings in 1963 but was present in 89% ofthe recordings in 2005-2006. Median levels including local ships are 6-9 dB higher than medianlevels chosen from times when local ship noise was absent. Biological sounds and the sound of winddriven waves controlled ambient noise levels in the absence of local ships. The median noise levelsat this site are low for an open water site due to the poor acoustic propagation and low average windspeeds. The quiet nature of this site in the absence of local ships allows correlation of wind speedto wave noise across the 10-220 Hz spectral band of this study.