Underwater Ambient Noise and Sperm Whale Click Detection during Extreme Wind Speed Conditions Available to Purchase

The Littoral Acoustic Demonstration Center (LA DC) deployed three Environmental Acoustic Recording System (EARS) buoys in the northern Gulf of Mexico during the summers of 2001 (LADC 01) and 2002 (LADC 02). The hydrophone of each buoy was approximately 50m from the bottom in water depths of 645m to 1034m. During LADC 01 Tropical Storm Barry passed within 93nmi east of the EARS buoys. During LADC 02 Tropical Storm Isidore and Hurricane Lili passed within approximately 73nmi and 116nmi, respectively, west of the EARS buoys. The proximity of these storm systems to the EARS buoys, in conjunction with wind speed data from three nearby NDBC weather buoys, allows for the direct comparison of underwater ambient noise levels with high wind speeds. These results are compared to the G. M. Wenz spectra at frequencies from 1kHz to 5.5kHz. In addition, the impact of storm conditions on sperm whale clicks was assessed. In particular, although the time period during the closest approach of TS Barry tended to produce lower click rates, this time period did not have the greatest incidence of non‐detection at all the EARS buoys. It follows that storm‐related masking noise could not have been responsible for all the observed trends. The data suggest that sperm whales may have left the vicinity of the deepest EARS buoy (nearest TS Barry’s storm track) during the storm and possibly moved into the shallower waters around the other EARS buoys. It also appears that sperm whales may not have returned to the deepest EARS area, or did not resume normal behavior immediately after the storm, as the click rate did not recover to pre‐storm levels during the period after TS Barry had dissipated. Results of these analyses and the ambient noise analysis will be presented. (Research supported by ONR).