Correlation of underwater ambient noise with wind speed in extreme conditions

Abstract

During August 2002, the Littoral Acoustic Demonstration Center (LADC) deployed three Environmental Acoustic Recording System (EARS) buoys, at approximately the same location in the northern Gulf of Mexico, in water depths of 645 m to 1034 m. The hydrophone of each buoy was approximately 50 m from the bottom. During the experiment, Hurricane Lili passed within approximately 116 nautical miles west of the EARS buoys. The proximity of this hurricane to the EARS buoys, in conjunction with wind speed data from three nearby NOAA weather buoys, allows for the direct correlation of underwater ambient noise with wind speed. During hurricane conditions, it is expected that the noise contribution due to local shipping would be absent. Time-series data from the shallowest and the deepest of the EARS buoys were processed to yield calibrated spectral levels. These spectra are compared to corresponding spectra derived from Wenz. In the wind-dependent frequency range, a general consistency of agreement is observed in spectral shape with the Wenz spectra and the calibrated spectral levels. General consistency is also observed with the NOAA buoy data and Beaufort scale estimates. Shallow water noise levels are generally higher than temporally corresponding deep-water levels. [Research supported by ONR.]