Spatial nonuniformity of noise measurements in the Gulf of Mexico LADC test area

Abstract

Long-term, omnidirectional underwater acoustic noise was measured by three buoys in the northeastern Gulf of Mexico during the summer of 2001 as part of the Littoral Acoustic Demonstration Center project, Phase I. The buoys were placed over the coastal slope above the 600-, 800- and 1000-m contours, approximately in a straight line, 18 km from the first to the last. Initial looks at the noise time series, processed in standard one-third-octave bands from 10 to 5000 Hz, show noise levels in close agreement at each buoy except in the lowest bands (roughly 25 Hz and lower) where the noise levels grow higher at the shallower sites. Results presented here address buoy-to-buoy comparisons of long-term temporal variability and the cross-spectral density of fluctuations across the frequency spectrum. [Research supported by ONR.]