Ambient noise directionality at two locations in the Gulf of Mexico

Low-frequency ambient noise directionality measurements were made by a towed line array in the Gulf of Mexico at two different sites. The first site was seaward of the continental shelf and north of the Yucatan Peninsula. The second site was near the entrance to the Gulf of Mexico. The presence of a shallow shelf at the first site effectively shields the array from long-range acoustic propagation from the south. This shielding, combined with favorable propagation conditions and high-density shipping to the north, is responsible for the high degree of anisotropy in the measured ambient noise horizontal directionality pattern at the first site. The measured ambient noise directionality pattern at the second site shows the strong influence of the shipping entering and exiting the Gulf of Mexico. Because the acoustic propagation conditions and the shipping in the Gulf of Mexico are approximately repeatable annually, these two directionality measurements are considered to be good estimates for the ambient noise for future years. A discussion of the horizontal directionality as well as additional ambient noise statistics for the two sites will be given.