Measurements of the Vertical Directivity of Ambient Sea Noise in the Deep Ocean

Abstract

Measurements of the vertical directivity of ambient sea noise in the deep ocean are presented. The measurements were made with a vertical array located near the bottom of the sound channel. The measurements were made with 10% filters at the frequencies of 35, 50, 100, 141, 200, 400, and 750 Hz. The ambient noise was found to be made up of two components. One component is nearly omnidirectional and is generated by the local wind; the second component is anisotropic with the maximum near the horizontal, presumably generated by sources at long range. A seasonal dependence was found in the shape of the anisotropic component. In the winter, when the vertical array was below the bottom of the sound channel, the maximum in the anisotropic component was in the horizontal direction, while in the summer, when the array was within the sound channel, the maximum in this component was approximately 9° above the horizontal. [This work was supported by the U. S. Navy Electronic Systems Command.]