Deep sound channel noise from high-latitude winds

Abstract

The contribution to underwater ambient noise from the persistent winds which blow at high latitude is discussed and estimated. Energy is ducted into low-loss paths in the deep sound channel by favorable horizontal sound-speed gradients. A concept of ‘‘wind-noise lanes’’ is developed into a simple model which is used to predict the resulting underwater ambient noise levels as a function of season and latitude. Three main oceans are considered—the Pacific, Atlantic, and Indian Oceans. In general terms, predicted omnidirectional levels at 50 Hz lie between 65 and 75 dB re: 1 μPa2/Hz and are comparable to those generally associated with light-to-moderate ship traffic. The spectral shape of high-latitude wind noise is also similar to that associated with ships. High-latitude wind noise arrives within ±15° of horizontal, and the predicted magnitude of this low-angle component also matches measurements well. It is concluded that the component of noise associated with high-latitude winds can be significant at low frequencies. Properties of omnidirectional noise, as well as vertical and horizontal directivity, may be dominated by this component under some conditions. It appears, however, to have been often overlooked in the interpretation of data.