동해에서 저주파 음파전파에 미치는 난수성 소용돌이의 영향

Abstract

It is well known that sound waves in the sea propagates under the influence of sea surface andbottom roughness, the sound speed profile, the water depth, and the density of sea floor sediment. Inparticular, an abrupt change of sound speed with depth can greatly affect sound propagation through aneddy. Eddies are frequently generated in the East Sea near the Korean Peninsula. A warm eddy withdiameter of about 150 km is often observed, and the sound speed profile is greatly changed within about400 m of water depth at the center by the eddy around the Ulleung Basin in the East Sea. The characteristicsof low-frequency sound propagation across a warm eddy are investigated by a sound propagation model inorder to understand the influence of warm eddies. The acoustic rays and propagation losses are calculatedby a range-dependent acoustic model in conditions where the eddy is both present and absent. We foundthat low-frequency sound propagation is affected by the warm eddy, and that the phenomena dominate theupper ocean within 800 m of water depth. The propagation losses of a 100 Hz frequency are variable within±15 dB with depth and range by the warm eddy. Such variations are more pronounced at the deep sourcenear the sound channel axis than the shallow source. Furthermore, low-frequency sound propagation fromthe eddy center to the eddy edge is more affected by the warm eddy than sound propagation from the eddyedge to the eddy center.