Vertical Coherence Measurements of Ambient Noise in Shallow Water off the East Coast of Korea

Abstract

Measurements of the vertical coherence of ambient noise in shallow water off the east coast of Korea are presented. The noise was received by a 15-m-length vertical line array covering the water column from 96.5 to 111.5 m, which was deployed in waters 160m deep. The level of the power spectral density for frequencies less than 300 Hz was relatively low, suggesting that the contribution of the shipping noise to the overall noise level was negligibly small. The results of the measured coherence imply that the noise field was fairly symmetrical about the horizontal but not isotropic. The vertical coherence of the wind-generated sea-surface noise is compared to theory, without the consideration of shipping noise. The comparison suggests that the primary source of ambient noise in the experimental site was wind-driven sea-surface noise. A small discrepancy is found in frequencies above approximately 3 kHz. Possible causes for this are discussed. (C) 2011 The Japan Society of Applied Physics