Coherence of Ambient Noise and the Signal from a Steady Source at Different Depths at a Deep Sea Location

摘要

A 200-foot vertical array of six irregularly spaced hydrophones has been used to obtain coherence information on the ambient sea noise and the sound from a distant 1120 Hz source. Data was recorded at different depths down to 12,000 feet in 13,600 feet of water. Time delay correlograms substantiate a binary ambient noise model consisting of a low frequency component of horizontally travelling noise from distant sources and a high frequency component of vertically arriving noise from local noise sources on the sea surface. The coherence at all frequencies was found to decrease with increasing frequency and hydrophone spacing. On the other hand, the coherence of the 1120 Hz signal was independent of spacing, and was higher and less variable in the direct sound field from the source than it was in the more distant bottom-reflected field. The results apply to the optimum design of vertical arrays in the deep sea. (Author)