Accession Number : AD0873875

Title :   Low-Frequency Coherence of Long Range Explosive Sounds and Ambient Noise in the Deep Sea,

Corporate Author : NAVAL ORDNANCE LAB WHITE OAK MD

Personal Author(s) : Urick, Robert J. ; Lund, George R.

Report Date : 15 JUL 1970

Pagination or Media Count : 26

Abstract : The coherence between the outputs of vertically separated hydrophones near the bottom of the deep sea has been measured for explosive shot signals received at ranges between 100 and 600 miles and for the ambient sea noise background. At frequencies from 25 to 200 Hz, the correlation coefficient of the principal arrival of an explosive signal has been found to fall to a value of 0.5 in a vertical inter-hydrophone distance of 8 wavelengths. On the other hand, the ambient background decorrelates to a value of 0.5 in about one wavelength, although it is not well normalizable in terms of wavelength for small values of the coefficient. The decorrelation of the explosive signal is independent of range in spite of the greater number of encounters of the major transmission path with the sea surface, and is apparently caused by the four closely adjacent paths between a near-surface source and a near-bottom receiver in deep water. (Author)

Descriptors :   (*UNDERWATER SOUND, PHASE DISTORTION), LOW FREQUENCY, BACKGROUND, DEEP WATER, HYDROPHONES, UNDERWATER EXPLOSIONS, UNDERWATER SOUND SIGNALS, CORRELATION TECHNIQUES, OCEAN BOTTOM, BERMUDA.

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE