MODELLING THE VERTICAL COHERENCE OF THE SHALLOW WATER AMBIENT NOISE FIELD

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Authors
  1. Desharnais, F.
  2. Chapman, D.M.F.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
A shallow water noise model is used to simulate the vertical coherence of an acoustic noise field due to sea surface noise. The coherence between two vertically separated sensors is calculated from the Fourier transform of the received noise intensity as a function of vertical arrival angle. The vertical noise directionality is derived from a uniform distribution of sources at the ocean surface, an energy flux propagation model and a plane-wave bottom reflection coefficient for a multi-layered elastic seabed. The propagation model allows for an arbitrary sound speed profile in the water column and includes attenuation by sea water. This simple model clearly demonstrates the influence of noise source directivity, seabed parameters, and the sound speed profile on the vertical coherence of the noise field. Data-model comparisons will be made with data collected on Western Bank, a shallow water area south of Nova Scotia where the geo-acoustics of the seabed is well known. Data were collected at frequencies from 15 Hz to 1200 Hz, for a sensor separation of 1 m.
Keywords
Sound speed profiles;Vertical coherence
Date of publication
01 Jul 1997
Number of Pages
8
DSTKIM No
97-02666
CANDIS No
502900
Format(s):
Hardcopy;Document Image stored on Optical Disk

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