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The Importance of Hybrid Ray Paths, Bottom Loss, and Facet Reflection on Ocean Bottom Reverberation

  • Dale D. Ellis
  • J. B. Franklin

Abstract

Mackenzie’s deep-water model for bottom reverberation [J. Acoust. Soc. Am. 23, 1498–1504 (1961)] has been extended to handle reverberation arriving later than the second fathometer return. The model uses straight-line ray paths, flat bathymetry, and a short pulse length. Energy is scattered from the bottom in all directions; in particular, the energy can return by a different path from the outgoing one (hence, the term hybrid path). A three-parameter backscattering function has been used which incorporates Lambert’s law at low grazing angles augmented by a facet-reflection process at steep angles. Also, three bottom loss curves based on the Rayleigh reflection coefficients for sand, silt and clay have been used for a sensitivity study. The results indicate that: (i) the facet-reflection process broadens the fathometer returns for a short pulse characteristic of an impulsive source; (ii) the hybrid paths are important (adding about 5 dB reverberation) when the bottom loss is low; and (iii) bottom loss is as important as the backscattering in determining the reverberation level. A correction to the isovelocity model to allow for a sound speed gradient indicates that (for omnidirectional sources and receivers) the effect of the sound speed profile is small. Thus, the isovelocity model seems to be a reasonable approximation to longer times than one might at first expect.

Keywords

Sound Speed Grazing Angle Impulsive Source Steep Angle Sound Speed Profile 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • Dale D. Ellis
    • 1
  • J. B. Franklin
    • 1
  1. 1.Defence Research Establishment AtlanticDartmouthCanada

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