Investigation of the Transmission Loss Issue in Bellhop

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Authors
  1. McCammon, D.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN);McCammon Acoustical Consulting, Waterville NS (CAN)
Abstract
Gaussian beam models such as Bellhop have demonstrated a discrepancy in level and phase that occurs whenever the bathymetry changes slope. This report has examined this discrepancy and attempted to determine its consequences for typical model usage. The effect of both simple geometric bottom contours and complex bathymetries taken from real environments have been analyzed, along with a comparison of the model against a parabolic model and experimental data. It is concluded that the model output using incoherent averaging would smooth out and cover most phase discrepancies and therefore is recommended for tactical decision aids and other standard Transmission Loss applications. This report has also examined other Bellhop inconsistencies that were evident in the newest World Wide Web version. These include an analysis of the updated formula for choosing the number of rays and providing recommendations. In addition, the new ray-tracing algorithm and the new interpolation between sound speed profiles have been investigated, resulting in a correction to the method of extrapolation when multiple sound speed profiles are specified.

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Keywords
Acoustic prediction;Simulation;Modeling
Report Number
DRDC-ATLANTIC-CR-2008-054 — Contractor Report
Date of publication
01 Oct 2008
Number of Pages
56
DSTKIM No
CA032398
CANDIS No
531511
Format(s):
CD ROM

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