DTIC ADA1047385: Onboard Prediction of Propagation Loss pdf

DTIC ADA1047385: Onboard Prediction of Propagation Loss

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Description of the Book:

This report examines the state of the art in the prediction of propagation loss in shallow water as it pertains to onboard performance prediction. The following conclusions are drawn: (1) For simple cases, i.e., homogeneous liquid bottom, linear sound-speed gradient, no surface or bottom roughness, a simple algebraic model, for depth averaged propagation loss works as well as the more complex mode model. (The model is derived in the report.); (2) The uncertainty in bottom parameters, particularly sound velocity and attenuation makes it impossible to set meaningful bounds on propagation loss particularly for negative gradients or slow bottoms. (Useful predictions, however, can probably be made when a positive gradient is present.); (3) Details of the sound-speed profile can cause significant changes in propagation loss, therefore even if bottoms were well characterized, sophisticated computer models would be required to predict propagation loss; (4) Virtually all propagation loss curves can be described to within a fraction of a dB by the function PL = B + 15 log R + AR + CR-squared with the C coefficient usually zero.

Thus, the output field can be described by two or, at most, three free parameters. Since there are no fewer than 24 input parameters it is thus easy to explain observed propagation loss and very difficult to predict it. Moreover, it is doubtful that propagation loss experiments can uniquely define bottom parameters; and (5) Certain aspects of the theory remain unverified and/or inadequately treated

• Creator/s: Defense Technical Information Center
• Date: 9/16/1981
• Year: 1981
• Book Topics/Themes: DTIC Archive, Rogers, P H, NAVAL RESEARCH LAB WASHINGTON DC, *SOUND TRANSMISSION, *UNDERWATER ACOUSTICS, *TRANSMISSION LOSS, PREDICTIONS, ACOUSTIC DETECTION, SHALLOW WATER, ACOUSTIC VELOCITY, ROUGHNESS, SEDIMENTS, ANTISUBMARINE WARFARE, OCEAN BOTTOM SOILS, GRADIENTS, BOTTOM LOSS

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