BOTTOM PROPERTIES FOR 

 LONG-RANGE PROPAGATION PREDICTION 



Aubrey L. Anderson 



Applied Research Laboratories 



The University of Texas at Austin 



Austin, Texas 



Loss of acoustical energy propagating to long ranges in the 

 ocean is predicted with computerized mathematical models 

 (propagation models) , many of which treat the ocean bottom 

 as either a reflecting interface or as part of the propaga- 

 tion path (a penetrable boundary) . In many models, the 

 bottom is included as an interface which is characterized 

 by a plane-wave amplitude reflection coefficient. The 

 reflection coefficient (or bottom loss) is obtained either 

 from bottom- loss measurements or from calculations using 

 mathematical models of the bottom as an acoustical reflec- 

 tor (bottom- loss models). Bottom-loss models require, as 

 input, detailed information on the physical properties and 

 layering of the bottom material. This presentation relates 

 the topics of bottom-loss measurements and models, bottom 

 physical properties and topography to long-range propaga- 

 tion. Sensitivity of propagation loss to bottom parameters 

 is discussed. 



INTRODUCTION 



The ocean bottom is one of the boundaries with which a propagating 

 underwater sound wave may interact. In some cases our present tech- 

 niques for including bottom interaction in propagation models do not 

 allow accurate prediction of propagation when bottom interaction is 

 significant. Perhaps this is because our input information is in- 

 complete, or perhaps our method of including the bottom influence 

 should be refined. 



Several topics are of interest in the bottom interaction problem. 

 These include: 



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