ANALYTICAL PREDICTION OF OCEANOGRAPHIC INFLUENCES 

 ON BOTTOM-REFLECTED SOUND -> 



by 



Rodney 0. Davidson 

 Vitro Laboratories 

 Division of Vitro Corporation of America 

 200 Pleasant Valley Way, West Orange, New Jersey 



INTRODUCTION 



This paper presents a technique for predicting selected acoustic para- 

 meters of a bottom-reflected sound field as a function of sonar range. The 

 technique is applicable under a wide spectrum of environmental and tactical 

 situations. It has the advantage that it obviates the need for case-by- 

 case sound ray computations and thus provides a means for tactical decision- 

 making without the use of elaborate computational schemes. The acoustic 

 parameters to be considered are: (l) slant range; (2) travel time; (3) 

 source or depression angle; Ox) receiver angle; (5) bottom grazing angle; 

 (6) geometrical spreading loss; (7) absorption loss. 



Assumptions 



In order for the technique to be applicable in a given situation the 

 following assumptions are made: 



(1) The ocean bottom and surface are horizontal planes; 



(2) The maximum sound velocity in the medium occurs at the ocean 

 bottom; 



(3) The distribution of sound velocity is cylindrically symmetric 

 about an axis perpendicular to the surface through the source; 



(Ii) The soimd source and receiver depths are fixed; 



(5) Ray theory is an adequate description of soiind transmission in 

 the ocean; 



(6) The values of sonar range must correspond to source angles be- 

 tween zero and Li2°; sonar rsinges not covered by this interval 

 cam be adequately treated by assuming that no refraction of the 

 sound rays takes place. 



* Research sponsored by the US Navy UndenJater Sound Laboratory under 

 Contract Ni)40(7002)i)76683B whose Technical Director has been 

 Mr, Thaddeus G. Bell. Mr. Carl T. Moore, US Naval Oceanographic Office, 

 assisted this research by supplying valuable environmental data. 



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