ABSTRACT 



The development of ray tracing techniques is reviewed, 

 and then the effects of various sound-speed representations 

 on the computed value of propagation loss are discussed. 

 Since modified ray theories designed to treat caustics lose 

 their effectiveness at the lower acoustic frequencies, an 

 alternative approach for the horizontally stratified case 

 is proposed. For oceans that are nearly horizontally 

 stratified, the method of horizontal rays is applicable. 

 Computed predictions are compared with measured data. 



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