PEDERSEN, GORDON, AND WHITE: SURFACE DECOUPLING EFFECTS 



Both the mode and ray theory approaches play an important role. 

 The mode theory serves as a control to indicate the accuracy of the 

 ray theory, while the ray theory approach yields results which are 

 easier to interpret and to apply. 



This paper will always present the surface-decoupling effect as 

 a function of receiver depth for a fixed source depth. However, since 

 reciprocity holds, one may reverse the roles of source and receiver. 

 Hence, any result presented here for receiver depth may be interpreted 

 also as a result for source depth. 



Unless stated to the contrary, all numerical computations of this 

 paper are based on a fixed source depth of 100 yards and an acoustic 

 frequency of 10 Hz. 



Most of the computations are based on a sound speed profile for 

 the Atlantic presented by Tolstoy and May (1960) . 



In the mode computations, only trapped modes are considered; 

 these are the modes with negligible damping and which propagate to 

 long range. The present study suppresses bottom bounce propagation. 

 At short ranges, where bottom bounce propagation is important, the 

 surface decoupling effect will be range dependent and is much more 

 complicated than the case treated here. 



Features of the remainder of this presentation are as follows: 



1) Examples of how the surface decoupling effect appears 

 in the detailed propagation loss computations of mode 

 theory 



2) Theory and examples which illustrate the concept of 

 surface decoupling from the mode theory standpoint 



3) Various ray theory approximations to surface decoupling 



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