OBJECTIVE 



Translate well-known differential equation solutions into a working program to com- 

 pute propagation in underwater acoustic ducts. Document the program methods, to assist 

 users of this and similar programs. 



RESULTS 



1 . An effective program for computing propagation loss in a layered ocean by normal 

 modes has been developed. Complete documentation for the program is contained herein. 



2. Sediment layers are modeled as fluids in which densities, sound speeds, and absorp- 

 tion can be specified. This permits a complete wave solution for bottom reflected sound 

 energy. 



3. A continued fraction technique for evaluating asymptotic series is shown to give 

 superior results in evaluating the auxiliary functions required in this program, the modified 

 Hankel functions of order 1 /3. 



4. A mode follower program given here is useful in tracing eigenvalues. Such traces 

 are needed to understand the eigenvalue structure. 



RECOMMENDATIONS 



1. Improve the mode locating ability of this normal-mode program to make it self- 

 contained. It currently requires user interaction to locate eigenvalues. 



2. Investigate methods to incorporate the effect of rough boundaries into this 

 program. 



