CONCLUSIONS 



1 . An effective program for computing propagation loss in a layered ocean by nor- 

 mal 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 ab- 

 sorption 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. 



REFERENCES 



1 . The Bilinear Modified-Index Profile, by WH Furry, in Propagation of Short Radio 



Waves, DE Kerr, ed; MIT Rad Lab series, vol 13, p 140-168, McGraw-Hill, New 

 York, 1951. 



2. Navy Underwater Sound Laboratory Report 111, Theory of the Anomalous Propaga- 



tion of Acoustic Waves in the Ocean, by HW Marsh, 1950. 



3. Normal-Mode Theory Apphed to Short-Range Propagation in an Underwater Acoustic 



Surface Duct, by MA Pedersen and DF Gordon; J Acoust Soc Am, vol 37, p 105- 

 118, January 1965. 



4. Naval Air Development Center Report NADC-72002-AE, Normal Mode Solutions and 



Computer Programs for Underwater Sound Propagation, by CL Bartberger and 

 LL Ackler, 4 April 1973. 



5. A Normal Mode Theory of an Underwater Acoustic Duct by Means of Green's Func- 



tions, by RL Deavenport; Radio Sci, vol 1, p 709-724, 1966. 



6. Analytic Description of the Low-Frequency Attenuation Coefficient, by WH Thorp; J 



Acoust Soc Am, vol 42, p 270, 1967. 



7. Some Effects of Velocity Structure on Low-Frequency Propagation in Shallow Water, 



by AO Williams; J Acoust Soc Am, vol 32, p 363-365, March 1960. 



8. Sound Attenuation as a Function of Depth in the Sea Floor, by EL Hamilton; J Acoust 



Soc Am, vol 59, p 528-535, March 1976. 



41 



