A final layer of negative sound speed gradient must always be added. A gradient of 

 -0.1 is chosen here for the top of this layer. 



The first three modes are determined by reading in approximate values. The magni- 

 tudes of the depth functions are plotted on a log scale at 2-m depths from 30 to 80 m. 

 Reflection coefficients are computed at interface 2, which is the water-sediment interface. 



The final profile is a deep-water profile with a 40-m deep sediment layer. The atten- 

 uation increases from 2 dB/km to 2.5 dB/km through this layer. The first mode, the first 

 bottom-reflected mode, and a higher bottom-reflected mode are found. Each step of the 

 mode iteration is printed out. Reflection coefficients are again computed. The amplitudes 

 and phase of the depth functions are printed out at 500-m depth and at each even 1000-m 

 depth for a 1 00-m source depth. 



On the last two profiles, a much larger set of modes is required to compute correct 

 propagation losses. 



The sample run given here required 6 seconds on a UNIVAC 1110, Exec 8 operating 

 system. The cost of the run was $ 1 .20. 



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