

Table B2. Functions of the control k 



eys. 



Key 



Setting 



Effect 



Function Affected 



1 







No output 



Print 



Plot on printer 



Depth functions 



2 





 1 



Print losses 

 Contour on printer 



Propagation losses 



3 







1 



No output 



Print all interfaces 



Reflection coefficients 





k>l 



Print interface k 





4 



k>0 



Change levels and symbols 



Contour on printer 



5 







1 



Sum only those given 

 Add to existing sum 



Number of modes 





k+ 10 



Punch modes on cards 





6 







1 



Long print 

 Short print 



Steps in mode iteration 





2 



Shortest print 





7 







1 



Phased addition 

 Random-phase addition 



Mode sum 



8 



1 



Change T-lim 







2 



Punch losses for up to 5 

 receivers 



Loss plot input 





3 



Punch losses for up to 26 

 receivers 



Contour plot input 



9 







No effect 



Number of modes 





k 



Use only 1st k modes 





The first profile in the input-output is a surface duct, 100 m deep. For the 500 Hz 

 frequency, 3 modes are found by searching from a phase velocity of 1520.5-1523 m/s. Two 

 additional modes are found by extrapolation. Forty receiver depths are then specified from 

 3 to 120 m, and propagation loss contours are drawn for a source at a depth of 20 m. The 

 modes are added in random phase, and loss contours of 80, 90, and 100 dB are requested to 

 be represented by the symbols 8, 9, and 0. A negative range then causes the program to read 

 new control keys, source and receivers. The depth functions are then printed out as ampli- 

 tudes and phase angles and propagation losses are computed. 



The second profile consists of two negative gradients over two layers of sediments in 

 shallow water. A velocity discontinuity exists at the top of each sediment layer. Negative 

 numbers in the input for the attenuation at the bottom of the sediment layers serve as flags 

 to request that the gradients at the top of the layers have no imaginary parts and that the 

 attenuation at the bottom will be whatever results from this. The change in ImC from 37.9 

 to 23.7 in the deeper sediment layer indicates that the attenuation changed by about 60 

 percent through the layer. 



75 



