PORTER: SOFAR PROPAGATION OF WIDE-BAND SIGNALS TO LONG RANGES 



decide what we want to compute. Do we want this structure or not? 

 That requires us to consider the uses of our output. 



Dr. Hersey: Preston, I agree with that very strongly, and so 

 far our decision has been to opt for guessing at broadband results on 

 the basis of CW programs in order to save money. That is implicit. 

 I think there isn't anyone in the room who wouldn't have done the 

 other if it had been cheap. Our whole field, going back 30 years, is 

 a study in taking advantage of high-powered methods that have become 

 cheap in money. We have been able to address problems that we simply 

 couldn't address before. We'd just better keep our eyes open for 

 the time, the moment even, when a new high-powered computer or a 

 clever device of some other sort becomes available to us. 



Mr. Spofford: 1 have one more comment. I think I would take 

 exception to the final question about going out and attempting to 

 verify this model with a measurement. I feel that probably the best 

 way to verify an approximation which could be very powerful if it 

 checks out and saves us from making all those normal mode runs would 

 be some very careful numerical experiments, if you will, to deter- 

 mine the range of validity of this technique. 



Unless I'm missing something in the technique, unless there's 

 something about it which says that the wave equation which we use and 

 which we solve for in normal mode programs is not the correct equation 

 for these broadband signals — and I don't think you were saying that. 



Dr. Porter: No. Of course I agree with the wave equation. The 

 reason that I am interested in seeing some experiments is to look at 

 some data from other oceans with axial shots and axial receivers. 

 I'm not interested per se in going out and running more experiments 

 if some already exist. But I would like to see if you can identify 

 the same kind of structure in some other oceans. 



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