SPINDEL: PHASE FLUCTUATIONS, COHERENCE AND INTERNAL WAVES 



Dr. Flatte: The chances of it vanishing are zero. 



Dr. Birdsa.ll: But it happens, though. That's the trouble with 

 probability zero. It always keeps happening. 



Dr. S. W. Marshall (Naval Research Laboratory) : This question 

 is to Bob Spindel. Bob, you made a statement that beyond the limit 

 that the environment places on the array you can expect to get gain 

 from that array. Please clarify that. 



Dr. Spindel: You can continue to get increased resolution by 

 increasing the size of your array. This is simply a consequence of 

 the fact that as you separate sensors, the phase fluctuations between 

 the two sensors appear to saturate at a particular level. They do 

 not increase beyond that level. 



So your angular resolution is determined by that phase fluctu- 

 ation divided by the length of the array. So that you can do better 

 and better by making your array longer and longer. It does not mean 

 that you should do that. You might be buying very little. As a 

 matter of fact, you do buy very little every time you double a long 

 array in terms of the expense of doing it. 



Dr. W. H. Munk (University of California at San Diego) : May 

 I make two comments? One, to those of us who are pushing internal 

 waves as a cause of acoustic fluctuations, it certainly is dis- 

 concerting, to say the least, that acoustic spectra seem to pay no 

 attention to the high frequency cutoff of internal waves. Spectra 

 merrily go by without change in slope. I don't like it. 



But I do want to point out something kind of interesting. The 

 same happened to be the case for measurements of the up and down 

 motion of the internal waves. All of such measurements before 



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