HAMILTON: TIME VARIATIONS OF SOUND SPEED OVER LONG PATHS IN THE OCEAN 



Br. Sykes : The reason for the question is I was trying to get an 

 estimate from you of how close acoustic and sound-speed measurements 

 should be made. That is, do you think a day apart is good enough? 

 Or a week apart? Or really a few hours? Must they really be simul- 

 taneous? 



Mr. Hamilton: You can see the individual variation from shot to 

 shot in Figure 11. For this purpose the sound-speed measurement 

 didn't seem to be very critical. 



But remember we aren't talking about the rays that are going 

 through the surface waters. We are talking about what is going 

 along the axis. The seawater temperature at Eleuthera on Figure 9 

 shows no correlation with the average axis sound speed to a nearby 

 hydrophone. The sound-speed measurement at a single site doesn't 

 seem to be important. 



The fact that variations in sound speed to the two Bermuda phones 

 correlate so beautifully for transmission over exactly the same ocean 

 transmission path in Figure 5 and that these do not correlate exactly 

 to hydrophones on nearby paths for Eleuthera in Figures 5 and 6 leads 

 me to believe that what is happening at the source is not very import- 

 ant. 



So I am coming to the conclusion that at least for this measure- 

 ment, the sound speed at either the source or the receiver is not 

 important for the average horizontal propagation speed along the 

 sound-channel axis. 



Ms. E. A. Christian (Naval Ordnance Laboratory): It's no more 

 important than the rest of the path? 



Mr . Hand 1 ton : Ri ght . 



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