ANDERSON: VERTICAL NOISE DISTRIBUTION 



the level did vary. It seemed there would be a little bit of change 

 from frequency to frequency, from data sample to data sample, and as 

 a result we were afraid that by trying to take it out we would be 

 adding more of an artifact than by leaving it in. We had no baseline 

 reference to say how much it really was. 



Dr. A. O. Sykes (Office of Naval Research): Was the ship's fre- 

 quency 60 Hz? 



Dr. Anderson: Yes, 60 Hertz. 



Dr. Sykes: In some of the early experiments with fitted arrays 

 we had that problem. We gave up and we used DC and it went away. 



Dr. Anderson: It could very well be associated with the generator. 

 None of these, however, were 60 Hertz lines. We didn't have any strong 

 60 Hertz itself. But any ship's generator is pretty noisy and has a 

 lot of broadband noise associated with it. It could very well be that. 



The problem is we didn't recognize this until after the fact, 

 because it doesn't appear on a single channel. It's only when you put 

 the array gain on it that you see it show up. It was only at the very 

 low noise conditions that it showed up. 



886 



