BUCK: ARCTIC ENVIRONMENTAL LF ACOUSTICS MEASUREMENTS, 

 MODELS AND PLANS 



Figure 12 shows cross correlations of the ambient noise-level and 

 wind time -functions at the ice island (left) and the two floe ice 

 stations (center and right) during the 2-month experiment in the spring 

 of 1970. The correlation is seen to be very high at the floe ice 

 stations as might be expected from the premise of ice dynamics being 

 the major source of noise since ice pack movement is caused primarily 

 by wind. The correlation for the ice island location is not as strong. 

 T3 is a very large solid mass of ice (3 billion tons displacement) 

 which has considerable inertia. A hydrophone mounted below its center 

 sees mostly noise generated at the ice island's edges where there is 

 considerable pressure-ridging activity. Naturally, there is some 

 correlation between noise and wind, but the inertial forces cause a 

 smearing which is evident in the periodicity of the T3 correlation 

 functions. 



Figure 13 shows the cross correlations of ambient-noise -level time 

 functions between two floe stations (left set of curves) which were 

 about 150 nautical miles apart at the southwest edge of the Gyre and 

 between a floe station and T3 (right) separated by about 750 nautical 

 miles. We believe the inference here is that windstorms are wide- 

 spread in the Arctic and not that noise sources are common. However, 

 the fall-off of correlation with frequency evident in these curves 

 argues the other way. We just do not have sufficient data at this 

 time to say. 



A test was run with a hydrophone below pack ice to determine 

 ambient noise level change with depth. The results are shown in 

 Figure 14 where the levels are plotted as a function of depth in 

 wavelengths. The noise level at each frequency is relative to the 

 noise at 2A. Deeper than IX to2A, the noise was almost constant. 

 These curves are the sort you would expect for approaching a pressure 



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