At the 1-percent level, the critical absolute value of the correla- 

 tion coefficient is about 0. 21. The second group suggests that all 

 frequencies with the exception of 20 c/s are unaffected by fluctua- 

 tion in sea height at ranges greater than 200 nautical miles (1- 

 percent absolute critical value for the second group is 0.25). 

 Again, the suggested relationship in this narrow frequency group- 

 ing is probably merely a coincidental result from the pre- 

 sence of 20-c/s signals, and not the result of distant storm 

 activity. 



Although the near-wind effect on noise has been described 

 in the literature, it was desired to use the data from the Navy 

 weather buoy for comparison with ambient -noise levels, and to 

 perform the same correlation computations on the same frequency 

 range as with the wave -height comparisons. There were several 

 advantages in using the buoy data — consistency of location of the 

 anemometer in relation to the surface and station, and accurate 

 wind-speed measurement. The wind data were compared with 

 noise data received from station D. The weather buoy was located 

 about 50 miles from the hydrophone location. The results (fig. 10) 

 show a high noise/wind correlation in the higher frequencies 

 (above 160 c/s) and no correlation for 10 to 16 c/s and 32 to 80 

 c/s . Minimum critical value at the 1-percent level for the 150 

 points is about 0. 208. Although the number of data points was 

 limited, a sufficient number of points existed to group the data 

 into categories of Beaufort 2 (4 to 6 knots), Beaufort 3 (7 to 10 

 knots), and Beaufort 4 (11 to 16 knots) 9 (fig. 11). Standard tests 

 (t statistic) on significance of mean-value differences for the 

 Beaufort groupings were run for select frequency bands. Differ- 

 ences in mean levels for the Beaufort groupings for frequencies of 

 200 c/s or greater were significant at a 1 -percent level. In the 

 20-to-25-c/s region only a few pairs (sound pressure level at 20 

 c/s for Beaufort 3 compared with Beaufort 2, for example) were 

 significant (5-percent level). 



20 



