MARTIN/PERRONE : GEOGRAPHICAL VARIATION OF AMBIENT NOISE IN THE OCEAN 

 FOR THE FREQUENCY RANGE FROM 1 HERTZ TO 5 KILOHERTZ 



or have a "humped" shape in the region 100 to 600 Hz. Assuming that 

 the only significant contributors to these spectra are wind speed 

 and shipping, it is possible to propose a synthesis of the two. 



In Figure 3, a possible breakdown of the two contributors is 

 shown. Results from the Ionian Sea, as well as Bermuda, are shown 

 here; the Ionian Sea results will be discussed later. The shape 

 of the curves is consistent with that suggested by Wenz (1962) . Wind 

 speed curves are purposely terminated at about 100 Hz on the low 

 frequency end because nothing in the data suggests a shape or trend 

 of these curves between 20 and 100 Hz; however, the measured data at 

 and near 10 Hz indicate that wind speed must contribute over this 

 range. Shipping noise in Figure 3 is shown to be significant to 

 1,000 Hz and possibly beyond for low wind speed conditions. These 

 shipping noise spectra and standard deviations result from consider- 

 ation of the spectra for the lowest wind speed condition. 



The statements made concerning wind and shipping with respect 

 to these data are quantified in Figure 4. These curves represent 

 the cross correlation of the ambient noise level time series at the 

 output of each analysis filter with the wind speed and wave height 

 time series as observed on instruments located at Argus Island some 

 distance away. Incidentally, while the shapes of the two correlation 

 curves (viz., wind speed and wave height) are approximately the same, 

 the fact that the wave height curve levels off at a correlation of 

 0.6 versus 0.8 for wind speed may be due to the lag in the time it 

 takes for seas to build up and in part to the fact that the wave 

 spectrum at Argus Island may be somewhat different due to it being 

 obtained in shallow water rather than in the deeper water of this 

 measurement site. These curves provide a quantitative average 



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