DAUBIN: STATISTICAL ANALYSIS OF SHIP GENERATED NOISE 



where 



Var(T) = / T^(R) p(R) dr - /t(R) p(R) dR 



(9) 



To apply these equations, we can construct models of transmission 

 and of surface ship density which correspond to an experimental 

 situation, and obtain an estimate of the variance of the transmission 



(Equation 9) . This is then combined with data for the variance and 

 mean value of source levels to yield the variance of the intensity 



(Equation 8) . Notice that we require only the statistics of source 

 level over the ensemble of ships, rather than the specific value for 

 any given ship. 



To illustrate the approach, we have run such a model on a Monte 

 Carlo basis — using ship densities of 0.1 ships per degree square 

 (as in Figure 6) and the simple empirical transmission curve shown 

 in Figure 7. The result is a modeled time series of ambient noise 

 and a distribution of levels given in Figure 8. 



Such examples do not relate too closely at this time to the 

 observed data, indicating perhaps that our distribution of ships is 

 wrong, but also perhaps that by removing these components from these 

 observed data we can then have a means of investigating the non-ship- 

 generated statistics in the foreground data. 



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