N is the total number of values, £t i'^x\) ~ t P^'^n^ "" f J j con- 

 sidered in the anal^/sis, L_j = L^j ; ^ =^l~-y^^, and 



/l^- U^ /At -m = an / T . 



The actual work of solving these equations was done by an IBM elect- 

 ronic computer at the Hydrographic Office » The apparent amplitudes, 

 ^ (/^}.")were then transformed into true amplitudes by modifying each dis- 

 crete spectral amplitude. This was done by using wave-staff correction 

 factors determined by the University of California OSh^) - The surface 

 wave record was obtained by the H„ 0. electric wave staff (Upham, 1955). 

 This is a floating wave staff which requires a correction for its natural 

 oscillatory character-is tics <. 



The set of individually-corrected values is the surface power spectrum. 

 To obtain the background pressure at the bottom, which is at «l s:8S0 feet, 

 it is necessarji^ to attenuate this surface power spectrum for discrete values 

 of the frequency i^L , Taking d^ ISO feet, it is possible to determine 

 the significant range of values for^» =■ aiT/x ^^°"' figure lo Clearly, 

 the frequencies range over the interval aTf/l to 'SJTJs^^ With these limiting 

 ^, § and corresponding values of K and J\ iP^i) i'^-^^ pressure power 

 spectrum follows directly from equation (l)= 



Tlie pressure power spectrum so obtained is shown in figure 2» The 

 experj^raental spectinam obtained from analysis of a pressure record at 1^0 

 feet, taken simultaneously with the surface record, is also shown. Quan- 

 titatively, the agreement in the significant range of fi-equencies between 

 the observed and predicted values, given in table I, is considered goodo 

 The curves defining the confidence limits for the predicted spectrum are 

 given in figure 2e These determine the ninety-percent confidence level. 



