to obtain the numbers by which the spectral ordinates must be multiplied 



to gain any desired percentage of confidence.* For example, consider the 



energy spectrum in Figure 11. This graph resulted from an analysis with 



a filter whose effective bandwidth was 5.63 cps; the record length was T = 2.81 



seconds. From Equation [10] it is seen that f = 31.64. The 90-percent 



confidence bands are found by entering 31.64 on the abscissa scale of 



Figure 10 and reading off the multiplying factor from the projections on 



the ordinate scale of the intersections of f = 31.64 with the 5-percent and 



95-percent curves. Figure 11 shows the energy spectrum of that seakeeping 



event with its associated 90-percent confidence bands. 



PROPOSED EXTENSION OF THE SEADAC 

 Even while the SEADAC is relatively new, some additional components 

 are being considered which will: (1) increase its efficiency through 

 saving of computational time, (2) extend its usefulness through new 

 operations, and (3) prepare magnetic tape for re-use in the field. 



Figure 12 is a block diagram showing the SEADAC, with the proposed 

 additions (dotted lines) . The magnetic-tape recording brought from the 

 field to the laboratory will be reproduced at 60 ips on a reel recorder, 

 as before. Instead of re-recording, at 1-7/8 ips, on the loop recorder, 

 this operation is now performed on another reel recorder. The benefits 

 derived from the addition of a reel recorder are two-fold: (1) all the 

 information on the reel may be transcribed on one re-recording and (2) the 

 loop recorder is always free to play data into the analyzer. No time will 



*Figure 10 was constructed from tables of the chi- square distribution found 

 in most textbooks on statistics. 



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