After the original tape is speeded-up and re-recorded, it is divided 

 into individual runs and each run is spliced into a loop. One loop may 

 be inserted into the loop recorder (Figure 1) and played into the analyzer 

 at 30 ips, a speed-up of 16 times that of the original recording of the 

 loop. Two of the possible 14 signals are sent to the "A" and "B" analyzers, 

 and then to their respective analog computers and X-Y plotters. The 

 resulting graphs (amplitude density, energy density, total energy) refer to 

 a frequency scale 512 (32 x 16) times the true frequencies in the 

 signals. Calibration signals are put on each plot, and the graphs are 

 given to the project engineer for statistical evaluation. The process may 

 be repeated for each of the signals on each of the loops. 



After all the data have been analyzed, the loops are placed in 

 plastic capsules, labeled, and filed. The "book" is filed when the 

 project engineer no longer requires visual checks. 



Figure 1 illustrates some of the shortcomings of the SEADAC as it 

 was originally assembled. When the data are being re-recorded onto 

 the loop recorder, the analyzer is inactive; when the analyzer is active, 

 data cannot be re-recorded. This seriously affects the time economics 

 involved in volume data analysis. More important is the inability of 

 the SEADAC to treat cross-spectrum analysis. A great deal of potential 

 information is available in the simultaneous recording of seakeeping 

 events which can only be extracted through cross-spectrum analysis. These 

 and other improvements will be discussed in the section on the proposed 

 extension of the SEADAC. 



