524 



OBSERVATIONS OF WAKE ECHOES 



published before;^' ^ others were obtained from the 

 files of the San Diego laboratory. During these ex- 

 periments, the echo-ranging vessel overtook the sub- 

 marine while proceeding on a parallel course; the 

 observations comprise surface runs, dives, and sub- 

 merged level runs. In order to-redude the uncertain- 



ular (/3 = degrees) and oblique (/3 = 60 degrees) 

 incidence of the sound beam on the wake. With a few 

 exceptions illustrated in Figures 5 and 6, the obser- 

 vations did not extend over sufficiently long periods 

 of time to reveal the gradual decay of the wakes. 

 Hence only average values of the wake strength W 



Table 4. Submarine wake strengths. 



* This run is illustrated in Figure 1 . Absolute values of the wake strength W are uncertain because of lack of adequate calibration. 



ties of the relative position during the submerged 

 portions of the runs, the submarine towed a marker 

 buoy. Pelorus bearings on this buoy were logged from 

 the echo-ranging vessel. With the aid of the original 

 logs, a diagram was constructed for each run, giving 

 the relative position of submarine and measuring 

 vessel. The distances behind the submarine to which 

 wake echoes belonged were then read from these dia- 

 grams. Measurements were made both for perpendic- 



are given in Table 4, together with the approximate 

 distances astern to which they refer. The transducers 

 used had a narrow directivity pattern horizontally 

 and a very wide pattern vertically, so that even dur- 

 ing the deepest dives — to 400 feet — there was no 

 significant loss of sensitivity. 



Although the point of the W scale in Figure 5 is 

 rather uncertain because an adequate calibration of 

 the sound gear is lacking for that particular day, the 



