LISTENING "VND ECHO RANGING 



485 



■ 4 - - ■■«■ i »^y E/i/0 





p.. 



yjWe*»u:^ 



SCREW NOISE 

 E.W.SCRIPPS PASSIKK 



SPHERE ECHOi 



RANGE 



Figure 1 . Sound range recorder traces of wake echoes 

 from E. W. Scripps. 



of the sphere echo is markedly diminished by the 

 two-wav transmission loss in the wake. Note the 



Figure 2. Sound range recorder traces of wake echoes 

 from E. W. Scripps. 



gradual widening of the wake toward the top of the 

 figure, as the wake grows older. 



The wakes were laid at right angles to the line 

 connecting the transducer on the Jasper with the 

 target sphere. In Figure 1 the projector was kept 

 trained at the sphere in order to study the decay 

 of a fixed part of the wake. Figure 2 shows the effect 

 of gradually changing the training of the projector 

 from its normal training; the range toward the near- 

 est boundary of the wake increases, and since the 

 sound beam now cuts obHquely through the wake, 

 the apparent width of the wake increases propor- 

 tionally to the secant of the angle included between 

 the sound beam and the normal to the wake. On 



