ECHOES FROM SURF.\CE VESSEL WAKES 



527 



100 



200 



300 



Figure 6. 



400 500 600 



TIME IN SECONDS 



Wake strength and distance astern. 



700 



800 



900 



1000 



Table 5. Surface vessel wake strengths. 



The same trend is definitely established by the values 

 of W for the 40-ft launch in Table 5, which are the 

 averages resulting from 16 wakes. 



33.4.2 



Deep Water 



By 1944 considerable progress had been made in 

 standardizing the sound gear at frequencies in the 



neighborhood of 24 kc. It is believed that the relia- 

 bility of the absolute calibration of the transducers 

 used for these later measurements is much greater at 

 these frequencies than during the earUer measure- 

 ments. Moreover, this program was executed in deep 

 water off San Diego, so that interference from bottom- 

 reflected sound was avoided. Pending a comprehen- 



