298 



DEEP-WATER REVERBERATION 



m 



o 



4 

 IE 



a 



< 

 o 

 z 



4 



Figure 25. Standard reverberation level at 1,500 yards for various dates and areas. 



Table 1 



(26) of Chapter 12, the differences between these 

 curves might be explained as a result of improved 

 transmission to long ranges with larger values of D^. 

 However, on the whole there is little dependence of 

 the curves on the parameter D^; certainly no de- 

 pendence is apparent at 1,500 yards. ■= 



° In this connection, more recent data obtained by 

 UCDWR are of interest. These data, as yet unpublished, 

 show that with NAN patterns (usually falling in the class 



The results of this subsection can be summarized 

 as follows. At ranges less than 1,500 yd, in standard 

 24-kc echo-ranging gear oriented so that the acoustic 



5 g ZJj < 10) there is frequently a hump in the reverberation 

 curve at a range which corresponds to the deep scattering layer 

 discussed previously. Presumably these humps are most com- 

 mon with NAN patterns because with strong downward re- 

 fraction the main sound beam usually strikes the deep layer 

 at a well-defined range. 



