136 



DEEP-WATER TRANSMISSION 



1000 



RANGE IN YARDS 



2000 3000 



4000 



s 



5 



2 

 O 



RANGE IN YARDS 

 1000 2000 3000 



Figure 56. Average transmission anomalies at 60 kc. 



Average transmission anomalies for a shallow 

 hydrophone at 60 kc are shown in Figure 56 for dif- 

 ferent values of D^. All runs for D^ between 20 and 

 160 ft are combined in the upper curve, since no 

 systematic variation of transmission anomaly with 

 changing D^ was noted for these data. The agreement 

 between the curves for D2 between 20 and 40 ft and 

 for greater D^ is in marked contrast to the differences 

 shown at 24 kc (see Figure 49). 



Another, more conclusive indication of the compli- 

 cated differences between the two frequencies is shown 

 by simultaneous measurements at both frequencies on 

 a single shallow hydrophone. Measurements were 

 made with a CHARLIE pattern (temperature dif- 

 ference about 0.5 F in the top 30 ft) and a thermocline 



10 



20 



30 



4000 



w 40 



Figure 57. Simultaneous transmission at 24 and 

 60 kc. 



at 50 ft. The resulting curves are shown in Figure 57. 

 The difference of anomalies between the two fre- 

 quencies increases by 15 to 20 db per kyd, as com- 

 pared to a corresponding difference of not more than 

 about 10 db per kyd in isothermal water; see Figure 

 17. If data from many more runs under somewhat 

 similar conditions are used, however, the average dif- 

 ference of transmission anomaly between 60 and 24 

 kc has a slope of about 9 db per kyd. This is in close 

 agreement with the difference of 8.5 db per kyd found 

 in Section 5.2.2 for isothermal water. Further data 

 on the difference of transmission loss between dif- 

 ferent frequencies are required to show how much and 

 in what way this difference varies. 



