SHORT-RANGE PROPAGATION IN DEEP WATER 



199 



80 

 0(— 



PEAK PRESSURE LEVEL IN DECIBELS, ARBITRARY SCALE 

 90 100 110 120 



130 



100 



4 200 



300 



400 



A RANGE 800 YARDS, MORNING 

 D RANGE 1400 YARDS, MORNING 

 O RANGE 1900 YARDS, MORNING 

 CURVES PREDICTED INTENSITY FROM RAY 

 THEORY, WITH SOURCE STRENGTH 

 CHOSEN TO GIVE BEST FIT TO 

 800 YARD POINTS 



1000 



RANGE IN YARDS 

 2000 



FEET PER SECOND 

 4000 4880 4900 4920 



RAY DIAGRAM 



Figure 4. Comparison of observed peak pressures with values calculated from ray theory for a negative gradient 

 extending to or almost to the surface. 



case is, as one would expect, more pronounced than 

 for Figure 3. 



A particularly interesting variation of intensity 

 with range is shown in Figure 5." This series of shots 

 w^as made at a single depth at various ranges, on a 



day when there was a moderate negative temperature 

 gradient at the surface. The velocity-depth curve and 

 ray diagrams are shown in Figure 6. The hydrophone 

 was placed at a depth of 54 ft, just below the knee of 

 the velocity-depth curve, which comes at 48 ft. This 



