200 300 400 



500 600 700 80 

 DISTANCE (FT) (X) 



The rays from a directional transducer (1/10 full 

 strength at i 8 degrees) mounted 10 feet below the 

 sea surface will refract when passing through the 

 average summer internal wave structure. The re- 

 fraction depends upon the angle of approach of the 

 sound rays. Note how the ray paths converge and 

 diverge as a result of the internal wave effects. 



600 700 800 900 

 DISTANCE (FT) (X) 



1000 1100 1200 1300 1400 



Above the thermocline the sound-level intensity 

 decreases approximately as the square of the dis- 

 tance, but below the thermocline there are regions of 

 high and low intensity. As the internal wave proceeds 

 past the tower the zones of high and low intensity 

 move in accordance with the refraction pattern. The 

 dB values given refer to a sound level of 60 dB 

 1 foot from the directional source. 



= > 15 dB 

 = 10-15 dB 

 = 5 - 10 dB 

 = - 5 dB 



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