< 

 a: 



-20 



20 -20 



20 -20 



ARRIVAL ANGLE 



20 -20 



20 



FIG. 7. Intensity as a function of verti- 

 cal arrival angle determined by a 700-m 

 vertical array of hydrophones (Gaussian a 

 = 180 m) centered on the sound-channel 

 axis (depth 1 km) al a range of 250 km 

 from the CW source. 



deg 



range, depth, and time. Results at 100 Hz show that 

 intensity fluctuations due to internal waves are signifi- 

 cant and comparable in size (5-30 dB) to those ob- 

 served in field experiments. Use of vertical beam- 

 formers as detectors has given insight into internal- 

 wave effects on the sound energy, and will probably 

 lead to a sensitive probe of the internal-wave spectrum. 

 In addition, selection of vertical arrival angle by use 



of a beamformer significantly reduces fluctuations over 

 the single-hydrophone result. 



We have presented only a small amount of data avail- 

 able from our computer simulation. In the future we 

 expect to present results on phase fluctuations, fre- 

 quency spectra of fluctuations, sensitivity to internal- 

 wave parameters, and comparison with simpler calcu- 



-10° 



-5° 



AXIS 

 RAY 



+5° 



50 100 



50 100 50 100 



TIME — h 



50 



100 



FIG. 8. Ray-peak transmission-loss 

 time series at several ranges and 

 depths. Each section shows the inten- 

 sity that would have been observed by 

 a 700-m vertical array (Gaussian er 

 = 180 m) looking at the ray peak. The 

 sections correspond exactly to those 

 shown in Fig. 6. The higher intensi- 

 ties in Fig. 8 are due to the summa- 

 tion over many hydrophones in the 

 vertical array. Note the lower fluc- 

 tuations in the single ray observations 

 here corripared to the single hydro- 

 phone (multiple ray) observations 

 shown in Fig. 6, 



207 



