LABIANCA/HARPER: A THEORETICAL APPROACH TO THE PREDICTION OF SIGNAL 

 FLUCTUATIONS DUE TO ROUGH-SURFACE SCATTERING 



The sideband curves are on top of one another. Figure 29 displays 

 the syininetric system function at the interference peak, while Figure 

 30 shows the corresponding acoustic spectrum. Figure 31 is a plot 

 of the symmetric system function at the null and Figure 32 is the 

 corresponding acoustic spectrum. 



The final set of results which I would like to display is that 

 of the z = z' symmetry. These were computed for the same surface 

 spectrum and a source and receiver depth of 50 m. The curves 

 illustrate the case 3 = 45° at a range of 2,000 m. This range is 

 beyond the surface-image interference region, the 12 dB per-double- 

 distance region. Figure 33 shows the spectral breakdown with the 

 equal sidebands. Figure 34 shows the symmetric system function and 

 Figure 35 shows the corresponding acoustic spectrum. It is interest- 

 ing to note that the z = z' symmetry which we have been predicting 

 theoretically has been observed experimentally. Figure 36 shows a 

 typical set of spectral plots from a recent paper by Brown and 

 Frisk (1974) . These plots show the acoustic spectrum superimposed 

 on the surface spectrum for a one-bounce configuration where the 

 source and receiver depths were equal. They display a marked 

 symmetry. 



In the future, we intend to explore the model's usefulness in 

 situations with refraction, with immediate emphasis on a deep surface 

 duct. 



REFERENCES 



Brock, H. W. , "Coherence of Multipath Transmission (U)," Bell Labora- 

 tories Ocean Systems Technology Paper, 0STP-3HWB, September 1, 

 1973 (CONFIDENTIAL) . 



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