RODERICK: FORWARD SCATTERED LOW-FREQUENCY SOUND FROM THE SEA SURFACE 



Roderick, W. I., "Frequency spectra of forward-scattered underwater 

 sound from a traveling sinusoidal surface," Navy Underwater Sound 

 Lab., Rpt. No. 988, 1969. 



Roderick, W. I., and B. F. Cron, "Frequency spectra of forward scattered 

 sound from the ocean surface," J. Acoust. Soc. Am. 43:759-766, 1970. 



DISCUSSION 



Dr. P. W. Smith (Bolt, Beranek, and Newman, Inc.): The example 

 or the explanation you gave of the asymmetrical sidebands suggested to 

 me that they were a peculiarity of the signal reflection that would 

 not result if you averaged over many reflections. 



Mr. Roderick: The spectrum I showed was a single time record 

 with only 2 degrees of freedom. In other spectra that have been 

 ensemble-averaged (including Brown's, DeFerrari's, and some results as 

 seen on the BIFI range) , one sideband can be down perhaps 5 or 6 dB. 

 You have a good statistical confidence in the spectrum due to the 

 large number of degrees of freedom. 



Dr. Ira Dyer (Department of Ocean Engineering, Massachusetts 

 Institute of Technology): Bill, what hope would you hold out in using 

 an acoustic system for getting the wave spectra, wave number spectra as 

 well, of the ocean surface or any other rough scatterer? 



Mr. Roderick: I think this can be done — with some qualifica- 

 tions. Bob Williams did his Ph.D. thesis on measuring the gravity 

 wave spectrum based on acoustic results. 



Unfortunately, he had a horrendous problem. His acoustic path 

 involved many surface reflections and he had very poor control over 

 geometry. I think he only got fair results, mostly because of the 

 experimental setup. I think it can be done. 



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