TM No. 377 



measured precisely,, These perturbations recorded on the array would permit a 

 better judgment of the records of the Savonius rotor systems. 



5. The study of the mechanism of the production of ambient acoustic noise 

 produced at the sea surface is still in its infancy. It is known, however, that 

 noise is associated with wind and wave turbulence in the region of the air-sea 

 interface • Further, it is evident that the intensity of wave turbulence over a 

 wide frequency (or wave number) range is directly related to the gross kinetic 

 energy associated with the wave motions. 



The wave meters can be used to estimate both the total wave kinetic energy 

 and its distribution with frequency from to 2. 5 cps. (Note that the variances 

 written as pic' L and pcu' 2 - are dynamic pressure quantities, quite analagous to 

 those which are sensed by a hydrophone, except at acoustic frequencies.) It 

 would be of interest to attempt to correlate both the total energy and the 

 spectral character of wind waves with similar properties of acoustic noise 

 measured simultaneously in the waves. 



If a sensible correlation of energy content were found in the two frequency 

 ranges, then conversely, one might consider using the statistical properties of 

 the wave-produced ambient noise to delineate sea state and, possibly, to study 

 the waves themselves. 



Analysis of the data obtained from the described BBELS wave measurements is 

 continuing under projects sponsored by NUWS and M.I.T. Additional field and 

 laboratory work is to follow. 



It is anticipated (and, indeed, hoped) that other workers will join in this 

 effort to directly measure wave motions, and that this report will serve as an 

 impetus and guide for future studies. The technology is available to overcome 

 the greatest difficulty -- that of developing instrumentation to accurately probe 

 ocean turbulence. We need only apply it with experience and boldness to attain 

 our goal. 



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