RECOMMENDATIONS 



If a tethered system is used, the cable system 

 should be slack, and for a simple system an all -buoyant 

 cable system should be used in preference to the non- 

 buoyant type for measurements from a ship on the open 

 ocean. 



Calibration of the system with the random noise 

 should be done during the slack period; otherwise the high 

 noise levels during towing may mask the random-noise 

 calibrate signal at the lower frequencies. 



Use a "pink" random noise (-3 dB/octave slope) for 

 calibration, when noise with a negative spectrum slope is 

 to be measured. With the same broadband level a pink 

 random noise has a higher spectrum level at low frequencies 

 than does a flat random noise. 



If available, an untethered system should be used to 

 obtain ambient-noise measurements from a platform in the 

 open ocean. This system should have the capability of 

 obtaining data at any selected depth. 



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