2. Perform calibration of the system with the random 

 noise during the slack period; otherwise the high noise 

 levels during towing may mask the random-noise calibrate 

 signal at the lower frequencies. 



3. 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 a flat random noise. 



4. Use an untethered system, if it is available, to 

 obtain ambient-noise measurements from a ship platform 

 in the open ocean. This system should have the capability 

 of obtaining data at any selected depth. 



