biological and sea noise. Data analysis is not presented of Rincon and Holly 

 data. Recordings will be made with the NOSC more sensitive, lower frequency 

 response system. 



The data plots from Ocean Bounty show a general upslope as the frequency 

 increases with a peak at about 80 Hz and a rolloff above that. In figure 7, a 

 plot of the measurements taken 50 feet from the rig, a rise of approximately 4 

 dB per octave is seen to the peak at 80 Hz, with a fall off after the peak of 

 about -6 dB per octave. 



When the noise was measured at a distance of 350 feet from the Ocean 



Bounty, figure 8, the 80 Hz peak is still evident, the overall level is lower, 



and the slopes have changed to +5 and about -4, steeper on the lower end and 

 less steep at the higher frequencies. 



Figure 9 shows data taken 800 feet from the rig. The level has again 

 dropped, the 80 Hz peak is still present although more rounded in shape, and 

 the lower end slope is now indefinite due to a general valley which is present 

 below 80 Hz. The slope above 80 Hz is now about -3 dB per octave. 



The falloff in level with distance is within the range expected. The 

 increase in level at the lowest one-third octave band is evident only on the 

 data from the Ocean Bounty and may indicate onei-gy from that rig is present at 

 lower frequencies than were analyzed. 



D-7 



