general coastal configuration, and the coastwise shipping lanes. Platforms 

 Hondo and Rincon, the most westerly and easterly of the platforms measured, 

 are shown as blue circles. 



The magnetic tape recordings of the underwater noise at the platforms 

 were made on January 19, 20 and 28, 1981. Large swells of height approximately 

 5 to 10 ft and period about 12 seconds were present from a storm offshore 

 to the west. The wind varied from about 5 to 10 knots at Platforms Hondo, 

 Holly, and Rincon to 15 to 20 knots for the remainder. 



Recordings were made from several boats, each drifting freely with all 

 motors secured. The boats were approximately 45 to 80 feet long. The hydro- 

 phone was lowered overside to a depth of 100 feet for measurements reported 

 herein. At times rolling motion of the recording boat generated interfering 

 noise. Tape sections used for analysis were carefully selected to reject 

 portions in which the self noise of the recording boat was noticeable. 



Each tape sample was recorded on two channels. The FM channel recorded 

 from to 2500 Hz and the direct channel from 100 to 30000 Hz. The analysis 

 was performed on the NOSC IDHACS facility, which utilizes a Spectral Dynamics 

 S.D. 360 to provide analysis of the FM channel from 1 to 300 Hz with an 

 analysis bandwidth of 0.8 Hz, and the direct channel from 100 to 6000 Hz 

 with an analysis bandwidth of 16 Hz. Data outputs were in the form of digital 

 printouts, and spectrum plots in analog graphic form. Data from the latter 

 were transcribed manually to spectrum plots of sound pressure spectrum level 



F-5 



