lack of DC recording capability. The hydrophone was capable of responding to 

 0.1 Hz signals, but the recorder limitation was -3dB at 15 Hz. 



The measurements around Platform Holly were taken throughout the day from 

 a 65-foot work boat used to supply the platform. Sea state was 1 with a 

 5-knot wind. When the boat had moved to within 50 feet of the platform, the 

 hydrophone was lowered, the boat engines were stopped, and a recording period 

 started as the boat drifted away from the platform. Low frequency roll-off on 

 the preamplifier was set to 1 Hz. The platform was producing at a rate of 

 about 6,000 barrels per day. During the morning drill pipe was being pulled. 

 During the afternoon drilling commenced using the dynadrill technique at about 

 850-foot depth. 



Island Rincon is essentially a sand core with protective outer rock. A 

 dock is located on the north side from which a small boat was launched. 

 Measurements were taken from the dock and trestleway and from the boat at 

 various points along the northern and eastern edges of the island. The major 

 airborne acoustic noise sources on the island are the Kobe Triplex pumps and 

 the steam generators. The major waterborne noise source was a salt water pump 

 located on the west of the dock area. A noticeable reduction in noise was 

 observed when the pump was turned off. 



The Cook Inlet, Alaska, measurements were made aboard ARCO platforms with 

 the instrumentation system purchased by NOSC. This system consists of a Bruel 

 and Kjaer Type 8101 hydrophone, Ithaco Model 451 preamplifier and a NAGRA T 

 instrumentation recorder. The 8101 hydrophone is about 25 dB more sensitive 

 than the 8103 hydrophone used at Holly and Rincon. The lower frequency 



D-3 



