The ACODAC ambient noise system

The ACOustic DAta Capsule (ACODAC) system was designed to obtain long term, unattended measurements of the ambient acoustic noise in the deep ocean. The instrument consists of a 40" diameter pressure vessel containing a 7-channel low speed analog tape recorder, a time code generator, automatic gain ranging data amplifiers and an acoustic telemetry system. An associated vertical array of six hydrophones spaced at various depths along an electromechanical cable extends from near the surface to the sea floor. Simultaneous recordings over the frequency range 10-400 Hz can be made from all hydrophones for periods of up to 30 days in water depths to 18,000 feet. The instrument has been deployed sixteen times during the past two years by the Woods Hole Oceanographic Institution with a total accmulation of approximately 850 hydrophone days of data. A brief description of the associated data reduction system is included along with some examples of the 1/3 octave and narrow band spectrum analysis performed on data from one deployment.