Acoustics at the ALOHA Cabled Observatory

Abstract

Since 6 June 2011, the ALOHA Cabled Observatory (ACO) has been collecting ocean acoustic data, continuing an earlier data set covering February 2007 - October 2008. The ACO is at Station ALOHA 100 km north of Oahu, the field site of the Hawaii Ocean Time-series (HOT) program that has collected biological, physical, and chemical oceanographic data since 1988. At 4728 m water depth, it is the world’s deepest operating cabled observatory. ACO provides power and communications to user instrumentation. Among the instrumentation there are two hydrophones 1 m off the bottom separated by 1 m. One is an OAS Model E-2PD meant for low frequencies (0.014 Hz to 8 kHz). A second (uncalibrated) hydrophone is meant for higher frequencies. Current sampling rates for both hydrophones are 96 kHz; subsampled 24 kHz data are streamed to the Web in real-time. The system will be described and examples of acoustic events and signals presented, including local and distant earthquakes, marine mammals, surface waves, wind, rain, ships, sonars, and implosions. Plans for future acoustics research will be discussed. [Work supported by the National Science Foundation.]