Environmental Acoustic Recording System (EARS) In the Gulf of Mexico

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Book Chapter

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The Littoral Acoustic Demonstration Center (LADC) was formed in early 2001 to utilize Environmental Acoustic Recording System (EARS) buoys developed by the Naval Oceanographic Office (NAVOCEANO) which has provided technical guidance and support to LADC. The purpose of LADC is to make environmental measurements, which is not part of the mission of NAVOCEANO. This chapter describes the Gulf of Mexico marine mammal measurements and related data analysis of LADC. LADC has also used the buoys to characterize the three-dimensional acoustic field of a seismic airgun array and to analyze the noise due to nearby storms. LADC is a consortium of scientists from universities and the U.S. Navy. The following institutions are or have been represented: initially, the University of New Orleans, the University of Southern Mississippi, and the Naval Research Laboratory-Stennis Space Center; and then the University of Louisiana at Lafayette, the Applied Research Laboratories at the University of Texas at Austin, and Oregon State University. The scientists are listed in the first section of the chapter. A technical overview of EARS technology is given in Sect. 6.2. The current Generation 2 EARS buoys can record four channels of up to 25 kHz each or one channel up to 96 kHz.

LADC has conducted marine mammal experiments in the Gulf of Mexico in 2001, 2002, 2007, and 2010. The 2007 experiments were at sites 9 and 23 miles from the Macondo Well Oil Spill. These sites as well as the 2001 and 2002 sites were recorded in the 2010 experiment to measure changes related to earlier measurements. LADC has also done seismic airgun array experiments in 2003 and 2007. The marine mammal experiments are summarized in Sect. 3, where experiments in the Mediterranean Sea, which had LADC participation, are also listed.

The remaining Sects. 6.4 through 6.11 describe the analysis to date of LADC data and also the analysis by LADC scientists of workshop data for detection, classification, and localization purposes. Section 6.4 describes sperm whale click structure analysis for click-train demarcation and identification of individual whales. The tendency of whales diving together to establish different cadences for their echolocation clicks to keep from interfering with each other is presented in Sect. 6.5. The identification of individual whales by clustering echolocation clicks of sperm and beaked whales and coda clicks of sperm whales is discussed in Sect. 6.6. The application of click change detection to know if the same or a different whale are speaking on successive clicks is described in Sect. 6.7. This method allows one to follow a turning sperm whale. A technique for localizing individual clicking whales is presented in Sect. 6.8. The integration of the above techniques is discussed in Sect. 6.9, which also suggests how whales might identify each other. Sperm whale coda classification and repertoire analysis are the subject of Sect. 6.10. Finally, statistical modeling for population estimation is given in Sect. 6.11.

Publication Title

Listening In the Ocean

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