Classification of beaked whale and dolphin clicks measured by environmental acoustic recording system buoys in the northern Gulf of Mexico

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The Littoral Acoustic Demonstration Center (LADC) has used its Environmental Acoustic Recording System (EARS) buoys to record sperm and beaked whales and dolphins, with frequencies up to 96 kHz, in the northern Gulf of Mexico in 2007 and 2010. The 2007 experiment was the first to record beaked whales in the Gulf. It has been found that there is considerable overlap in the band of beaked whale signals from 20 to 60 kHz with deep-water dolphin clicks, so traditional energy-band detectors have a high occurrence of false positives. Although acoustic measurements in this frequency range validated by visual observations have been limited, for the Gulf of Mexico species, progress is being made in automatically delineating clicks that belong to beaked whale species observed in the Gulf and those originating from dolphins. Spectrograms of the classified clicks are shown and compared to known spectrograms for beaked whale and dolphin species. Many of the spectrograms show an upsweep in the observed spectrum but others do not. Improved classifiers can provide higher accuracy estimates of the regional abundance trends and effects of environmental changes on both beaked whale and dolphin groups. [Research supported by BP/GOMRI, SPAWAR, ONR, NSF, and Greenpeace.]