Simultaneous passive and active detection and localization of humpback whales using data recorded on a towed horizontal receiving array.

Abstract

A large number of marine mammal vocalizations, most likely from humpback whales, were passively recorded by a towed horizontal receiver array during the ocean acoustic waveguide remote sensing (OAWRS) Gulf of Maine 2006 Experiment. Spectral analyzes show that most of the vocalizations were random broadband signals with short time duration, typically lasting 1–2 s in the 300–600-Hz frequency range. The array invariant method [Lee and Makris, J. Acoust. Soc. Am. (2006)] is applied to localize the whales in bearing and range after conventional plane-wave beamforming and matched filtering of passively recorded vocalizations on the array. The source levels of a sequence of whale calls in a 110-min time period, belonging to a number of individuals, are estimated based on the localization results. The estimation results are consistent with previous studies. We also examine the feasibility of actively detecting and localizing whales with OAWRS at low-to-mid frequencies in a random range-dependent ocean waveguide. A full-field waveguide scattering model is applied to determine the scattered field level from whales, as a function of range and depth location of the whale, and compared to environmental reverberation measured in the Gulf of Maine. The dominant source of scattering from whales at these frequencies is their air-filled lungs.

Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away

“…In the absence of effective far field source level (SL) data, we cannot make inference on the effects of the OAWRS signal on those humpback whales that may have been closer to the sound source than our study site. Yet, Gong et al [39] recorded marine mammal vocalizations, presumably humpback whales, on George's Bank much closer to the source ( Figure 1 ), concurrent with the 2006 OAWRS experiment. However, as these authors present no data on humpback whales' use of George's Bank at any time other than during this experiment it is difficult to make inference on its effect on humpback whale behavior at these closer spatial ranges.…”