Automated acoustic localization and call association for vocalizing humpback whales on the Navy's Pacific Missile Range Facility

Abstract

Time difference of arrival (TDOA) methods for acoustically localizing multiple marine mammals have been applied to recorded data from the Navy's Pacific Missile Range Facility in order to localize and track humpback whales. Modifications to established methods were necessary in order to simultaneously track multiple animals on the range faster than real-time and in a fully automated way, while minimizing the number of incorrect localizations. The resulting algorithms were run with no human intervention at computational speeds faster than the data recording speed on over forty days of acoustic recordings from the range, spanning multiple years. Spatial localizations based on correlating sequences of units originating from within the range produce estimates having a standard deviation typically 10 m or less (due primarily to TDOA measurement errors), and a bias of 20 m or less (due primarily to sound speed mismatch). An automated method for associating units to individual whales is presented, enabling automated humpback song analyses to be performed.

Swim track kinematics and calling behavior attributed to Bryde's whales on the Navy's Pacific Missile Range Facility

“…The process for obtaining whale locations can be subdivided into three steps: detection and feature extraction, cross-correlation of those features to obtain TDOAs, and TDOA-based localization. These steps are outlined in detail using humpback whale calls in Helble et al 16 and, therefore, are not repeated in this paper.…”

“…Processing methods for localizing whales using the time difference of arrival (TDOA) of recorded acoustic signals have been established on the PMRF range. 16 The techniques were initially developed for humpback whales (Megaptera novaeangliae), but have since been expanded and used successfully for Bryde's, sei (Balaenoptera borealis), fin (Balaenoptera physalus), blue (Balaenoptera musculus), and minke (Balaenoptera acutorostrata) whales. The TDOA method was facilitated with the use of the generalized power-law (GPL) detector 17 and enhanced with a spectral "templating" procedure to characterize individual vocalizations by extracting a fundamental for each vocalization and setting the remainder of the spectrogram to zero.…”

“…Cross-correlations of the templates allowed for localization of multiple animals concurrently with an incorrect localization rate of 2% or less. 16 Additional software was developed in order to positively associate each whale vocalization with a location. This step was necessary in order to accurately obtain the intercall interval (ICI) of the Bryde's calls, which is an important metric needed for density estimation.…”

Estimation of minke whale abundance from an acoustic line transect survey of the Mariana Islands

“…If combined with biopsy and sex data (e.g., using skin samples collected incidentally from tags, or from biopsy samples), sex ratio biases with respect to vocalization rates could also be obtained. The possibility of determining movements and calling behaviors of animals in response to vessel presence can be examined using existing seafloor hydrophone systems and data to conduct detailed analysis of animal tracks (e.g., Helble et al 2015) in relation to vessel movements. Third, a potential decrease in calling in response to vessel presence could be explored using acoustic data collected from sonobuoys and/or fixed seafloor hydrophones that have sufficient temporal and spatial coverage to track and monitor vocalization rates of individuals as the survey vessel passes nearby.…”

Baleen whale responses to a high frequency active pinger: Implications for upper frequency hearing limits

“…Using multi-hydrophone arrays and time difference of arrival (TDOA) methods, vocalizing marine mammals can be localized and successive vocalizations can be tracked over time. When enough hydrophones exist over a large spatial extent, animals can be tracked for long periods of time and over broad distances as long as they continue to vocalize, as has been done for humpback whales (Megaptera novaeangliae), Bryde's whales (Balaenoptera brydei), and minke whales (Balaenoptera acutorostrata) at the Pacific Missile Range Facility (PMRF) near the island of Kauai in the Hawaiian archipelago (Helble, Ierley, Gerald, and Martin, 2015;Martin, Martin, Matsuyama, and Henderson 2015;Helble, Martin, Ierley, and Henderson, 2016). However, when an animal ceases to vocalize they can no longer be tracked, and assumptions must be made when a new vocalization bout begins as to whether or not it is the same or a different animal.…”