Highly Defined Whale Group Tracking by Passive Acoustic Stochastic Matched Filter

In this paper, we compare two low cost time-domain tracking algorithms based on passive acoustics. The problem consists in tracking an unknown number of sperm whales (Physeter catodon). Clicks are recorded on two datasets of 20 and 25 minutes on an open-ocean widely-spaced bottom-mounted hydrophone array. The output of the method is the track(s) of the Marine Mammal(s) (MM) in 3D space and time. Firstly, we briefly review studies of the Stochastic Matched Filter (SMF) detector and its performances with a reflected click cancellation, the Teager-Kaiser-Mallat (TKM) filtering, the source separation methods and the main characteristics of MM signals. Then, we propose a real-time algorithm for MM transient call localization. We also recall the Cramer-Rao Lower Bound (CRLB) Kay (1993) and the confidence ellipses theory to predict the reachable accuracy and compare it to the tracking results. In Section 3 we show and compare results of track estimates with results from specialized teams and compare SMF versus TKM localization. Then, the system is evaluated with the confidence ellipses on the trajectories. Finally, we discuss on the possible dynamic behavior of the whale that these localizations offer, like hunting and foraging strategies. This paper deals with the 3D tracking of MM using a widely-spaced bottom-mounted hydrophone array in deep water. It focuses on sperm whale clicks. There were previous algorithms developed in the state of the art Giraudet & Glotin (2006a;b); Morrissey et al. (2006); Nosal & Frazer (2006) but none of them has satisfying results for multiple tracks and most of them are far from being real-time. Our main goal is to build a robust and real-time tracking model, despite ocean noise, multiple reflected clicks, imprecise sound speed profiles, an unknown number ofMM, and the non-linear time-frequency structure ofmostMM signals. Background ocean noise results from the addition of several noises: sea state, biological noises, ship noise and molecular turbulence. Propagation characteristics from an acoustic source to an array of hydrophones include multipath effects (and reverberations, Fig. 1), which create secondary peaks in the Cross-Correlation (CC) function that the generalized CC methods cannot eliminate. In Caudal & Glotin (2008b); Glotin et al. (2008), we gave an extension of Giraudet & Glotin (2006b) that shows multiple tracking using TKM. Here we improve this model using SMF which also allows an efficient Inter-Click-Interval and reflected click removal process. Highly Defined Whale Group Tracking by Passive Acoustic Stochastic Matched Filter 28