Male sperm whale acoustic behavior observed from multipaths at a single hydrophone

Abstract

Sperm whales generate transient sounds ͑clicks͒ when foraging. These clicks have been described as echolocation sounds, a result of having measured the source level and the directionality of these signals and having extrapolated results from biosonar tests made on some small odontocetes. The authors propose a passive acoustic technique requiring only one hydrophone to investigate the acoustic behavior of free-ranging sperm whales. They estimate whale pitch angles from the multipath distribution of click energy. They emphasize the close bond between the sperm whale's physical and acoustic activity, leading to the hypothesis that sperm whales might, like some small odontocetes, control click level and rhythm. An echolocation model estimating the range of the sperm whale's targets from the interclick interval is computed and tested during different stages of the whale's dive. Such a hypothesis on the echolocation process would indicate that sperm whales echolocate their prey layer when initiating their dives and follow a methodic technique when foraging.

3D tracking of foraging belugas from their clicks: Experiment from a coastal hydrophone array

“…In particular, the relatively low-frequency click series with long inter-click intervals (ICI) produced by sperm whales during a large part of their long dives have been used to track the animals in 3D and study their underwater behaviour [1][2][3][4][5][6][7]. Similarly, deep diving beaked whales have been tracked from their higher-frequency and shorter ICI foraging click series [8][9][10][11].…”

3D source location using overlapping multipath propagation

“…For a source at 2000 m range and 30 m depth, the observed times of arrival obtained after the warping preprocessing will be the mean arrival time of the first three overlapping paths (direct, first surface and first bottom reflected paths) and the fourth path. Using (2) and (3) with the observed time differences of arrival will lead to a wrong estimation of 550 m range and 48 m depth. Fig.…”

“…The feasibility of using a single receiver for range and depth estimation has been demonstrated in ray theory ( [1], [2], [3]). While 3D (range, depth, azimuth) localization usually requires a vertical or horizontal array, more recent work has demonstrated its feasibility with a single receiver by using azimuth-dependent bathymetric information for bearing estimation [4].…”

Marine mammal tracks from two-hydrophone acoustic recordings made with a glider

“…In the case of marine mammal calls, the location and distance of the animals with respect to the recording sensor are not known a priori. Multipath can sometimes be used to aid in localizing whales (e.g., Laplanche et al, 2005). However, in order to automatically distinguish multipath in the recorded data, highly specialized algorithms are necessary.…”