Using broadband humpback whale vocalizations to locate nonvocal whales in shallow water

Abstract

In a previous paper [Makris and Cato, J. Acoust. Soc. Am. 96, 3270 (1994)], it was shown that a vocal member of a humpback whale herd can be used as a source of opportunity to locate nonvocal members with a passive towed array. That analysis employed full-field but narrow-band propagation and scattering models to emphasize the high spatial array gains available. In the present paper, full-field simulations are performed to determine the structure of actual broadband humpback whale vocalizations after scattering from whales in a shallow-water waveguide. The simulations show that the time signature of a whale vocalization is significantly altered during each of the three stages of (1) propagating from vocal to nonvocal whale, (2) scattering from the nonvocal whale, and (3) propagating from the nonvocal whale to a receiver. The large time-bandwidth gains available in humpback vocalizations then cannot be optimally exploited without first modeling broadband propagation and scattering of the whale vocalization for the given waveguide and bistatic geometry. This raises serious questions about whether the humpbacks themselves, who have limited spatial gains over the noise, can actively detect nonvocal herd members with their vocalizations, as was discussed in the above reference.

Localising Cetacean Sounds for the Real-Time Mitigation and Long-Term Acoustic Monitoring of Noise

“…The solution introduced in this paper is conceptually based on both ANI and multi-static active solutions, where the active sources are produced by surrounding foraging sperm whales at greater depths (from 200 m downwards), which vocalize on their way down and at foraging depths (Zimmer et al, 2003), and in reported cases, likely on their way up until a few minutes before surfacing (Jaquet et al, 2001). The full analysis can be found in Delory et al, 2007. A comparable approach was introduced for the humpback whale (Megaptera novaeangliae) off eastern Australia (Makris & Cato, 1994;Makris et al, 1999). In this study, if the solution were to be applied for monitoring purposes, it would be difficult to implement due to the need for near real-time shallow water propagation modelling as humpback whale vocalizations' spectra peaks are at rather low frequencies and as a result happen to be severely altered in the shallow water waveguide.…”

Feasibility of Acoustic Remote Sensing of Large Herring Shoals and Seafloor by Baleen Whales

“…Here, feasibility of the possible echolocation function is investigated for large and dense herring aggregations. This differs substantially from the possible ability of baleen whales to detect other whales by active acoustics, which has been previously discussed [15][16][17][18][19][20].…”

Humpback whale (Megaptera novaeangliae) sonar: Ten predictions.

“…Some researchers have concluded that humpback whales are unable to echolocate using either click trains or tonal sounds. They argue that the echoes generated by such sounds would either be buried in ambient noise/reverberation, or, in contexts where multiple whales are audible, would be lost in the din created by the other vocalizing whales (Au et al, 2001; Makris, Lai, & Cato, 1999). There is clear evidence that at least some sounds produced by humpback whales are prone to generating reverberation (Clark & Ellison, 2004; Mercado, 2016) and that whales often vocalize in locations that are conducive to reverberation (MacKay, Wursig, Bacon, & Selwayn, 2016), suggesting that humpback whales are likely to encounter situations where sounds and echoes produced by other whales may interfere with their ability to detect and localize self-generated echoes (as well as direct signals from other whales).…”