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Three-dimensional finite element simulation of acoustic propagation in spiral bubble net of humpback whale

Three-dimensional finite element simulation of acoustic propagation in spiral bubble net of humpback whale
Three-dimensional finite element simulation of acoustic propagation in spiral bubble net of humpback whale
In 2004, Leighton hypothesized that the acoustic calls emitted by humpback whales when feeding using bubble nets, may enhance the effectiveness of the net in confining prey (such as herring) by forming a “wall of sound” with a quiet zone within. Modelling of the acoustics of this phenomenon was previously restricted to 2D; this paper conducts a 3D model of the propagation of signals resembling those emitted by humpback whales when bubble netting, projected into an upward spiral bubble net which data to date suggests is the accurate form for the bubble net in 3D space. In this study, the feeding calls were analyzed in the time-frequency domain to extract acoustic information sufficient to allow modeling of the resulting spatial distribution of acoustic pressure and particle velocity, and how they vary over the duration of the call. Sound propagation in the bubble net was described by using a linear steady-state formulation for an effective medium of bubbly water. Using the predicted attenuation, phase velocity and density in bubbly water, a 3D finite element model was constructed to numerically simulate the upward-spiral bubble net which consists of a mixture of bubbles that exhibit a range of radii. The acoustic pressure field and particle motion field were both calculated within the bubble net. The simulation results show that the energy of the whale feeding call could be effectively focused in the bubble net, generating intensive sound pressure and particle motion fields in the bubbly arm of the net, but with some “quiet” regions closer to the center of the net, as Leighton hypothesized. Furthermore, when the hearing ability of herring is taken into consideration, the results suggest that this acoustic focusing effect could be a plausible factor in trapping them in the bubble net. It also allows speculation on the possible enhancement that the time-varying nature of the call during feeding could give to the whale in this mechanism for the bubble net feeding by humpback whales.
Acoustics, humback whale, bubble net, herring, fish, fishing, hunting, prey
0001-4966
Qing, Xin
aabb8203-e22e-4467-8c91-c947be7ecbea
White, Paul
2dd2477b-5aa9-42e2-9d19-0806d994eaba
Leighton, Timothy
3e5262ce-1d7d-42eb-b013-fcc5c286bbae
Liu, Songzuo
435625cd-399e-457a-a923-ebcd9e671aa6
Qiao, Gang
7451b185-6f9b-4b50-bd71-c61930a73a8f
Zhang, Yu
e1d9894c-dae8-477c-bed3-abee2a838d57
Qing, Xin
aabb8203-e22e-4467-8c91-c947be7ecbea
White, Paul
2dd2477b-5aa9-42e2-9d19-0806d994eaba
Leighton, Timothy
3e5262ce-1d7d-42eb-b013-fcc5c286bbae
Liu, Songzuo
435625cd-399e-457a-a923-ebcd9e671aa6
Qiao, Gang
7451b185-6f9b-4b50-bd71-c61930a73a8f
Zhang, Yu
e1d9894c-dae8-477c-bed3-abee2a838d57

Qing, Xin, White, Paul, Leighton, Timothy, Liu, Songzuo, Qiao, Gang and Zhang, Yu (2019) Three-dimensional finite element simulation of acoustic propagation in spiral bubble net of humpback whale. Journal of the Acoustical Society of America, 146 (3), [1982]. (doi:10.1121/1.5126003).

Record type: Article

Abstract

In 2004, Leighton hypothesized that the acoustic calls emitted by humpback whales when feeding using bubble nets, may enhance the effectiveness of the net in confining prey (such as herring) by forming a “wall of sound” with a quiet zone within. Modelling of the acoustics of this phenomenon was previously restricted to 2D; this paper conducts a 3D model of the propagation of signals resembling those emitted by humpback whales when bubble netting, projected into an upward spiral bubble net which data to date suggests is the accurate form for the bubble net in 3D space. In this study, the feeding calls were analyzed in the time-frequency domain to extract acoustic information sufficient to allow modeling of the resulting spatial distribution of acoustic pressure and particle velocity, and how they vary over the duration of the call. Sound propagation in the bubble net was described by using a linear steady-state formulation for an effective medium of bubbly water. Using the predicted attenuation, phase velocity and density in bubbly water, a 3D finite element model was constructed to numerically simulate the upward-spiral bubble net which consists of a mixture of bubbles that exhibit a range of radii. The acoustic pressure field and particle motion field were both calculated within the bubble net. The simulation results show that the energy of the whale feeding call could be effectively focused in the bubble net, generating intensive sound pressure and particle motion fields in the bubbly arm of the net, but with some “quiet” regions closer to the center of the net, as Leighton hypothesized. Furthermore, when the hearing ability of herring is taken into consideration, the results suggest that this acoustic focusing effect could be a plausible factor in trapping them in the bubble net. It also allows speculation on the possible enhancement that the time-varying nature of the call during feeding could give to the whale in this mechanism for the bubble net feeding by humpback whales.

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Accepted/In Press date: 8 July 2019
e-pub ahead of print date: 30 September 2019
Published date: September 2019
Keywords: Acoustics, humback whale, bubble net, herring, fish, fishing, hunting, prey

Identifiers

Local EPrints ID: 434003
URI: http://eprints.soton.ac.uk/id/eprint/434003
ISSN: 0001-4966
PURE UUID: ba9935a0-a9c8-4209-aa08-876f6e49b96a
ORCID for Paul White: ORCID iD orcid.org/0000-0002-4787-8713
ORCID for Timothy Leighton: ORCID iD orcid.org/0000-0002-1649-8750

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Date deposited: 10 Sep 2019 16:30
Last modified: 12 Jul 2024 04:03

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Contributors

Author: Xin Qing
Author: Paul White ORCID iD
Author: Songzuo Liu
Author: Gang Qiao
Author: Yu Zhang

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