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  • 1
    facet.materialart.
    Unknown
    Three-dimensional beam pattern of regular sperm whale clicks confirms bent-horn hypothesis (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2005. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 117 (2005): 1473-1485, doi:10.1121/1.1828501.
    Description: The three-dimensional beam pattern of a sperm whale (Physeter macrocephalus) tagged in the Ligurian Sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale. The tag defined the orientation of the whale, while sightings and beamformer data were used to locate the whale with respect to the ship. The existence of a narrow, forward-directed P1 beam with source levels exceeding 210 dBpeak re: 1 µPa at 1 m is confirmed. A modeled forward-beam pattern, that matches clicks 〉20° off-axis, predicts a directivity index of 26.7 dB and source levels of up to 229 dBpeak re: 1 µPa at 1 m. A broader backward-directed beam is produced by the P0 pulse with source levels near 200 dBpeak re: 1 µPa at 1 m and a directivity index of 7.4 dB. A low-frequency component with source levels near 190 dBpeak re: 1 µPa at 1 m is generated at the onset of the P0 pulse by air resonance. The results support the bent-horn model of sound production in sperm whales. While the sperm whale nose appears primarily adapted to produce an intense forward-directed sonar signal, less-directional click components convey information to conspecifics, and give rise to echoes from the seafloor and the surface, which may be useful for orientation during dives.
    Description: This work was funded by grants from the Office of Naval Research Grants N00014-99-1-0819 and N00014-01-1-0705, and the Packard Foundation.
    Keywords: Bioacoustics ; Biocommunications ; Array signal processing ; Echo ; Hydrophones ; Multidimensional signal processing ; Underwater sound ; Sonar signal processing
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Unknown
    Amazon river dolphins (Inia geoffrensis) use a high-frequency short-range biosonar (2015)
    The Company of Biologists
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Company of Biologists, 2015. This article is posted here by permission of The Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 218 (2015): 3091-3101, doi:10.1242/jeb.120501.
    Description: Toothed whales produce echolocation clicks with source parameters related to body size; however, it may be equally important to consider the influence of habitat, as suggested by studies on echolocating bats. A few toothed whale species have fully adapted to river systems, where sonar operation is likely to result in higher clutter and reverberation levels than those experienced by most toothed whales at sea because of the shallow water and dense vegetation. To test the hypothesis that habitat shapes the evolution of toothed whale biosonar parameters by promoting simpler auditory scenes to interpret in acoustically complex habitats, echolocation clicks of wild Amazon river dolphins were recorded using a vertical seven-hydrophone array. We identified 404 on-axis biosonar clicks having a mean SLpp of 190.3±6.1 dB re. 1 µPa, mean SLEFD of 132.1±6.0 dB re. 1 µPa2s, mean Fc of 101.2±10.5 kHz, mean BWRMS of 29.3±4.3 kHz and mean ICI of 35.1±17.9 ms. Piston fit modelling resulted in an estimated half-power beamwidth of 10.2 deg (95% CI: 9.6–10.5 deg) and directivity index of 25.2 dB (95% CI: 24.9–25.7 dB). These results support the hypothesis that river-dwelling toothed whales operate their biosonars at lower amplitude and higher sampling rates than similar-sized marine species without sacrificing high directivity, in order to provide high update rates in acoustically complex habitats and simplify auditory scenes through reduced clutter and reverberation levels. We conclude that habitat, along with body size, is an important evolutionary driver of source parameters in toothed whale biosonars.
    Description: Field work was funded by Danish National Research Council grants to P.T.M., Associação Amigos do Peixe Boi da Amazônia (AMPA) and Petrobras Ambiental grants to V.M.F.d.S., Augustinus Fonden grants to M.L. and a travelling fellowship awarded to M.d.F. by Journal of Experimental Biology. M.L. was funded by a PhD stipend from the Faculty of Science and Technology, Aarhus University, and National Research Council grants to P.T.M. F.H.J. was funded by a Carlsberg Foundation travel grant.
    Description: 2016-10-07
    Keywords: Beamwidth ; Clutter ; Directionality ; Echolocation ; Habitat ; Toothed whale
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    facet.materialart.
    Unknown
    Estimated communication range and energetic cost of bottlenose dolphin whistles in a tropical habitat (2012)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 582-592, doi:10.1121/1.3662067.
    Description: Bottlenose dolphins (Tursiops sp.) depend on frequency-modulated whistles for many aspects of their social behavior, including group cohesion and recognition of familiar individuals. Vocalization amplitude and frequency influences communication range and may be shaped by many ecological and physiological factors including energetic costs. Here, a calibrated GPS-synchronized hydrophone array was used to record the whistles of bottlenose dolphins in a tropical shallow-water environment with high ambient noise levels. Acoustic localization techniques were used to estimate the source levels and energy content of individual whistles. Bottlenose dolphins produced whistles with mean source levels of 146.7±6.2 dB re. 1 μPa(RMS). These were lower than source levels estimated for a population inhabiting the quieter Moray Firth, indicating that dolphins do not necessarily compensate for the high noise levels found in noisy tropical habitats by increasing their source level. Combined with measured transmission loss and noise levels, these source levels provided estimated median communication ranges of 750 m and maximum communication ranges up to 5740 m. Whistles contained less than 17 mJ of acoustic energy, showing that the energetic cost of whistling is small compared to the high metabolic rate of these aquatic mammals, and unlikely to limit the vocal activity of toothed whales.
    Description: This study received support from the Danish Ph.D. School of Aquatic Sciences (SOAS), Aarhus University, DK, WWF Verdensnaturfonden and Aase & Ejnar Danielsens Foundation, the Siemens Foundation, the Faculty of Science at the University of Aarhus, DK, and the Danish Natural Science Foundation via a Steno scholarship and a logistics grant to PTM.
    Keywords: Acoustic arrays ; Acoustic noise ; Acoustic radiators ; Acoustic variables measurement ; Acoustic wave transmission ; Biocommunications ; Global Positioning System ; Hydrophones ; Underwater sound
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 4
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    Unknown
    Single-click beam patterns suggest dynamic changes to the field of view of echolocating Atlantic spotted dolphins (Stenella frontalis) in the wild (2015)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Company of Biologists, 2015. This is the author's version of the work. It is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology (2015), doi:10.1242/​jeb.116285.
    Description: Echolocating animals exercise an extensive control over the spectral and temporal properties of their biosonar signals to facilitate perception of their actively generated auditory scene when homing in on prey. The intensity and directionality of the biosonar beam defines the field of view of echolocating animals by affecting the acoustic detection range and angular coverage. However, the spatial relationship between an echolocating predator and its prey changes rapidly, resulting in different biosonar requirements throughout prey pursuit and capture. Here we measured single click beam patterns using a parametric fit procedure to test whether free-ranging Atlantic spotted dolphins (Stenella frontalis) modify their biosonar beamwidth. We recorded echolocation clicks using a linear array of receivers and estimated the beamwidth of individual clicks using a parametric spectral fit, cross-validated with well-established composite beam pattern estimates. The dolphins apparently increased the biosonar beamwidth, to a large degree without changing the signal frequency, when they approached the recording array. This is comparable to bats that also expand their field of view during prey capture, but achieve this by decreasing biosonar frequency. This behaviour may serve to decrease the risk that rapid escape movements of prey take them outside the biosonar beam of the predator. It is likely that shared sensory requirements have resulted in bats and toothed whales expanding their acoustic field of view at close range to increase the likelihood of successfully acquiring prey using echolocation, representing a case of convergent evolution of echolocation behaviour between these two taxa.
    Description: The study was funded by frame grants from the Danish Natural Science Foundation to PTM and MW, and by the National Oceanographic Partnership Programme via a research agreement between La Laguna University (NAS) and the Woods Hole Oceanographic Institution (MJ). FHJ was supported by the Danish Council for Independent Research | Natural Sciences, and is currently funded by a postdoctoral fellowship from the Carlsberg Foundation.
    Description: 2016-03-12
    Keywords: Echolocation ; Directionality ; Field of view ; Perception ; Dolphin ; Prey capture
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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