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Cotter E, McVey J, Weicht L, Haxel J. Performance of three hydrophone flow shields in a tidal channel. JASA EXPRESS LETTERS 2024; 4:016001. [PMID: 38197794 DOI: 10.1121/10.0024333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 12/22/2023] [Indexed: 01/11/2024]
Abstract
Pseudosound caused by turbulent pressure fluctuations in fluid flow past a hydrophone, referred to as flow noise, can mask propagating sounds of interest. Flow shields can mitigate flow noise by reducing non-acoustic pressure fluctuations sensed by a hydrophone. We evaluate the performance of three hydrophone flow shields (two nylon fabrics and an oil-filled enclosure) in a tidal channel with peak current speed of 1.3 m s-1. All three flow shields reduced flow noise without attenuating propagating sound below 20 kHz. The oil-filled enclosure performed best, reducing flow noise by over 30 dB at frequencies below 40 Hz.
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Affiliation(s)
- Emma Cotter
- Coastal Sciences Division, Pacific Northwest National Laboratory, Sequim, Washington 98382, , , ,
| | - James McVey
- Coastal Sciences Division, Pacific Northwest National Laboratory, Sequim, Washington 98382, , , ,
| | - Linnea Weicht
- Coastal Sciences Division, Pacific Northwest National Laboratory, Sequim, Washington 98382, , , ,
| | - Joseph Haxel
- Coastal Sciences Division, Pacific Northwest National Laboratory, Sequim, Washington 98382, , , ,
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Tenorio-Hallé L, Thode AM, Lammers MO, Conrad AS, Kim KH. Multi-target 2D tracking method for singing humpback whales using vector sensors. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:126. [PMID: 35105036 DOI: 10.1121/10.0009165] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
Acoustic vector sensors allow estimating the direction of travel of an acoustic wave at a single point by measuring both acoustic pressure and particle motion on orthogonal axes. In a two-dimensional plane, the location of an acoustic source can thus be determined by triangulation using the estimated azimuths from at least two vector sensors. However, when tracking multiple acoustic sources simultaneously, it becomes challenging to identify and link sequences of azimuthal measurements between sensors to their respective sources. This work illustrates how two-dimensional vector sensors, deployed off the coast of western Maui, can be used to generate azimuthal tracks from individual humpback whales singing simultaneously. Incorporating acoustic transport velocity estimates into the processing generates high-quality azimuthal tracks that can be linked between sensors by cross-correlating features of their respective azigrams, a particular time-frequency representation of sound directionality. Once the correct azimuthal track associations have been made between instruments, subsequent localization and tracking in latitude and longitude of simultaneous whales can be achieved using a minimum of two vector sensors. Two-dimensional tracks and positional uncertainties of six singing whales are presented, along with swimming speed estimates derived from a high-quality track.
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Affiliation(s)
- Ludovic Tenorio-Hallé
- Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0238, USA
| | - Aaron M Thode
- Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0238, USA
| | - Marc O Lammers
- Hawaiian Islands Humpback Whale National Marine Sanctuary, 726 S. Kihei Rd, Kihei, Hawaii 96753, USA
| | - Alexander S Conrad
- Greeneridge Sciences, Inc., 5266 Hollister Avenue, Suite 107, Santa Barbara, California 93111, USA
| | - Katherine H Kim
- Greeneridge Sciences, Inc., 5266 Hollister Avenue, Suite 107, Santa Barbara, California 93111, USA
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Assessment of Arrow-of-Time Metrics for the Characterization of Underwater Explosions. SENSORS 2021; 21:s21175952. [PMID: 34502843 PMCID: PMC8434639 DOI: 10.3390/s21175952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/30/2021] [Accepted: 08/31/2021] [Indexed: 11/16/2022]
Abstract
Anthropogenic impulsive sound sources with high intensity are a threat to marine life and it is crucial to keep them under control to preserve the biodiversity of marine ecosystems. Underwater explosions are one of the representatives of these impulsive sound sources, and existing detection techniques are generally based on monitoring the pressure level as well as some frequency-related features. In this paper, we propose a complementary approach to the underwater explosion detection problem through assessing the arrow of time. The arrow of time of the pressure waves coming from underwater explosions conveys information about the complex characteristics of the nonlinear physical processes taking place as a consequence of the explosion to some extent. We present a thorough review of the characterization of arrows of time in time-series, and then provide specific details regarding their applications in passive acoustic monitoring. Visibility graph-based metrics, specifically the direct horizontal visibility graph of the instantaneous phase, have the best performance when assessing the arrow of time in real explosions compared to similar acoustic events of different kinds. The proposed technique has been validated in both simulations and real underwater explosions.
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Thode AM, Norman RG, Conrad AS, Tenorio-Hallé L, Blackwell SB, Kim KH. Measurements of open-water arctic ocean noise directionality and transport velocity. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:1954. [PMID: 34598615 DOI: 10.1121/10.0006206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 08/19/2021] [Indexed: 06/13/2023]
Abstract
Measurements from bottom-mounted acoustic vector sensors, deployed seasonally between 2008 and 2014 on the shallow Beaufort Sea shelf along the Alaskan North Slope, are used to estimate the ambient sound pressure power spectral density, acoustic transport velocity of energy, and dominant azimuth between 25 and 450 Hz. Even during ice-free conditions, this region has unusual acoustic features when compared against other U.S. coastal regions. Two distinct regimes exist in the diffuse ambient noise environment: one with high pressure spectral density levels but low directionality, and another with lower spectral density levels but high directionality. The transition between the two states, which is invisible in traditional spectrograms, occurs between 73 and 79 dB re 1 μPa2/Hz at 100 Hz, with the transition region occurring at lower spectral levels at higher frequencies. Across a wide bandwidth, the high-directionality ambient noise consistently arrives from geographical azimuths between 0° and 30° from true north over multiple years and locations, with a seasonal interquartile range of 40° at low frequencies and high transport velocities. The long-term stability of this directional regime, which is believed to arise from the dominance of wind-driven sources along an east-west coastline, makes it an important feature of arctic ambient sound.
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Affiliation(s)
- Aaron M Thode
- Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0238, USA
| | - Robert G Norman
- Greeneridge Sciences, Inc., 5266 Hollister Ave, Suite 107, Santa Barbara, California 93111, USA
| | - Alexander S Conrad
- Greeneridge Sciences, Inc., 5266 Hollister Ave, Suite 107, Santa Barbara, California 93111, USA
| | - Ludovic Tenorio-Hallé
- Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0238, USA
| | - Susanna B Blackwell
- Greeneridge Sciences, Inc., 5266 Hollister Ave, Suite 107, Santa Barbara, California 93111, USA
| | - Katherine H Kim
- Greeneridge Sciences, Inc., 5266 Hollister Ave, Suite 107, Santa Barbara, California 93111, USA
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