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  • 1
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Acoustical Society of America, 1998. 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 103 (1998): 330-335, doi:10.1121/1.421092.
    Beschreibung: Amplitude and phase fluctuations of monochromatic acoustic signals traveling through diffuse mid-ocean ridge hydrothermal vent plumes are modeled using existing theory in an attempt to find suitable frequencies and path lengths for plume monitoring. Weak-scattering solutions are evaluated numerically, with model parameters adjusted to match observed plume characteristics. Constraints required for weak-scattering solutions to be valid can be met for transmission ranges of 500–2000 m and frequencies of 20–80 kHz. Therefore, because fluid structure and scattering strength are more closely linked for weak scattering than for stronger scattering, inversion for fluid statistical properties may be possible, enabling diffuse vent monitoring. Such monitoring would be subject to geometric assumptions such as transmission entirely within a statistically homogeneous plume. Performance-limiting phase fluctuations have also been computed for a 13–17 kHz geodetic survey system.
    Beschreibung: This work was supported by the Woods Hole Oceanographic Institution with research funds provided by the Mellon Foundation.
    Schlagwort(e): Underwater sound ; Oceanography ; Acoustic wave scattering ; Seafloor phenomena
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Acoustical Society of America, 2006. 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 119 (2006): 3717-3725, doi:10.1121/1.2200699.
    Beschreibung: Expressions governing coherence scales of sound passing through a moving packet of nonlinear internal waves in a continental shelf environment are presented. The expressions describe the temporal coherence scale at a point, and the horizontal coherence scale in a plane transverse to the acoustic path, respectively. Factors in the expressions are the wave packet propagation speed, wave packet propagation direction, the fractional distance from the packet to the source, and the spatial scale S of packet displacement required to cause acoustic field decorrelation. The scale S is determined by the details of coupled mode propagation within the packet and the waveguide. Here, S is evaluated as a function of frequency for one environment, providing numerical values for the coherence scales of this environment. Coherence scales derived from numerical simulation of coupled mode acoustic propagation through moving wave packets substantiate the expressions.
    Beschreibung: This work was funded by grants from the Ocean Acoustics Program of the U.S. Office of Naval Research.
    Schlagwort(e): Underwater sound ; Acoustic wave propagation ; Acoustic field ; Acoustic waveguides ; Acoustic wave scattering
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © Acoustical Society of America, 2011. 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 130 (2011): 1173-1187, doi:10.1121/1.3605565.
    Beschreibung: A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional parabolic equation computational code, and the results are compared to measured propagation along fixed 3 and 6 km source/receiver paths. The measurements were made on the shelf of the South China Sea northeast of Tung-Sha Island. Construction of the time-varying three-dimensional sound-speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data. Computed three-dimensional propagation results compare well with field observations. The simulations allow identification of time-dependent sound forward scattering and ducting processes within the curved internal gravity waves. Strong acoustic intensity enhancement was observed during passage of high-amplitude nonlinear waves over the source/receiver paths, and is replicated in the model. The waves were typical of the region (35 m vertical displacement). Two types of ducting are found in the model, which occur asynchronously. One type is three-dimensional modal trapping in deep ducts within the wave crests (shallow thermocline zones). The second type is surface ducting within the wave troughs (deep thermocline zones).
    Beschreibung: Grants from the Office of Naval Research funded this work. Use of the vessels Ocean Researcher I and Ocean Researcher II in this experiment was funded by the Taiwan National Science Council.
    Schlagwort(e): Acoustic field ; Acoustic focusing ; Acoustic intensity ; Acoustic wave scattering ; Acoustic wave velocity ; Ocean waves ; Oceanographic regions ; Underwater acoustic propagation
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
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    Acoustical Society of America
    Publikationsdatum: 2022-05-25
    Beschreibung: 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 118 (2005): 2899-2903, doi:10.1121/1.2062127.
    Beschreibung: The relative importance of internal-wave strain and internal-wave shear on perturbation of acoustic ray trajectories in the ocean is analyzed. Previous estimates based on the Garrett-Munk internal-wave spectral model are updated using data from recent field studies of internal waves. Estimates of the ratio of the rms shear effect to the rms strain effect based on data from the upper kilometer of ocean are as high as 0.25–0.4, exceeding the estimates of 0.08–0.17 stemming from the model. Increased strength of three phenomena that have shear to strain ratios higher than the internal-wave average can cause this effect. These are near-inertial waves, internal tides, and vortical modes.
    Beschreibung: This work was funded by grants from the U.S. Office of Naval Research.
    Schlagwort(e): Ocean waves ; Tides ; Underwater sound ; Acoustic wave scattering
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Publikationsdatum: 2022-05-25
    Beschreibung: 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 132 (2012): 2224-2231, doi:10.1121/1.4747617.
    Beschreibung: Data collected during the 2004 Long-range Ocean Acoustic Propagation Experiment provide absolute intensities and travel times of acoustic pulses at ranges varying from 50 to 3200 km. In this paper a subset of these data is analyzed, focusing on the effects of seafloor reflections at the shortest transmission range of approximately 50 km. At this range bottom-reflected (BR) and surface-reflected, bottom-reflected energy interferes with refracted arrivals. For a finite vertical receiving array spanning the sound channel axis, a high mode number energy in the BR arrivals aliases into low mode numbers because of the vertical spacing between hydrophones. Therefore, knowledge of the BR paths is necessary to fully understand even low mode number processes. Acoustic modeling using the parabolic equation method shows that inclusion of range-dependent bathymetry is necessary to get an acceptable model-data fit. The bottom is modeled as a fluid layer without rigidity, without three dimensional effects, and without scattering from wavelength-scale features. Nonetheless, a good model-data fit is obtained for sub-bottom properties estimated from the data.
    Beschreibung: This work was supported by the Office of Naval Research, Code 322, Grant Nos. N00014- 10-1-0987, N00014-11-1-0194, and N00014-10-1-0510.
    Schlagwort(e): Acoustic wave reflection ; Acoustic wave scattering ; Acoustic wave transmission ; Bathymetry ; Parabolic equations ; Uunderwater acoustic propagation
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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