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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of acoustic backscatter in the vicinity of the Dry Tortugas (1997)
    Springer
    Geo-marine letters 17 (1997), S. 325-334 
    Details
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Experimental measurements of the bottom backscattering strength from carbonate sediments were made with a 200-kHz multibeam sonar mounted on a remotely operated vehicle. Results were obtained from eight different sites, which may be grouped into three categories, labeled soft, medium and hard, according to measured sediment sound speed. Sediment samples were gathered at or near each site to help interpret the acoustic results. The acoustic results are compared with extant published data and with the BOGGART bottom backscatter model. Backscattering strength values measured in the soft and medium sites fell within the main cluster of previously published values from sediments of similar grain sizes. The values from the hard region fell close to the upper limit. Dependence of the apparent backscattering strength on sonar height above bottom, particularly for the lower values of height above bottom, was observed, which suggests that the scattering process is a multiple-scattering one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003670050044
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    Paper (German National Licenses)
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  • 2
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    Analysis of acoustic backscatter in the vicinity of the Dry Tortugas (1997)
    Springer
    Details
    Publication Date: 1997-12-15
    Print ISSN: 0276-0460
    Electronic ISSN: 1432-1157
    Topics: Geosciences
    Published by Springer
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  • 3
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    Estimate of the bottom compressional wave speed profile in the northeastern South China Sea using "Sources of Opportunity" (2006)
    IEEE
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1231-1248, doi:10.1109/JOE.2004.834681.
    Description: The inversion of a broad-band "source of opportunity" signal for bottom geoacoustic parameters in the northeastern South China Sea (SCS) is presented, which supplements the towed source and chirp sonar bottom inversions that were performed as part of the Asian Seas International Acoustics Experiment (ASIAEX). This source of opportunity was most likely a "dynamite fishing" signal, which has sufficient low-frequency content (5-500 Hz) to make it complimentary to the somewhat higher frequency J-15-3 towed source (50-260 Hz) signals and the much higher frequency (1-10 kHz) chirp signals. This low frequency content will penetrate deeper into the bottom, thus extending the other inverse results. Localization of the source is discussed, using both a horizontal array for azimuthal steering and the "water wave" part of the pulse arrival for distance estimation. A linear broad-band inverse is performed, and three new variants of the broad-band inverse, based on: 1) the Airy phase; 2) the cutoff frequency; and 3) a range-dependent medium are presented. A multilayer model of the bottom compressional wave speed is obtained, and error estimates for this model are shown, both for the range-independent approximation to the waveguide and for the range-dependent waveguide. Directions for future research are discussed.
    Description: This work was supported by the Office of Naval Research under Grant N0 001 498-1-0413, Grant N00014-00-0931, and Grant N00014-01-0772 and by the National Science Council, Taiwan, R.O.C. under Grant NSC92-2611-E-002-005-CCS.
    Keywords: Broadband geoacoustic inversions ; Shallow water acoustics ; South China Sea
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 1203211 bytes
    Format: application/pdf
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  • 4
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    Inversion of surficial sediment thickness from under-ice acoustic transmission measurement (2021)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Acoustical Society of America, 2021. 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 149(1), (2021): 371, https://doi.org/10.1121/10.0003328.
    Description: The under-ice acoustic transmission experiment of 2013, conducted under ice cover in the Fram Strait, was analyzed for bottom interactions for the purpose of developing a model of the seabed. Using the acoustic signals, as well as data from other sources, including cores, gravimetric, refraction, and seismic surveys, it was deduced that the seabed may be modeled as a thin surficial layer overlaid on a deeper sediment. The modeling was based on the Biot–Stoll model for acoustic propagation in porous sediments, aided by more recent developments that improve parameter estimation and depth dependence due to consolidation. At every stage, elastic and fluid approximations were explored to simplify the model and improve computational efficiency. It was found the surficial layer could be approximated as a fluid, but the deeper sediment required an elastic model. The full Biot–Stoll model, while instrumental in guiding the model construction, was not needed for the final computation. The model could be made to agree with the measurements by adjusting the surficial layer thickness.
    Description: The fieldwork was performed under funding from the Research Council of Norway through the UNDER-ICE (Grant No. 226373) project and ENGIE E&P Norway providing additional support. This analysis was supported by the United States Office of Naval Research, Ocean Acoustics Program.
    Description: 2021-07-15
    Repository Name: Woods Hole Open Access Server
    Type: Article
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