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  • 1995-1999  (4)
  • Comparative Studies. Non-European Languages/Literatures  (4)
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Publisher
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  • 1995-1999  (4)
Year
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Subjects(RVK)
  • Comparative Studies. Non-European Languages/Literatures  (4)
RVK
  • 1
    Online Resource
    Online Resource
    Bottom volume scattering—Modeling and data analysis
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 5_Supplement ( 1998-05-01), p. 3060-3061
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 5_Supplement ( 1998-05-01), p. 3060-3061
    Abstract: As part of the Acoustic Reverberation Special Research Program (ARSRP), low-frequency bottom scattering from a deep ocean sediment pond was measured using an omnidirectional source and a vertical line-receiving array deployed near the bottom. Sediment volume heterogeneities were found to be the major contributor to the measured scattered fields [Tang et al., J. Acoust. Soc. Am. 98, 508–516 (1995)]. Taking advantage of the experimental geometry, a model is developed which can generate realizations of three-dimensional random inhomogeneities in sediments and can simulate scattered fields based on these realizations using a perturbation approach. In this model, the broadband propagator (the Green’s function) is obtained using an exact numerical method. Therefore, the model can handle any layered sediment environments with scatterers distributed within any of the layers. The model predictions are compared to the experimental data across the available frequency band, and the results are favorable. [Work supported by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.422813
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Low-frequency acoustic backscattering by volumetric inhomogeneities in deep-ocean sediments
    Acoustical Society of America (ASA) ; 1995
    In:  The Journal of the Acoustical Society of America Vol. 98, No. 1 ( 1995-07-01), p. 508-516
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 98, No. 1 ( 1995-07-01), p. 508-516
    Abstract: An experiment to study acoustic backscattering from deep-ocean sediments was conducted in July 1993 as part of the Acoustic Reverberation Special Research Program sponsored by the Office of Naval Research. An acoustic source transmitting chirp signals in the frequency range 250–650 Hz and a 24-element vertical receiving array attached to the source were suspended near the seafloor over a sediment pond in the vicinity of the Mid-Atlantic Ridge. The array steered in the normal incidence (endfire) direction is used to determine the sediment structure, while the array steered at oblique angles is used to determine backscattering strength. It is found that the sediment is stratified with gentle horizontal changes, except for two irregular regions, with thicknesses of about 20 m, located approximately 18 and 60 m beneath the seafloor. These inhomogeneous regions are shown to be the dominant influence on the backscattered field, and the backscattering strength of each region as a function of grazing angle is estimated. It is found that the removal of coherent reflections from subbottom stratified layers is essential to the analysis of bottom backscattering phenomena.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.413641
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1995
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Evaluation of sound propagation models used in bottom volume scattering studies
    Acoustical Society of America (ASA) ; 1996
    In:  The Journal of the Acoustical Society of America Vol. 100, No. 4_Supplement ( 1996-10-01), p. 2712-2712
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 100, No. 4_Supplement ( 1996-10-01), p. 2712-2712
    Abstract: The proper evaluation of sound propagation between sources/receivers and scatterers is important in characterizing bottom volume scattering. In this work, several sound propagation models used in bottom volume scattering studies are evaluated and their results compared to the exact solution obtained through a numerical wave-number integration technique. It is found that Hines’ approach [J. Acoust. Soc. Am. 88, 324–334 (1990)] works well for the two isovelocity half-space case except when the grazing angle is close to the critical angle. The far-field approximation, given by Ivakin [Sov. Phys. Acoust. 32(6), 492–496 (1986)] and Mourad and Jackson [J. Acoust. Soc. Am. 94, 344–358 (1993)] has a performance depending upon the sound-speed structure in the sediment. For an isovelocity slow bottom, it agrees well with the exact solution. However, discrepancies arise for an isovelocity fast bottom or a bottom with a complex sound-speed structure. In addition, the appropriateness of using the equivalent surface scattering strength as a function of grazing angle in volume scattering characterizations is studied. In conclusion, precautions need to be taken in modeling both the propagation effects and the scattering mechanisms associated with the bottom volume scattering process. [Work supported by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966
    URL: Article
    DOI: 10.1121/1.416120
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1996
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Vertical spatial and temporal coherence of ocean bottom reverberation.
    Acoustical Society of America (ASA) ; 1996
    In:  The Journal of the Acoustical Society of America Vol. 99, No. 4_Supplement ( 1996-04-01), p. 2499-2500
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 99, No. 4_Supplement ( 1996-04-01), p. 2499-2500
    Abstract: An experiment to study acoustic backscattering from deep-ocean sediments was conducted in July 1993 as part of the Acoustic Reverberation Special Research Program (ARSRP). An acoustic source transmitting chirp signals in the frequency range 250–650 Hz and a 24-element vertical receiving array attached to the source were suspended near the seafloor over a sediment pond in the vicinity of the Mid-Atlantic Ridge. In a previous paper [Tang et al., J. Acoust. Soc. Am. 98 508–516 (1995)], a study on bottom scattering due to sediment volume inhomogeneities in this area was presented. Here, the spatial and temporal coherence of the scattered field using the data collected on the vertical array will be examined. The scatterers are modeled as point scatterers. It is shown that when the coherently reflected signals due to sediment layering are removed from the measurements, the results of the point scatter coherence model agree satisfactorily with data. [Work supported by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.415661
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1996
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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