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    The contribution of normal modes in the bottom to the acoustic field in the ocean

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    WHOI 81-21.pdf (7.651Mb)
    Date
    1981-04
    Author
    Macpherson, Mark K.  Concept link
    Frisk, George V.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/10241
    DOI
    10.1575/1912/10241
    Keyword
     Ocean bottom; Acoustic models 
    Abstract
    The effects of normal modes in the bottom on the acoustic field in the ocean are examined. The ocean bottom model consists of a slow isovelocity layer overlying an isovelocity half-space to simulate the characteristic sound velocity drop at the water-bottom interface. Attention is focused on the perfectly trapped modes which are excited in the layer by inhomogeneous waves emitted by a point source in the water column. The relative normal mode contribution to the total acoustic field in the water is calculated analytically for a near-bottom source/receiver geometry and evaluated for representative ocean bottom examples. It is shown that, for combined source/receiver heights less than a wavelength, the field is dominated by the leaky mode contribution at short ranges ( $ 2 km) and the trapped mode contribution at long ranges ( ~ 2 km). For fixed bottom parameters, the trapped mode contribution increases exponentially with decreasing combined source/receiver height. It is also shown that, for a fixed layer wavenumber-thickness product and fixed layer sound speed, the leaky mode fields at different frequencies are approximately range-scaled versions of the same field.
    Description
    Also published as: Journal of the Acoustical Society of America 68 (1980): 602-612
    Collections
    • Applied Ocean Physics and Engineering (AOP&E)
    • WHOI Technical Reports
    Suggested Citation
    Macpherson, M. K., & Frisk, G. V. (1981). The contribution of normal modes in the bottom to the acoustic field in the ocean. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/10241
     

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