Abstract:
Some regions of the ocean consist of bottom layers, which have imbedded
bubbles. The bubbles may consist of methane gas. The consequence is that the
particular layer has a sound speed, which is lower than in the overlying layer.
Depending on the wavelength of the sound source relative to the layer thickness,
sound may either reflect off the layer, or it may partially tunnel through the
layer to the next set of layers. This effect is frequency dependent, and at some
point, when the wavelength in the layer is small relative to the layer
thickness, no sound will traverse the layer. The effect of this is that the
modal eigenspectrum will be altered and will be largely characterized by the
gaseous layer structure in horizontal and vertical directions. The influence of
range-dependent gaseous regions on modal spectrum and measured signal structure
in different underwater waveguides, which can be considered as strongly range
dependent for spatially localized gaseous regions, is modeled by the normal mode
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