2019_programme: SEMI-ANALYTIC MODELING OF SOUND PROPAGATION AND NOISE CROSS-CORRELATIONS IN A COASTAL OCEAN

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  • Session: 17. Modeling techniques for underwater acoustic scattering and propagation
    Organiser(s): Gunderson Aaron, Isakson Marcia
  • Lecture: SEMI-ANALYTIC MODELING OF SOUND PROPAGATION AND NOISE CROSS-CORRELATIONS IN A COASTAL OCEAN [invited]
    Paper ID: 974
    Author(s): Godin Oleg A.
    Presenter: Godin Oleg A.
    Presentation type: oral
    Abstract: Sound propagation in the coastal ocean over ranges large compared to water depth involves multiple interactions with the ocean surface and bottom. Bathymetric variations and time-dependence of the ocean surface lead to 3-D (such as horizontal refraction) and 4-D (arising from an evolution of the environmental parameters with time) effects being more pronounced in the coastal ocean than in typical deep-water settings. Understanding and modeling sound propagation in horizontally inhomogeneous ocean with time-dependent parameters remains a challenging problem. In this paper, we investigate 3-D and 4-D propagation effects from the prospective of acoustic remote sensing. Analytical techniques are employed to quantify the effects of horizontal refraction on amplitudes and travel times of adiabatic normal modes. Depending on orientation of the propagation path relative to the prevailing seafloor slope, different patterns emerge of the systematic deviation of apparent dispersion curves of adiabatic modes from the dispersion curves in the range-independent waveguide. It is found that, when mode travel times are used as input information for geoacoustic inversions, moderate bottom slopes can lead to large errors in retrieved geoacoustic parameters and cause a positive bias in the bottom sound speed estimates if the horizontal refraction is ignored. In passive acoustic remote sensing, two-point noise cross-correlation functions replace acoustic fields due to a compact controlled sound source as the probing signals which interrogate the environment. Noise averaging times that are necessary to measure two-point cross-correlation functions are much larger than the acoustic propagation times between the two points. As a result, 4-D effects prove to be much stronger in the passive than active remote sensing regime. It will be shown how wind waves and tides limit the usable frequency band of passive acoustic remote sensing in the coastal ocean.
      Download the full paper
  • Corresponding author: Prof Godin Oleg A.
    Affiliation: Physics Dept., Naval Postgraduate School
    Country: United States
    e-mail:

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