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Monday, July 8 • 16:50 - 17:10
APPLICATION OF TIME-WARPING TRANSFORM FOR SEPARATION OF ACOUSTIC NORMAL MODES IN HORIZONTALLY INHOMOGENEOUS WAVEGUIDES

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Time-warping transform is often used in underwater acoustics to separate normal mode components of a broadband signal recorded by a single hydrophone. An important application of time warping is retrieval of modal dispersion curves for subsequent inversion of the measured mode dispersion for unknown geoacoustic parameters. The time-warping transform was developed for range-independent shallow-water waveguides. Physical parameters of the ocean are never quite constant in the horizontal plane, with bathymetry variations being typically responsible for the bulk of the waveguide's range dependence as well as horizontal refraction of sound in the coastal ocean. We use simple, exactly solvable models of shallow-water waveguides to illustrate the effects that the range dependence and horizontal refraction have on the performance of the warping transform and the inferred geoacoustic parameters. Horizontal refraction due to generic bathymetric variations is addressed in the adiabatic approximation using perturbation techniques. Theoretical predictions are verified using numerical simulations. It is found that moderate bottom slopes can lead to large errors in retrieved geoacoustic parameters and cause positive bias in bottom sound speed estimates if horizontal refraction is ignored.

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avatar for VENUGOPALAN PALLAYIL

VENUGOPALAN PALLAYIL

DEPUTY HEAD/SENIOR RESEARCH FELLOW, ACOUSTIC RESEARCH LAB, NATIONAL UNIVERSITY OF SINGAPORE
A senior researcher with 30 years of experience in underwater acoustics research. Senior member of IEEE, Member of IIAV, ASA and Society of Acoustics Singapore. IEEE OES AdCom and JOAB member, General Chair for OCEANS 2020 Singapore and co-Chair for ICSV 28 Singapore. See my technical... Read More →

Authors

Monday July 8, 2019 16:50 - 17:10 EDT
Westmount 5
  T12 Underwater & marit. noise, RS01 Underwater sound