Application of time-warping transform for separation of acoustic normal modes in horizontally inhomogeneous waveguides

Oleg A. Godin, Tsu Wei Tan, Boris G. Katsnelson

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

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

Original languageEnglish
Title of host publicationProceedings of the 26th International Congress on Sound and Vibration, ICSV 2019
PublisherCanadian Acoustical Association
ISBN (Electronic)9781999181000
StatePublished - 2018
Event26th International Congress on Sound and Vibration, ICSV 2019 - Montreal, Canada
Duration: 7 Jul 201911 Jul 2019

Publication series

NameProceedings of the 26th International Congress on Sound and Vibration, ICSV 2019

Conference

Conference26th International Congress on Sound and Vibration, ICSV 2019
Country/TerritoryCanada
CityMontreal
Period7/07/1911/07/19

Bibliographical note

Funding Information:
of the acoustic normal modes supported by the waveguide. Here cn is the phase speed of n-th normal mode, n = 1, 2, … .

Publisher Copyright:
© Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.

Keywords

  • Shallow-water waveguides
  • Underwater acoustics

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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