Estimation of time and angle variations for perturbations in an acoustic oceanic waveguide - Archive ouverte HAL
Communication Dans Un Congrès Année : 2013

Estimation of time and angle variations for perturbations in an acoustic oceanic waveguide

Anca Cristea
  • Fonction : Auteur
  • PersonId : 980297
Herve Liebgott
Barbara Nicolas

Résumé

Variations of travel-times (TT), directions-of-arrival (DOA) and directions-of-departure (DOD) of acoustic waves are conventional observables used to recover information on local underwater sound speed perturbations. To compute these variations, acoustic waves are propagated between a source array and a receiver array, in both the unperturbed and perturbed states of the medium. The recorded signals undergo a two-step processing: 1) the acoustic-arrival separation and 2) the observable extraction, where precision is essential. We propose contributions for both steps. For the acoustic-arrival separation, we propose a version of the double beamforming (DBF) method, which we have modified by introducing oscillations along the angle dimensions. As suggested by studies done in the field of medical ultrasound imaging, lateral oscillations can be obtained in DBF by using specific aperture apodization functions. It has been shown that this feature facilitates the observable extraction later on. For the observable extraction, we propose two displacement estimators, both working with phase information. The first one is based on the Fourier transform of the signal intercorrelation-function, and can be applied on data processed by either classical DBF or DBF with lateral oscillations. The latter takes benefit of specific lateral-oscillation models which enable to explicit an analytic relationship of the observable variations. These estimators have been tested on simulations with a double-array configuration. Different waves travelling through mediums having homogenous and inhomogeneous sound speed were considered. The robustness against noise has also been evaluated. The results obtained show that the first estimator (based on intercorrelation) provides precise results with both classical DBF and DBF with lateral oscillations, but is sensitive to noise. The second estimator (analytic) is more robust to noise, but can only be used with the DBF with lateral oscillations.
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Dates et versions

hal-00935396 , version 1 (23-01-2014)

Identifiants

  • HAL Id : hal-00935396 , version 1

Citer

Anca Cristea, Florian Aulanier, Herve Liebgott, Barbara Nicolas. Estimation of time and angle variations for perturbations in an acoustic oceanic waveguide. UA 3013 - 1st International Conference and Exhibition on Underwater Acoustics, Jun 2013, Corfou, Greece. pp.n/c. ⟨hal-00935396⟩
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