A Sensitivity Study for Full-Field Inversion of Geo-Acoustic Data with a Towed Array in Shallow Water

Jesus, S. M.

doi:10.1007/978-94-015-8476-0_18

Cited by 6 publications

(3 citation statements)

References 8 publications

(8 reference statements)

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“…Changing source receiver range has a similar behaviour depending on the modal interference pattern versus range. In both cases placing the source and the array at high energy transfer locations improves sensitivity [19].…”

Section: Iii1 Parameter Sensitivity Studymentioning

confidence: 99%

Estimating Geoacoustic Bottom Properties From Towed Array Data

Jesus

Caiti

1996

J. Comp. Acous.

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Estimating the seabottom geophysical structure from the analysis of acoustic returns of an explosive source (air-gun, sparker,…) has been used for a longtime as a routine survey technique. Recent work showed the possibility of using well-suited numerical models to invert the acoustic field for estimating detailed geoacoustic sediment properties. Common implementations used long synthetic aperture arrays (up to 2 km and more) in order to resolve potential environmental ambiguities of the acoustic field. Others, used vertical arrays of sensors covering a significant part of the water column to identify the channel normal mode structure and thus gather information for the bottom physical relevant properties. This paper investigates, with simulated data, the concept of using a moderate aperture physical line array and a sound source simultaneously towed by a single ship for inverting the bottom geoacoustic structure from the acoustic returns received on the array. First, bottom parameter estimators are derived and their system sensitivity is investigated. In particular, it is shown that such a system may be used to sense compressional and shear velocities on the bottom first layers. Density and attenuations (both compressional and shear) have in general small influence on the acoustic field structure and are therefore difficult to estimate. Increasing the signal frequency bandwidth by incoherent module averaging has no significant influence on sensitivity. Mismatch cases, mainly those related to array/source relative position, showed that deviations of more than λ/3 in range and λ/5 in depth may give erroneous extremum location and therefore biased final estimates. Second, two bottom parameter estimators are compared and their performance tested on a typical shallow water environment. In order to solve the underlying multiparameter inverse problem, global search optimization is used. In particular, it is shown that the use of an adaptive genetic algorithm may, in conjunction with a well-suited maximum likelihood based parameter estimator, rapidly converge to the surface extremum. Inversion results are in agreement with the predictions obtained from the sensitivity study. The mean relative error at 10 dB signal-to-noise ratio is within 1% for the compressional velocity, while greater errors are reported for the shear velocity, Comparison with recent results obtained with a radial basis functions (RBF) inversion strategy showed similar performance. Finally, results obtained with a 156 m aperture towed array showed a good agreement between the inverted compressional velocities and the ground truth measurements.

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Section: Iii1 Parameter Sensitivity Studymentioning

confidence: 99%

Estimating Geoacoustic Bottom Properties From Towed Array Data

Jesus

Caiti

1996

J. Comp. Acous.

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“…Today, study of the sea bottom includes the attempts of combining the results of full-scale acoustic measurements with geological and geophysical data, for the purpose of the identification of bottom regions 1 and the development of systems for the determination of the morphological structure of the sea bottom. 2 An important area of investigation is the development of new computational techniques for both the determination of the reflection coefficients at an elastic bottom [3][4][5] and the correct description of the effect of a layered elastic bottom on underwater sound propagation. [6][7][8] Detailed study of the effect of a layered bottom structure on the frequency characteristics of phase velocities, attenuation coefficients, and distribution of the amplitudes of normal modes in depth in a shallow sea were performed by Ageeva and Krupin.…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of Layered Elastic Bottom Characteristics by the Frequency Dependence of Sound Reflectivity

Fokin

Fokina

2001

J. Comp. Acous.

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The relation between the sound reflection losses measured at fixed grazing angles and the characteristics of the sediment layer and underlying half-space is considered. Based on this relation, a method of the reconstruction of the sea bottom characteristics is developed for a ocean bottom consisting of a single sediment layer overlaying a semi-infinite elastic half-space. Using this bottom model, the reconstruction of the characteristics of a layered elastic bottom is performed from the numerically simulated data with induced synthetic error.

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“…Examples can be found elsewhere. 16,18,31 In the examples of Sec. II it will be shown how the accuracy of the estimate is affected by the influence of the various parameters on the acoustic field.…”

Section: Selection Of the Geoacoustic Parametersmentioning

confidence: 99%

Acoustic estimation of seafloor parameters: A radial basis functions approach

Caiti

Jesus

1996

The Journal of the Acoustical Society of America

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A novel approach to the estimation of seafloor geoacoustic parameters from the measurement of the acoustic field in the water column is introduced. The approach is based on the idea of approximating the inverse function that links the geoacoustic parameters with the measured field through a series expansion of radial basis functions. In particular, Gaussian basis functions are used in order to ensure continuity and smoothness of the approximated inverse. The main advantage of the proposed approach relies on the fact that the series expansion can be computed off-line from simulated data as soon as the experimental configuration is known. Data inversion can then be performed in true real time as soon as the data are acquired. Simulation results are presented in order to show the advantages and limitations of the method. Finally, some inversion results from horizontal towed array data are reported, and are compared with independent estimates of geoacoustic bottom properties.

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A Sensitivity Study for Full-Field Inversion of Geo-Acoustic Data with a Towed Array in Shallow Water

Cited by 6 publications

References 8 publications

Estimating Geoacoustic Bottom Properties From Towed Array Data

Estimating Geoacoustic Bottom Properties From Towed Array Data

Reconstruction of Layered Elastic Bottom Characteristics by the Frequency Dependence of Sound Reflectivity

Acoustic estimation of seafloor parameters: A radial basis functions approach

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