Reflection and scattering by water-saturated sediments

Abstract : Sound reflection from water-saturated sand with flattened surface was studied in controlled laboratory conditions in a very wide frequency range [200 kHz-7MHz]. In the “low frequency” domain and for medium sand, the reflected level has been shown to be in good agreement with both measurements and classical theories of reflection for fluid-porous media. This level is known to be practically independent from frequency; however, when the frequency increases, it has been observed a strong decrease of this level, which can be due to incoherent scattering. In the very high frequency regime (> 3MHz), this measured level is more than 20 dB below the classical level and remains constant at higher frequencies. Same experiments were carried out with coarse sand in order to study the influence of grain size on the reflection loss. It was mainly observed a translation with frequency of the observed phenomena. These effects have been confirmed by repeating the experiments with glass beads of different sizes. The anomalies observed for the reflected level seem to be directly connected to the ratio between grain size and wavelength. These strong scattering effects were also confirmed by backscattering measurements at shallow grazing angles. One of the main conclusions of this work is that the effect of the granular structure of the sea bottom cannot be neglected when the wavelength becomes comparable to the size of the sand particles
Type de document :
Communication dans un congrès
Diffraction Days 08, Jun 2008, St Petersbourg, Russia
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https://hal.archives-ouvertes.fr/hal-00455802
Contributeur : Jean-Pierre Sessarego <>
Soumis le : jeudi 11 février 2010 - 11:36:37
Dernière modification le : lundi 29 janvier 2018 - 16:06:02

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  • HAL Id : hal-00455802, version 1

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Jean-Pierre Sessarego, Régine Guillermin, Anatoly Ivakin. Reflection and scattering by water-saturated sediments. Diffraction Days 08, Jun 2008, St Petersbourg, Russia. 〈hal-00455802〉

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