2023_programme: Studying reflections and backscattering from gas-saturated sediments using a phased hydrophone array
- Session: 06. Marine sediment acoustics
Organiser(s): Megan Ballard, Kevin Lee and Nick Chotiros
- Lecture: Studying reflections and backscattering from gas-saturated sediments using a phased hydrophone array
Paper ID: 1999
Author(s): Uzhansky Ernst, Katsnelson Boris, Katsman Regina, Lunkov Andrey, Ivakin Anatoliy
Presenter: Uzhansky Ernst
Abstract: Gas-rich sediments have long been of high interest due to their contribution to sediment destabilization and global warming and due to the unusual nature of the propagation, reflection, and backscattering of sound from such sediments. Although volume scattering and reflection coefficient resonances on individual bubbles and the half-wavelength layer significantly complicate the analysis of the recorded field, this information can be used to estimate such bottom parameters as sound speed, gas layer thickness, gas content, and characteristic bubble size. In this work, sound propagation in deep fresh Lake Kinneret is investigated. The lake bottom consists of a thin (1 m) layer with high (up to ~1%) gas content, lying on top of a gas-free silty-clay bottom, which can be represented as a half-space. The experiment was carried out in January 2023, when water in the lake is completely mixed and the temperature profile is uniform. A broadband sound source attached to a phased array of 10 hydrophones with 20 cm spacing was used. The array was used in both horizontal and vertical modes. Both simple tonal short signals (with a waveform length of less than the lake depth) and chirp signals of various duration were emitted. The recorded signals experience multiple boundary reflections due to highly reflective gas-saturated sediments. Spectrograms of specular reflections and backscattering from the bottom are studied. The results of the experiment are discussed.
- Corresponding author: Dr Ernst Uzhansky
Affiliation: Dynamics Laboratory, Faculty of Mechanical Engineering, Technion – Israel Institute of Technology
Country: Israel
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