Acoustic propagation in gassy intertidal marine sediments: An experimental study

Leighton, Timothy G.; Dogan, Hakan; Fox, Paul; Mantouka, Agni; Best, Angus ORCID: https://orcid.org/0000-0001-9558-4261; Robb, Gary B. R.; White, Paul R.. 2021 Acoustic propagation in gassy intertidal marine sediments: An experimental study. The Journal of the Acoustical Society of America, 150 (4). 2705-2716. https://doi.org/10.1121/10.0006530

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Official URL: http://dx.doi.org/10.1121/10.0006530

Abstract/Summary

The need to predict acoustic propagation through marine sediments that contain gas bubbles has become increasingly important for civil engineering and climate studies. There are relatively few in situ acoustic wave propagation studies of muddy intertidal sediments, in which bubbles of biogenic gas (generally methane, a potent greenhouse gas) are commonly found. We used a single experimental rig to conduct two in situ intertidal acoustical experiments to improve understanding of acoustic remote sensing of gassy sediments, eventually including gas bubble size distributions. In the first experiment, we measured sediment sound speed and attenuation between four aligned hydrophones for a quasi-plane wave propagating along the array. The second experiment involved a focused insonified sediment volume created by two transducers emitting coincident sound beams at different frequencies that generated bubble-mediated acoustic signals at combination frequencies. The results from sediment core analyses, and comparison of in situ acoustic velocity and attenuation values with those of water-saturated sediments, together provide ample evidence for the presence of in situ gas bubbles in the insonified volumes of sediments. These datasets are suitable for linear and non-linear inversion studies that estimate in situ greenhouse gas bubble populations, needed for future acoustical remote sensing applications.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1121/10.0006530
Programmes:	NOC Programmes > Ocean BioGeosciences
ISSN:	0001-4966
Date made live:	07 Apr 2022 22:53 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/532387

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1121/10.0006530

Programmes:

NOC Programmes > Ocean BioGeosciences

ISSN:

0001-4966

Date made live:

07 Apr 2022 22:53 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/532387