Acoustic propagation in gassy intertidal marine sediments: An experimental study

Area of Science:

• Marine acoustics
• Geophysics
• Environmental science

Background:

• Accurate prediction of acoustic propagation in marine sediments with gas bubbles is crucial for civil engineering and climate studies.
• In situ studies of acoustic wave propagation in muddy intertidal sediments, often containing biogenic methane gas, are scarce.
• Methane is a potent greenhouse gas, making its detection and quantification important.

Purpose of the Study:

• To enhance understanding of acoustic remote sensing techniques for gassy sediments.
• To investigate acoustic wave propagation in situ within muddy intertidal sediments.
• To lay groundwork for estimating in situ greenhouse gas bubble populations.

Main Methods:

• Conducted two in situ acoustical experiments using a single experimental rig.
• Measured sediment sound speed and attenuation using aligned hydrophones for quasi-plane wave propagation.
• Generated bubble-mediated acoustic signals at combination frequencies using focused sound beams from two transducers.

Main Results:

• Sediment core analyses provided evidence for in situ gas bubbles.
• Comparison of in situ acoustic velocity and attenuation values with water-saturated sediments confirmed gas presence.
• The experimental datasets are suitable for inversion studies to estimate gas bubble populations.

Conclusions:

• The study successfully demonstrated in situ acoustic measurements in gassy intertidal sediments.
• The findings support the development of advanced acoustic remote sensing for quantifying greenhouse gas bubbles.
• This research contributes to better environmental monitoring and climate change studies.