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On the acoustic diffraction by the edges of benthic shells
Timothy K Stanton1, Dezhang Chu
1Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543-1053, USA. tstanton@whoi.edu
The Journal of the Acoustical Society of America
|August 7, 2004
Summary
Acoustic backscattering from benthic shells is strongest near broadside incidence due to the shell surface. Away from broadside, shell edge diffraction significantly contributes to lower echo levels, impacting seafloor acoustic models.
Area of Science:
- Acoustics
- Marine Geophysics
- Geological Oceanography
Background:
- Acoustic backscattering from the seafloor is crucial for geological surveys.
- Benthic shell contributions to seafloor acoustics are not fully understood.
- Previous studies often model shells as simple surfaces, neglecting edge effects.
Purpose of the Study:
- To differentiate acoustic echoes from shell surfaces versus shell edges.
- To quantify the contribution of shell edge diffraction to backscattering.
- To assess the impact of shell edge scattering on seafloor acoustic models.
Main Methods:
- Laboratory measurements of acoustic backscattering from individual benthic shells.
- Isolation of edge-diffracted echoes from surface-related echoes.
- Analysis of backscattering intensity across various incidence angles.
Main Results:
- Acoustic echoes are strongest near broadside incidence, primarily from the shell surface.
- At off-broadside angles, echo levels decrease and are dominated by shell edge diffraction.
- Observed decreases in echo levels align with seafloor backscattering patterns.
Conclusions:
- Shell edge diffraction is a significant factor in off-normal acoustic backscattering from shell-covered seafloors.
- Edge scattering can influence acoustic signals in multiple directions, including at subcritical angles.
- Accurate seafloor acoustic modeling requires incorporating shell edge diffraction effects.