Contemporary high-resolution sonar systems use broadband pulses and long arrays to achieve high resolution. It is important to understand effects that high-resolution sonar systems might have on quantitative measures of the scattered field due to the seafloor. A quantity called the broadband scattering cross section is defined, appropriate for high-resolution measurements. The dependence of the broadband scattering cross section, σbb, and the scintillation index, SI, on resolution was investigated for one-dimensional rough surfaces with power-law spectra and backscattering geometries. Using integral equations and Fourier synthesis, no resolution dependence of σbb was found. The incoherently averaged frequency-domain scattering cross section has negligible bandwidth dependence. SI increases as resolution increases, grazing angle decreases, and spectral strength increases. This trend is confirmed for center frequencies of 100 and 10 kHz, as well as for power-law spectral exponents of 1.5, 2, and 2.5. The hypothesis that local tilting at the scale of the acoustic resolution is responsible for intensity fluctuations was examined using a representative model for the effect of slopes (inspired by the composite roughness approximation). It was found that slopes are responsible in part for the fluctuations, but other effects, such as multiple scattering and shadowing may also play a role.
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January 2021
January 05 2021
Resolution dependence of rough surface scattering using a power law roughness spectrum
Derek R. Olson
;
Derek R. Olson
a)
1
Oceanography Department, Naval Postgraduate School
, Monterey, California 93943, USA
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Anthony P. Lyons
Anthony P. Lyons
2
University of New Hampshire
, Durham, New Hampshire 03824, USA
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a)
Electronic mail: dolson@nps.edu, ORCID: 0000-0002-7928-0468.
J Acoust Soc Am 149, 28–48 (2021)
Article history
Received:
September 24 2019
Accepted:
December 07 2020
Citation
Derek R. Olson, Anthony P. Lyons; Resolution dependence of rough surface scattering using a power law roughness spectrum. J Acoust Soc Am 1 January 2021; 149 (1): 28–48. https://doi.org/10.1121/10.0002974
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