Modelling of High-Frequency Roughness Scattering from Various Rough Surfaces through the Small Slope Approximation of First Order
- 1 Passive Acoustics, Superior National School of Advanced Techniques of Brittany, Brest, France
- 2 GIPSA-LAB, SIGMAPHY, French National Centre for Scientific Research, Grenoble, France
- 3 The Naval Hydrographic and Oceanographic Service, Brest, France
- 4 Passive Acoustics, Superior National School of Advanced Techniques of Brittany, Brest, France
Abstract
The first-order small slope approximation is applied to model the scattering strength from a rough surface in underwater acoustics to account for seafloor for high frequencies from 10 kHz to hundreds of kilohertz. Emphasis is placed on simulating the response from two-dimensional anisotropic rough surfaces. Several rough surfaces are described based on structure functions such as the particular sandy ripples shape. The scattering strength is predicted by the small slope approximation and is first compared to a well known bistatic method, interpolating the Kirchhoff approximation and the small perturbations model, assuming that the rough interface is isotropic. Results obtained from the two different models are similar and show a higher level in the specular direction than in the other directions. For an isotropic surface, changing the propagation plane gives similar results. Then, SSA, which lets us adapt the structure function of the roughness straight away, is tested trough several anisotropic surfaces. In a longitudinal direction of ripples, the scattering strength is mostly in the specular direction, whereas in the transversal direction of ripples, the scattering strength prediction shows high values for different angular directions. Thus the scattering strength is spread in a very different way strictly related to the particular features of the ripples. Combine our results, indicates the importance of taking into account the anisotropy of a surface in a scattering prediction process, taking into account the positions of the emitter and of the receiver which are naturally significant when predicting scattering strength.
- J. T. Anderson, D. Van Holliday, R. Kloser, D. G. Reid and Y. Simard, “Acoustic Seabed Classification: Current Practice and Future Directions,” ICES Journal of Marine Science, Vol. 65, No. 6, 2008, pp. 1004-1011. doi:10.1093/icesjms/fsn061
- A. J. Kenny, I. Cato, M. Desprez, G. Fader, R. T. E. Schüttenhelm and J. Side, “An Overview of Seabed-Mapping Technologies in the Context of Marine Habitat Classification,” ICES Journal of Marine Science, Vol. 60, No. 2, 2003, pp. 411-418. doi:10.1016/S1054-3139(03)00006-7
- K. Siemes, M. Snellen, D. G. Simons, J.-P. Hermand, M. Meyer and J.-C. Le Gac, “High Frequency Multibeam Echosounder Classification for Rapid Assessment,” Acoustics’08, Paris, 29 June-4 July 2008, pp. 4259-4264.
- L. Hellequin, J.-M. Boucher and X. Lurton, “Processing of High-Frequency Multibeam Echo Sounder Data for Seafloor Characterization,” IEEE Journal of Oceanic Engineering, Vol. 28, No. 1, 2003, pp. 78-89. doi:10.1109/JOE.2002.808205
- C. Eckart, “The Scattering of Sound from the Sea Surface,” Journal of the Acoustical Society of America, Vol. 25, No. 3, 1953, pp. 566-570. doi:10.1121/1.1907123
- E. I. Thorsos, “The Validity of Kirchhoff Approximation for Rough Surface Scattering Using a Gaussian Roughness Spectrum,” Journal of the Acoustical Society of America, Vol. 83, No. 1, 1988, pp. 78-92. doi:10.1121/1.396188
- F. G. Bass and I. M. Fuks, “Wave Scattering from Statistically Rough Surfaces,” Pergamon Press, New York, 1979.
- E. I. Thorsos and D. R. Jackson, “The Validity of Perturbation Approximation for Rough Surface Scattering Using a Gaussian Roughness Spectrum,” Journal of the Acoustical Society of America, Vol. 86, No. 1, 1989, pp. 261-277. doi:10.1121/1.398342
- D. R. Jackson, D. P. Winebrenner and A. Ishimaru, “Application of the Composite Roughness Model to High-Frequency Bottom Backscattering,” Journal of the Acoustical Society of America, Vol. 79, No. 5, 1986, pp. 1410-1422. doi:10.1121/1.393669
- D. R. Jackson, “APL-UW High-Frequency Ocean Environmental Acoustic Model Handbook,” Technical Report, Seattle, 1994.
- K. W. Williams and D. R. Jackson, “Bistatic Bottom Scattering: Model, Experiments, and Model/Data Comparison,” Journal of the Acoustical Society of America, Vol. 103, No. 1, 1998, pp. 169-181. doi:10.1121/1.421109
- D. R. Jackson and M. D. Richardson, “High Frequency Seafloor Acoustics,” The Underwater Acoustics Series, Springer, New York, 2007.