Low-frequency bottom backscattering data analysis using multiple constraints beamforming

Li, Dan

doi:10.1575/1912/5606

Cited by 2 publications

(8 citation statements)

References 33 publications

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“…The ineffectiveness of the conventional beamformer had been confirmed by simulations [10]. To overcome this, a multipleconstraints beamformer was developed [10] and its beampattern for the same setup as in the above conventional single-constraint beamformer is shown in Fig. 6-7.…”

Section: Data Processingmentioning

confidence: 96%

“…Therefore, there was a great possibility that the above shown sidelobe levels in the normal and near normal incidence directions were not low enough to reject those unwanted returns. The ineffectiveness of the conventional beamformer had been confirmed by simulations [10]. To overcome this, a multipleconstraints beamformer was developed [10] and its beampattern for the same setup as in the above conventional single-constraint beamformer is shown in Fig.…”

Section: Data Processingmentioning

confidence: 97%

“…Simulations in Ref. [10] saw much more favorable results compared to those with conventional single-constraint beamforming.…”

Section: Data Processingmentioning

confidence: 97%

“…The model is expected to interpret the phenomena which have been observed in the ARSRP site A sediment scattering experiment [9,10].…”

Section: Objective and Approachmentioning

confidence: 98%

“…The actual array shape is estimated by using the direct and bottom reflected arrival times on each hydrophone. The details of the array element localization method was given in [10]. …”

Section: Experiments Descriptionmentioning

confidence: 99%

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Modeling of monostatic bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data

Li¹

1997

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Acoustic propagation in the ocean inevitably encounters inhomogeneities of various types, which give rise to scattering. Acoustic scattering from rough water /bottom interfaces comprised of exposed rocks and sea mountains gives way to volumetric scattering in areas with fiat interfaces and thick sediment cover. The data analysis of the ARSRP backscattering experiment revealed that random inhomogeneities in two irregular layers beneath the seafloor were the primary contributors to oblique backscattering in a sediment pond on the western flank of the Mid-Atlantic Ridge. In this thesis, an attempt has been made to model monostatic backscattering from 3-D volume inhomogeneities in the sediment and to compare the results with the ARSRP backscattering data.A scattering process cannot be modeled correctly without a proper account of the incident field . Several approximate propagation models have been evaluated against the exact solution, while the appropriateness of using the equivalent surface scattering strength in volume scattering characterizations is studied. This study concludes that precautions need to be taken in modeling both the propagation effects and the scattering mechanisms associated with the bottom volume scattering process.A volume scattering model based on perturbation theory and the Born approximation is developed incorporating contributions from both sound speed and density fluctuations. With the propagation part handled accurately by OASES and random fluctuations generated effectively by a new scheme modified from the spectral method, the model is capable of simulating the monostatic backscattered field and time series due to 3-D volumetric sediment inhomogeneities. Both the characteristic length scale and power spectrum descriptions of the random inhomogeneities are shown to have great impact on the backscattered field by parameter studies in a free-space scenario. The important roles played by horizontal anisotropy and the vertical correlation of the random field have been demonstrated. Density fluctuations are further confirmed to be the dominant force in backscattering. The model matches the ARSRP backscattering data very well , with the fluctuations of sound speed and density in the two irregular layers described by a power law type of power spectrum. To my fellow-students in 5-007 and 5-435, thank you for t he wonderful atmosphere that you have created and t he team-work spirit t hat I have enjoyed. Believe me, you are t he best.Life would not have been so fun without all my friends. Qing, Henry, and Chenyang, how about playing some Tetris the next t ime we get together? And t hank you for introducing me t o the "real world" . Wenjie and Co. , guess no card game is scheduled for now. Thank you, Elaine, for many "Sloanish" advice, Lia ng-wu, for the ride to chase t he sunset, Richard , for the parties, and Feng, for making me a part-time Ashdowner. Helen, Lan and Xiaoou, I will surely not forget t he summer at Cape Cod.My most grateful thanks goes to my parents and my sister. You are ...

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Section: Data Processingmentioning

confidence: 96%

Section: Data Processingmentioning

confidence: 97%

“…Simulations in Ref. [10] saw much more favorable results compared to those with conventional single-constraint beamforming.…”

Section: Data Processingmentioning

confidence: 97%

“…The model is expected to interpret the phenomena which have been observed in the ARSRP site A sediment scattering experiment [9,10].…”

Section: Objective and Approachmentioning

confidence: 98%

“…The actual array shape is estimated by using the direct and bottom reflected arrival times on each hydrophone. The details of the array element localization method was given in [10]. …”

Section: Experiments Descriptionmentioning

confidence: 99%

See 3 more Smart Citations

Modeling of monostatic bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data

Li¹

1997

Self Cite

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Modeling of bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data

Frisk

Tang

2001

The Journal of the Acoustical Society of America

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In this paper, backscattering from 3D volume inhomogeneities in the seabed is modeled and the results compared with experimental data at 250-650 Hz. The experiment was part of the Acoustic Reverberation Special Research Program (ARSRP) and the data were obtained in a sediment pond on the western flank of the Mid-Atlantic Ridge. A volume scattering model based on first-order perturbation theory is developed incorporating contributions from both sound speed and density fluctuations. With the propagators, i.e., the Green's functions, handled accurately through numerical wave number integration and random fluctuations generated effectively by a new scheme modified from the spectral method, the model is capable of simulating monostatic, backscattered fields in the frequency domain as well as in the time domain owing to 3D volumetric sediment inhomogeneities. The model compares favorably and consistently with the ARSRP backscattering data over the entire frequency band, with the fluctuations of sound speed and density in two irregular sediment layers, identified from the data analysis, described by a power-law type of power spectrum.

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Low-frequency bottom backscattering data analysis using multiple constraints beamforming

Cited by 2 publications

References 33 publications

Modeling of monostatic bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data

Modeling of monostatic bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data

Modeling of bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data

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