Correcting the Kirchhoff rough boundary. Interaction model for scattering (original) (raw)

Sound scattering from a randomly rough fluid-solid interface

The Journal of the Acoustical Society of America, 1987

DDD12. High-resolution acoustic bottom roughness measurement in support of bottom echo interaction modeling. W. P. Dammann and C. A. Lauter (Ocean Acoustics Division, NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149) A high-resolution acoustic bottom profiler using an extremely narrow-beam, 3-MHz echo sounder was developed at the Ocean Acoustic Division of NOAA/AOML. The device was used to measure bottom roughness over a range of scales from less than 1 cm to several meters. Roughness measurements were made in the lower Chesapeake Bay area over mud, fine to medium grain sand, and course grain sand. The data produced were used to appraise the performance of an acoustic echo formation model that predicts the effects of marine bottom characteristics on a reflected acoustic pulse envelope. Major aspects of the design and use of the system, procedures for processing generated data, and examples of processed output are presented. 2:23 DDD13. Characterization of seafloor type and roughness from 12-kHz acoustic backscattering measurements.

Measurements and modelling of high-frequency acoustic scattering by a rough seafloor and sea surface

Acoustic scattering by a rough, possibly dynamic interface is experimentally studied by insonifying the seabed and the sea surface at high frequency at various incident angles. A directional source working at 300 kHz was placed at the top of a 3.5 m high tower deployed on the seabed. A vertical array of 3 omnidirectional hydrophones was suspended from a portable frame, which was deployed in bistatic configuration at a variable range between 30 and 70 m. A selection of the results is presented to evaluate the sea surface and seabed scattering amplitude in the nominal specular reflection direction. Scattering by the sea surface was measured during relatively long periods of time in order to correlate its value with the sea state. Model-data comparison was conducted between the scattering data and a time-domain, three-dimensional rough surface scattering model (BORIS-SSA). Model- based analysis allows for a better understanding of some aspects of high-frequency multipath reverberation ...

The Effects of Seafloor Roughness on Acoustic Scattering: Manipulative Experiments

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The Dependence of Long-Range Reverberation on Bottom Roughness

2004

At long-range, shallow-water reverberation can be driven by sub-critical-angle scattering, i.e. by rough interrace scattering. The Naval Research Laboratory has recently developed a small-slope model for elastic seafloors that provides physics-based estimates of the dependence of scattering on the incident and scattered angles, and physical descriptors of the environment. In this paper, this incoherent model is used as kernels in reverberation models, which in turn are used to assess the sensitivity at 3.5 kHz of long-range monostatic reverberation to the roughness of the water-sediment interface. It is shown that when sub-critical-angle scattering dominates, the acoustic field could be quite sensitive to the parameter values of the roughness, thus arguing for the need for regional in-situ methods for its estimation.

Effects of Changing Roughness on Acoustic Scattering: (1) Natural Changes

1999

High resolution (~0.1-1 cm) measurements of seafloor roughness with underwater stereo photogrammetry were performed during the shallow-water SAX99 acoustic experiment. Changes in morphology due to hydrodynamic and biological processes were observed, and documented by changes in the values of measured slope and spectral strength of the seafloor roughness power spectrum. Roughness spectral and geoacoustic parameters were used in the first-order

High-frequency bottom backscattering: Roughness versus sediment volume scattering

The Journal of the Acoustical Society of America, 1992

High-frequency bottom acoustic and geoacoustic data from three well-characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy. PACS numbers: 43.30. Hw, 43.30. Gv, 43.20.Fn I. EXPERIMENTAL METHODS Geoacoustic and backscattering data were obtained at three separate shallow-water sites. The "Quinault" site ( 17 km west of the coast of the State of Washington, 47ø34'N, 124ø35'W) has a fine-sand bottom with pronounced directional ripples. The Arafura Sea site (255 km north-northwest of Cape Arnhem, Australia, 10ø0 I'S, 137ø50'E) has a relatively smooth bottom composed of a silt-clay mixture with numerous buried shell fragments. The "San Francisco" site (180 km northwest of San Francisco, 38ø39'N, 123ø29'W) has a silty bottom of moderate roughness. The San Francisco data were gathered as part of the STRESS ( Sediment TRansport Events on Shelves and Slopes) experiment. The site considered in the present work is known as the STRESS "mid-shelf' site. A. Geoacoustic measurements The Quinault, Arafura Sea, and San Francisco experiment sites were surveyed by means of box coring and stereophotography and found to be relatively uniform within a 1km 2 area surrounding the acoustic measurement locations. Subsamples from box cores were collected as described by Briggs et al. (1985) with 6.1-cm-diam cylindrical cores for 962 J. Acoust. Soc. Am. 92 (2), Pt. 1, August 1992 0001-4966/92/080962-16500.80