During the past decade there has been a renewed interest in active sonar systems at both low and medium frequencies. More recently this interest has been extended to very high frequencies in shallow water. Reverberation often limits the detection performance of these systems, and there is a need to understand the underlying mechanisms that cause the scattering. With more emphasis being given to reverberation phenomena in the Scientific Program of Work at the SACLANT Undersea Research Centre, it was considered an opportune time to host a meeting, bringing together scientists from NATO countries…mehr
During the past decade there has been a renewed interest in active sonar systems at both low and medium frequencies. More recently this interest has been extended to very high frequencies in shallow water. Reverberation often limits the detection performance of these systems, and there is a need to understand the underlying mechanisms that cause the scattering. With more emphasis being given to reverberation phenomena in the Scientific Program of Work at the SACLANT Undersea Research Centre, it was considered an opportune time to host a meeting, bringing together scientists from NATO countries to foster cross-disciplinary dialogue and generate ideas for new research directions. Consequently the Ocean Reverberation Symposium was held 25-29 May 1992 in La Spezia, Italy. Over 60 presentations were made on a diverse selection of topics, of which ten papers will be published as a SACLANTCEN Conference Proceedings. The papers in this volume are grouped into 8 sections, usually in the same order as presented at the corresponding session of the Symposium: Section 1 - Scattering Mechanisms Section 2 - High Frequency Measurements and Mechanisms Section 3 - Reverberation Modelling Section 4 - ARSRP Mid-Atlantic Ridge Experiment Section 5 - Low Frequency Measurements Section 6 - Volume Scattering Section 7 - Signal Processing Issues Section 8 - Applications Taken together the papers show some emerging trends in the research.
Section 1 - Scattering Mechanisms.- Sea surface reverberation (Invited paper).- Properties of bubble distributions relevant to surface reverberation (Invited paper).- Sound scattering from microbubble distributions near the sea surface (Invited paper).- Theoretical modeling of low frequency acoustic scattering from subsurface bubble structures.- Discrete backscatter can be dominant in rough bottom reverberation.- Sea-bottom reverberation: the role of volume inhomogeneities of the sediment.- The perturbation characterization of ocean reverberations.- The reduction of surface backscatter and ambient noise by mono-molecular films on the ocean surface.- Section 2 - High Frequency Measurements and Mechanisms.- Measurements of high frequency reverberation in shallow water.- High frequency acoustic bottom backscatter mechanisms at shallow grazing angles.- Frequency response measurements on backscattering from a shallow sea floor, using a parametric source.- Measurements of acoustic backscattering of the near-surface layer.- Section 3 - Reverberation Modelling.- Numerical modeling of three-dimensional reverberation from bottom facets (Invited paper).- Numerical simulations of lower-frequency acoustic propagation and backscatter from solitary internal waves in a shallow water environment.- Reverberation modeling with the two-way parabolic equation.- Calculations of ocean bottom and sub-bottom backscattering using a time-domain finite-difference code.- Time and angle spreading from rough sediments.- Rough surface scattering as seen through the Renormalization Group.- Long range 3-D reverberation and scattering modeling methodology.- Range-dependent, normal-mode reverberation model for bistatic Geometries.- Measurement, characterization, and modeling of ice and bottombackscattering and reverberation in the Arctic Ocean.- A reverberant-undersea model for bottom-limited environments.- Shallow water reverberation modeling.- Section 4 - ARSRP Mid-Atlantic Ridge Experiment.- An overview of the 1991 Reconnaissance Cruise of the Acoustic Reverberation Special Research Program.- Long-range measurements of seafloor reverberation in the Mid-Atlantic Ridge area.- Ocean-basin scale inversion of reverberation data.- ARSRP reconn results and BISSM modeling of direct path backscatter.- Directional processing of the simulated direct path, broadbandv reverberation data and its interpretation.- Numerical scattering results for a rough, unsedimented seafloor.- The effects of seafloor roughness on reverberation: finite difference and Kirchhoff simulations.- A numerical scattering chamber for studying reverberation in the seafloor.- Section 5 Low Frequency Measurements.- Low-frequency direct-path surface and volume scattering measured using narrowband and broadband pulses.- Low-frequency surface and bottom scattering strengths measured using SUS charges.- Upslope propagation data versus two-way PE.- Section 6 - Volume Scattering.- Low-frequency volume reverberation measurements.- Low-frequency volume scatter and distant reverberation: 200-1500 Hz.- GINRUNS - A 1991 volume scattering and convergence zone experiment in the Norwegian Sea.- Volume reverberation at mid frequencies in the Norwegian Sea.- Volume reverberation in the marginal ice zone of Fram Strait.- Section 7 - Signal Processing Issues.- Analytical description and experimental results for reverberation-resistant acoustic tracking signals.- Broadband adaptive beamformer for linear-frequency-modulation active signals.- Broadband pulse distortion: waveform design issues for activesystems.- Active matched field processing for clutter rejection.- Reverberation suppression and modeling.- Sub-bottom scattering at low frequencies.- Broadband detection and classification of underwater sources.- Section 8 - Applications.- A geometrical approach to medium low frequency reverberation modeling (Invited paper).- The reverberation array heading surface.- Bistatic ocean reverberation effects.- Modeling of wide area ocean reverberation and noise.- Rapid environmental acoustic survey and modeling system.- List of Participants.- Author Index.
Section 1 - Scattering Mechanisms.- Sea surface reverberation (Invited paper).- Properties of bubble distributions relevant to surface reverberation (Invited paper).- Sound scattering from microbubble distributions near the sea surface (Invited paper).- Theoretical modeling of low frequency acoustic scattering from subsurface bubble structures.- Discrete backscatter can be dominant in rough bottom reverberation.- Sea-bottom reverberation: the role of volume inhomogeneities of the sediment.- The perturbation characterization of ocean reverberations.- The reduction of surface backscatter and ambient noise by mono-molecular films on the ocean surface.- Section 2 - High Frequency Measurements and Mechanisms.- Measurements of high frequency reverberation in shallow water.- High frequency acoustic bottom backscatter mechanisms at shallow grazing angles.- Frequency response measurements on backscattering from a shallow sea floor, using a parametric source.- Measurements of acoustic backscattering of the near-surface layer.- Section 3 - Reverberation Modelling.- Numerical modeling of three-dimensional reverberation from bottom facets (Invited paper).- Numerical simulations of lower-frequency acoustic propagation and backscatter from solitary internal waves in a shallow water environment.- Reverberation modeling with the two-way parabolic equation.- Calculations of ocean bottom and sub-bottom backscattering using a time-domain finite-difference code.- Time and angle spreading from rough sediments.- Rough surface scattering as seen through the Renormalization Group.- Long range 3-D reverberation and scattering modeling methodology.- Range-dependent, normal-mode reverberation model for bistatic Geometries.- Measurement, characterization, and modeling of ice and bottombackscattering and reverberation in the Arctic Ocean.- A reverberant-undersea model for bottom-limited environments.- Shallow water reverberation modeling.- Section 4 - ARSRP Mid-Atlantic Ridge Experiment.- An overview of the 1991 Reconnaissance Cruise of the Acoustic Reverberation Special Research Program.- Long-range measurements of seafloor reverberation in the Mid-Atlantic Ridge area.- Ocean-basin scale inversion of reverberation data.- ARSRP reconn results and BISSM modeling of direct path backscatter.- Directional processing of the simulated direct path, broadbandv reverberation data and its interpretation.- Numerical scattering results for a rough, unsedimented seafloor.- The effects of seafloor roughness on reverberation: finite difference and Kirchhoff simulations.- A numerical scattering chamber for studying reverberation in the seafloor.- Section 5 Low Frequency Measurements.- Low-frequency direct-path surface and volume scattering measured using narrowband and broadband pulses.- Low-frequency surface and bottom scattering strengths measured using SUS charges.- Upslope propagation data versus two-way PE.- Section 6 - Volume Scattering.- Low-frequency volume reverberation measurements.- Low-frequency volume scatter and distant reverberation: 200-1500 Hz.- GINRUNS - A 1991 volume scattering and convergence zone experiment in the Norwegian Sea.- Volume reverberation at mid frequencies in the Norwegian Sea.- Volume reverberation in the marginal ice zone of Fram Strait.- Section 7 - Signal Processing Issues.- Analytical description and experimental results for reverberation-resistant acoustic tracking signals.- Broadband adaptive beamformer for linear-frequency-modulation active signals.- Broadband pulse distortion: waveform design issues for activesystems.- Active matched field processing for clutter rejection.- Reverberation suppression and modeling.- Sub-bottom scattering at low frequencies.- Broadband detection and classification of underwater sources.- Section 8 - Applications.- A geometrical approach to medium low frequency reverberation modeling (Invited paper).- The reverberation array heading surface.- Bistatic ocean reverberation effects.- Modeling of wide area ocean reverberation and noise.- Rapid environmental acoustic survey and modeling system.- List of Participants.- Author Index.
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