"September 1999"
Topic: ACOUSTIC SCATTERING
121
121
Oct 7, 2015
10/15
by
Schalm, David A.
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"September 1999"
Topic: ACOUSTIC SCATTERING
Inversion techniques are used to infer bottom sedimentary characteristics using AN/SQS-53C Reverberation Level (RL) data gathered during Exercise LWAD 99-1. Analysis was conducted to determine the correlation between sediment type and beam RL time series statistics, including slope and detrended higher order statistics (standard deviation, skew, and kurtosis). A geographic contour plot of the spatial distribution of sediments was generated from the deviation of the RL slope of individual...
Topic: ACOUSTIC SCATTERING
371
371
Jun 17, 2010
06/10
by
Obukhov, A. M
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Acoustic scattering in turbulent flow - sound propagation equations
Topics: ACOUSTIC SCATTERING, AEROACOUSTICS, AERODYNAMIC NOISE, SOUND PROPAGATION, TURBULENT FLOW, ACOUSTIC...
The long term goal of our shallow water acoustics work is to understand the nature of low frequency (10-1500 Hz) acoustic propagation and scattering in shallow water when strong oceanic variability in the form of fronts, eddies, boundary layers, and internal waves is present. The long term goal of our FY06 fieldwork planning and preparation task is to develop and eventually execute a scientifically sound and Navy relevant basic research experiment in shallow water acoustics, concentrating on...
Topics: DTIC Archive, WOODS HOLE OCEANOGRAPHIC INSTITUTION MA, *ACOUSTIC SCATTERING, *SHALLOW WATER
During Ice Exercise (ICEX) 2018, a 120-kHz echosounder was used to investigate the ocean environment underneath the Arctic ice sheet in the southern Beaufort Sea down to a depth of 200 meters. Returns from the echosounder, coupled with data from an Acoustic Doppler Current Profiler (ADCP) and a Conductivity, Temperature, and Depth (CTD) profiler, suggest the presence of sharp, sound-speed gradients throughout the water column, occurring more often at greater depths. The pattern of returns can...
Topics: acoustical oceanography, acoustic scattering, ADCP, Arctic, Beaufort Sea, echosounder, ICEX,...
One of the most objectional noises produced by a helicopter is due to interaction of a rotor blade with a previously shed vortex. Various methods have been proposed to reduce this blade/vortex interaction (BVI) noise; this investigation is concerned with BVI noise reduction by rotor blade tip design modifications. Potentially much can be learned regarding the prospect for success of a candidate rotor blade design at greatly reduced time and money by performing acoustic scattering measurements...
Topics: Blade-vortex interaction (BVI), Acoustic scattering measurements, Anechoic chamber, Helicopter...
The ultimate limits of long-range sonar are imposed by ocean variability and the ambient sound field. Scattering due to internal waves and other ocean processes limits the temporal and spatial coherence of the received signal. The objectives of the North Pacific Acoustic Laboratory (NPAL) program are to understand the basic physics of low-frequency, long-range, broadband propagation, the effects of environmental variability on signal stability and coherence, and the fundamental limits to signal...
Topics: DTIC Archive, SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA, *ACOUSTIC SCATTERING, BATHYMETRY
The goal of this research is to better understand the physics and mechanisms of sound-seabed interaction, including acoustic penetration, propagation, attenuation and scattering in marine sediments. The scientific objective of this research is to develop analytical and numerical approaches to describe and quantify acoustic scattering from rough heterogeneous sea beds with discrete inclusions.
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *OCEAN BOTTOM,...
Improved knowledge of the physical and biological mechanisms and interactions responsible for forming and maintaining aggregations of biological sound-scatterers in the ocean.
Topics: DTIC Archive, DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA), *ZOOPLANKTON,...
The ultimate limits of long-range sonar are imposed by ocean variability and the ambient sound field. Scattering due to internal waves and other ocean processes limits the temporal and spatial coherence of the received signal. The objectives of the North Pacific Acoustic Laboratory (NPAL) program are to understand the basic physics of low-frequency, long-range, broadband propagation, the effects of environmental variability on signal stability and coherence, and the fundamental limits to signal...
Topics: DTIC Archive, SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA, *ACOUSTIC SCATTERING, BATHYMETRY,...
Rough surface scattering plays a crucial role in the statistics of acoustic propagation signals, especially at mid-frequencies and higher (e.g., acoustic communications systems). For many years, the effects of rough surface scattering were computed using simple models that were applied in two dimensions (2-D) only. A prescribed method of computing 2-D rough surface scattering directly in a parabolic equation model based on the Split-Step Fourier algorithm was introduced by Tappert and...
Topics: Acoustic Propagation, Acoustic Scattering, Sea Surface Perturbations, Split- Step Fourier...
Our long term goal is a quantitative, mechanistic and predictive understanding of the dynamics of bubbles and bubble populations in marine sediments. We believe that this information can be used to improve and test acoustic backscatter models for sediments and to better understand the ebullitive flux of methane, an important greenhouse gas, to the atmosphere.
Topics: DTIC Archive, DALHOUSIE UNIV HALIFAX (NOVA SCOTIA) DEPT OF OCEANOGRAPHY, *ACOUSTIC SCATTERING,...
Our long-term goal is to develop the capability to predict the spatial dimensions and temporal occurrence of aggregations of the nearshore sound-scattering layer in the coastal ocean.
Topics: DTIC Archive, OREGON STATE UNIV CORVALLIS COLL OF OCEANOGRAPHY, *ACOUSTIC SCATTERING, *UNDERWATER...
Our long-term goal is to improve methods for estimating zooplankton biomass by species and lifestage as a function of three-dimensional location and time. The objective of this research program is to integrate sophisticated acoustic scattering models of zooplankton with mathematical inverse theory to develop advanced broadband and multiple-frequency methods that produce rapid and accurate results from bioacoustical field studies in a form that can be understood and trusted by biological...
Topics: DTIC Archive, BAE SYSTEMS SAN DIEGO CA, *ACOUSTIC SCATTERING, *INVERSION, *ZOOPLANKTON, BROADBAND,...
The long-term goal is to develop tools and techniques to remotely quantify the three-dimensional spectrum of scalar and vector ocean turbulence using high frequency broadband multi-static acoustic scatter from medium variability. The objectives are to validate the application of far-field weak scattering theory to thermal-saline turbulent jets and compare the acoustic spectral estimates with the universal gradient spectral model for the inertial and Batchelor sub-ranges.
Topics: DTIC Archive, COASTAL SYSTEMS STATION PANAMA CITY FL, *TURBULENCE, *UNDERWATER ACOUSTICS, ACOUSTIC...
This research aims to improve the Monterey-Miami Parabolic Equation model (MMPE) by incorporating a higher-order hybrid boundary treatment and Fred D. Tappert’s field transformational model to add surface scattering to the existing models. The impact of these two additions is investigated for improvements in accuracy and stability to the current MMPE model under rough surface conditions. Both models were treated with a Pierson-Moskowitz rough surface spectrum. It was hoped that the hybrid...
Topics: Acoustic propagation, rough sea surface scattering, acoustic scattering, split-step Fourier...
The central goal of this project is for the Primary Investigator, Gareth Lawson, to design, execute, and defend his doctoral thesis research. In terms of its scientific purpose, this research seeks to contribute to our understanding of spatial and temporal patchiness in the distribution of high-frequency acoustic volume backscattering stemming from zooplankton (e.g., Figure 1).
Topics: DTIC Archive, WOODS HOLE OCEANOGRAPHIC INSTITUTION MA, *ACOUSTIC SCATTERING, *ZOOPLANKTON,...
Investigations of scattered transient waveforms from conducting bodies have shown that it is possible to classify electromagnetic scatterers. The concept is based upon the natural resonance modes which are part of the scatterer response to an incident excitation. A new approach for describing natural resonance modes using recursive systems is introduced. A discrete auto- regressive moving-average (ARMA) type model for the case of the space-time wave equation is presented. This model results...
Topics: Sonar, Radar., Natural resonances, electromagnetic scattering, acoustic scattering, radar target...
The objective of this grant is to examine issues supportive of the SWAMSI team effort by improving the understanding of acoustic scattering processes relevant to MCM and the shallow water environment. The current emphasis is on the interpretation of bistatic synthetic aperture sonar and acoustic holographic images. Other objectives involved improved understanding and modeling of scattering mechanisms that are broader in scope and are outlined below.
Topics: DTIC Archive, WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS, *ACOUSTIC SCATTERING, *SHALLOW WATER,...
The goal is to develop and test certain ideas relevant to the coupling of sound with small targets buried in the ocean bottom. This is a Graduate Traineeship Award in Ocean Acoustics. The main objective is to understand consequences of incident wave evanescence on (existing or underutilized) scattering observables. It is also planned to explore conditions whereby surface roughness enhances the coupling of sound to simulated buried targets. Resolving these issues should be helpful for...
Topics: DTIC Archive, WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS, *ACOUSTIC WAVES, *DIFFRACTION,...
The goals of this study are to develop species- and life-stage-specific acoustic scattering models based on morphologically-accurate digitizations of preserved or live-imaged zooplankton from coastal waters. These models will estimate scattering strength as a function of acoustical frequency, animal size, taxon, and orientation relative to the incidence angle. These predictions will improve our ability to estimate animal abundances by taxon/morphological class via inversion.
Topics: DTIC Archive, BAE SYSTEMS SAN DIEGO CA, *ACOUSTIC SCATTERING, *ZOOPLANKTON, CLASSIFICATION, COASTAL...
A series of monostatic and bistatic acoustic scattering measurements were conducted to investigate discrimination and classification capabilities based on the acoustic response of targets for underwater un- exploded ordnance (UXO) applications. The measurements were performed during March 2010 and are referred to as Pond Experiment 2010 or simply PondEx10. The measurements utilized a rail system with a mobile tower and a stationary sonar tower. Each tower is instrumented with receivers while...
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *UNEXPLODED AMMUNITION, ACOUSTIC...
The long-term goal is to develop an understanding of physical parameters of aggregations of fish that control clutter and produce improved scattering models that incorporate those parameters. This project was part of the Office of Naval Research (ONR) Basic Research Challenge formally entitled Acoustic Uncertainty due to Marine Mammals and Fish, which was informally known as the Fish BRC. The project was conducted in conjunction with the Naval Research Laboratory (NRL) Fish BRC project entitled...
Topics: DTIC Archive, BAYOUACOUSTICS ABITA SPRINGS LA, *FISHES, *SEA CLUTTER, ACOUSTIC SCATTERING,...
295
295
Jul 26, 2010
07/10
by
Laubacher, Brian A.; Richards, M. C
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The propulsion performance and reconstructed mass properties data from Thiokol's RSRM-13 motors which were assigned to the STS-41 launch are presented. The SRM propellant, TP-H1148, is a composite type solid propellant, formulated of polybutadiene acrylic acid acryonitrile terpolymer binder, epoxy curing agent, ammonium perchlorate oxidizer, and aluminum powder fuel. A small amount of burning rate catalyst (iron oxide) was added to achieve the desired propellant burn rate. The propellant...
Topics: ACOUSTIC SCATTERING, SIMULATION, ATMOSPHERIC TURBULENCE, REFRACTION, SOUND PRESSURE, SOUND...
The long-term goal is to contribute to a better understanding of the environmental parameters that are most appropriate for use in predicting acoustic surface scattering strengths (SSS) in both shallow and deep-water environments.
Topics: DTIC Archive, ROSENSTIEL SCHOOL OF MARINE AND ATMOSPHERIC SCIENCE MIAMI FL, *ACOUSTIC SCATTERING,...
The long-range objective of this project is to understand both acoustic and microwave scattering from rough water surfaces sufficiently well to be able to implement them in operational models and, if possible, to remotely sense microscale breaking on the sea surface.
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *OCEAN SURFACE,...
The long term goal is to improve performance of low-mid frequency active sonar systems against clutter. The objectives are to identify/understand the mechanisms that lead to clutter and develop models that predict the temporal/spatial/frequency dependence of the observed clutter and background diffuse reverberation.
Topics: DTIC Archive, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *CLUTTER, *ACOUSTIC...
The long-range objective of this project is to understand both acoustic and microwave scattering from rough water surfaces sufficiently well to be able to implement them in operational models and, if possible, to remotely sense microscale breaking on the sea surface.
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *MICROWAVES,...
The backscattering of sound from two regularly arranged bubbles is studied theoretically and experimentally. In wall-controlled laboratory experiments a bistatic acoustic system is used to interrogate the scatterers, which are placed on a very fine thread at the same distance d from the combined beam axis of the set of transmitting and receiving transducers. The radius of each bubble is 585 micrometers. The frequency range is 80-140 kHz, and d is varied so that the variable kd spans the range...
Topics: DTIC Archive, Kapodistrias, George, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *BUBBLES,...
Rough surface scattering plays a crucial role in the statistics of acoustic propagation signals, especially at mid-frequencies and higher (e.g., acoustic communications systems). For many years, the effects of rough surface scattering were computed using simple models that were applied in two dimensions (2-D) only. A prescribed method of computing 2-D rough surface scattering directly in a parabolic equation model based on the Split-Step Fourier algorithm was introduced by Tappert and...
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *ACOUSTIC SCATTERING, ALGORITHMS, FINITE...
Long-term goals: To develop physics-based, predictive sonar models for: (a) propagation and detection in littoral conditions (b) mid- to high-frequency acoustic scattering and reflection from the air-sea interface. Objectives: (1) Analyze, model, and report results from Asian Seas International Acoustics Experiment (ASIAEX) conducted in the East China Sea (May-June 2001). (2) Prepare for 2006 LEAR (Littoral Environmental Acoustics Research) experiment in 2006 (a follow-on experiment to ASIAEX)....
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE COLL OF OCEAN AND FISHERY SCIENCES, *ACOUSTIC SCATTERING,...
Our long term goal is a quantitative, mechanistic and predictive understanding of the dynamics of bubbles and bubble populations in marine sediments. We believe that this information can be used to improve and test acoustic backscatter models for sediments and to better understand the ebullitive flux of methane, an important greenhouse gas , to the atmosphere.
Topics: DTIC Archive, DALHOUSIE UNIV HALIFAX (NOVA SCOTIA) DEPT OF OCEANOGRAPHY, *BUBBLES, *SEDIMENTS,...
This is part of the Shallow-Water Autonomous Mine Sensing Initiative (SWAMSI) to improve the reliability of acoustic methods using a wide frequency range and scattering data not necessarily limited to monostatic signatures.
Topics: DTIC Archive, WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS, *ACOUSTIC SCATTERING, *TARGET...
Statement of Work: The contractor shall review the existing under-ice asoustic modeling capaability and sufficiency of requisite environmental and acoustic data bases to provide an objective assessment efforts during the arctic experiment. The Contractor shall provide an assessment of the applicability of the AEAS draft measurements plan to enhance the understanding of existing models' capabilities and provide significant data base contributions and acoustic measurements to assist in the...
Topics: DTIC Archive, Greene,Robert R, SCIENCE APPLICATIONS INTERNATIONAL CORP MCLEAN VA, *ACOUSTIC...
The US Navy needs to know how distributions and abundances of light-scattering and sound-scattering organisms in the ocean vary in space and time, particularly in the vertical dimension. Recent field observations have shown that many biological properties may vary substantially over small (e.g. centimeter) scales, commonly referred to as thin layers (e.g. Cowles et al. 1998, 1999, Hanson & Donaghay 1998, Holliday et al. 1998, 1999, Dekshenieks et al. 2001, Alldredge et al. 2002, Rines et...
Topics: DTIC Archive, WASHINGTON STATE UNIV VANCOUVER, *ZOOPLANKTON, ACOUSTIC SCATTERING, CARBON, CHEMICAL...
The long-term goals of this research are to improve the ability of benthic biologists and biological oceanographers to observe life on and in the seabed; to describe the interactions between the animals that live there, their neighbors and their food; to improve our understanding of the coupling between the benthic and the pelagic communities; and to assess biologically mediated changes in those physical properties of the seabed that affect the scattering and penetration of sound from and into...
Topics: DTIC Archive, BAE SYSTEMS SAN DIEGO CA, *ACOUSTIC SCATTERING, *AQUATIC ANIMALS, *OCEAN BOTTOM,...
The goals of this research are to understand the acoustic reverberation properties of zooplankton and microstructure. The results will lead to improved capability in 1) predicting sonar performance and 2) use of sonars in the mapping of the zooplankton and microstructure. The objectives are to understand the physics of the scattering by naturally occurring (complex) bodies so that realistic acoustic scattering models of zooplankton and microstructure can be developed.
Topics: DTIC Archive, WOODS HOLE OCEANOGRAPHIC INSTITUTION MA, *ACOUSTIC SCATTERING, *ZOOPLANKTON, INTERNAL...
A modification of the classical effective wave vector in randomly inhomogeneous media ksubp * = ksubp + 2pinfsubp(1,0)/ksubp is discussed, which replaces the single particle far field forward scattering amplitude, fsubp(1,0), by an average pair scattering amplitude, fsubp(2,0). The Perkus-Yevick radial distribution function is used to find the average of fsubp(2,0) over radial separations extending to the first nearest neighbor maximum. The results is applied to random distributions of mass...
Topics: DTIC Archive, Scharnhorst, Kurt P, NAVAL SURFACE WARFARE CENTER SILVER SPRING MD, *ACOUSTIC...
The Office of Naval Research initiated a series of detailed surface and bottom reverberation planning meetings as part of the Office of Naval Research Acoustic Reverberation Special Research Program (SRP). As an outgrowth of these meetings surface and bottom reverberation field measurement groups have been formed to engage in the detailed planning of surface and bottom reverberation experiments.
Topics: DTIC Archive, Hodgkiss, W S, SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE PHYSICAL LAB,...
340
340
May 27, 2011
05/11
by
Herring, Jackson; Kyle, Herbert L
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A discussion of the Opik-Singer theory of the density of a planetary exosphere is presented. Their density formula permits the calculation of the depth of the exosphere. Since the correctness of their derivation of the basic formula for the density distribution has been questioned, an alternate method based directly on Liouville's theorem is given. It is concluded that the Opik-Singer formula seems valid for the ballistic component of the exosphere; but for a complete description of the...
Topics: JET AIRCRAFT NOISE, DATA ACQUISITION, NOISE MEASUREMENT, REFLECTION, NUMERICAL ANALYSIS,...
The long-term goal is to develop a comprehensive understanding of (1) high-frequency scattering from the air-sea interface and its relation to the directional wave spectrum, including scattering from bubbles near this interface, and (2) of high-frequency acoustic propagation and scattering in bubbly media characteristic of the surf zone, and the near-surface acoustic environment. The ultimate goal is to obtain realistic, physics-based, predictive models for scattering and propagation phenomena....
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *AIR WATER...
179
179
May 23, 2011
05/11
by
Hakkila, Jo
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The investigative team for the CCRO Cycle 5 Guest Investigation 'Gamma-Ray Burst Model Constraints Imposed by Burst and Transient Source Experiment (BATSE) Observations' consisted of myself, Dr. Charles A. Meegan (NASA/MSFC), Dr. Geoffrey N. Pendleton (UAH), Dr. John M. Horack (NASA/MSFC), and Dr. Michael S. Briggs (UAH). The purpose of the research was to continue studying the BATSE gamma-ray burst angular and intensity distributions in order to better determine the gamma-ray burst distance...
Topics: AEROACOUSTICS, MATRICES (MATHEMATICS), SOUND WAVES, BOUNDARY CONDITIONS, FINITE DIFFERENCE THEORY,...
The long-term goal is to quantify properties of mid-frequency acoustic reverberation in terms of the physical and biological properties of the environment. The results will improve the ability to predict sonar performance. This component of the TREX13 program concerns characterizing the contributions of acoustic scattering by fish to the reverberation. The clutter characteristics of the fish will also be quantified.
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY, *ACOUSTIC SCATTERING,...
The goals of this research is to better understand the physics and mechanisms of sound-seabed interaction, including acoustic penetration, propagation, attenuation and scattering in marine sediments.
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *OCEAN BOTTOM...
Monostatic synthetic aperture sonar (SAS) data sets for the scattering from a target in a waveguide can be simulated via a fast model that combines an acoustic ray approximation for propagation in the waveguide with far-field scattering from a target in free-space. With the assumption that acoustic rays arise from the source and receiver and their images, the problem of wave propagation and scattering from a target within the waveguide is replaced by a superposition of a set of free-field...
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *SYNTHETIC APERTURE SONAR, ACOUSTIC...
The goal of this work is to further develop and test models of volume scattering by utilizing the existing suite of instrumentation previously developed at APL- UW for the study of high-frequency acoustics. These models include perturbation models applied to scattering from the seafloor due to heterogeneities in the sediment properties, recently developed models by Dr. Ivakin [1], which model scattering from inclusions in the sediment such as shells and coarse grains, models which account for...
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *SEDIMENTS,...
My long-term goals are to try to better understand the relationships between ocean processes (particularly those with relatively high wavenumbers and frequencies like internal waves, finestructure, and microstructure) on acoustic scattering in the ocean.
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *OCEAN...
The long-term goal of the proposed research is to develop a fundamental understanding of high-frequency acoustic scattering from small-scale physical processes that occur in the ocean interior. The primary scientific objective of the proposed research is to measure, characterize, and understand the physics of high-frequency acoustic scattering from controlled, laboratory-generated microstructure, with a focus on double diffusion. The initial development of simple physics based scattering models...
Topics: DTIC Archive, WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF APPLIED OCEAN PHYSICS AND...
The goal of this research is to better understand the physics and mechanisms of sound-seabed interaction, including acoustic penetration, propagation, attenuation and scattering in marine sediments.
Topics: DTIC Archive, WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB, *ACOUSTIC SCATTERING, *OCEAN BOTTOM,...
