| Supplemental Student Support: Detection and Identification of Buried Targets using Time Reversal Acoustics |
04-Nov-2009 |
283 pages |
| Authors:
Ronald A Roy; Zachary J Walters; BOSTON UNIV MA
|
 | The presence of noise and coherent returns from clutter often confounds efforts to acoustically detect and identify target objects buried in inhomogeneous media. Using iterative time reversal with a single channel transducer, returns from resonant targets are enhanced, yielding convergence to a narrowband waveform characteristic of the dominant mode in a target's elastic scattering response. The procedure consists of exciting the target with a broadband acoustic pulse, sampling the return ... |
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| Fuzzy Logic Approach for Impact Source Identification in Ceramic Plates (Slides) |
13-Jul-2009 |
20 pages |
| Authors:
Thomas Meitzler; Ivan Wong; Harpreet Singh; Thomas Reynolds; Shashank Kamthan; Arati M Dixit; Vijay Shrama; WAYNE STATE UNIV DETROIT MI DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| This briefing looks at the use of fuzzy logic in non-destructive identification techniques. The method is based on the fact different impacting materials will generate different impact acoustic waves. |
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| Nonlinear Acoustics in Cicada Mating Calls Enhance Sound Propagation |
01-Mar-2009 |
12 pages |
| Authors:
Derke R Hughes; Albert H Nuttall; Richard A Katz; G C Carter; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| An analysis of cicada mating calls, measured in field experiments, indicates that the very high levels of acoustic energy radiated by this relatively small insect are mainly attributed to the nonlinear characteristics of the signal. The cicada emits one of the loudest sounds in all of the insect population with a sound production system occupying a physical space typically less than 3 cc. The sounds made by tymbals are amplified ... |
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| Bone Conducted Noise and Mitigation Techniques |
Mar-2009 |
20 pages |
| Authors:
Richard L McKinley; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN EFFECTIVENESS DIRECTORATE
|
| Very high level noises, up to 150 dB, can cause special problems in hearing protection. In order to achieve a 15 minute exposure within an 85 dB, 8 hour, 3 dB/doubling criteria, the hearing protector must provide 50 dB of overall noise attenuation. The issue becomes the flanking pathway provided by bone conduction with an attenuation at 2 kHz of approximately 40-45 dB. In this case, the flanking pathway becomes ... |
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| Acoustic Excitation of Liquid Fuel Droplets and Coaxial Jets |
Jan-2009 |
271 pages |
| Authors:
Juan I Rodriguez; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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| This experimental study focuses on two important problems relevant to acoustic coupling with condensed phase transport processes, with special relevance to liquid rocket engine and airbreathing engine combustion instabilities. The first part of this dissertation describes droplet combustion characteristics of various fuels during exposure to external acoustical perturbations. Methanol, ethanol, a liquid synthetic fuel derived from coal gasification via the Fischer-Tropsch process, and a blend of aviation fuel and the ... |
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| General Procedure for Protective Cooling and Equipment Evaluations Relative to Heat and Cold Stress |
01-Sep-2008 |
27 pages |
| Authors:
Catherine O'Brien; Bruce S Cadarette; Thomas L Endrusick; Laurie A Blanchard; Xiaoxiang Xu; Larry G Berglund; Michael N Sawka; Reed W Hoyt; ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA THERMAL AND MOUNTAIN MEDICINE DIVISION
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| As part of the U.S. Army materiel development and acquisition process, clothing and individual equipment (CIE) must undergo a Health Hazard Assessment (HHA) conducted by the U. S. Army Center for Health Promotion and Preventive Medicine. Scientists at the U.S. Army Research Institute of Environmental Medicine (USARIEM) are world experts in thermal physiology, biophysics, and biomedical modeling and are uniquely capable of providing technical measurements and subject matter expertise for ... |
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| Improving Accuracy of Acoustic Prediction in the Philippine Sea through Incorporation of Mesoscale Environmental Effects |
01-Jun-2008 |
69 pages |
| Authors:
Kimberly M Freitas; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| An understanding of ocean acoustic fields, their statistics, and relation to the oceanographic environment is the sine qua non of undersea warfare. In the tactically important Philippine Sea, powerful mesoscale eddies can have strong effects on acoustic fields. To quantify eddy effects, a mesoscale sound-speed model was developed and interfaced with a parabolic equation acoustic simulation. Eight combinations of frequency (20Hz/250Hz), wavenumber spectra (Stammer/Lorentzian) and source depth (50m/200m) were simulated ... |
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| Revisiting the Nonlinear Response of a Plate to Acoustic Loading |
Apr-2008 |
14 pages |
| Authors:
Joseph J Hollkamp; Robert W Gordon; Timothy J Beberniss; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH ANALYTICAL STRUCTURAL MECHANICS BRANCH
|
| Accurate prediction of the structural response of stiffened aircraft skins to acoustic loading is necessary for the design of future Air Force vehicles. Response prediction requires time integration of nonlinear models. Recently, methods have emerged where a nonlinear finite element model is reduced to a low-order system of nonlinear equations to better enable the computations. Well-characterized experiments are needed to validate these methods. In a previous study, experimental data from ... |
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| Nano-Mechanical Properties of Heat Inactivated Bacillus anthracis and Bacillus thuringiensis Spores |
01-Mar-2008 |
85 pages |
| Authors:
Jessica L Poindexter; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| B. thuringiensis spores must have similar properties to B. anthracis spores to be a good simulant in counter-proliferation studies. In particular, they must behave in a similar way when exposed to high temperatures for short periods of time as would be caused by an explosion. This research project compares surface elasticities for four different spore sample types, B. anthracis spores, heat inactivated B. anthracis spores, B. thuringiensis spores, and heat ... |
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| Investigating the Relationship Between Fin and Blue Whale Locations, Zooplankton Concentrations and Hydrothermal Venting on the Juan de Fuca Ridge |
Jan-2008 |
10 pages |
| Authors:
William S Wilcock; Richard E Thomson; WASHINGTON UNIV SEATTLE SCHOOL OF OCEANOGRAPHY
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| We are investigating the potential correlation between whale tracks, enhanced zooplankton concentrations and hydrothermal vents above the Juan de Fuca Ridge with the long-term goal of understanding such correlations in terms of the influences of globally distributed hydrothermal plumes on the trophic ecology of the deep ocean. We are conducting a retrospective study using existing seismic and bio-acoustical data sets from the Juan de Fuca Ridge with the following four ... |
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| Acoustic Doppler Current Profiler (ADCP) Velocity Verification Experiments in the Navy's Large Cavitation Channel (LCC) |
DEC 2007 |
38 pages |
| Authors:
Dylan A. Chirchella; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
|
| The Resistance and Powering Division (Code 5200) of The Naval Surface Warfare Center, Carderock Division (NSWCCD) conducted verification experiments on a 20 degree Acoustic Doppler Current Profiler (ADCP) unit produced by RD Instruments (RDI) of San Diego, California. These experiments were conducted in the Navy's Large Cavitation Channel (LCC) located in Memphis, Tennessee. Although they have many other possible future uses, currently the ADCP units tested during this series are ... |
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| Maritime Surveillance Using a Wideband Hydrophone |
SEP 2007 |
69 pages |
| Authors:
Jason K. Wilson; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Undersea acoustic moderns acquire wideband acoustic time series through an electro-acoustic transducer and use on-board digital signal processing for receiving acoustic communications. These component devices can potentially serve a dual use for passive sensing of radiated acoustic energy from maritime vessels. This thesis examines the characteristic Lloyd's mirror interference pattern present in the acoustic spectrogram of a passing surface target and applies two-path ray theory and waveguide invariant theory to ... |
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| Currents, Eddies, and a "Fish Story" in the Southwestern Japan/East Sea |
30 JUL 2007 |
14 pages |
| Authors:
D. R. Watts; Mark Wimbush; Karen L. Tracey; William J. Teague; Jae-Hun Park; Douglas A. Mitchell; Jong-Hwan Yoon; Moon-Sik Suk; Kyung-Il Chang; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| As part of the Japan/East Sea (JES) initiative supported by the U.S. Office of Naval Research, we conducted an observational experiment to understand the physics of the mesoscale circulation in the Ulleung Basin, located in the south-western corner of the JES. The current passing through the Korea Strait divides upon entering the JES, with portions of the current flowing along the Korean and Japanese coasts. The variability of these currents ... |
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| Modeling of High-Frequency Acoustic Propagation in Shallow Water |
JUN 2007 |
150 pages |
| Authors:
Juan C. Torres; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| This research involves numerical modeling of acoustic signals through shallow water channels. The sound is computationally modeled in a vertical plane as a dense fan of beams radiating from the transmitter location. The cross section of each 2-dimensional beam is represented as a Gaussian distribution of acoustic energy. The Gaussian beam travels axially along rays governed by Snell's Law, dispersing in width as a function of travel distance. At arbitrary ... |
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| Detection of Localized Heat Damage in a Polymer Matrix Composite by Thermo-Elastic Method (Preprint) |
FEB 2007 |
16 pages |
| Authors:
John Welter; Shamachary Sathish; Erik Ripberger; Eric Lindgren; DAYTON UNIV OH RESEARCH INST
|
| Reduction of strength of polymer matrix composites when exposed to high temperatures is a major concern in aerospace industry. Loss of mechanical strength can be measured only through established destructive techniques; there is a need for detection and evaluation of heat damage in PMC. This paper describes a thermo-elastic based non-contact nondestructive technique for detection and evaluation of heat damage in PMC. The efficiency of the material to convert acoustic ... |
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| Dynamic Response of an Insonified Sonar Window Interacting with a Tonpilz Transducer Array |
03 JAN 2007 |
38 pages |
| Authors:
Andrew J. Hull; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| This report derives and evaluates an analytical model of a sonar window in contact with an array of Tonpilz transducers. The window is fully elastic so that all wave components are present in the analysis. The system is insonified with a plane acoustic wave so that the sonar system is operating in an acoustic receive mode. The output of the model is a transfer function of a transducer element output ... |
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| Basic Hearing and Echolocation Mechanisms of Marine Mammals: Measured Auditory Evoked Potential and Behavioral Experiments FY 2007 |
Jan-2007 |
8 pages |
| Authors:
Paul E Nachtigall; HAWAII INST OF MARINE BIOLOGY KAILUA HI MARINE MAMMAL RESEARCH PROGRAM
|
| Marine Mammal sensory systems have evolved to effectively use acoustic energy in the oceans. My objectives are to develop a basic understanding of hearing and echolocation so that knowledge can then be applied to the solution of practical problems as they arise. The most basic hearing measurement is the audiogram which is a series of thresholds across frequencies. Of the 85 species of cetaceans we now have audiograms on 14 ... |
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| Simulation of the Northern Adriatic Circulation During Winter 2003 |
19 DEC 2006 |
13 pages |
| Authors:
P. J. Martin; J. W. Book; J. D. Doyle; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Numerical simulations of the Adriatic Sea were conducted with the Navy Coastal Ocean Model during the Adriatic Circulation Experiment in the fall and winter of 2002/2003, and results were compared with observations. The ocean model used a I-km resolution grid over the entire Adriatic Sea. Model forcing included atmospheric fluxes from the Coupled Ocean-Atmosphere Mesoacale Prediction System (COAMPS), tides, boundary conditions from a global model, and freshwater river and runoff ... |
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| Effect of Internal Solitary Waves on Mine Detection in the Western Philippine Sea East of Taiwan |
DEC 2006 |
138 pages |
| Authors:
Chung-Ping Hsieh; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Upper layer temperature in the western Philippine Sea near Taiwan was sampled using a coastal monitoring buoy with fifteen thermistors attached from July 28 August 7, 2005. Internal waves and internal solitons (IS) were identified using the empirical orthogonal function analysis. Without the IW and IS, the power spectra, structure functions, and singular measures (representing the intermittency) of the temperature field satisfy the power law with multi-scale characteristics at all ... |
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| Object-Oriented Approach to Manipulating Acoustic and Seismic Spectra |
DEC 2006 |
42 pages |
| Authors:
D. K. Wilson; Jacob I. Torrey; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
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| The software design and underlying mathematics for an object-oriented, Java-based approach to creating and manipulating frequency-dependent functions, such as power spectral densities, is described. The frequency dependence is modeled as a series of power-law bands, which provides a high degree of flexibility and efficiency for representing common spectral models such as evenly spaced bands, octave bands, narrow spectral lines, broadband noise, and power laws. Conversions between the various spectral models ... |
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| Seismic Measurement of Concrete Strength Properties |
DEC 2006 |
84 pages |
| Authors:
Haley P. Bell; ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB
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| An assessment of the portable seismic pavement analyzer (PSPA) was conducted during the period February to April 2005 on three military airfields in order to determine the feasibility of rapidly obtaining the modulus and flexural strength of portland cement concrete and asphalt concrete pavements. The PSPA is a nondestructive testing device that measures seismic modulus using ultrasonic surface waves. The objective of this research is to evaluate the PSPA as ... |
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| A Dual-Mode Noise-Immune Stethoscope for Use in Noisy Vehicles |
NOV 2006 |
7 pages |
| Authors:
Adrianus J. Houtsma; Ian P. Curry; John M. Sewell; William N. Bernhard; ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
|
| In combat casualty and civilian environments, an unmet need exists for a stethoscope that can hear heart and especially breathing sounds while inside helicopters, fixed-wing aircraft, or ambulances where noise levels preclude auscultation with standard stethoscopes. Without this capability, patients can suffer from unidentified collapsed lungs or loss of intubation integrity with the threat of loss of life. A conventional acoustic stethoscope will not function in background noise levels beyond ... |
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| Outdoor Sound Propagation Modelling in Complex Environments: Recent Developments in the Parabolic Equation Method |
01 OCT 2006 |
17 pages |
| Authors:
Philippe Blanc-Benon; ECOLE CENTRALE DE LYON ECULLY (FRANCE)
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| In complex environments the modelling of outdoor sound propagation implies to take into account the mixed influence of ground characteristics (topography, obstacles, impedance, etc.) and atmospheric conditions (refraction and turbulence). During the last decade significant progress has been made in the modelling of sound propagation over distances ranging from hundreds meters to kilometres, and the agreement between calculated and measured fields has been greatly improved. New developments appear in the ... |
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| Marine Seismic Surveys with Vector Acoustic Sensors |
01 OCT 2006 |
6 pages |
| Authors:
Dennis Lindwall; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE
|
| Vector acoustic data will allow accurate three-dimensional imaging of a complex environment while corresponding pressure hydrophone data will fail. Newly developed sensors make vector acoustic-based surveys practical. This concept is demonstrated with data from an acoustic water tank. Using a simple but novel imaging algorithm, all of the main structures in the water tank were correctly located. This imaging algorithm uses none of the existing imaging or inversion methods common ... |
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| Study of Nonlinear Oscillations of Elastic Membrane |
26 SEP 2006 |
5 pages |
| Authors:
Vladmir Varlamov; Andras Balogh; PAN AMERICAN UNIV EDINBURG TX DEPT OF MATHEMATICS
|
| Nonlinear oscillations of a circular elastic membrane with a simply supported boundary are investigated. They are caused by a source of acoustic waves, so that the membrane serves as an acoustic receiver. Vertical deflections of the membrane and the acoustic pressure are to be found and, if possible, the direction to the source. The boundary value problem is solved by a nonlinear version of the method of eigenfunction expansions. Vertical ... |
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| Passive Control of Limit Cycle Oscillations in a Thermoacoustic System using Asymmetry |
05 SEP 2006 |
15 pages |
| Authors:
Bryan Eisenhower; Gregory Hagen; Andrzej Banaszuk; Igor Mezic; CALIFORNIA UNIV SANTA BARBARA DEPT OF MECHANICAL AND ENVIRONMENTAL ENGINEERING
|
| In this paper, we investigate oscillations of a dynamical system containing passive dynamics driven by a positive feedback and how spatial characteristics (i.e. symmetry) affect the amplitude and stability of its nominal limit cycling response. The physical motivation of this problem is thermoacoustic dynamics in a gas turbine combustor. The spatial domain is periodic (passive annular acoustics) which are driven by heat released from a combustion process, and with sufficient ... |
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| Impact of GFO Satellite on Naval Antisubmarine Warfare |
01-Sep-2006 |
54 pages |
| Authors:
David Cwalina; Guillermo Amezaga; Peter C Chu; Eric L Gottshall; NAVAL POSTGRADUATE SCHOOL MONTEREY CA NAVAL OCEAN ANALYSIS AND PREDICTION LAB
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| Localization of Radiating Sources along the Hull of a Submarine Using a Vector Sensor Array |
Sep-2006 |
4 pages |
| Authors:
Joseph A Clark; Gerald Tarasek; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
|
| Mappings of sound sources on submarine hulls provide an important diagnostic tool for analyzing the radiated signature, and evaluating noise deficiencies and silencing improvements of U.S. Navy submarines. The acoustic imaging problem is particularly difficult because the resolution of signals required to provide useful information is usually on a scale that it is several times smaller than the acoustic wavelength. Recent testing with acoustic vector sensors (combined pressure and particle ... |
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| Supercritical and Transcritical Shear Flows in Microgravity: Experiments and Direct Numerical Simulations |
AUG 2006 |
314 pages |
| Authors:
Dustin W. Davis; Bruce Chehroudi; Douglas G. Talley; Josette Bellan; Nora Okong'o; ENGINEERING RESEARCH AND CONSULTING INC (ERC INC) EDWARDS AFB CA
|
| Experiments and direct numerical simulations (DNS) were conducted on shear layers at subcritical to supercritical pressures. The experiments were performed on single-component coaxial jets, where the slower inner flow was liquid nitrogen, the faster outer flow was cold gaseous nitrogen, and the environment was room temperature gaseous nitrogen. The experiments were performed with and without the effects of transverse acoustic waves. Careful attention was given to measuring all the initial ... |
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| Shockwave Propagation in Nonequilibrium Air Plasma |
JUL 2006 |
43 pages |
| Authors:
Biswa N. Ganguly; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE
|
| The effects of acoustic shock wave propagation in nonequilibrium plasmas with Mach number from 1.5 up to 2.5 have been investigated. The effects of shock wave induced double layer on local excitation and ionization enhancement have been measured. Also, the effect of local gas heating induced by the energy dissipation in the double layer has been measured in a dielectric barrier discharge. |
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| Beaked Whale Hearing and Noise Impact Models |
20 JUN 2006 |
|
| Authors:
Darlene R. Ketten; David Mountain; Roger Hillson; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
 | This project capitalized on and extended data, methodologies, and partnerships formed under the ONR funded Effect of Sound in the Marine Environment (ESME). The work comprised two years of collaborative effort focusing on sophistication and refinement of the baseline auditory model developed previously by these team members under ESME and employed the same model architecture and organizational structure that proved successful in the ESME project. The impact modeling effort developed ... |
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| Monitoring Cancer Oxygenation Changes Induced by Ultrasound |
JUN 2006 |
8 pages |
| Authors:
Anastasios Maurudis; Quing Zhu; CONNECTICUT UNIV STORRS
|
| Chemotherapy is becoming more important in breast cancer treatment. It offers a perfect opportunity to evaluate the utility of newer targeted drugs. Despite the development of new techniques to characterize the biologic features of breast tumors, the factors influencing the quality of response to therapy remain obscure. One factor that may influence response to systemic chemotherapy is tumor perfusion. Tumors with relatively poor perfusion may receive inadequate delivery of systemic ... |
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| Three-Dimensional Analysis of Azimuthal Dependence of Sound Propagation through Shallow-Water Internal Solitary Waves |
JUN 2006 |
62 pages |
| Authors:
Douglas L. Roush; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Results from shallow-water observational studies have shown acoustic field fluctuations in excess of 10 dB due primarily to non-linear internal solitary waves (ISWs). This work concentrates on three limitations ISWs pose to shallow-water acoustic propagation: anisotropy, quasi-deterministic-stochastic nature, and frequency dependence. These aspects are explored for low frequencies of 75 and 150 Hz through the development of a full-wave three-dimensional parabolic equation model in which a single ISW is introduced ... |
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| On the Behavior of a Shear-Coaxial Jet, Spanning Sub- to Supercritical Pressures, with and without an Externally Imposed Transverse Acoustic Field |
MAY 2006 |
262 pages |
| Authors:
Dustin W. Davis; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF MECHANICAL AND NUCLEAR ENGINEERING
|
| In the past, liquid rocket engines (LRE) have experienced high-frequency combustion instability, which impose an acoustic field in the combustion chamber. The acoustic field interacts with the fluid jets issuing from the injectors, thus altering the behavior of the jet compared to that of stable operation of the LRE. It is possible that this interaction could be a substantial feed back mechanism driving the combustion instability. In order to understand ... |
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| Harbor/Mooring Area Defense Concept |
MAY 2006 |
5 pages |
| Authors:
David L. Bradley; Kyle M. Becker; PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
|
| The goals of the proposed work are an initial feasibility study, including calculations, demonstrating the ability to direct or focus low-frequency acoustic energy. For given source configurations, acoustic propagation modeling was conducted for simple, idealized, harbor type environments. The calculations yielded spatial plots of acoustic energy as a function of depth and range which provide information on source location and power requirements. |
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| Acoustic Identification of Filler Materials in Unexploded Ordnance |
APR 2006 |
70 pages |
| Authors:
Wesley Cobb; DENVER RESEARCH INST CO
|
| The objective of this project is to utilize acoustic waves to identify the materials inside sealed unexploded ordnance (UXO). Acoustic waves are high frequency pressure fluctuations (sound) that travel through materials. Small sensors clamped to the outside of the ordnance send low-energy acoustic waves through the container walls and filler. The received signals are analyzed to determine the characteristic acoustic properties of the filler material. To identify the filler, these ... |
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| Behavior of a Rocket-Like Coaxial Injector in an Acoustic Field (PREPRINT) |
24 MAR 2006 |
13 pages |
| Authors:
D. W. Davis; B. Chehroudi; D. G. Talley; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| A non-reacting-flow experimental investigation was undertaken to gain a better understanding of some of the underlying physics associated with the interaction of acoustic waves and a coaxial-jet injector similar to those used in cryogenic liquid rockets. Liquid nitrogen (the round inner jet) and gaseous nitrogen (the annular outer jet) were used under subcritical, near critical, and supercritical chamber pressures, with and without acoustic excitation. High-speed digital imaging provided information on ... |
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| Conference on Mathematical and Numerical Aspects of Waves (WAVES'05) (7th) |
22 MAR 2006 |
3 pages |
| Authors:
Jan S. Hesthaves; BROWN UNIV PROVIDENCE RI DIV OF APPLIED MATHEMATICS
|
| This was a grant to cover partial cost of the organization of the 7th International;Conference on Mathematical and Numerical Aspects of Waves, held at Brown University, Providence, RI, on June 2-24. 2005. It was the 7th WAVES conference with the first-one taking place in Strasburg, France in 1991 and every 2nd or 3rd year since then. |
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| Development of a Sidescan Imagery Automated Roughness Estimation Algorithm |
Mar-2006 |
9 pages |
| Authors:
Geary Layne; Maura C Lohrenz; Marlin L Gendron; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS
|
| An accurate estimation of seafloor roughness derived from sidescan imagery (SSI) is one of the components needed to determine bottom type of a geographic area for mine warfare. Analysts at the Naval Oceanographic Office (NAVOCEANO) historically have estimated roughness manually. This paper describes the development and testing of a prototype algorithm capable of deriving roughness from SSI. It also presents results from a feasibility study that showed that the algorithm ... |
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| Notes for Geoacoustic_TDFD |
FEB 2006 |
|
| Authors:
Ralph A. Stephen; S. T. Bolmer; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF GEOLOGY AND GEOPHYSICS
|
| These notes were written to help users run the WHOl TDFD (Time Domain Finite Difference) elastic wave equation code that was prepared for distribution through the ONR Ocean Acoustics Library (http://www.hlsresearch.com/oalib/). The code and documentation are based on materials that were developed for a Numerical Wave Propagation class given at MIT in the Fall of 2000. The code used is the full two-dimensional time-domain finite-difference code developed at WHOI over ... |
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| Acoustic Focusing in Shallow Water and Bubble Radiation Effects |
20 OCT 2005 |
9 pages |
| Authors:
Grant B. Deane; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE PHYSICAL LAB
|
| The long-term goals of the "Acoustic Focusing in Shallow Water and Bubble Radiation Effects" project is as follows: (1) understand the role of wave-induced bubbles in the upper ocean boundary layer on the performance of underwater communications systems and ambient noise generation, (2) study the implications of focusing by surface gravity waves on Doppler sonar and acoustic communications systems in shallow and very shallow water, and (3) study the performance ... |
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| Sound Wave Mitigation Through the Design of Surface Impedance |
21 SEP 2005 |
36 pages |
| Authors:
Weng C. Chew; Gong L. Wang; ILLINOIS UNIV AT URBANA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| An artificial soft surface is proposed to reduce and attenuate the propagation of acoustic waves along the surface of hard ground. An infinitesimal pressure line source is used as the excitation. Instead of an ideal periodic structure, a quasi-periodic structure is used where a finite number of grooves are incorporated to model exactly the realistic situation. Two boundary integral equation methods are proposed, one is based on the free space ... |
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| The Effects of Seafloor Roughness on Acoustic Scattering: Manipulative Experiments |
SEP 2005 |
9 pages |
| Authors:
M. D. Richardson; K. B. Briggs; K. L. Williams; D. Tang; D. R. Jackson; E. I. Thorsos; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE
|
| Deliberate manipulations of the seafloor during SAX04 (Sediment Acoustics Experiment-2004) in the form of quasi-periodic ripples features were carried out to examine the effects of interface roughness on high-frequency acoustic scattering. Manipulative experiments were conducted in the field of view of a bottom-mounted acoustic tower (40 kHz) and in the field of view of acoustic transducers (30-90 kHz) attached to a mobile rail system. The center wavelength of ripple-like features ... |
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| Non-Lethal Weapons: Opportunities for R&D |
24 AUG 2005 |
|
| Authors:
Harold Stocker; John Dick; Gilles Berube; DEFENCE RESEARCH AND DEVELOPMENT CANADAOTTAWA (ONTARIO)
|
| The aim of this overview study is to recommend the Non-Lethal Weapon (NLW) research and development that Defence Research and Development Canada (DRDC) could conduct over the next decade (and possibly beyond) in response to emerging defence and security NLW requirements. It summarizes the DRDC perspective of NLW technologies, which includes non-lethal applications of electro-magnetic and acoustic directed energy. The study shows that by channeling existing expertise and effort, DRDC ... |
|
| Monitoring Cancer Oxygenation Changes Induced by Ultrasound |
JUL 2005 |
6 pages |
| Authors:
Anastasios Maurudis; Quing Zhu; CONNECTICUT UNIV STORRS
|
| Preliminary studies with 5 tumor-bearing rats performed by the original PI, Dr. Daqing Piao, demonstrated that ultrasonic vibrations could either generate significant effects (early stage tumors) on optical measurements or no effects on optical measurements (late stage tumors). During the first two years, the original PI had devoted his efforts on quantifying both acoustic vibration and optical measurement of oxygenation. He had completed the first two proposed tasks and partially ... |
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| Subcritical Acoustic Penetration into Sandy Sediments with Negligible Interface Roughness |
06 JUN 2005 |
33 pages |
| Authors:
Rogert W. Meredith; Steve Stanic; Edgar T. Kennedy; Brian Houston; Harry Simpson; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS
|
| Recent observations of anomalous subcritical penetration in sandy sediments has renewed interest in the physics of acoustic sediment interaction. This paper presents measurements conducted at subcritical grazing angles over the frequency range of 1-12 kHz and examines the effects of multipath arrivals on the bottom penetration. Broadband signals, over a frequency range of 500 Hz to 12 kHz, were transmitted from a fixed source tower into the sediment and were ... |
|
| Investigations of Parametric Excitation in Physical Systems |
JUN 2005 |
79 pages |
| Authors:
Michael T. Janssen; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Parametric excitation can occur when the value of a parameter of an oscillator is modulated at twice the natural frequency of the oscillator. The response grows exponentially and is only limited by a nonlinearity of the system, so large response amplitudes typically occur. However, there is no response unless the parametric drive amplitude is above a threshold value that is dictated by the damping. We investigate parametric excitation in three ... |
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| ADCP Observations of the Western Adriatic Slope Current During Winter of 2001 |
23 MAY 2005 |
19 pages |
| Authors:
Jeffrey W. Book; Henry T. Perkins; Luigi Cavaleri; James D. Doyle; Julie D. Pullen; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
|
| Data from an Acoustic Doppler Current Profiler (ADCP) mooring maintained during the winter of 2001 in 57 m of water near Senigallis, Italy are used to describe the winter conditions of the Western Adriatic Current in the northern Adriatic Sea. Wind and water temperature measurements from the Acqua Alta tower in 19 m water depth off Venice and winds from a 4-km resolution reanalysis model, COAMPS, are used to interpret ... |
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| Dynamic Calibration Technique for Thermal Shear-Stress Sensors with Mean Flow |
11 MAY 2005 |
11 pages |
| Authors:
V. Chandrasekaran; A. Cain; T. Nishida; L. N. Cattafesta; M. Sheplak; FLORIDA UNIV GAINESVILLE MECHANICAL AND AEROSPACE ENGINEERING
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| This paper presents the development of a dynamic calibration technique for thermal shear-stress sensors using acoustic plane wave excitation. The technique permits the independent variation in the mean and fluctuating shear stresses. The theoretical development and the practical implementation of the technique are presented. The studied conguration has the capability to dynamically calibrate shear-stress sensors up to 20 kHz. An illustrative application of this technique to an uncompensated silicon micromachined ... |
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| Environmental Acoustic Transfer Functions and the Filtering of Acoustic Signals |
21 MAR 2005 |
75 pages |
| Authors:
Brandon P. Dias; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| Signal processing is the method of taking a given signal and extracting useful information, usually by a means of a transformation of some kind. Acoustic signals are functions of time in which the output is a pressure or a velocity potential response. An acoustic signal is affected by the environment in which it propagates, so one can attempt to remove the environmental effects to extract the useful information, in this ... |
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Reports by Keyword(s)
ACOUSTIC WAVES
