Science.gov

Sample records for acoustic source location

  1. Determining low-frequency source location from acoustic phase measurements

    NASA Astrophysics Data System (ADS)

    Poole, Travis L.; Frisk, George V.

    2002-11-01

    For low-frequency cw sound sources in shallow water, the time rate-of-change of the measured acoustic phase is well approximated by the time rate-of-change of the source-receiver separation distance. An algorithm for determining a locus of possible source locations based on this idea has been developed. The locus has the general form of a hyperbola, which can be used to provide a bearing estimation at long ranges, and an estimate of source location at short ranges. The algorithm uses only acoustic phase data and receiver geometry as input, and can be used even when the source frequency is slightly unstable and/or imprecisely known. The algorithm has been applied to data from low-frequency experiments (20-300 Hz), both for stable and unstable source frequencies, and shown to perform well. [Work supported by ONR and WHOI Academic Programs Office.

  2. MEMS directional acoustic sensor for locating sound sources

    NASA Astrophysics Data System (ADS)

    Karunasiri, Gamani; Alves, Fabio; Swan, William

    2016-02-01

    The conventional directional sound sensing systems employ an array of spatially separated microphones to achieve directional sensing. However, there are insects such as Ormia ochracea fly that can determine the direction of sound using a miniature hearing organ much smaller than the wavelength of sound it detects. The MEMS based sensors mimicking the fly's hearing system was fabricated using SOI substrate with 25 micrometer device layer. The sensor was designed to operate around 1.7 kHz, consists of two 1.2 mm × 1.2 mm wings connected in the middle by a 3 mm × 30 micrometer bridge. The entire structure is connected to the substrate by two torsional legs at the center. The sensor operates at its bending resonance frequency and has cosine directional characteristics similar to that of a pressure gradient microphone. For unambiguously determining the direction of sound, two sensors were assembled with a canted angle and outputs of the two sensors were processed to uniquely locate the bearing. At the bending resonant frequency (1.7 kHz) an output voltage of about 25 V/Pa was measured. The uncertainty of the bearing of sound ranged from less than 0.3 degrees close to the normal axis (0 degree) to 3 degrees at the limits of coverage (+/- 60 degrees) based on the 30 degree canted angle used. These findings indicate the potential use of a dual MEMS direction finding sensor assembly to locate sound sources with high accuracy.

  3. Continuous wavelet transform analysis and modal location analysis acoustic emission source location for nuclear piping crack growth monitoring

    SciTech Connect

    Mohd, Shukri; Holford, Karen M.; Pullin, Rhys

    2014-02-12

    Source location is an important feature of acoustic emission (AE) damage monitoring in nuclear piping. The ability to accurately locate sources can assist in source characterisation and early warning of failure. This paper describe the development of a novelAE source location technique termed 'Wavelet Transform analysis and Modal Location (WTML)' based on Lamb wave theory and time-frequency analysis that can be used for global monitoring of plate like steel structures. Source location was performed on a steel pipe of 1500 mm long and 220 mm outer diameter with nominal thickness of 5 mm under a planar location test setup using H-N sources. The accuracy of the new technique was compared with other AE source location methods such as the time of arrival (TOA) techniqueand DeltaTlocation. Theresults of the study show that the WTML method produces more accurate location resultscompared with TOA and triple point filtering location methods. The accuracy of the WTML approach is comparable with the deltaT location method but requires no initial acoustic calibration of the structure.

  4. Acoustic emission non-destructive testing of structures using source location techniques.

    SciTech Connect

    Beattie, Alan G.

    2013-09-01

    The technology of acoustic emission (AE) testing has been advanced and used at Sandia for the past 40 years. AE has been used on structures including pressure vessels, fire bottles, wind turbines, gas wells, nuclear weapons, and solar collectors. This monograph begins with background topics in acoustics and instrumentation and then focuses on current acoustic emission technology. It covers the overall design and system setups for a test, with a wind turbine blade as the object. Test analysis is discussed with an emphasis on source location. Three test examples are presented, two on experimental wind turbine blades and one on aircraft fire extinguisher bottles. Finally, the code for a FORTRAN source location program is given as an example of a working analysis program. Throughout the document, the stress is on actual testing of real structures, not on laboratory experiments.

  5. Toward a probabilistic acoustic emission source location algorithm: A Bayesian approach

    NASA Astrophysics Data System (ADS)

    Schumacher, Thomas; Straub, Daniel; Higgins, Christopher

    2012-09-01

    Acoustic emissions (AE) are stress waves initiated by sudden strain releases within a solid body. These can be caused by internal mechanisms such as crack opening or propagation, crushing, or rubbing of crack surfaces. One application for the AE technique in the field of Structural Engineering is Structural Health Monitoring (SHM). With piezo-electric sensors mounted to the surface of the structure, stress waves can be detected, recorded, and stored for later analysis. An important step in quantitative AE analysis is the estimation of the stress wave source locations. Commonly, source location results are presented in a rather deterministic manner as spatial and temporal points, excluding information about uncertainties and errors. Due to variability in the material properties and uncertainty in the mathematical model, measures of uncertainty are needed beyond best-fit point solutions for source locations. This paper introduces a novel holistic framework for the development of a probabilistic source location algorithm. Bayesian analysis methods with Markov Chain Monte Carlo (MCMC) simulation are employed where all source location parameters are described with posterior probability density functions (PDFs). The proposed methodology is applied to an example employing data collected from a realistic section of a reinforced concrete bridge column. The selected approach is general and has the advantage that it can be extended and refined efficiently. Results are discussed and future steps to improve the algorithm are suggested.

  6. Acoustic emission source location in complex structures using full automatic delta T mapping technique

    NASA Astrophysics Data System (ADS)

    Al-Jumaili, Safaa Kh.; Pearson, Matthew R.; Holford, Karen M.; Eaton, Mark J.; Pullin, Rhys

    2016-05-01

    An easy to use, fast to apply, cost-effective, and very accurate non-destructive testing (NDT) technique for damage localisation in complex structures is key for the uptake of structural health monitoring systems (SHM). Acoustic emission (AE) is a viable technique that can be used for SHM and one of the most attractive features is the ability to locate AE sources. The time of arrival (TOA) technique is traditionally used to locate AE sources, and relies on the assumption of constant wave speed within the material and uninterrupted propagation path between the source and the sensor. In complex structural geometries and complex materials such as composites, this assumption is no longer valid. Delta T mapping was developed in Cardiff in order to overcome these limitations; this technique uses artificial sources on an area of interest to create training maps. These are used to locate subsequent AE sources. However operator expertise is required to select the best data from the training maps and to choose the correct parameter to locate the sources, which can be a time consuming process. This paper presents a new and improved fully automatic delta T mapping technique where a clustering algorithm is used to automatically identify and select the highly correlated events at each grid point whilst the "Minimum Difference" approach is used to determine the source location. This removes the requirement for operator expertise, saving time and preventing human errors. A thorough assessment is conducted to evaluate the performance and the robustness of the new technique. In the initial test, the results showed excellent reduction in running time as well as improved accuracy of locating AE sources, as a result of the automatic selection of the training data. Furthermore, because the process is performed automatically, this is now a very simple and reliable technique due to the prevention of the potential source of error related to manual manipulation.

  7. Acoustic emission source location on large plate-like structures using a local triangular sensor array

    NASA Astrophysics Data System (ADS)

    Aljets, Dirk; Chong, Alex; Wilcox, Steve; Holford, Karen

    2012-07-01

    A new acoustic emission (AE) source location method was developed for large plate-like structures, which evaluates the location of the source using a combined time of flight and modal source location algorithm. Three sensors are installed in a triangular array with a sensor to sensor distance of just a few centimeters. The direction from the sensor array to the AE source can be established by analysing the arrival times of the A0 component of the signal to the three sensors whilst the distance can be evaluated using the separation of S0 and A0 mode at each sensor respectively. The close positioning of the sensors allows the array to be installed in a single housing. This simplifies mounting, wiring and calibration procedures for non-destructive testing (NDT) and structural health monitoring (SHM) applications. Furthermore, this array could reduce the number of sensors needed to monitor large structures compared to other methods. An automatic wave mode identification method is also presented.

  8. Acoustic source location in a jet-blown flap using a cross-correlation technique

    NASA Technical Reports Server (NTRS)

    Becker, R. S.; Maus, J. R.

    1977-01-01

    The acoustic source strength distribution in a turbulent flow field was measured for two far field microphones at 45 deg above and below the plane of the flap surface. A processed signal from an inclined hot-film anemometry probe was cross correlated with the signal from the appropriate far field microphone. The contribution made by the sources associated with the fluctuating pressure on the flap surface to the sound received at far field microphone was estimated by cross correlating the processed signals of microphones which were embedded in the flap surface with the far field microphone signals. In addition, detailed fluid dynamic measurements were made in the flow field of the jet flap using dual sensor hot-film anemometry probes.

  9. Effect of Anisotropic Velocity Structure on Acoustic Emission Source Location during True-Triaxial Deformation Experiments

    NASA Astrophysics Data System (ADS)

    Ghofrani Tabari, Mehdi; Goodfellow, Sebastian; Young, R. Paul

    2016-04-01

    Although true-triaxial testing (TTT) of rocks is now more extensive worldwide, stress-induced heterogeneity due to the existence of several loading boundary effects is not usually accounted for and simplified anisotropic models are used. This study focuses on the enhanced anisotropic velocity structure to improve acoustic emission (AE) analysis for an enhanced interpretation of induced fracturing. Data from a TTT on a cubic sample of Fontainebleau sandstone is used in this study to evaluate the methodology. At different stages of the experiment the True-Triaxial Geophysical Imaging Cell (TTGIC), armed with an ultrasonic and AE monitoring system, performed several velocity surveys to image velocity structure of the sample. Going beyond a hydrostatic stress state (poro-elastic phase), the rock sample went through a non-dilatational elastic phase, a dilatational non-damaging elasto-plastic phase containing initial AE activity and finally a dilatational and damaging elasto-plastic phase up to the failure point. The experiment was divided into these phases based on the information obtained from strain, velocity and AE streaming data. Analysis of the ultrasonic velocity survey data discovered that a homogeneous anisotropic core in the center of the sample is formed with ellipsoidal symmetry under the standard polyaxial setup. Location of the transducer shots were improved by implementation of different velocity models for the sample starting from isotropic and homogeneous models going toward anisotropic and heterogeneous models. The transducer shot locations showed a major improvement after the velocity model corrections had been applied especially at the final phase of the experiment. This location improvement validated our velocity model at the final phase of the experiment consisting lower-velocity zones bearing partially saturated fractures. The ellipsoidal anisotropic velocity model was also verified at the core of the cubic rock specimen by AE event location of

  10. Acoustic Emission Source Location in Unidirectional Carbon-Fibre-Reinforced Plastic Plates Using Virtually Trained Artificial Neural Networks

    SciTech Connect

    Caprino, G.; Lopresto, V.; Leone, C.; Papa, I.

    2010-06-02

    Acoustic emission source location in a unidirectional carbon-fibre-reinforced plastic plate was attempted employing Artificial Neural Network (ANN) technology. The acoustic emission events were produced by a lead break, and the response wave received by piezoelectric sensors, type VS150-M resonant at 150 kHz. The waves were detected by a Vallen AMSY4 eight-channel instrumentation. The time of arrival, determined through the conventional threshold crossing technique, was used to measure the dependence of wave velocity on fibre orientation. A simple empirical formula, relying on classical lamination and suggested by wave propagation theory, was able to accurately model the experimental trend. Based on the formula, virtual training and testing data sets were generated for the case of a plate monitored by three transducers, and adopted to select two potentially effective ANN architectures. For final validation, experimental tests were carried out, positioning the source at predetermined points evenly distributed within the plate area. A very satisfactory correlation was found between the actual source locations and the ANN predictions.

  11. Explosion Source Location Study Using Collocated Acoustic and Seismic Networks in Israel

    NASA Astrophysics Data System (ADS)

    Pinsky, V.; Gitterman, Y.; Arrowsmith, S.; Ben-Horin, Y.

    2013-12-01

    infrasonic phases of the two distant arrays; 2) a standard robust grid-search location procedure based on phase picks and a constant celerity for a phase (tropospheric or stratospheric) was applied; 3) a joint coordinate grid-search procedure using array waveforms and phase picks was tested, 4) the Bayesian Infrasonic Source Localization (BISL) method, incorporating semi-empirical model-based prior information, was modified for array+network configuration and applied to the ground-truth events. For this purpose we accumulated data of the former observations of the air-to-ground infrasonic phases to compute station specific ground-truth Celerity-Range Histograms (ssgtCRH) and/or model-based CRH (mbCRH), which allow to essentially improve the location results. For building the mbCRH the local meteo-data and the ray-tracing modeling in 3 available azimuth ranges, accounting seasonal variations of winds directivity (quadrants North:315-45, South: 135-225, East 45-135) have been used.

  12. Acoustic source for generating an acoustic beam

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2016-05-31

    An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

  13. Practical aspects of acoustic plastic pipe location

    SciTech Connect

    Huebler, J.E.; Campbell, B.K.; Ching, G.K.

    1993-12-31

    Many gas distribution company operation and maintenance activities require precise knowledge of the location of buried plastic piping. Plastic pipe cannot be located if the tracer wire is gone or was never installed. Under sponsorship of the Southern California Gas Company, IGT successfully demonstrated an acoustic plastic pipe location technique and is developing the technique into a practical field instrument an acoustic signal is injected directly into the gas at a service. The acoustic signal travels in the gas in the pipes, not in the pipe wall. As the acoustic wave travels along the pipe, some of the sound radiates from the pipe through the soil to the surface of the ground. An array of sensors on the surface of the ground perpendicular to the pipe detects the acoustic signal, thereby locating the Pipe. Two different acoustic measurements are used. The first measurement locates the pipe to within {plus_minus} 3-ft. Then the second technique determines the location of the pipe to within {plus_minus} 6-in.

  14. LOCATING LEAKS WITH ACOUSTIC TECHNOLOGY

    EPA Science Inventory

    Many water distribution systems in this country are almost 100 years old. About 26 percent of piping in these systems is made of unlined cast iron or steel and is in poor condition. Many methods that locate leaks in these pipes are time-consuming, costly, disruptive to operations...

  15. Properties of acoustic sources in the Sun

    NASA Technical Reports Server (NTRS)

    Kumar, Pawan

    1994-01-01

    The power spectrum of solar acoustic oscillations shows peaks extending out to frequencies much greater than the acoustic cutoff frequency of approximately 5.3 mHz, where waves are no longer trapped. Kumar & Lu (1991) proposed that these peaks arise from the interference of traveling waves which are generated by turbulent convection. According to this model, the frequencies of the peaks in the power spectrum depend on the static structure of the Sun as well as the radial location of the sources. Kumar & Lu used this idea to determine the depth of the acoustic sources. However, they ignored dissipative effects and found that the theoretically computed power spectrum was falling off much more rapidly than the observed spectrum. In this paper, we include the interaction of radiation with acoustic waves in the computation of the power spectrum. We find that the theoretically calculated power spectra, when radiative damping is included are in excellent agreement with the observed power spectra over the entire observed frequency range of 5.3 to 7.5 mHz above the acoustic cutoff frequency. Moreover, by matching the peak frequencies in the observed and theoretical spectra we find the mean depth of acoustic sources to be 140 +/- 60 km below the photosphere. We show that the spectrum of solar turbulence near the top of the solar convection zone is consistent with the Kolmogorov spectrum, and that the observed high frequency power spectrum provides strong evidence that the acoustic sources in the Sun are quadrupolar. The data, in fact, rules out dipole sources as significant contributors to acoustic wave generation in the Sun. The radial extent of the sources is poorly determined and is estimated to be less than about 550 km.

  16. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions.

    PubMed

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  17. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

    PubMed Central

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  18. Location of Sources of Radiation Using a Weighted Hyperbolic Technique

    NASA Technical Reports Server (NTRS)

    Thomson, E. M.

    1995-01-01

    The specific problem objective was to locate the sources of radiated electric field from lightning using an overdetermined set of measurements of time-of-arrival. A similar problem exists for epicentral sources in earthquake location, acoustic sources of thunder, and terrestrial navigation using LORAN and GPS.

  19. ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

    2004-10-31

    The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement.

  20. ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

    2004-12-01

    The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement.

  1. Source Identification and Location Techniques

    NASA Technical Reports Server (NTRS)

    Weir, Donald; Bridges, James; Agboola, Femi; Dougherty, Robert

    2001-01-01

    Mr. Weir presented source location results obtained from an engine test as part of the Engine Validation of Noise Reduction Concepts program. Two types of microphone arrays were used in this program to determine the jet noise source distribution for the exhaust from a 4.3 bypass ratio turbofan engine. One was a linear array of 16 microphones located on a 25 ft. sideline and the other was a 103 microphone 3-D "cage" array in the near field of the jet. Data were obtained from a baseline nozzle and from numerous nozzle configuration using chevrons and/or tabs to reduce the jet noise. Mr. Weir presented data from two configurations: the baseline nozzle and a nozzle configuration with chevrons on both the core and bypass nozzles. This chevron configuration had achieved a jet noise reduction of 4 EPNdB in small scale tests conducted at the Glenn Research Center. IR imaging showed that the chevrons produced significant improvements in mixing and greatly reduced the length of the jet potential core. Comparison of source location data from the 1-D phased array showed a shift of the noise sources towards the nozzle and clear reductions of the sources due to the noise reduction devices. Data from the 3-D array showed a single source at a frequency of 125 Hz. located several diameters downstream from the nozzle exit. At 250 and 400 Hz., multiple sources, periodically spaced, appeared to exist downstream of the nozzle. The trend of source location moving toward the nozzle exit with increasing frequency was also observed. The 3-D array data also showed a reduction in source strength with the addition of chevrons. The overall trend of source location with frequency was compared for the two arrays and with classical experience. Similar trends were observed. Although overall trends with frequency and addition of suppression devices were consistent between the data from the 1-D and the 3-D arrays, a comparison of the details of the inferred source locations did show differences. A

  2. 76 FR 52734 - Underwater Locating Devices (Acoustic) (Self-Powered)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-23

    ...This notice announces the planned revocation of all Technical Standard Order authorizations (TSOA) issued for the production of Underwater Locating Devices (Acoustic) (Self-Powered) manufactured to the TSO-C121 and TSO-C121a specifications. These actions are necessary because the planned issuance of TSO-C121b, Underwater Locating Devices (Acoustic) (Self-Powered), with a minimum performance......

  3. 77 FR 13174 - Underwater Locating Devices (Acoustic) (Self-Powered)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-05

    ...This is a confirmation notice for the planned revocation of all Technical Standard Order authorizations issued for the production of Underwater Locating Devices (Acoustic) (Self-Powered) manufactured to the TSO-C121 and TSO-C121a specifications. These actions are necessary because the planned issuance of TSO-C121b, Underwater Locating Devices (Acoustic) (Self-Powered), minimum performance......

  4. Passive acoustic source localization using sources of opportunity.

    PubMed

    Verlinden, Christopher M A; Sarkar, J; Hodgkiss, W S; Kuperman, W A; Sabra, K G

    2015-07-01

    The feasibility of using data derived replicas from ships of opportunity for implementing matched field processing is demonstrated. The Automatic Identification System (AIS) is used to provide the library coordinates for the replica library and a correlation based processing procedure is used to overcome the impediment that the replica library is constructed from sources with different spectra and will further be used to locate another source with its own unique spectral structure. The method is illustrated with simulation and then verified using acoustic data from a 2009 experiment for which AIS information was retrieved from the United States Coast Guard Navigation Center Nationwide AIS database.

  5. Vehicular sources in acoustic propagation experiments

    NASA Technical Reports Server (NTRS)

    Prado, Gervasio; Fitzgerald, James; Arruda, Anthony; Parides, George

    1990-01-01

    One of the most important uses of acoustic propagation models lies in the area of detection and tracking of vehicles. Propagation models are used to compute transmission losses in performance prediction models and to analyze the results of past experiments. Vehicles can also provide the means for cost effective experiments to measure acoustic propagation conditions over significant ranges. In order to properly correlate the information provided by the experimental data and the propagation models, the following issues must be taken into consideration: the phenomenology of the vehicle noise sources must be understood and characterized; the vehicle's location or 'ground truth' must be accurately reproduced and synchronized with the acoustic data; and sufficient meteorological data must be collected to support the requirements of the propagation models. The experimental procedures and instrumentation needed to carry out propagation experiments are discussed. Illustrative results are presented for two cases. First, a helicopter was used to measure propagation losses at a range of 1 to 10 Km. Second, a heavy diesel-powered vehicle was used to measure propagation losses in the 300 to 2200 m range.

  6. System and method for sonic wave measurements using an acoustic beam source

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2015-08-11

    A method and system for investigating structure near a borehole are described herein. The method includes generating an acoustic beam by an acoustic source; directing at one or more azimuthal angles the acoustic beam towards a selected location in a vicinity of a borehole; receiving at one or more receivers an acoustic signal, the acoustic signal originating from a reflection or a refraction of the acoustic wave by a material at the selected location; and analyzing the received acoustic signal to characterize features of the material around the borehole.

  7. Optimal estimation of undersea acoustic transponder locations

    NASA Technical Reports Server (NTRS)

    Carta, D. G.

    1978-01-01

    Using principles from multilateration and optimal estimation theories an approach is derived for estimating the relative positions of three or more submerged and anchored acoustic transponders. The procedure is not constrained to processing range data collected at special points or on special trajectories. While the data normally collected over transponders and between transponder pairs can be processed, simultaneous ranges from anywhere on the surface to three or more transponders can also be processed. Simulated examples involving four stations in different geometries with different range collection schemes demonstrate the effectiveness of the procedure.

  8. Acoustic source analysis of supersonic jets from complex nozzles

    NASA Astrophysics Data System (ADS)

    Nichols, Joseph W.; Kreitzman, Jordan

    2015-11-01

    We compute acoustic source terms corresponding to Goldstein's generalized acoustic analogy from an unstructured high-fidelity large eddy simulation of a supersonic jet issuing from a rectangular nozzle with chevrons. The simulation data are validated against experimental measurements of mean and turbulence flow statistics as well as far-field noise. We evaluate fourth-order correlations from the simulation data to assess assumptions of quasi-normality and statistical axisymmetry that underpin reduced-order acoustic source models originally developed for round jets. A spatial analysis of these correlations in relation to the complex geometry of the nozzle reveals locations where the validity of these assumptions begins to break down. Using two point two-time correlations of the simulation data, we also directly evaluate and compare the accuracy of four different acoustic source models, including the Gaussian, moving-frame, fixed-frame, and modified distance models. Computational resources were provided by the Argonne Leadership Computing Facility.

  9. Location of Impulsive Acoustic Sources in Urban Environments Using Finite-Difference, Time-Domain Modeling of Time Reversal with Data from Small Sensor Arrays

    DTIC Science & Technology

    2006-12-01

    the environment that causes the sound scattering (such as buildings) can be modeled on a computer and adequate sensor data can be collected, one can...way, for example, high-energy ultrasound can be precisely focused to break up a gallstone or kidney stone.6, 7 In the process of locating a sound

  10. Pulsed-Source Interferometry in Acoustic Imaging

    NASA Technical Reports Server (NTRS)

    Shcheglov, Kirill; Gutierrez, Roman; Tang, Tony K.

    2003-01-01

    A combination of pulsed-source interferometry and acoustic diffraction has been proposed for use in imaging subsurface microscopic defects and other features in such diverse objects as integrated-circuit chips, specimens of materials, and mechanical parts. A specimen to be inspected by this technique would be mounted with its bottom side in contact with an acoustic transducer driven by a continuous-wave acoustic signal at a suitable frequency, which could be as low as a megahertz or as high as a few hundred gigahertz. The top side of the specimen would be coupled to an object that would have a flat (when not vibrating) top surface and that would serve as the acoustical analog of an optical medium (in effect, an acoustical "optic").

  11. Acoustic Source Bearing Estimation (ASBE) computer program development

    NASA Technical Reports Server (NTRS)

    Wiese, Michael R.

    1987-01-01

    A new bearing estimation algorithm (Acoustic Source Analysis Technique - ASAT) and an acoustic analysis computer program (Acoustic Source Bearing Estimation - ASBE) are described, which were developed by Computer Sciences Corporation for NASA Langley Research Center. The ASBE program is used by the Acoustics Division/Applied Acoustics Branch and the Instrument Research Division/Electro-Mechanical Instrumentation Branch to analyze acoustic data and estimate the azimuths from which the source signals radiated. Included are the input and output from a benchmark test case.

  12. Directivity of acoustic radiation from sources

    NASA Technical Reports Server (NTRS)

    Lansing, D. L.

    1979-01-01

    The radiation properties of acoustic monopoles and dipoles are described. The directivity of radiation from these sources in a free field and in the presence of an absorptive surface is described. The kinematic effects on source radiation due to translation and rotation are discussed. Experimental measurements of sound from an acoustic monopole in motion and the characteristics of helicopter rotor and propeller noise are reviewed. An introduction is provided to several essential concepts required by noise control engineers making measurements of noise from moving sources in the proximity of the ground.

  13. Directivity of acoustic radiation from sources

    NASA Technical Reports Server (NTRS)

    Lansing, D. L.

    1979-01-01

    The radiation properties of acoustic monopoles and dipoles are described, as well as the directivity of radiation from these sources in a free field and in the presence of an absorptive surface. The kinematic effects on source radiation due to translation and rotation are discussed. Experimental measurements of sound from an acoustic monopole in motion and the characteristics of helicopter rotor and propeller noise are reviewed. Several essential concepts required by noise control engineers making measurements of noise from moving sources in the proximity of the ground are introduced.

  14. Broadband source localization using horizontal-beam acoustic intensity striations.

    PubMed

    Turgut, Altan; Orr, Marshall; Rouseff, Daniel

    2010-01-01

    Waveguide invariant theory is applied to horizontal line array (HLA) beamformer output to localize moving broadband noise sources from measured acoustic intensity striation patterns. Acoustic signals emitted by ships of opportunity (merchant ships) were simultaneously recorded on a HLA and three hydrophones separated by 10 km during the RAGS03 (relationship between array gain and shelf-break fluid processes) experiment. Hough transforms are used to estimate both the waveguide invariant parameter "beta" and the ratio of source range at the closest point of approach to source speed from the observed striation patterns. Broadband (50-150-Hz) acoustic data-sets are used to demonstrate source localization capability as well as inversion capability of waveguide invariant parameter beta. Special attention is paid to bathymetric variability since the acoustic intensity striation patterns seem to be influenced by range-dependent bathymetry of the experimental area. The Hough transform method is also applied to the HLA beam-time record data and to the acoustic intensity data from three distant receivers to validate the estimation results from HLA beamformer output. Good agreement of the results from all three approaches suggests the feasibility of locating broadband noise sources and estimating waveguide invariant parameter beta in shallow waters.

  15. Locating groundwater flow in karst by acoustic emission surveys

    SciTech Connect

    Stokowski, S.J. Jr.; Clark, D.A.

    1985-01-01

    An acoustic emission survey of Newala Fm. (primarily dolomite) karst has helped to locate subsurface water flow. This survey was performed on the Rock Quarry Dome, Sevier County, Tennessee. A Dresser RS-4 recording seismograph, adjusted to provide a gain of 1000, collected acoustic emission data using Mark Products CN368 vertical geophones with 3-inch spikes. Data was collected for 5-15 second intervals. The geophones were laid out along traverses with 10, 20, or 30-ft spacing and covered with sand bags in locations of high ambient noise. Traverses were laid out: along and across lineaments known to correspond with groundwater flow in natural subsurface channels; across and along a joint-controlled sink suspected of directing groundwater flow; and across a shallow sinkhole located tangentially to the Little Pigeon River and suspected of capturing river water for the groundwater system. Acoustic emissions of channelized flowing groundwater have a characteristic erratic spiked spectral signature. These acoustic emission signatures increase in amplitude and number in the immediate vicinity of the vertical projection of channelized groundwater flow if it occurs within approximately 30 feet of the surface. If the groundwater flow occurs at greater depths the emissions may be offset from the projection of the actual flow, due to propagation of the signal along rock pinnacles or attenuation by residual soils.

  16. Mapping thunder sources by inverting acoustic and electromagnetic observations

    NASA Astrophysics Data System (ADS)

    Anderson, J. F.; Johnson, J. B.; Arechiga, R. O.; Thomas, R. J.

    2014-12-01

    We present a new method of locating current flow in lightning strikes by inversion of thunder recordings constrained by Lightning Mapping Array observations. First, radio frequency (RF) pulses are connected to reconstruct conductive channels created by leaders. Then, acoustic signals that would be produced by current flow through each channel are forward modeled. The recorded thunder is considered to consist of a weighted superposition of these acoustic signals. We calculate the posterior distribution of acoustic source energy for each channel with a Markov Chain Monte Carlo inversion that fits power envelopes of modeled and recorded thunder; these results show which parts of the flash carry current and produce thunder. We examine the effects of RF pulse location imprecision and atmospheric winds on quality of results and apply this method to several lightning flashes over the Magdalena Mountains in New Mexico, USA. This method will enable more detailed study of lightning phenomena by allowing researchers to map current flow in addition to leader propagation.

  17. Location and acoustic scale cues in concurrent speech recognition1

    PubMed Central

    Ives, D. Timothy; Vestergaard, Martin D.; Kistler, Doris J.; Patterson, Roy D.

    2010-01-01

    Location and acoustic scale cues have both been shown to have an effect on the recognition of speech in multi-speaker environments. This study examines the interaction of these variables. Subjects were presented with concurrent triplets of syllables from a target voice and a distracting voice, and asked to recognize a specific target syllable. The task was made more or less difficult by changing (a) the location of the distracting speaker, (b) the scale difference between the two speakers, and∕or (c) the relative level of the two speakers. Scale differences were produced by changing the vocal tract length and glottal pulse rate during syllable synthesis: 32 acoustic scale differences were used. Location cues were produced by convolving head-related transfer functions with the stimulus. The angle between the target speaker and the distracter was 0°, 4°, 8°, 16°, or 32° on the 0° horizontal plane. The relative level of the target to the distracter was 0 or −6 dB. The results show that location and scale difference interact, and the interaction is greatest when one of these cues is small. Increasing either the acoustic scale or the angle between target and distracter speakers quickly elevates performance to ceiling levels. PMID:20550271

  18. Waveform Based Acoustic Emission Detection and Location of Matrix Cracking in Composites

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.

    1995-01-01

    The operation of damage mechanisms in a material or structure under load produces transient acoustic waves. These acoustic waves are known as acoustic emission (AE). In composites they can be caused by a variety of sources including matrix cracking, fiber breakage, and delamination. AE signals can be detected and analyzed to determine the location of the acoustic source by triangulation. Attempts are also made to analyze the signals to determine the type and severity of the damage mechanism. AE monitoring has been widely used for both laboratory studies of materials, and for testing the integrity of structures in the field. In this work, an advanced, waveform based AE system was used in a study of transverse matrix cracking in cross-ply graphite/epoxy laminates. This AE system featured broad band, high fidelity sensors, and high capture rate digital acquisition and storage of acoustic signals. In addition, analysis techniques based on plate wave propagation models were employed. These features provided superior source location and noise rejection capabilities.

  19. Impact of source depth on coherent underwater acoustic communications.

    PubMed

    Song, Aijun; Badiey, Mohsen; Song, H C; Hodgkiss, W S

    2010-08-01

    A recent paper [Song et al., J. Acoust. Soc. Am. 123, 856-865 (2008)] investigated ocean variability impact on coherent underwater acoustic communications (8-16 kHz) for a single near-seafloor transmitter in shallow water during an extended period (27 h). This letter extends that investigation to various source depths and receiver subarrays. Specifically, the middle water column source, which is either in or out of the thermocline, experiences performance variability of 6-7 dB in terms of output signal-to-noise ratio. Further, the source below the thermocline consistently outperforms the source above the thermocline when the receiver subarray is located below the thermocline.

  20. Measurements of acoustic sources in motion

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Norum, T. D.

    1978-01-01

    Results of the far-field pressures measured from three different types of moving sources are presented. These acoustic sources consist of a point monopole, a small model jet, and an aircraft. Results for the pressure time history produced by the point source show good agreement with those predicted analytically. Both actual and simulated forward motion of the model jet show reductions in noise levels with forward speed at all angles between the source and observer. Measurement with the aircraft over both an anechoic floor and over the ground yields a method for evaluating the transfer function for ground reflections at various angles between the moving aircraft and measurement position.

  1. Acoustic emission location on aluminum alloy structure by using FBG sensors and PSO method

    NASA Astrophysics Data System (ADS)

    Lu, Shizeng; Jiang, Mingshun; Sui, Qingmei; Dong, Huijun; Sai, Yaozhang; Jia, Lei

    2016-04-01

    Acoustic emission location is important for finding the structural crack and ensuring the structural safety. In this paper, an acoustic emission location method by using fiber Bragg grating (FBG) sensors and particle swarm optimization (PSO) algorithm were investigated. Four FBG sensors were used to form a sensing network to detect the acoustic emission signals. According to the signals, the quadrilateral array location equations were established. By analyzing the acoustic emission signal propagation characteristics, the solution of location equations was converted to an optimization problem. Thus, acoustic emission location can be achieved by using an improved PSO algorithm, which was realized by using the information fusion of multiple standards PSO, to solve the optimization problem. Finally, acoustic emission location system was established and verified on an aluminum alloy plate. The experimental results showed that the average location error was 0.010 m. This paper provided a reliable method for aluminum alloy structural acoustic emission location.

  2. An Expendable Source for Measuring Shallow Water Acoustic Propagation and Geo-Acoustic Bottom Properties

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. An Expendable Source for Measuring Shallow Water Acoustic ...Propagation and Geo- Acoustic Bottom Properties Harry A DeFerrari RSMAS – University of Miami 4600 Rickenbacker Causeway Miami FL. 33149...broadband source is being developed that transmits high gain m-sequence to clandestinly measure pulse response of shallow water acoustic propagation

  3. Locating POPs Sources with Tree Bark.

    PubMed

    Peverly, Angela A; Salamova, Amina; Hites, Ronald A

    2015-12-01

    Locating sources of persistent organic pollutants (POPs) to the atmosphere can sometimes be difficult. We suggest that tree bark makes an excellent passive atmospheric sampler and that spatial analysis of tree bark POPs concentrations can often pinpoint their sources. This is an effective strategy because tree bark is lipophilic and readily adsorbs and collects POPs from the atmosphere. As such, tree bark is an ideal sampler to find POPs sources globally, regionally, or locally. This article summarizes some work on this subject with an emphasis on kriged maps and a simple power-law model, both of which have been used to locate sources. Three of the four examples led directly to the pollutant's manufacturing plant.

  4. Locating Microseism Sources in Offshore Southern California

    NASA Astrophysics Data System (ADS)

    Tian, X.; Clayton, R. W.

    2007-12-01

    We use the broadband stations from the S. California network to locate the apparent origin of secondary microseisms energy (5-8 Hz band). The procedure is to grid the offshore region and using each grid point as the source point, predict the response of a Rayleigh wave at each station. These predicted waveforms are then correlated with the data over a time window that is typically a 1/2 hour in length and composited at the grid point. The length of the time window controls a tradeoff between the spatial-temporal resolution of the sources and the robustness on the image. The procedure is valid for multiple sources. This results show that during periods of high microseism activity the sources are distinct at several locations in a region approximately 50-100 km offshore. For an 11/09/2002 Southern Ocean storm, for example, two zones parallel to each other and perpendicular to the coast are imaged.

  5. Acoustic Source Elevation Angle Estimates Using Two Microphones

    DTIC Science & Technology

    2014-06-01

    Acoustic Source Elevation Angle Estimates Using Two Microphones by Kirsten A. Walker and W.C. Kirkpatrick Alberts, II ARL-TR-6976 June...TR-6976 June 2014 Acoustic Source Elevation Angle Estimates Using Two Microphones Kirsten A. Walker and W.C. Kirkpatrick Alberts, II...3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Acoustic Source Elevation Angle Estimates Using Two Microphones 5a. CONTRACT NUMBER 5b

  6. Developing general acoustic model for noise sources and parameters estimation

    NASA Astrophysics Data System (ADS)

    Madoliat, Reza; Nouri, Nowrouz Mohammad; Rahrovi, Ali

    2017-02-01

    Noise measured at various points around the environment can be evaluated by a series of acoustic sources. Acoustic sources with wide surface can be broken down in fluid environment using some smaller acoustic sources. The aim of this study is to make a model to indicate the type, number, direction, position and strength of these sources in a way that the main sound and the sound of equivalent sources match together in an acceptable way. When position and direction of the source is given, the strength of the source can be found using inverse method. On the other hand, considering the non-uniqueness of solution in inverse method, a different acoustic strength is obtained for the sources if different positions are selected. Selecting an arrangement of general source and using the optimization algorithm, the least possible mismatch between the main sound and the sound of equivalent sources can be achieved.

  7. The acoustical cues to sound location in the guinea pig (Cavia porcellus).

    PubMed

    Greene, Nathaniel T; Anbuhl, Kelsey L; Williams, Whitney; Tollin, Daniel J

    2014-10-01

    There are three main acoustical cues to sound location, each attributable to space- and frequency-dependent filtering of the propagating sound waves by the outer ears, head, and torso: Interaural differences in time (ITD) and level (ILD) as well as monaural spectral shape cues. While the guinea pig has been a common model for studying the anatomy, physiology, and behavior of binaural and spatial hearing, extensive measurements of their available acoustical cues are lacking. Here, these cues were determined from directional transfer functions (DTFs), the directional components of the head-related transfer functions, for 11 adult guinea pigs. In the frontal hemisphere, monaural spectral notches were present for frequencies from ∼10 to 20 kHz; in general, the notch frequency increased with increasing sound source elevation and in azimuth toward the contralateral ear. The maximum ITDs calculated from low-pass filtered (2 kHz cutoff frequency) DTFs were ∼250 μs, whereas the maximum ITD measured with low-frequency tone pips was over 320 μs. A spherical head model underestimates ITD magnitude under normal conditions, but closely approximates values when the pinnae were removed. Interaural level differences (ILDs) strongly depended on location and frequency; maximum ILDs were <10 dB for frequencies <4 kHz and were as large as 40 dB for frequencies >10 kHz. Removal of the pinna reduced the depth and sharpness of spectral notches, altered the acoustical axis, and reduced the acoustical gain, ITDs, and ILDs; however, spectral shape features and acoustical gain were not completely eliminated, suggesting a substantial contribution of the head and torso in altering the sounds present at the tympanic membrane.

  8. The acoustical cues to sound location in the Guinea pig (cavia porcellus)

    PubMed Central

    Greene, Nathanial T; Anbuhl, Kelsey L; Williams, Whitney; Tollin, Daniel J.

    2014-01-01

    There are three main acoustical cues to sound location, each attributable to space-and frequency-dependent filtering of the propagating sound waves by the outer ears, head, and torso: Interaural differences in time (ITD) and level (ILD) as well as monaural spectral shape cues. While the guinea pig has been a common model for studying the anatomy, physiology, and behavior of binaural and spatial hearing, extensive measurements of their available acoustical cues are lacking. Here, these cues were determined from directional transfer functions (DTFs), the directional components of the head-related transfer functions, for eleven adult guinea pigs. In the frontal hemisphere, monaural spectral notches were present for frequencies from ~10 to 20 kHz; in general, the notch frequency increased with increasing sound source elevation and in azimuth toward the contralateral ear. The maximum ITDs calculated from low-pass filtered (2 kHz cutoff frequency) DTFs were ~250 µs, whereas the maximum ITD measured with low frequency tone pips was over 320 µs. A spherical head model underestimates ITD magnitude under normal conditions, but closely approximates values when the pinnae were removed. Interaural level differences (ILDs) strongly depended on location and frequency; maximum ILDs were < 10 dB for frequencies < 4 kHz and were as large as 40 dB for frequencies > 10 kHz. Removal of the pinna reduced the depth and sharpness of spectral notches, altered the acoustical axis, and reduced the acoustical gain, ITDs, and ILDs; however, spectral shape features and acoustical gain were not completely eliminated, suggesting a substantial contribution of the head and torso in altering the sounds present at the tympanic membrane. PMID:25051197

  9. Accurate Simulation of Acoustic Emission Sources in Composite Plates

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Gorman, M. R.

    1994-01-01

    Acoustic emission (AE) signals propagate as the extensional and flexural plate modes in thin composite plates and plate-like geometries such as shells, pipes, and tubes. The relative amplitude of the two modes depends on the directionality of the source motion. For source motions with large out-of-plane components such as delaminations or particle impact, the flexural or bending plate mode dominates the AE signal with only a small extensional mode detected. A signal from such a source is well simulated with the standard pencil lead break (Hsu-Neilsen source) on the surface of the plate. For other sources such as matrix cracking or fiber breakage in which the source motion is primarily in-plane, the resulting AE signal has a large extensional mode component with little or no flexural mode observed. Signals from these type sources can also be simulated with pencil lead breaks. However, the lead must be fractured on the edge of the plate to generate an in-plane source motion rather than on the surface of the plate. In many applications such as testing of pressure vessels and piping or aircraft structures, a free edge is either not available or not in a desired location for simulation of in-plane type sources. In this research, a method was developed which allows the simulation of AE signals with a predominant extensional mode component in composite plates requiring access to only the surface of the plate.

  10. Seismo-Acoustic Observations of Explosive Sources

    NASA Astrophysics Data System (ADS)

    Chael, E. P.; Hart, D. M.; Jones, K. R.

    2011-12-01

    Since January 2011, the Sandia National Laboratories Facility for Acceptance, Calibration and Testing (FACT) has operated a seismo-acoustic station with the purpose of recording local explosions on Kirtland Air Force Base (KAFB). Our immediate goals are to develop a catalog of events and a database of seismo-acoustic waveforms from ordnance disposal and Defense Threat Reduction Agency (DTRA) events. The catalog of events will include metadata such as shot time, size, type and location. The waveform archive includes a three-channel GS-13 seismometer and a single infrasound sensor (Chaparral 25 with 50' porous hose wind reduction system). In June of 2011 a weather station was added to complement the monitoring system by providing accurate wind conditions at the times of the explosive events. Monthly internal reports compiled by KAFB provided us with the metadata for the ordnance disposal explosions, and an agreement with DTRA has enabled us to obtain metadata on their events. To date 157 explosions have been identified, including 153 ordnance disposal events and 4 DTRA tests. Along with the catalog of events we have developed automated processing routines to extract both seismic and infrasound arrivals and measure basic waveform characteristics. These include amplitudes of pre-event noise, the direct seismic arrival, air-coupled seismic arrival, infrasound arrival, and wind speed/direction. Using the waveform measurements from the pre-event noise and air-coupled seismic arrival we calculate the SNR for the seismic component of the event. We also calculate the SNR for the infrasonic component of the event using pre-event noise and the direct infrasound arrival. Using the metadata and seismic and infrasonic SNR values we are able to calculate an air-to-ground coupling ratio for each event. For local (<10 km) explosion monitoring, the wind speed and direction can influence all of the analysis parameters. It will affect the pre-event noise level as well as the infrasound

  11. Acoustic radiation from lined, unflanged ducts: Acoustic source distribution program

    NASA Technical Reports Server (NTRS)

    Beckemeyer, R. J.; Sawdy, D. T.

    1971-01-01

    An acoustic radiation analysis was developed to predict the far-field characteristics of fan noise radiated from an acoustically lined unflanged duct. This analysis is comprised of three modular digital computer programs which together provide a capability of accounting for the impedance mismatch at the duct exit plane. Admissible duct configurations include circular or annular, with or without an extended centerbody. This variation in duct configurations provides a capability of modeling inlet and fan duct noise radiation. The computer programs are described in detail.

  12. Acoustic intensity in the interaction region of a parametric source

    NASA Astrophysics Data System (ADS)

    Lauchle, G. C.; Gabrielson, T. B.; van Tol, D. J.; Kottke, N. F.; McConnell, J. A.

    2003-10-01

    The goal of this project was to measure acoustic intensity in the strong interaction region of a parametric source in order to obtain a clear definition of the source-generation region and to separate the local generation (the reactive field) from propagation (the real or active field). The acoustic intensity vector was mapped in the interaction region of a parametric projector at Lake Seneca. The source was driven with primary signals at 22 kHz and 27 kHz. Receiving sensors were located 8.5 meters from the projector. At that range, the secondary at 5 kHz was between 40 and 45 dB below either primary. For the primary levels used, the plane-wave shock inception distance would have been at least 14 meters. Furthermore, the Rayleigh distance for the projector was about 4 meters so the measurements at 8.5 meters were in the strong interaction region but not in saturation. Absorption was negligible over these ranges. The intensity measurements were made at fixed range but varying azimuth angle and varying depth thus developing a two-dimensional cross-section of the secondary beam. Measurements of both the active and reactive intensity vectors will be presented along with a discussion of measurement error. [Work supported by ONR Code 321SS.

  13. Developing a system for blind acoustic source localization and separation

    NASA Astrophysics Data System (ADS)

    Kulkarni, Raghavendra

    This dissertation presents innovate methodologies for locating, extracting, and separating multiple incoherent sound sources in three-dimensional (3D) space; and applications of the time reversal (TR) algorithm to pinpoint the hyper active neural activities inside the brain auditory structure that are correlated to the tinnitus pathology. Specifically, an acoustic modeling based method is developed for locating arbitrary and incoherent sound sources in 3D space in real time by using a minimal number of microphones, and the Point Source Separation (PSS) method is developed for extracting target signals from directly measured mixed signals. Combining these two approaches leads to a novel technology known as Blind Sources Localization and Separation (BSLS) that enables one to locate multiple incoherent sound signals in 3D space and separate original individual sources simultaneously, based on the directly measured mixed signals. These technologies have been validated through numerical simulations and experiments conducted in various non-ideal environments where there are non-negligible, unspecified sound reflections and reverberation as well as interferences from random background noise. Another innovation presented in this dissertation is concerned with applications of the TR algorithm to pinpoint the exact locations of hyper-active neurons in the brain auditory structure that are directly correlated to the tinnitus perception. Benchmark tests conducted on normal rats have confirmed the localization results provided by the TR algorithm. Results demonstrate that the spatial resolution of this source localization can be as high as the micrometer level. This high precision localization may lead to a paradigm shift in tinnitus diagnosis, which may in turn produce a more cost-effective treatment for tinnitus than any of the existing ones.

  14. Locating industrial VOC sources with aircraft observations.

    PubMed

    Toscano, P; Gioli, B; Dugheri, S; Salvini, A; Matese, A; Bonacchi, A; Zaldei, A; Cupelli, V; Miglietta, F

    2011-05-01

    Observation and characterization of environmental pollution, focussing on Volatile Organic Compounds (VOCs), in a high-risk industrial area, are particularly important in order to provide indications on a safe level of exposure, indicate eventual priorities and advise on policy interventions. The aim of this study is to use the Solid Phase Micro Extraction (SPME) method to measure VOCs, directly coupled with atmospheric measurements taken on a small aircraft environmental platform, to evaluate and locate the presence of VOC emission sources in the Marghera industrial area. Lab analysis of collected SPME fibres and subsequent analysis of mass spectrum and chromatograms in Scan Mode allowed the detection of a wide range of VOCs. The combination of this information during the monitoring campaign allowed a model (Gaussian Plume) to be implemented that estimates the localization of emission sources on the ground.

  15. Near-field beamforming analysis for acoustic emission source localization.

    PubMed

    He, Tian; Pan, Qiang; Liu, Yaoguang; Liu, Xiandong; Hu, Dayong

    2012-07-01

    This paper attempts to introduce a near-field acoustic emission (AE) beamforming method to estimate the AE source locations by using a small array of sensors closely placed in a local region. The propagation characteristics of AE signals are investigated based on guided wave theory to discuss the feasibility of using beamforming techniques in AE signal processing. To validate the effectiveness of the AE beamforming method, a series of pencil lead break tests at various regions of a thin steel plate are conducted. The potential of this method for engineering applications are explored through rotor-stator rubbing tests. The experimental results demonstrate that the proposed method can effectively determine the region where rubbing occurs. It is expected that the work of this paper may provide a helpful analysis tool for near-field AE source localization.

  16. Tracking Moving Acoustic Sources With a Network of Sensors

    DTIC Science & Technology

    2002-10-01

    Tracking Moving Acoustic Sources With a Network of Sensors by Richard J. Kozick and Brian M. Sadler ARL-TR-2750 October 2002 Approved for public...October 2002 Tracking Moving Acoustic Sources With a Network of Sensors Richard J. Kozick Bucknell University, Electrical Engineering Department Brian M...Model for a Nonmoving Source 4 2.1 Cramér-Rao Bound (CRB) . . . . . . . . . . . . . . . . . . . . 6 2.2 Examples

  17. Blind deconvolution and source separation in acoustics

    NASA Astrophysics Data System (ADS)

    Sibul, Leon H.; Roan, Michael J.; Coviello, Christian M.

    2005-09-01

    Blind deconvolution (BDC) and blind source separation (BSS) are active research topics with many important applications in acoustics. The goal of deconvolution is to recover original input signal from the output of a convolution filter. In blind deconvolution details of the convolution filter and input signals are not known. The fundamental assumption in BDC is that the input signal is a non-Gaussian stochastic process. A topic closely related to BDC is BSS. BSS is a process that is an inverse operation to a mixing process. In BSS it is assumed that inputs to the mixing systems are statistically independent stochastic processes, where only one input may be Gaussian, others must be non-Gaussian. Standard criterion functions for BDC and BSS are reviewed. Limitations of the second-order statistics and need for higher-order statistics (HOS) or information theoretic criteria that lead to nonlinear optimization algorithms are pointed out. Advantages of various information theoretic criteria for BDC and BSS are discussed. Because gradients of these criteria are nonlinear, resulting optimization algorithms are nonlinear. Linear and non-linear algorithms for BDC and BSS are examined. [Work supported by ONR Codes 321US and 333.

  18. Acoustic Source Localization in Aircraft Interiors Using Microphone Array Technologies

    NASA Technical Reports Server (NTRS)

    Sklanka, Bernard J.; Tuss, Joel R.; Buehrle, Ralph D.; Klos, Jacob; Williams, Earl G.; Valdivia, Nicolas

    2006-01-01

    Using three microphone array configurations at two aircraft body stations on a Boeing 777-300ER flight test, the acoustic radiation characteristics of the sidewall and outboard floor system are investigated by experimental measurement. Analysis of the experimental data is performed using sound intensity calculations for closely spaced microphones, PATCH Inverse Boundary Element Nearfield Acoustic Holography, and Spherical Nearfield Acoustic Holography. Each method is compared assessing strengths and weaknesses, evaluating source identification capability for both broadband and narrowband sources, evaluating sources during transient and steady-state conditions, and quantifying field reconstruction continuity using multiple array positions.

  19. Sparsity-driven Passive Tracking of Underwater Acoustic Sources

    DTIC Science & Technology

    2015-08-01

    bend ✴ Temperature , pressure and salinity D epth Range Source localization map (SLM) 2 Shallow water sound -speed profile Modeling...Difficult due to complexities of the propagation environment • Ocean behaves as an acoustic waveguide • Varying sound -speed causes acoustic signals to

  20. Acoustic monitoring of laboratory faults: locating the origin of unstable slip events

    NASA Astrophysics Data System (ADS)

    Korkolis, Evangelos; Niemeijer, André; Spiers, Christopher

    2015-04-01

    Over the past several decades, much work has been done on studying the frictional properties of fault gouges at earthquake nucleation velocities. In addition, post-experiment microstructural analyses have been performed in an attempt to link microphysical mechanisms to the observed mechanical data. However, all observations are necessarily post-mortem and it is thus difficult to directly link transients to microstructural characteristics. We are developing an acoustic monitoring system to be used in sliding experiments using a ring shear apparatus. The goal is to locate acoustic emission sources in sheared granular assemblages and link them to processes that act on microstructures responsible for the frictional stability of the simulated fault gouge. The results will be used to develop and constrain microphysical models that explain the relation of these processes to empirical friction laws, such as rate- and state-dependent friction. The acoustic monitoring setup is comprised of an array of 16 piezo-electric sensors installed on the top and bottom sides of an annular sample, at 45 degree intervals. Acoustic emissions associated with slip events can be recorded at sampling rates of up to 50 MHz, in triggered mode. Initial experiments on 0.1 to 0.2 mm and 0.4 to 0.5 mm diameter glass beads, at 1 to 5 MPa normal stress and 1 to 30 um/s load point velocity, have been conducted to estimate the sensitivity of the sensor array. Preliminary results reveal that the intensity of the audible signal is not necessarily proportional to the magnitude of the associated stress drop for constant loading conditions, and that acoustic emissions precede slip events by a small amount of time, in the order of a few milliseconds. Currently, our efforts are focused on developing a suitable source location algorithm with the aim to identify differences in the mode of (unstable) sliding for different types of materials. This will help to identify the micromechanical mechanisms operating

  1. An optoacoustic point source for acoustic scale model measurements.

    PubMed

    Bolaños, Javier Gómez; Pulkki, Ville; Karppinen, Pasi; Hæggström, Edward

    2013-04-01

    A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

  2. Acoustic positioning using a tetrahedral ultrashort baseline array of an acoustic modem source transmitting frequency-hopped sequences.

    PubMed

    Beaujean, Pierre-Philippe J; Mohamed, Asif I; Warin, Raphael

    2007-01-01

    Acoustic communications and positioning are vital aspects of unmanned underwater vehicle operations. The usage of separate units on each vehicle has become an issue in terms of frequency bandwidth, space, power, and cost. Most vehicles rely on acoustic modems transmitting frequency-hopped multiple frequency-shift keyed sequences for command-and-control operations, which can be used to locate the vehicle with a good level of accuracy without requiring extra signal transmission. In this paper, an ultrashort baseline acoustic positioning technique has been designed, simulated, and tested to locate an acoustic modem source in three dimensions using a tetrahedral, half-wavelength acoustic antenna. The position estimation is performed using the detection sequence contained in each message, which is a series of frequency-hopped pulses. Maximum likelihood estimation of azimuth and elevation estimation is performed using a varying number of pulse and various signal-to-noise ratios. Simulated and measured position estimation error match closely, and indicate that the accuracy of this system improves dramatically as the number of pulses processed increases, given a fixed signal-to-noise ratio.

  3. Normal mode solutions for seismo-acoustic propagation resulting from shear and combined wave point sources.

    PubMed

    Nealy, Jennifer L; Collis, Jon M; Frank, Scott D

    2016-04-01

    Normal mode solutions to range-independent seismo-acoustic problems are benchmarked against elastic parabolic equation solutions and then used to benchmark the shear elastic parabolic equation self-starter [Frank, Odom, and Collis, J. Acoust. Soc. Am. 133, 1358-1367 (2013)]. The Pekeris waveguide with an elastic seafloor is considered for a point source located in the ocean emitting compressional waves, or in the seafloor, emitting both compressional and shear waves. Accurate solutions are obtained when the source is in the seafloor, and when the source is at the interface between the fluid and elastic layers.

  4. ACOUSTIC LOCATION OF LEAKS IN PRESSURIZED UNDER- GROUND PETROLEUM PIPELINES

    EPA Science Inventory

    Experiments were conducted at the Underground Storage Tank (UST) Test Apparatus Pipeline in which three acoustic sensors separated by a maximum distance of 38.1 m (125 ft) were used to monitor signals produced by 11.4-, 5.7-, and 3.8-L/h (3.0-, 1.5-, and 1.0-gal/h) leaks in th...

  5. Partial sound field decomposition in multireference near-field acoustical holography by using optimally located virtual references

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Joe; Bolton, J. Stuart; Kwon, Hyu-Sang

    2004-04-01

    It has been shown previously that the multiple reference and field signals recorded during a scanning acoustical holography measurement can be used to decompose the sound field radiated by a composite sound source into mutually incoherent partial fields. To obtain physically meaningful partial fields, i.e., fields closely related to particular component sources, the reference microphones should be positioned as close as possible to the component physical sources that together comprise the complete source. However, it is not always possible either to identify the optimal reference microphone locations prior to performing a holographic measurement, or to place reference microphones at those optimal locations, even if known, owing to physical constraints. Here, post-processing procedures are described that make it possible both to identify the optimal reference microphone locations and to place virtual references at those locations after performing a holographic measurement. The optimal reference microphone locations are defined to be those at which the MUSIC power is maximized in a three-dimensional space reconstructed by holographic projection. The acoustic pressure signals at the locations thus identified can then be used as optimal ``virtual'' reference signals. It is shown through an experiment and numerical simulation that the optimal virtual reference signals can be successfully used to identify physically meaningful partial sound fields, particularly when used in conjunction with partial coherence decomposition procedures.

  6. Use of acoustic intensity measurements in the characterization of jet noise sources

    NASA Astrophysics Data System (ADS)

    Musafir, R. E.; Slama, J. G.; Zindeluk, M.

    The usefulness of two-microphone acoustic-intensity (AI) measurements for characterizing the acoustic field of a jet flow is investigated by means of numerical simulations. The theoretical principles and data basis for the simulations are explained, and the intensity patterns generated by the simulation are presented graphically. It is found that the vector information in AI data from the near field are useful in understanding complex sources, but that far-field intensity charts cannot locate separate sources and may be misleading if not analyzed in terms of a sound physical model.

  7. On the output of acoustical sources

    NASA Technical Reports Server (NTRS)

    Levine, H.

    1979-01-01

    Contents: (1) a theoretical basis for local power calculation; (2) source radiation in the presence of a half-plane; (3) radiation from a line source near an edge at which a Kutta condition holds; (4) radiation by a point source above a plane independence boundary; and (5) power output of a point source in a uniform flow.

  8. Reconstruction of moving acoustic sources in heterogeneous elastic solid

    NASA Astrophysics Data System (ADS)

    Lloyd, Stephen F.; Jeong, Chanseok

    2016-04-01

    A novel computational framework for reconstructing spatial and temporal profiles of moving acoustic sources from wave responses measured at sparsely distributes sensors is introduced in this paper. This method can be applied to a broad range of acoustic-source inversion (ASI) problems for heterogeneous, complex-shaped coupled dynamic systems. The finite element method (FEM) is used to obtain wave response solutions due guessed moving sources. An adjoint-gradient based optimization technique iteratively improves the guesses so that the guessed moving sources converge on the actual moving sources. To reconstruct acoustic source profiles without a-priori knowledge of sources, we will employ high-resolution discretization of source functions in space and time. Because of such dense discretization, the order of magnitude of number of inversion parameters could range from millions to billions. Numerical experiments prove the robustness of this method by reconstructing spatial and temporal profiles of multiple dynamic moving body forces in a one-dimensional heterogeneous solid bar. The sources create stress waves propagating through the bar. The guessed source functions are spatially discretized by using linear shape functions with an element size of 1m at discrete times with a time step of 0.001s. Thus, the total number of control parameters in this example is 100,000 (i.e., 100 (in space) by 1000 (in time)). The convergence toward the target in the numerical examples is excellent, reconstructing the spatial and temporal footprints of the sources.

  9. Acoustic source analysis of a rectangular supersonic jet

    NASA Astrophysics Data System (ADS)

    Kreitzman, Jordan; Nichols, Joseph W.

    2014-11-01

    We apply Goldstein's generalized acoustic analogy to identify acoustic sources in two high-fidelity unstructured large eddy simulation databases of a Mach 1.4 rectangular jet with and without chevrons. Two-point, two-time correlations of the acoustic source terms are evaluated at different positions in the three dimensional flow that develops downstream of the complex nozzle. Two-point statistics are compared to single-point statistics to test the quasi-normality hypothesis and other noise source models for a non-axisymmetric jet. In particular, we assess the predictive capability of a Gaussian model, a fixed-frame model and a modified-distance model. The nozzle geometries used for the simulations exactly match an experimental configuration tested at the NASA Glenn Research Center, allowing for validation in terms of both farfield noise as well as turbulence statistics. We gratefully acknowledge computational resources provided by the Argonne Leadership Computing Facility.

  10. Optimization of Microphone Locations for Acoustic Liner Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; June, J. C.

    2015-01-01

    Two impedance eduction methods are explored for use with data acquired in the NASA Langley Grazing Flow Impedance Tube. The first is an indirect method based on the convected Helmholtz equation, and the second is a direct method based on the Kumaresan and Tufts algorithm. Synthesized no-flow data, with random jitter to represent measurement error, are used to evaluate a number of possible microphone locations. Statistical approaches are used to evaluate the suitability of each set of microphone locations. Given the computational resources required, small sample statistics are employed for the indirect method. Since the direct method is much less computationally intensive, a Monte Carlo approach is employed to gather its statistics. A comparison of results achieved with full and reduced sets of microphone locations is used to determine which sets of microphone locations are acceptable. For the indirect method, each array that includes microphones in all three regions (upstream and downstream hard wall sections, and liner test section) provides acceptable results, even when as few as eight microphones are employed. The best arrays employ microphones well away from the leading and trailing edges of the liner. The direct method is constrained to use microphones opposite the liner. Although a number of arrays are acceptable, the optimum set employs 14 microphones positioned well away from the leading and trailing edges of the liner. The selected sets of microphone locations are also evaluated with data measured for ceramic tubular and perforate-over-honeycomb liners at three flow conditions (Mach 0.0, 0.3, and 0.5). They compare favorably with results attained using all 53 microphone locations. Although different optimum microphone locations are selected for the two impedance eduction methods, there is significant overlap. Thus, the union of these two microphone arrays is preferred, as it supports usage of both methods. This array contains 3 microphones in the upstream

  11. A review of underwater acoustic systems and methods for locating objects lost at sea

    NASA Technical Reports Server (NTRS)

    Lovelady, R. W.; Ferguson, R. L.

    1983-01-01

    Information related to the location of objects lost at sea is presented. Acoustic devices attached to an object prior to being transported is recommended as a homing beacon. Minimum requirements and some environmental constraints are defined. Methods and procedures for search and recovery are also discussed. Both an interim system and a more advanced system are outlined. Controlled acoustic emission to enhance security is the theme followed.

  12. B-scan based acoustic source reconstruction for magnetoacoustic tomography with magnetic induction (MAT-MI).

    PubMed

    Mariappan, Leo; Li, Xu; He, Bin

    2011-03-01

    We present in this study, an acoustic source reconstruction method using focused transducer with B-mode imaging for magnetoacoustic tomography with magnetic induction (MAT-MI). MAT-MI is an imaging modality proposed for noninvasive conductivity imaging with high spatial resolution. In MAT-MI, acoustic sources are generated in a conductive object by placing it in a static and a time-varying magnetic field. The acoustic waves from these sources propagate in all directions and are collected with transducers placed around the object. The collected signal is then used to reconstruct the acoustic source distribution and to further estimate the electrical conductivity distribution of the object. A flat piston transducer acting as a point receiver has been used in earlier MAT-MI systems to collect acoustic signals. In this study, we propose to use B-mode scan scheme with a focused transducer that gives a signal gain in its focus region and improves the MAT-MI signal quality. A simulation protocol that can take into account different transducer designs and scan schemes for MAT-MI imaging is developed and used in our evaluation of different MAT-MI system designs. It is shown in our computer simulations that as compared to the earlier approach, the MAT-MI system using B-scan with a focused transducer allows MAT-MI imaging at a closer distance and has improved system sensitivity. In addition, the B-scan imaging technique allows reconstruction of the MAT-MI acoustic sources with a discrete number of scanning locations, which greatly increases the applicability of the MAT-MI approach, especially when a continuous acoustic window is not available in real clinical applications. We have also conducted phantom experiments to evaluate the proposed method, and the reconstructed image shows a good agreement with the target phantom.

  13. ACOUSTIC DETECTING AND LOCATING GAS PIPE LINE INFRINGEMENT

    SciTech Connect

    John L Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-04-01

    The West Virginia University natural gas transmission line leak detection research is only considering using readily available 1/2 inch pipeline access ports for the detection of leak generated signals. The main problem with leak signals is the low signal to noise ratio. One of the acoustic signals associated with gas escaping through a leak is only temporary and is in the form of a rarefaction wave originating when the leak is formed. Due to pipeline friction, over distance such a step function transitions to a ramp function. The ability to identify a leak by pipeline monitoring and signal processing depends a great deal on the quality and signal to noise ratio of the characteristics of the detectors used. Combinations of sensing devices are being used for the WVU sensor package and are contained in a removable sensor housing. The four sensors currently installed are a 1/2 inch 3 Hz-40 Khz microphone, an audible range moving coil sensor, a piezo-electric pressure transducer, and the WVU designed floating 3 inch diameter diaphragm to detect flow transient induced pressure ramp type signals. The WVU diaphragm sensor, which is currently under development, uses the same diaphragm principle as a high quality capacitance type microphone, but utilizes aerodynamic signal amplification. This type of amplification only amplifies the ramp-signal itself, not the random pipeline noise.

  14. Source location of the 19 February 2008 Oregon bolide using seismic networks and infrasound arrays

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer T.; Hedlin, Michael A. H.; de Groot-Hedlin, Catherine; Vergoz, Julien; Le Pichon, Alexis; Drob, Douglas P.

    2010-12-01

    On 19 February 2008 a bolide traveled across the sky along a southern trajectory ending in a terminal burst above Oregon. The event was well recorded by the USArray, other seismic networks, four infrasound arrays, and several video cameras. We compare the results of locating the burst using these different sensor networks. Specifically, we reverse time migrate acoustic-to-seismic coupled signals recorded by the USArray out to 800 km range to image the source in 2-D space and time. We also apply a grid search over source altitude and time, minimizing the misfit between observed and predicted arrival times using 3-D ray tracing with a high-resolution atmospheric velocity model. Our seismic and video results suggest a point source rather than a line source associated with a hypersonic trajectory. We compare the seismic source locations to those obtained by using different combinations of observed infrasound array signal back azimuths and arrival times. We find that all locations are consistent. However, the seismic location is more accurate than the infrasound locations due to the larger number of seismic sensors, a more favorable seismic source-receiver geometry, and shorter ranges to the seismometers. For the infrasound array locations, correcting for the wind improved the accuracy, but implementing arrival times while increasing the precision reduced the accuracy presumably due to limitations of the source location method and/or atmospheric velocity model. We show that despite known complexities associated with acoustic-to-seismic coupling, aboveground infrasound sources can be located with dense seismic networks with remarkably high accuracy and precision.

  15. Localization of short-range acoustic and seismic wideband sources: Algorithms and experiments

    NASA Astrophysics Data System (ADS)

    Stafsudd, J. Z.; Asgari, S.; Hudson, R.; Yao, K.; Taciroglu, E.

    2008-04-01

    We consider the determination of the location (source localization) of a disturbance source which emits acoustic and/or seismic signals. We devise an enhanced approximate maximum-likelihood (AML) algorithm to process data collected at acoustic sensors (microphones) belonging to an array of, non-collocated but otherwise identical, sensors. The approximate maximum-likelihood algorithm exploits the time-delay-of-arrival of acoustic signals at different sensors, and yields the source location. For processing the seismic signals, we investigate two distinct algorithms, both of which process data collected at a single measurement station comprising a triaxial accelerometer, to determine direction-of-arrival. The direction-of-arrivals determined at each sensor station are then combined using a weighted least-squares approach for source localization. The first of the direction-of-arrival estimation algorithms is based on the spectral decomposition of the covariance matrix, while the second is based on surface wave analysis. Both of the seismic source localization algorithms have their roots in seismology; and covariance matrix analysis had been successfully employed in applications where the source and the sensors (array) are typically separated by planetary distances (i.e., hundreds to thousands of kilometers). Here, we focus on very-short distances (e.g., less than one hundred meters) instead, with an outlook to applications in multi-modal surveillance, including target detection, tracking, and zone intrusion. We demonstrate the utility of the aforementioned algorithms through a series of open-field tests wherein we successfully localize wideband acoustic and/or seismic sources. We also investigate a basic strategy for fusion of results yielded by acoustic and seismic arrays.

  16. A hybrid deconvolution approach to separate static and moving single-tone acoustic sources by phased microphone array measurements

    NASA Astrophysics Data System (ADS)

    Mo, Pinxi; Jiang, Weikang

    2017-02-01

    Beamforming approaches are developed to locate and quantify either static or moving acoustic sources by phased microphone array measurements. They would meet difficulties in mapping combined sources consisting of both static and moving sources. In this work, a hybrid deconvolution approach is proposed to separate static and moving single-tone sources. The approach is derived based on the source independence assumption as in the Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS). The static beamforming and the moving beamforming are integrated to construct a linear matrix equation. The source distributions for the static sources and moving sources are simultaneously obtained by solving the equation. Numerical simulations and experiments were implemented on the combined sources with one static source and one rotating source. From the results, the hybrid deconvolution approach shows its effectiveness in separating the two sources, even with large source strength differences.

  17. Military jet noise source imaging using multisource statistically optimized near-field acoustical holography.

    PubMed

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; McKinley, Richard L; James, Michael M

    2016-04-01

    The identification of acoustic sources is critical to targeted noise reduction efforts for jets on high-performance tactical aircraft. This paper describes the imaging of acoustic sources from a tactical jet using near-field acoustical holography techniques. The measurement consists of a series of scans over the hologram with a dense microphone array. Partial field decomposition methods are performed to generate coherent holograms. Numerical extrapolation of data beyond the measurement aperture mitigates artifacts near the aperture edges. A multisource equivalent wave model is used that includes the effects of the ground reflection on the measurement. Multisource statistically optimized near-field acoustical holography (M-SONAH) is used to reconstruct apparent source distributions between 20 and 1250 Hz at four engine powers. It is shown that M-SONAH produces accurate field reconstructions for both inward and outward propagation in the region spanned by the physical hologram measurement. Reconstructions across the set of engine powers and frequencies suggests that directivity depends mainly on estimated source location; sources farther downstream radiate at a higher angle relative to the inlet axis. At some frequencies and engine powers, reconstructed fields exhibit multiple radiation lobes originating from overlapped source regions, which is a phenomenon relatively recently reported for full-scale jets.

  18. A Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) Determined from Phased Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M., Jr.

    2004-01-01

    Current processing of acoustic array data is burdened with considerable uncertainty. This study reports an original methodology that serves to demystify array results, reduce misinterpretation, and accurately quantify position and strength of acoustic sources. Traditional array results represent noise sources that are convolved with array beamform response functions, which depend on array geometry, size (with respect to source position and distributions), and frequency. The Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) method removes beamforming characteristics from output presentations. A unique linear system of equations accounts for reciprocal influence at different locations over the array survey region. It makes no assumption beyond the traditional processing assumption of statistically independent noise sources. The full rank equations are solved with a new robust iterative method. DAMAS is quantitatively validated using archival data from a variety of prior high-lift airframe component noise studies, including flap edge/cove, trailing edge, leading edge, slat, and calibration sources. Presentations are explicit and straightforward, as the noise radiated from a region of interest is determined by simply summing the mean-squared values over that region. DAMAS can fully replace existing array processing and presentations methodology in most applications. It appears to dramatically increase the value of arrays to the field of experimental acoustics.

  19. A Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) Determined from Phased Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M.

    2006-01-01

    Current processing of acoustic array data is burdened with considerable uncertainty. This study reports an original methodology that serves to demystify array results, reduce misinterpretation, and accurately quantify position and strength of acoustic sources. Traditional array results represent noise sources that are convolved with array beamform response functions, which depend on array geometry, size (with respect to source position and distributions), and frequency. The Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) method removes beamforming characteristics from output presentations. A unique linear system of equations accounts for reciprocal influence at different locations over the array survey region. It makes no assumption beyond the traditional processing assumption of statistically independent noise sources. The full rank equations are solved with a new robust iterative method. DAMAS is quantitatively validated using archival data from a variety of prior high-lift airframe component noise studies, including flap edge/cove, trailing edge, leading edge, slat, and calibration sources. Presentations are explicit and straightforward, as the noise radiated from a region of interest is determined by simply summing the mean-squared values over that region. DAMAS can fully replace existing array processing and presentations methodology in most applications. It appears to dramatically increase the value of arrays to the field of experimental acoustics.

  20. A refined wideband acoustical holography based on equivalent source method

    PubMed Central

    Ping, Guoli; Chu, Zhigang; Xu, Zhongming; Shen, Linbang

    2017-01-01

    This paper is concerned with acoustical engineering and mathematical physics problem for the near-field acoustical holography based on equivalent source method (ESM-based NAH). An important mathematical physics problem in ESM-based NAH is to solve the equivalent source strength, which has multiple solving algorithms, such as Tikhonov regularization ESM (TRESM), iterative weighted ESM (IWESM) and steepest descent iteration ESM (SDIESM). To explore a new solving algorithm which can achieve better reconstruction performance in wide frequency band, a refined wideband acoustical holography (RWAH) is proposed. RWAH adopts IWESM below a transition frequency and switches to SDIESM above that transition frequency, and the principal components of input data in RWAH have been truncated. Further, the superiority of RWAH is verified by the comparison of comprehensive performance of TRESM, IWESM, SDIESM and RWAH. Finally, the experiments are conducted, confirming that RWAH can achieve better reconstruction performance in wide frequency band. PMID:28266531

  1. A refined wideband acoustical holography based on equivalent source method

    NASA Astrophysics Data System (ADS)

    Ping, Guoli; Chu, Zhigang; Xu, Zhongming; Shen, Linbang

    2017-03-01

    This paper is concerned with acoustical engineering and mathematical physics problem for the near-field acoustical holography based on equivalent source method (ESM-based NAH). An important mathematical physics problem in ESM-based NAH is to solve the equivalent source strength, which has multiple solving algorithms, such as Tikhonov regularization ESM (TRESM), iterative weighted ESM (IWESM) and steepest descent iteration ESM (SDIESM). To explore a new solving algorithm which can achieve better reconstruction performance in wide frequency band, a refined wideband acoustical holography (RWAH) is proposed. RWAH adopts IWESM below a transition frequency and switches to SDIESM above that transition frequency, and the principal components of input data in RWAH have been truncated. Further, the superiority of RWAH is verified by the comparison of comprehensive performance of TRESM, IWESM, SDIESM and RWAH. Finally, the experiments are conducted, confirming that RWAH can achieve better reconstruction performance in wide frequency band.

  2. New approaches for automatic threedimensional source localization of acoustic emissions--Applications to concrete specimens.

    PubMed

    Kurz, Jochen H

    2015-12-01

    The task of locating a source in space by measuring travel time differences of elastic or electromagnetic waves from the source to several sensors is evident in varying fields. The new concepts of automatic acoustic emission localization presented in this article are based on developments from geodesy and seismology. A detailed description of source location determination in space is given with the focus on acoustic emission data from concrete specimens. Direct and iterative solvers are compared. A concept based on direct solvers from geodesy extended by a statistical approach is described which allows a stable source location determination even for partly erroneous onset times. The developed approach is validated with acoustic emission data from a large specimen leading to travel paths up to 1m and therefore to noisy data with errors in the determined onsets. The adaption of the algorithms from geodesy to the localization procedure of sources of elastic waves offers new possibilities concerning stability, automation and performance of localization results. Fracture processes can be assessed more accurately.

  3. Accelerated food source location in aging Drosophila.

    PubMed

    Egenriether, Sada M; Chow, Eileen S; Krauth, Nathalie; Giebultowicz, Jadwiga M

    2015-10-01

    Adequate energy stores are essential for survival, and sophisticated neuroendocrine mechanisms evolved to stimulate foraging in response to nutrient deprivation. Food search behavior is usually investigated in young animals, and it is not known how aging alters this behavior. To address this question in Drosophila melanogaster, we compared the ability to locate food by olfaction in young and old flies using a food-filled trap. As aging is associated with a decline in motor functions, learning, and memory, we expected that aged flies would take longer to enter the food trap than their young counterparts. Surprisingly, old flies located food with significantly shorter latency than young ones. Robust food search behavior was associated with significantly lower fat reserves and lower starvation resistance in old flies. Food-finding latency (FFL) was shortened in young wild-type flies that were starved until their fat was depleted but also in heterozygous chico mutants with reduced insulin receptor activity and higher fat deposits. Conversely, food trap entry was delayed in old flies with increased insulin signaling. Our results suggest that the difference in FFL between young and old flies is linked to age-dependent differences in metabolic status and may be mediated by reduced insulin signaling.

  4. Deconvolution methods and systems for the mapping of acoustic sources from phased microphone arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor); Humphreys, Jr., William M. (Inventor)

    2010-01-01

    A method and system for mapping acoustic sources determined from a phased microphone array. A plurality of microphones are arranged in an optimized grid pattern including a plurality of grid locations thereof. A linear configuration of N equations and N unknowns can be formed by accounting for a reciprocal influence of one or more beamforming characteristics thereof at varying grid locations among the plurality of grid locations. A full-rank equation derived from the linear configuration of N equations and N unknowns can then be iteratively determined. A full-rank can be attained by the solution requirement of the positivity constraint equivalent to the physical assumption of statically independent noise sources at each N location. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with the phased microphone array in order to compile an output presentation thereof, thereby removing the beamforming characteristics from the resulting output presentation.

  5. The Doppler Effect based acoustic source separation for a wayside train bearing monitoring system

    NASA Astrophysics Data System (ADS)

    Zhang, Haibin; Zhang, Shangbin; He, Qingbo; Kong, Fanrang

    2016-01-01

    Wayside acoustic condition monitoring and fault diagnosis for train bearings depend on acquired acoustic signals, which consist of mixed signals from different train bearings with obvious Doppler distortion as well as background noises. This study proposes a novel scheme to overcome the difficulties, especially the multi-source problem in wayside acoustic diagnosis system. In the method, a time-frequency data fusion (TFDF) strategy is applied to weaken the Heisenberg's uncertainty limit for a signal's time-frequency distribution (TFD) of high resolution. Due to the Doppler Effect, the signals from different bearings have different time centers even with the same frequency. A Doppler feature matching search (DFMS) algorithm is then put forward to locate the time centers of different bearings in the TFD spectrogram. With the determined time centers, time-frequency filters (TFF) are designed with thresholds to separate the acoustic signals in the time-frequency domain. Then the inverse STFT (ISTFT) is taken and the signals are recovered and filtered aiming at each sound source. Subsequently, a dynamical resampling method is utilized to remove the Doppler Effect. Finally, accurate diagnosis for train bearing faults can be achieved by applying conventional spectrum analysis techniques to the resampled data. The performance of the proposed method is verified by both simulated and experimental cases. It shows that it is effective to detect and diagnose multiple defective bearings even though they produce multi-source acoustic signals.

  6. Locating the source of projectile fluid droplets

    NASA Astrophysics Data System (ADS)

    Varney, Christopher R.; Gittes, Fred

    2011-08-01

    The ill-posed projectile problem of finding the source height from spattered droplets of viscous fluid is a longstanding obstacle to accident reconstruction and crime-scene analysis. It is widely known how to infer the impact angle of droplets on a surface from the elongation of their impact profiles. However, the lack of velocity information makes finding the height of the origin from the impact position and angle of individual drops not possible. From aggregate statistics of the spatter and basic equations of projectile motion, we introduce a reciprocal correlation plot that is effective when the polar launch angle is concentrated in a narrow range. The vertical coordinate depends on the orientation of the spattered surface and equals the tangent of the impact angle for a level surface. When the horizontal plot coordinate is twice the reciprocal of the impact distance, we can infer the source height as the slope of the data points in the reciprocal correlation plot. If the distribution of launch angles is not narrow, failure of the method is evident in the lack of linear correlation. We perform a number of experimental trials, as well as numerical calculations and show that the height estimate is relatively insensitive to aerodynamic drag. Besides its possible relevance for crime investigation, reciprocal-plot analysis of spatter may find application to volcanism and other topics and is most immediately applicable for undergraduate science and engineering students in the context of crime-scene analysis.

  7. Studies of acoustic emission from point and extended sources

    NASA Technical Reports Server (NTRS)

    Sachse, W.; Kim, K. Y.; Chen, C. P.

    1986-01-01

    The use of simulated and controlled acoustic emission signals forms the basis of a powerful tool for the detailed study of various deformation and wave interaction processes in materials. The results of experiments and signal analyses of acoustic emission resulting from point sources such as various types of indentation-produced cracks in brittle materials and the growth of fatigue cracks in 7075-T6 aluminum panels are discussed. Recent work dealing with the modeling and subsequent signal processing of an extended source of emission in a material is reviewed. Results of the forward problem and the inverse problem are presented with the example of a source distributed through the interior of a specimen.

  8. Determining the sources of sounds: Psychological acoustics

    NASA Astrophysics Data System (ADS)

    Yost, William A.

    2002-05-01

    Perhaps the most important task performed by an organism's sensory system is determining objects in the world surrounding the organism. This is a challenging task for the auditory system, especially when many objects exist at the same time. The peripheral auditory system provides the neural code for the spectral-temporal structure of the complex sound impinging on the ears. It does not code for the sources of the sound. Neural centers beyond the periphery most analyze this spectral-temporal code in order to form perceptual images that make up the auditory scene. Recent psychoacoustical and perceptual research on sound source determination and segregation will be described. This research is just beginning to suggest ways in which the auditory scene is determined. [Work sponsored by NIDCD.

  9. Initial Arctic Acoustic Source Design Study

    DTIC Science & Technology

    1995-01-01

    Novgorod, Russia, 1995. This work was supported in part by Subcontract No. 31-960019-94. The United States Government has a royalty- free license...source for cable emitting complex 5. Weght-size and energy characteristics of emitting complex 6. Installation and elevation of emitting complex 7...transition of the shelf to the region of the continental boderland slope. This will permit, on the one hand, to avoid additional loss caused by - 5

  10. Deconvolution Methods and Systems for the Mapping of Acoustic Sources from Phased Microphone Arrays

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F. (Inventor); Humphreys, Jr., William M. (Inventor)

    2012-01-01

    Mapping coherent/incoherent acoustic sources as determined from a phased microphone array. A linear configuration of equations and unknowns are formed by accounting for a reciprocal influence of one or more cross-beamforming characteristics thereof at varying grid locations among the plurality of grid locations. An equation derived from the linear configuration of equations and unknowns can then be iteratively determined. The equation can be attained by the solution requirement of a constraint equivalent to the physical assumption that the coherent sources have only in phase coherence. The size of the problem may then be reduced using zoning methods. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with a phased microphone array (microphones arranged in an optimized grid pattern including a plurality of grid locations) in order to compile an output presentation thereof, thereby removing beamforming characteristics from the resulting output presentation.

  11. Underwater acoustic source localization using closely spaced hydrophone pairs

    NASA Astrophysics Data System (ADS)

    Sim, Min Seop; Choi, Bok-Kyoung; Kim, Byoung-Nam; Lee, Kyun Kyung

    2016-07-01

    Underwater sound source position is determined using a line array. However, performance degradation occurs owing to a multipath environment, which generates incoherent signals. In this paper, a hydrophone array is proposed for underwater source position estimation robust to a multipath environment. The array is composed of three pairs of sensors placed on the same line. The source position is estimated by performing generalized cross-correlation (GCC). The proposed system is not affected by a multipath time delay because of the close distance between closely spaced sensors. The validity of the array is confirmed by simulation using acoustic signals synthesized by eigenrays.

  12. Three precise gamma-ray burst source locations

    NASA Technical Reports Server (NTRS)

    Cline, T. L.; Desai, U. D.; Teegarden, B. J.; Barat, C.; Hurley, K.; Niel, M.; Vedrenne, G.; Evans, W. D.; Klebesadel, R. W.; Laros, J. G.

    1984-01-01

    The precise source regions of three moderately intense gamma ray bursts are derived. These events were observed with the first interplanetary burst sensor network. The optimum locations of the detectors, widely separated throughout the inner solar system, allowed for high accuracy, over-determined source fields of size 0.7 to 7.0 arc-min(2). All three locations are at fairly high galactic latitude in regions of low source confusion; none can be identified with a steady source object. Archived photographs were searched for optical transients that are able to be associated with these source fields; one such association was made.

  13. Observations and Bayesian location methodology of transient acoustic signals (likely blue whales) in the Indian Ocean, using a hydrophone triplet.

    PubMed

    Le Bras, Ronan J; Kuzma, Heidi; Sucic, Victor; Bokelmann, Götz

    2016-05-01

    A notable sequence of calls was encountered, spanning several days in January 2003, in the central part of the Indian Ocean on a hydrophone triplet recording acoustic data at a 250 Hz sampling rate. This paper presents signal processing methods applied to the waveform data to detect, group, extract amplitude and bearing estimates for the recorded signals. An approximate location for the source of the sequence of calls is inferred from extracting the features from the waveform. As the source approaches the hydrophone triplet, the source level (SL) of the calls is estimated at 187 ± 6 dB re: 1 μPa-1 m in the 15-60 Hz frequency range. The calls are attributed to a subgroup of blue whales, Balaenoptera musculus, with a characteristic acoustic signature. A Bayesian location method using probabilistic models for bearing and amplitude is demonstrated on the calls sequence. The method is applied to the case of detection at a single triad of hydrophones and results in a probability distribution map for the origin of the calls. It can be extended to detections at multiple triads and because of the Bayesian formulation, additional modeling complexity can be built-in as needed.

  14. S-Band Shallow Bulk Acoustic Wave (SBAW) microwave source

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Techniques necessary to fabricate a high performance S-band microwave single source using state-of-the-art shallow bulk acoustic wave (SBAW) were explored. The bulk wave structures of the AlN/Al 2O3 were investigated for both the R plane and basal plane of sapphire. A 1.072 GHz SBAW delay line and oscillators were developed. A method of selecting and setting oscillator output frequency by selecting substrate orientation angle was also established.

  15. Acoustic source analysis of a supersonic rectangular chevron jet

    NASA Astrophysics Data System (ADS)

    Kreitzman, Jordan Richard

    Source terms corresponding to Goldstein's generalized acoustic analogy are computed from a high-fidelity simulation of a supersonic jet issuing from a rectangular nozzle with chevrons. Simulated data are validated against experimental data. We investigate the theoretical underpinning of reduced-order acoustic source models by testing the assumptions of quasi-normality and statistical axisymmetry. It is found that the flow is not quasi-normal in the axial direction but is quasi-normal in the transverse directions. Our analysis also shows that the flow is locally statistically axisymmetric close to the edges of the flow but not near the center. Fourth order correlation statistics are fit to previously used acoustic source models originally developed for axisymmetric jets. This thesis performs a detailed analysis of four different models: the Gaussian, moving-frame, fixed-frame, and modified-distance models. The latter three models are found to be similar in accuracy, while the Gaussian model is found to be a poorer fit.

  16. Accuracy of an acoustic location system for monitoring the position of duetting songbirds in tropical forest

    PubMed Central

    Mennill, Daniel J.; Burt, John M.; Fristrup, Kurt M.; Vehrencamp, Sandra L.

    2008-01-01

    A field test was conducted on the accuracy of an eight-microphone acoustic location system designed to triangulate the position of duetting rufous-and-white wrens (Thryothorus rufalbus) in Costa Rica’s humid evergreen forest. Eight microphones were set up in the breeding territories of twenty pairs of wrens, with an average inter-microphone distance of 75.2±2.6 m. The array of microphones was used to record antiphonal duets broadcast through stereo loudspeakers. The positions of the loudspeakers were then estimated by evaluating the delay with which the eight microphones recorded the broadcast sounds. Position estimates were compared to coordinates surveyed with a global-positioning system (GPS). The acoustic location system estimated the position of loudspeakers with an error of 2.82±0.26 m and calculated the distance between the “male” and “female” loudspeakers with an error of 2.12±0.42 m. Given the large range of distances between duetting birds, this relatively low level of error demonstrates that the acoustic location system is a useful tool for studying avian duets. Location error was influenced partly by the difficulties inherent in collecting high accuracy GPS coordinates of microphone positions underneath a lush tropical canopy, and partly by the complicating influence of irregular topography and thick vegetation on sound transmission. PMID:16708941

  17. On the location of frequencies of maximum acoustic-to-seismic coupling

    SciTech Connect

    Sabatier, J.M.; Bass, H.E.; Elliott, G.R.

    1986-10-01

    Measurements of the acoustic-to-seismic transfer function (ratio of the normal soil particle velocity at a depth d to the acoustic pressure at the surface) for outdoor ground surfaces quite typically reveal a series of maxima and minima. In a publication (Sabatier et al., J. Acoust. Soc. Am. 80, 646--649 (1986)), the location and magnitude of these maxima are measured and predicted for several outdoor ground surfaces using a layered poroelastic model of the ground surface. In this paper, the seismic transfer function for a desert site is compared to the seismic transfer function for holes dug in the desert floor which were filled with pumice (volcanic rock). The hole geometry was rectangular and the hole depths varied from 0.25--2.0 m. The p- and s-wave speeds, densities, porosities, and flow resistivities for the desert floor and pumice were all measured. By varying the hole depth and the fill material, the maxima in the seismic transfer function can be shifted in frequency and the locations of the maxima compare reasonably with that of a hard-backed layer calculation. The area or extent of the acoustic-to-seismic coupling for pumice was determined to be less than 1 m/sup 2/.

  18. Prediction of the Acoustic Field Associated with Instability Wave Source Model for a Compressible Jet

    NASA Technical Reports Server (NTRS)

    Golubev, Vladimir; Mankbadi, Reda R.; Dahl, Milo D.; Kiraly, L. James (Technical Monitor)

    2002-01-01

    This paper provides preliminary results of the study of the acoustic radiation from the source model representing spatially-growing instability waves in a round jet at high speeds. The source model is briefly discussed first followed by the analysis of the produced acoustic directivity pattern. Two integral surface techniques are discussed and compared for prediction of the jet acoustic radiation field.

  19. Bio-inspired UAV routing, source localization, and acoustic signature classification for persistent surveillance

    NASA Astrophysics Data System (ADS)

    Burman, Jerry; Hespanha, Joao; Madhow, Upamanyu; Pham, Tien

    2011-06-01

    A team consisting of Teledyne Scientific Company, the University of California at Santa Barbara and the Army Research Laboratory* is developing technologies in support of automated data exfiltration from heterogeneous battlefield sensor networks to enhance situational awareness for dismounts and command echelons. Unmanned aerial vehicles (UAV) provide an effective means to autonomously collect data from a sparse network of unattended ground sensors (UGSs) that cannot communicate with each other. UAVs are used to reduce the system reaction time by generating autonomous collection routes that are data-driven. Bio-inspired techniques for search provide a novel strategy to detect, capture and fuse data. A fast and accurate method has been developed to localize an event by fusing data from a sparse number of UGSs. This technique uses a bio-inspired algorithm based on chemotaxis or the motion of bacteria seeking nutrients in their environment. A unique acoustic event classification algorithm was also developed based on using swarm optimization. Additional studies addressed the problem of routing multiple UAVs, optimally placing sensors in the field and locating the source of gunfire at helicopters. A field test was conducted in November of 2009 at Camp Roberts, CA. The field test results showed that a system controlled by bio-inspired software algorithms can autonomously detect and locate the source of an acoustic event with very high accuracy and visually verify the event. In nine independent test runs of a UAV, the system autonomously located the position of an explosion nine times with an average accuracy of 3 meters. The time required to perform source localization using the UAV was on the order of a few minutes based on UAV flight times. In June 2011, additional field tests of the system will be performed and will include multiple acoustic events, optimal sensor placement based on acoustic phenomenology and the use of the International Technology Alliance (ITA

  20. 48 CFR 19.202-2 - Locating small business sources.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 19.202-2 Locating small business sources. The contracting officer must, to the extent practicable, encourage maximum participation by small...

  1. 48 CFR 2919.202-2 - Locating small business sources.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 7 2011-10-01 2011-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS AND SMALL DISADVANTAGED BUSINESS CONCERNS Policies 2919.202-2 Locating small business sources. Any procurement conducted on an unrestricted basis will include solicitations...

  2. 48 CFR 319.202-2 - Locating small business sources.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 319.202-2 Locating small business sources. (a) OPDIVs shall foster, to the extent practicable, maximum participation by small businesses in HHS...

  3. 48 CFR 2919.202-2 - Locating small business sources.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS AND SMALL DISADVANTAGED BUSINESS CONCERNS Policies 2919.202-2 Locating small business sources. Any procurement conducted on an unrestricted basis will include solicitations...

  4. 48 CFR 2919.202-2 - Locating small business sources.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 7 2013-10-01 2012-10-01 true Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS AND SMALL DISADVANTAGED BUSINESS CONCERNS Policies 2919.202-2 Locating small business sources. Any procurement conducted on an unrestricted basis will include solicitations...

  5. 48 CFR 319.202-2 - Locating small business sources.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 4 2011-10-01 2011-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 319.202-2 Locating small business sources. (a) OPDIVs shall foster, to the extent practicable, maximum participation by small businesses in HHS...

  6. 48 CFR 19.202-2 - Locating small business sources.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 19.202-2 Locating small business sources. The contracting officer must, to the extent practicable, encourage maximum participation by small...

  7. 48 CFR 319.202-2 - Locating small business sources.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 4 2014-10-01 2014-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 319.202-2 Locating small business sources. (a) OPDIVs shall foster, to the extent practicable, maximum participation by small businesses in HHS...

  8. 48 CFR 319.202-2 - Locating small business sources.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 4 2013-10-01 2013-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 319.202-2 Locating small business sources. (a) OPDIVs shall foster, to the extent practicable, maximum participation by small businesses in HHS...

  9. 48 CFR 319.202-2 - Locating small business sources.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 4 2012-10-01 2012-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 319.202-2 Locating small business sources. (a) OPDIVs shall foster, to the extent practicable, maximum participation by small businesses in HHS...

  10. 48 CFR 19.202-2 - Locating small business sources.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Locating small business... SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 19.202-2 Locating small business sources. The contracting officer must, to the extent practicable, encourage maximum participation by small...

  11. Method of monaural localization of the acoustic source direction from the standpoint of the active perception theory

    NASA Astrophysics Data System (ADS)

    Gai, V. E.; Polyakov, I. V.; Krasheninnikov, M. S.; Koshurina, A. A.; Dorofeev, R. A.

    2017-01-01

    Currently, the scientific and educational center of the “Transport” of NNSTU performs work on the creation of the universal rescue vehicle. This vehicle is a robot, and intended to reduce the number of human victims in accidents on offshore oil platforms. An actual problem is the development of a method for determining the location of a person overboard in low visibility conditions, when a traditional vision is not efficient. One of the most important sensory robot systems is the acoustic sensor system, because it is omnidirectional and does not require finding of an acoustic source in visibility scope. Features of the acoustic sensor robot system can complement the capabilities of the video sensor in the solution of the problem of localization of a person or some event in the environment. This paper describes the method of determination of the direction of the acoustic source using just one microphone. The proposed method is based on the active perception theory.

  12. Auditory Selective Attention Reveals Preparatory Activity in Different Cortical Regions for Selection Based on Source Location and Source Pitch

    PubMed Central

    Lee, Adrian K. C.; Rajaram, Siddharth; Xia, Jing; Bharadwaj, Hari; Larson, Eric; Hämäläinen, Matti S.; Shinn-Cunningham, Barbara G.

    2012-01-01

    In order to extract information in a rich environment, we focus on different features that allow us to direct attention to whatever source is of interest. The cortical network deployed during spatial attention, especially in vision, is well characterized. For example, visuospatial attention engages a frontoparietal network including the frontal eye fields (FEFs), which modulate activity in visual sensory areas to enhance the representation of an attended visual object. However, relatively little is known about the neural circuitry controlling attention directed to non-spatial features, or to auditory objects or features (either spatial or non-spatial). Here, using combined magnetoencephalography (MEG) and anatomical information obtained from MRI, we contrasted cortical activity when observers attended to different auditory features given the same acoustic mixture of two simultaneous spoken digits. Leveraging the fine temporal resolution of MEG, we establish that activity in left FEF is enhanced both prior to and throughout the auditory stimulus when listeners direct auditory attention to target location compared to when they focus on target pitch. In contrast, activity in the left posterior superior temporal sulcus (STS), a region previously associated with auditory pitch categorization, is greater when listeners direct attention to target pitch rather than target location. This differential enhancement is only significant after observers are instructed which cue to attend, but before the acoustic stimuli begin. We therefore argue that left FEF participates more strongly in directing auditory spatial attention, while the left STS aids auditory object selection based on the non-spatial acoustic feature of pitch. PMID:23335874

  13. Locating the source of spreading in temporal networks

    NASA Astrophysics Data System (ADS)

    Huang, Qiangjuan; Zhao, Chengli; Zhang, Xue; Yi, Dongyun

    2017-02-01

    The topological structure of many real networks changes with time. Thus, locating the sources of a temporal network is a creative and challenging problem, as the enormous size of many real networks makes it unfeasible to observe the state of all nodes. In this paper, we propose an algorithm to solve this problem, named the backward temporal diffusion process. The proposed algorithm calculates the shortest temporal distance to locate the transmission source. We assume that the spreading process can be modeled as a simple diffusion process and by consensus dynamics. To improve the location accuracy, we also adopt four strategies to select which nodes should be observed by ranking their importance in the temporal network. Our paper proposes a highly accurate method for locating the source in temporal networks and is, to the best of our knowledge, a frontier work in this field. Moreover, our framework has important significance for controlling the transmission of diseases or rumors and formulating immediate immunization strategies.

  14. Experimental Results of Underwater Cooperative Source Localization Using a Single Acoustic Vector Sensor

    PubMed Central

    Felisberto, Paulo; Rodriguez, Orlando; Santos, Paulo; Ey, Emanuel; Jesus, Sérgio M.

    2013-01-01

    This paper aims at estimating the azimuth, range and depth of a cooperative broadband acoustic source with a single vector sensor in a multipath underwater environment, where the received signal is assumed to be a linear combination of echoes of the source emitted waveform. A vector sensor is a device that measures the scalar acoustic pressure field and the vectorial acoustic particle velocity field at a single location in space. The amplitudes of the echoes in the vector sensor components allow one to determine their azimuth and elevation. Assuming that the environmental conditions of the channel are known, source range and depth are obtained from the estimates of elevation and relative time delays of the different echoes using a ray-based backpropagation algorithm. The proposed method is tested using simulated data and is further applied to experimental data from the Makai'05 experiment, where 8–14 kHz chirp signals were acquired by a vector sensor array. It is shown that for short ranges, the position of the source is estimated in agreement with the geometry of the experiment. The method is low computational demanding, thus well-suited to be used in mobile and light platforms, where space and power requirements are limited. PMID:23857257

  15. Experimental results of underwater cooperative source localization using a single acoustic vector sensor.

    PubMed

    Felisberto, Paulo; Rodriguez, Orlando; Santos, Paulo; Ey, Emanuel; Jesus, Sérgio M

    2013-07-12

    This paper aims at estimating the azimuth, range and depth of a cooperative broadband acoustic source with a single vector sensor in a multipath underwater environment, where the received signal is assumed to be a linear combination of echoes of the source emitted waveform. A vector sensor is a device that measures the scalar acoustic pressure field and the vectorial acoustic particle velocity field at a single location in space. The amplitudes of the echoes in the vector sensor components allow one to determine their azimuth and elevation. Assuming that the environmental conditions of the channel are known, source range and depth are obtained from the estimates of elevation and relative time delays of the different echoes using a ray-based backpropagation algorithm. The proposed method is tested using simulated data and is further applied to experimental data from the Makai'05 experiment, where 8-14 kHz chirp signals were acquired by a vector sensor array. It is shown that for short ranges, the position of the source is estimated in agreement with the geometry of the experiment. The method is low computational demanding, thus well-suited to be used in mobile and light platforms, where space and power requirements are limited.

  16. Infrasonic source location imaging with the USArray: Application to one year of seismic data

    NASA Astrophysics Data System (ADS)

    Walker, K. T.; Shelby, R.; Hedlin, M. A.; Degroot-Hedlin, C. D.

    2010-12-01

    The USArray directly measures ground motion, which can mostly be attributed to ocean waves, earthquakes, volcanoes, and weather systems that load the Earth’s surface. Another source of ground motion is the transfer of atmospheric acoustic energy into seismic energy at the Earth’s surface. Infrasound (low frequency sound below ~20 Hz) can travel great distances unattenuated in atmospheric ducts. The infrasonic wave field is rich due to a variety of anthropogenic and geophysical phenomena including earthquakes, volcanoes, landslides, meteors, lightning and sprites, auroras, and oceanic and atmospheric processes. Globally spaced microbarometer arrays with apertures of 100 m to 2 km are typically used to study these sources. However, these arrays are separated by thousands of kilometers, which places considerable limits on what they can teach us about infrasound source physics. The USArray is in a position to study infrasound sources in unprecedented detail. Here we apply reverse-time migration to acoustic-to-seismic coupled signals recorded by the USArray to detect and locate in two-dimensional space and time several hundred infrasound sources in the western U.S. that occurred during 2008. Each event is visually inspected and assigned a quality rating. Confidence regions are determined using a bootstrap technique. The highest quality signals can be observed out to at least 1500 km range. We report the source location parameters for these events and investigate detection and location patterns. These results suggest that seismic networks near nuclear test monitoring infrasound arrays could be used to reduce the false alarm rate by identifying nearby, repeating sources of infrasound that create signals that are detected by the infrasound arrays. More fundamentally, these detected events comprise a ground truth database that can be used to validate or improve atmospheric velocity models.

  17. Location optimization of a long T-shaped acoustic resonator array in noise control of enclosures

    NASA Astrophysics Data System (ADS)

    Yu, Ganghua; Cheng, Li

    2009-11-01

    Acoustic resonators are widely used in various noise control applications. In the pursuit of better performance and broad band control, multiple resonators or a resonator array are usually needed. The interaction among resonators significantly impacts on the control performance and leads to the requirement for a systematic design tool to determine their locations. In this work, simulated annealing (SA) algorithm is employed to optimize the locations of a set of long T-shaped acoustic resonators (TARs) for noise control inside an enclosure. Multiple optimal configurations are shown to exist. The control performance in terms of sound pressure level reduction, however, seems to be independent of the initial resonator-locations. Optimal solutions obtained from the SA approach are shown to outperform other existing methods for a TAR array design. Numerical simulations are systematically verified by experiments. Optimal locations are then synthesized, leading to a set of criteria, applicable to the present configuration, to guide engineering applications. It is concluded that the proposed optimization approach provides a systematic and effective tool to optimize the locations of TARs in noise control inside enclosures.

  18. Wave equation based microseismic source location and velocity inversion

    NASA Astrophysics Data System (ADS)

    Zheng, Yikang; Wang, Yibo; Chang, Xu

    2016-12-01

    The microseismic event locations and velocity information can be used to infer the stress field and guide hydraulic fracturing process, as well as to image the subsurface structures. How to get accurate microseismic event locations and velocity model is the principal problem in reservoir monitoring. For most location methods, the velocity model has significant relation with the accuracy of the location results. The velocity obtained from log data is usually too rough to be used for location directly. It is necessary to discuss how to combine the location and velocity inversion. Among the main techniques for locating microseismic events, time reversal imaging (TRI) based on wave equation avoids traveltime picking and offers high-resolution locations. Frequency dependent wave equation traveltime inversion (FWT) is an inversion method that can invert velocity model with source uncertainty at certain frequency band. Thus we combine TRI with FWT to produce improved event locations and velocity model. In the proposed approach, the location and model information are interactively used and updated. Through the proposed workflow, the inverted model is better resolved and the event locations are more accurate. We test this method on synthetic borehole data and filed data of a hydraulic fracturing experiment. The results verify the effectiveness of the method and prove it has potential for real-time microseismic monitoring.

  19. Detection and Location of Transverse Matrix Cracks in Cross-Ply Gr/Ep Composites Using Acoustic Emission

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Jackson, K. E.; Kellas, S.; Smith, B. T.; McKeon, J.; Friedman, A.

    1995-01-01

    Transverse matrix cracking in cross-ply gr/ep laminates was studied with advanced acoustic emission (AE) techniques. The primary goal of this research was to measure the load required to initiate the first transverse matrix crack in cross-ply laminates of different thicknesses. Other methods had been previously used for these measurements including penetrant enhanced radiography, optical microscopy, and audible acoustic microphone measurements. The former methods required that the mechanical test be paused for measurements at load intervals. This slowed the test procedure and did not provide the required resolution in load. With acoustic microphones, acoustic signals from cracks could not be clearly differentiated from other noise sources such as grip damage, specimen slippage, or test machine noise. A second goal for this work was to use the high resolution source location accuracy of the advanced acoustic emission techniques to determine whether the crack initiation site was at the specimen edge or in the interior of the specimen.In this research, advanced AE techniques using broad band sensors, high capture rate digital waveform acquisition, and plate wave propagation based analysis were applied to cross-ply composite coupons with different numbers of 0 and 90 degree plies. Noise signals, believed to be caused by grip damage or specimen slipping, were eliminated based on their plate wave characteristics. Such signals were always located outside the sensor gage length in the gripped region of the specimen. Cracks were confirmed post-test by microscopic analysis of a polished specimen edge, backscatter ultrasonic scans, and in limited cases, by penetrant enhanced radiography. For specimens with three or more 90 degree plies together, there was an exact 1-1 correlation between AE crack signals and observed cracks. The ultrasonic scans and some destructive sectioning analysis showed that the cracks extended across the full width of the specimen. Furthermore, the

  20. Acoustic source localization in mixed field using spherical microphone arrays

    NASA Astrophysics Data System (ADS)

    Huang, Qinghua; Wang, Tong

    2014-12-01

    Spherical microphone arrays have been used for source localization in three-dimensional space recently. In this paper, a two-stage algorithm is developed to localize mixed far-field and near-field acoustic sources in free-field environment. In the first stage, an array signal model is constructed in the spherical harmonics domain. The recurrent relation of spherical harmonics is independent of far-field and near-field mode strengths. Therefore, it is used to develop spherical estimating signal parameter via rotational invariance technique (ESPRIT)-like approach to estimate directions of arrival (DOAs) for both far-field and near-field sources. In the second stage, based on the estimated DOAs, simple one-dimensional MUSIC spectrum is exploited to distinguish far-field and near-field sources and estimate the ranges of near-field sources. The proposed algorithm can avoid multidimensional search and parameter pairing. Simulation results demonstrate the good performance for localizing far-field sources, or near-field ones, or mixed field sources.

  1. Control of boundary layer transition location and plate vibration in the presence of an external acoustic field

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Grosveld, F. W.

    1991-01-01

    The experiment is aimed at controlling the boundary layer transition location and the plate vibration when excited by a flow and an upstream sound source. Sound has been found to affect the flow at the leading edge and the response of a flexible plate in a boundary layer. Because the sound induces early transition, the panel vibration is acoustically coupled to the turbulent boundary layer by the upstream radiation. Localized surface heating at the leading edge delays the transition location downstream of the flexible plate. The response of the plate excited by a turbulent boundary layer (without sound) shows that the plate is forced to vibrate at different frequencies and with different amplitudes as the flow velocity changes indicating that the plate is driven by the convective waves of the boundary layer. The acoustic disturbances induced by the upstream sound dominate the response of the plate when the boundary layer is either turbulent or laminar. Active vibration control was used to reduce the sound induced displacement amplitude of the plate.

  2. Locating an atmospheric contamination source using slow manifolds

    NASA Astrophysics Data System (ADS)

    Tang, Wenbo; Haller, George; Baik, Jong-Jin; Ryu, Young-Hee

    2009-04-01

    Finite-size particle motion in fluids obeys the Maxey-Riley equations, which become singular in the limit of infinitesimally small particle size. Because of this singularity, finding the source of a dispersed set of small particles is a numerically ill-posed problem that leads to exponential blowup. Here we use recent results on the existence of a slow manifold in the Maxey-Riley equations to overcome this difficulty in source inversion. Specifically, we locate the source of particles by projecting their dispersed positions on a time-varying slow manifold, and by advecting them on the manifold in backward time. We use this technique to locate the source of a hypothetical anthrax release in an unsteady three-dimensional atmospheric wind field in an urban street canyon.

  3. A Procedure to Determine the Optimal Sensor Positions for Locating AE Sources in Rock Samples

    NASA Astrophysics Data System (ADS)

    Duca, S.; Occhiena, C.; Sambuelli, L.

    2015-03-01

    Within a research work aimed to better understand frost weathering mechanisms of rocks, laboratory tests have been designed to specifically assess a theoretical model of crack propagation due to ice segregation process in water-saturated and thermally microcracked cubic samples of Arolla gneiss. As the formation and growth of microcracks during freezing tests on rock material is accompanied by a sudden release of stored elastic energy, the propagation of elastic waves can be detected, at the laboratory scale, by acoustic emission (AE) sensors. The AE receiver array geometry is a sensitive factor influencing source location errors, for it can greatly amplify the effect of small measurement errors. Despite the large literature on the AE source location, little attention, to our knowledge, has been paid to the description of the experimental design phase. As a consequence, the criteria for sensor positioning are often not declared and not related to location accuracy. In the present paper, a tool for the identification of the optimal sensor position on a cubic shape rock specimen is presented. The optimal receiver configuration is chosen by studying the condition numbers of each of the kernel matrices, used for inverting the arrival time and finding the source location, and obtained for properly selected combinations between sensors and sources positions.

  4. Acoustical analysis and multiple source auralizations of charismatic worship spaces

    NASA Astrophysics Data System (ADS)

    Lee, Richard W.

    2004-05-01

    Because of the spontaneity and high level of call and response, many charismatic churches have verbal and musical communication problems that stem from highly reverberant sound fields, poor speech intelligibility, and muddy music. This research looks at the subjective dimensions of room acoustics perception that affect a charismatic worship space, which is summarized using the acronym RISCS (reverberation, intimacy, strength, coloration, and spaciousness). The method of research is to obtain acoustical measurements for three worship spaces in order to analyze the objective parameters associated with the RISCS subjective dimensions. For the same spaces, binaural room impulse response (BRIR) measurements are done for different receiver positions in order to create an auralization for each position. The subjective descriptors of RISCS are analyzed through the use of listening tests of the three auralized spaces. The results from the measurements and listening tests are analyzed to determine if listeners' perceptions correlate with the objective parameter results, the appropriateness of the subjective parameters for the use of the space, and which parameters seem to take precedent. A comparison of the multi-source auralization to a conventional single-source auralization was done with the mixed down version of the synchronized multi-track anechoic signals.

  5. A fast source for quantitative acoustic emission and its application

    NASA Astrophysics Data System (ADS)

    Masaki, Ryuji; Takemoto, Mikio; Ono, Kanji

    1999-12-01

    We demonstrate a new artificial fracture source for quantitative acoustic emission (AE) characterization. The source utilizes the break-down of silicone oil (or other liquids) placed inside a crack (or a slit). This is a dipole source with a rise time under 0.1 μs. It is much faster than a pencil-lead-break source and allows the calibration of a sensor-structure system to 7-10 MHz. We irradiated a focused Q-switched Nd-YAG laser beam (15 to 90 mJ energy) on silicon placed in a slit on a cylindrical block. The out-of-plane displacement produced by the resultant bulk waves was monitored on the outside surface using a heterodyne-type laser interferometer. This break-down source was employed to determine the transfer functions of an AE transducer and propagation medium. Finally, we studied AE signals due to the delayed fracture of a butt-welded dual-phase stainless steel, using the break-down source for calibration. Brittle-fracture events were successfully characterized.

  6. Array Receivers and Sound Sources for Three Dimensional Shallow Water Acoustic Field Experiments

    DTIC Science & Technology

    2016-12-06

    Water Acoustic Field Experiments NOOO 14-15-1-2893 Sc. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sd. PROJECT NUMBER Ying Tsong-Lin 132893SP Se. TASK...testing. 1S. SUBJECT TERMS acoustics, shallow water , Arctic Ocean , 3-D acoustic propagation, shelfbreak 16. SECURITY CLASSIFICATION OF: R b...Approved f or public release; distribution is unlimited. Array Receivers and Sound Sources for Three-Dimensional Shallow- Water Acoustic Field

  7. Providing Source-Location Privacy in Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Li, Yun; Ren, Jian

    Wireless sensor networks (WSN) have been widely used in many areas for unattended event monitoring. Mainly due to lack of a protected physical boundary, wireless communications are vulnerable to unauthorized detection, interception and and even node capture. Privacy is becoming one of the major issues that jeopardize the successful deployment and survivability of wireless sensor networks. While confidentiality of the message can be ensured through content encryption, it is much more difficult to adequately address the source-location privacy. For WSN, source-location privacy service is further complicated by the fact that the sensor nodes consist of low-cost and low-power radio devices, computationally intensive cryptographic algorithms (such as public-key cryptosystems) and large scale broadcasting-based protocols are not suitable for WSN. In this paper, we propose a two-step routing strategy for the messages to be routed from the actual source node to the SINK node through either a single, or multiple, randomly selected intermediate node(s) away from the source node so that it is to make it infeasible for the adversaries to trace back to the source node through hop-by-hop routing analysis. In the first protocol, the messages will be routed to a single intermediate node. This scheme can provide very good local source-location privacy. We also propose routing through multiple randomly selected intermediate nodes based on angle and quadrant to further improve the performance and security. While providing source-location privacy for WSN, our simulation results demonstrate that the proposed schemes are very efficient in energy consumption, and transmission latency. The proposed schemes can also assurance high message delivery ratio. Therefore, they can be used for many practical applications.

  8. Locating and estimating air emissions from sources of epichlorohydrin

    SciTech Connect

    Not Available

    1985-09-01

    To assist groups interested in inventorying air emissions of various potentially toxic substances, EPA is preparing a series of documents such as this to compile available information on sources and emissions of these substances. This document deals specifically with epichlorohydrin. Its intended audience includes Federal, State and local air pollution personnel and others interested in locating potential emitters of epichlorohydrin in making gross estimates of air emissions therefrom. This document presents information on 1) the types of sources that may emit epichlorohydrin; 2) process variations and release points that may be expected within these sources; and 3) available emissions information indicating the potential for epichlorohydrin release into the air from each operation.

  9. Intelligent background noise reduction technology in cable fault locator using the magneto-acoustic synchronous method

    NASA Astrophysics Data System (ADS)

    Mi, JianWei; Huang, JiFa; Fang, XiaoLi; Fan, LiBin

    2017-01-01

    The magneto-acoustic synchronous method has found wide application in accurate positioning of power cable fault due to its advantages of high accuracy and strong ability to reject interference. In the view of principle, the magneto-acoustic synchronous method needs to detect the discharge sound signal and electromagnetic signal emitted from the fault point, but the discharge sound signal is easy to be interfered by the ambient noise around and the magnetic sound synchronization. Therefore, it is challenging to quickly and accurately detect the fault location of cable especially in strong background noise environment. On the other hand, the spectral subtraction is a relatively traditional and effective method in many intelligent background noise reduction technologies, which is characterized by a relatively small computational cost and strong real-time performance. However, its application is limited because the algorithm displays poor performance in low Signal to Noise Ratio (SNR) environment. Aiming at the shortcoming of the spectral subtraction that de-noising effect is weak in low SNR environment, this paper proposes an improved spectral subtraction combining the magnetic sound synchronous principle and analyzing the properties of discharging sound. This method can accurately estimate noise in real time and optimize the performance of the basic spectral subtraction thus solving the problem that the magneto-acoustic synchronous method is unsatisfactory for positioning cable fault in the strong background noise environment.

  10. Acoustic power of a moving point source in a moving medium

    NASA Technical Reports Server (NTRS)

    Cole, J. E., III; Sarris, I. I.

    1976-01-01

    The acoustic power output of a moving point-mass source in an acoustic medium which is in uniform motion and infinite in extent is examined. The acoustic medium is considered to be a homogeneous fluid having both zero viscosity and zero thermal conductivity. Two expressions for the acoustic power output are obtained based on a different definition cited in the literature for the average energy-flux vector in an acoustic medium in uniform motion. The acoustic power output of the source is found by integrating the component of acoustic intensity vector in the radial direction over the surface of an infinitely long cylinder which is within the medium and encloses the line of motion of the source. One of the power expressions is found to give unreasonable results even though the flow is uniform.

  11. Noncontact detection of surface-breaking cracks using a laser acoustic source and an electromagnetic acoustic receiver

    SciTech Connect

    Dewhurst, R.J.; Edwards, C.; Palmer, S.B.

    1986-08-01

    An electromagnetic acoustic transducer (EMAT) is used to detect laser-generated surface acoustic transients. The surface acoustic waves are broadband and can be used to detect and size surface-breaking cracks if used in conjunction with a broadband detector. A broadband EMAT is described and its use to locate artificial surface-breaking defects in both aluminum and steel is demonstrated. A second study reveals that it can also be used for the detection of real surface-breaking cracks, even on rusty steel surfaces. 10 references.

  12. Modeling of Jovian Hectometric Radiation Source Locations: Ulysses Observations

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Reiner, M. J.

    1996-01-01

    The Unified Radio and Plasma Wave (URAP) experiment on Ulysses has provided unique high latitude measurements of Jovian hectometric radiation (HOM) during its encounter with Jupiter in February 1992. URAP was the first radio instrument in the Jovian environment with radio direction-finding capability, which was previously used to determine the HOM source locations in the Jovian magnetosphere. These initial source location determinations were based on several assumptions, including the neglect of refractive effects, which may be tested. We have, for the first time, combined the measured incident ray-direction at the spacecraft with a model magnetosphere to directly trace the rays back to the HOM source. We concentrate on the observations of HOM from high northern latitudes when Ulysses was at distances less than 15 R(sub j). The three- dimensional ray-tracing calculations presented here indicate that the HOM sources probably lie on L shells in the range 3 less than or approximately equal to L less than 7 (tilted dipole magnetic field model) consistent with previous determinations that ignored the effects of refraction. The ray-tracing results, however, indicate that wave refraction due to the Io torus and the magnetic field can significantly influence the precise source location. We show that constraints on the locations imposed by the gyroemission mechanism suggest that the lo torus density may have experienced temporal and/or spatial fluctuations during the Ulysses observations of HOM. Finally, in the cold plasma approximation we demonstrate that even if the emission were nearly linearly polarized near the source region, almost circular polarization will be observed at Ulysses, in agreement with observations.

  13. Lamb wave detection and source location using fiber Bragg gratin rosettes

    NASA Astrophysics Data System (ADS)

    Betz, Daniel C.; Thursby, Graham; Culshaw, Brian; Staszewski, Wieslaw J.

    2003-07-01

    We describe a novel fiber-optic system that is able to detect both ultrasonic Lamb waves and the location of their source. The aim of the system is to detect damage in structures such as those found in aerospace applications. Our system involves the use of fiber Bragg gratings, which may be either bonded to the surface of the material or embedded within it in order to detect the linear strain component produced by the acoustic waves. Interrogation of the Bragg gratings is carried out using a laser, which is tuned to the wavelength that gives the maximum sensitivity on the grating response curve. An amplitude modulated signal is produced by the interaction of the Lamb wave with the grating. The well defined directional properties of the Bragg grating (compared to the isotropic response of the more commonly used piezoceramic disc transducers) are used to determine the direction of propagation of the acoustic waves by mounting three of the gratings in a rosette configuration. Two suitably spaced rosettes are used to locate the source of the ultrasound by taking the intersection of the directions given by each rosette. This will become important when we extend the technique to include the study of the use of changes in the propagation properties of Lamb waves as a method of damage detection. We will present both theoretical and practical results on the interaction of the Lamb waves with the grating and the extraction of directional information from the response of the rosettes.

  14. An inverse source location algorithm for radiation portal monitor applications

    SciTech Connect

    Miller, Karen A; Charlton, William S

    2010-01-01

    Radiation portal monitors are being deployed at border crossings throughout the world to prevent the smuggling of nuclear and radiological materials; however, a tension exists between security and the free-flow of commerce. Delays at ports-of-entry have major economic implications, so it is imperative to minimize portal monitor screening time. We have developed an algorithm to locate a radioactive source using a distributed array of detectors, specifically for use at border crossings. To locate the source, we formulated an optimization problem where the objective function describes the least-squares difference between the actual and predicted detector measurements. The predicted measurements are calculated by solving the 3-D deterministic neutron transport equation given an estimated source position. The source position is updated using the steepest descent method, where the gradient of the objective function with respect to the source position is calculated using adjoint transport calculations. If the objective function is smaller than the convergence criterion, then the source position has been identified. This paper presents the derivation of the underlying equations in the algorithm as well as several computational test cases used to characterize its accuracy.

  15. Modal acoustic emission source determination in silicon carbide matrix composites

    NASA Astrophysics Data System (ADS)

    Morscher, G. N.

    2000-05-01

    Modal acoustic emission has been used to monitor damage accumulation in woven silicon carbide (SiC) fiber reinforced SiC matrix composites during tensile testing. There are several potential sources of damage in these systems including transverse matrix cracking, fiber/matrix interphase debonding and sliding, longitudinal cracks in between plies, and fiber breakage. In the past, it has been shown that modal AE is excellent at detecting when damage occurs and subsides, where the damage occurs along the length of the sample, and the loss in material stiffness as a consequence of damage accumulation. The next step is to determine the extent that modal AE can be used to identify specific physical sources. This study will discuss the status of this aim for this composite system. Individual events were analyzed and correlated to specific sources based on the characteristics of the received waveforms, e.g., frequency spectrum and energy, and when the event occurred during the stress-history of the tensile test. Post-test microstructural examination of the test specimens enabled some correlation between specific types of AE events and damage sources.

  16. Acoustic source inversion to estimate volume flux from volcanic explosions

    NASA Astrophysics Data System (ADS)

    Kim, Keehoon; Fee, David; Yokoo, Akihiko; Lees, Jonathan M.

    2015-07-01

    We present an acoustic waveform inversion technique for infrasound data to estimate volume fluxes from volcanic eruptions. Previous inversion techniques have been limited by the use of a 1-D Green's function in a free space or half space, which depends only on the source-receiver distance and neglects volcanic topography. Our method exploits full 3-D Green's functions computed by a numerical method that takes into account realistic topographic scattering. We apply this method to vulcanian eruptions at Sakurajima Volcano, Japan. Our inversion results produce excellent waveform fits to field observations and demonstrate that full 3-D Green's functions are necessary for accurate volume flux inversion. Conventional inversions without consideration of topographic propagation effects may lead to large errors in the source parameter estimate. The presented inversion technique will substantially improve the accuracy of eruption source parameter estimation (cf. mass eruption rate) during volcanic eruptions and provide critical constraints for volcanic eruption dynamics and ash dispersal forecasting for aviation safety. Application of this approach to chemical and nuclear explosions will also provide valuable source information (e.g., the amount of energy released) previously unavailable.

  17. The influence of phonetic context and formant measurement location on acoustic vowel space

    NASA Astrophysics Data System (ADS)

    Turner, Greg S.; Hutchings, David T.; Sylvester, Betsy; Weismer, Gary

    2003-04-01

    One way of depicting vowel production is by describing vowels within an F1/F2 acoustic vowel space. This acoustic measure illustrates the dispersion of F1 and F2 values at a specific moment in time (e.g., the temporal midpoint of a vowel) for the vowels of a given language. This measure has recently been used to portray vowel production in individuals with communication disorders such as dysarthria and is moderately related to the severity of the speech disorder. Studies aimed at identifying influential factors effecting measurement stability of vowel space have yet to be completed. The focus of the present study is to evaluate the influence of phonetic context and spectral measurement location on vowel space in a group of neurologically normal American English speakers. For this study, vowel space was defined in terms of the dispersion of the four corner vowels produced within a CVC syllable frame, where C includes six stop consonants in all possible combinations with each vowel. Spectral measures were made at the midpoint and formant extremes of the vowels. A discussion will focus on individual and group variation in vowel space as a function of phonetic context and temporal measurement location.

  18. Equilibrium shape and location of a liquid drop acoustically positioned in a resonant rectangular chamber

    NASA Technical Reports Server (NTRS)

    Jackson, H. W.; Barmatz, M.; Shipley, C.

    1988-01-01

    The effect of a standing wave field in a rectangular chamber on the shape and location of an acoustically positioned drop or bubble is calculated. The sample deformation and equilibrium position are obtained from an analysis of the spherical harmonic projections of the total surface stress tensor. The method of calculation relies on the assumed condition that the sample is only slightly distorted from a spherical form. The equilibrium location of a levitated drop is combined with a formula introduced by Hasegawa (1979) to calcualte the ka dependence of the radiation force function. The present theory is valid for large as well as small ka values. Calculations in the small ka limit agree with previous theories and experimental results. Examples are presented for nonplane-wave modes as well as plane-wave rectangular modes.

  19. Accurate Damage Location in Complex Composite Structures and Industrial Environments using Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Eaton, M.; Pearson, M.; Lee, W.; Pullin, R.

    2015-07-01

    The ability to accurately locate damage in any given structure is a highly desirable attribute for an effective structural health monitoring system and could help to reduce operating costs and improve safety. This becomes a far greater challenge in complex geometries and materials, such as modern composite airframes. The poor translation of promising laboratory based SHM demonstrators to industrial environments forms a barrier to commercial up take of technology. The acoustic emission (AE) technique is a passive NDT method that detects elastic stress waves released by the growth of damage. It offers very sensitive damage detection, using a sparse array of sensors to detect and globally locate damage within a structure. However its application to complex structures commonly yields poor accuracy due to anisotropic wave propagation and the interruption of wave propagation by structural features such as holes and thickness changes. This work adopts an empirical mapping technique for AE location, known as Delta T Mapping, which uses experimental training data to account for such structural complexities. The technique is applied to a complex geometry composite aerospace structure undergoing certification testing. The component consists of a carbon fibre composite tube with varying wall thickness and multiple holes, that was loaded under bending. The damage location was validated using X-ray CT scanning and the Delta T Mapping technique was shown to improve location accuracy when compared with commercial algorithms. The onset and progression of damage were monitored throughout the test and used to inform future design iterations.

  20. Detection of impulsive sources from an aerostat-based acoustic array data collection system

    NASA Astrophysics Data System (ADS)

    Prather, Wayne E.; Clark, Robert C.; Strickland, Joshua; Frazier, Wm. Garth; Singleton, Jere

    2009-05-01

    An aerostat based acoustic array data collection system was deployed at the NATO TG-53 "Acoustic Detection of Weapon Firing" Joint Field Experiment conducted in Bourges, France during the final two weeks of June 2008. A variety of impulsive sources including mortar, artillery, gunfire, RPG, and explosive devices were fired during the test. Results from the aerostat acoustic array will be presented against the entire range of sources.

  1. Access to patents as sources to musical acoustics inventions

    NASA Astrophysics Data System (ADS)

    Brock-Nannestad, George

    2005-09-01

    Patents are important sources for the development of any technology. The paper addresses modern methods of access to patent publications relating to musical acoustics, in particular the constructions of instruments and components for instruments, methods for tuning, methods for teaching, and measuring equipment. The patent publications available are, among others, from the U.S., England, France, Germany, Japan, Russia, and the date range is from ca. 1880 to the present day. The two main searchable websites use different classification systems in their approach, and by suitable combination of the information it is possible to target the search efficiently. The paper will demonstrate the recent transfer of inventions relating to physical instruments to electronic simulations, and the fact that most recent inventions were made by independent inventors. A specific example is given by discussing the proposals for improved pipe organ and violin constructions invented in Denmark in the 1930s by Jarnak based on patented improvements for telephone reproducers.

  2. Acoustic Source Modeling for High Speed Air Jets

    NASA Technical Reports Server (NTRS)

    Goldstein, Marvin E.; Khavaran, Abbas

    2005-01-01

    The far field acoustic spectra at 90deg to the downstream axis of some typical high speed jets are calculated from two different forms of Lilley s equation combined with some recent measurements of the relevant turbulent source function. These measurements, which were limited to a single point in a low Mach number flow, were extended to other conditions with the aid of a highly developed RANS calculation. The results are compared with experimental data over a range of Mach numbers. Both forms of the analogy lead to predictions that are in excellent agreement with the experimental data at subsonic Mach numbers. The agreement is also fairly good at supersonic speeds, but the data appears to be slightly contaminated by shock-associated noise in this case.

  3. Source analysis of auditory steady-state responses in acoustic and electric hearing.

    PubMed

    Luke, Robert; De Vos, Astrid; Wouters, Jan

    2017-02-15

    Speech is a complex signal containing a broad variety of acoustic information. For accurate speech reception, the listener must perceive modulations over a range of envelope frequencies. Perception of these modulations is particularly important for cochlear implant (CI) users, as all commercial devices use envelope coding strategies. Prolonged deafness affects the auditory pathway. However, little is known of how cochlear implantation affects the neural processing of modulated stimuli. This study investigates and contrasts the neural processing of envelope rate modulated signals in acoustic and CI listeners. Auditory steady-state responses (ASSRs) are used to study the neural processing of amplitude modulated (AM) signals. A beamforming technique is applied to determine the increase in neural activity relative to a control condition, with particular attention paid to defining the accuracy and precision of this technique relative to other tomographies. In a cohort of 44 acoustic listeners, the location, activity and hemispheric lateralisation of ASSRs is characterised while systematically varying the modulation rate (4, 10, 20, 40 and 80Hz) and stimulation ear (right, left and bilateral). We demonstrate a complex pattern of laterality depending on both modulation rate and stimulation ear that is consistent with, and extends, existing literature. We present a novel extension to the beamforming method which facilitates source analysis of electrically evoked auditory steady-state responses (EASSRs). In a cohort of 5 right implanted unilateral CI users, the neural activity is determined for the 40Hz rate and compared to the acoustic cohort. Results indicate that CI users activate typical thalamic locations for 40Hz stimuli. However, complementary to studies of transient stimuli, the CI population has atypical hemispheric laterality, preferentially activating the contralateral hemisphere.

  4. Modal Acoustic Emission Used at Elevated Temperatures to Detect Damage and Failure Location in Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    1999-01-01

    Ceramic matrix composites are being developed for elevated-temperature engine applications. A leading material system in this class of materials is silicon carbide (SiC) fiber-reinforced SiC matrix composites. Unfortunately, the nonoxide fibers, matrix, and interphase (boron nitride in this system) can react with oxygen or water vapor in the atmosphere, leading to strength degradation of the composite at elevated temperatures. For this study, constant-load stress-rupture tests were performed in air at temperatures ranging from 815 to 960 C until failure. From these data, predictions can be made for the useful life of such composites under similar stressed-oxidation conditions. During these experiments, the sounds of failure events (matrix cracking and fiber breaking) were monitored with a modal acoustic emission (AE) analyzer through transducers that were attached at the ends of the tensile bars. Such failure events, which are caused by applied stress and oxidation reactions, cause these composites to fail prematurely. Because of the nature of acoustic waveform propagation in thin tensile bars, the location of individual source events and the eventual failure event could be detected accurately.

  5. Autonomous robotic platforms for locating radio sources buried under rubble

    NASA Astrophysics Data System (ADS)

    Tasu, A. S.; Anchidin, L.; Tamas, R.; Paun, M.; Danisor, A.; Petrescu, T.

    2016-12-01

    This paper deals with the use of autonomous robotic platforms able to locate radio signal sources such as mobile phones, buried under collapsed buildings as a result of earthquakes, natural disasters, terrorism, war, etc. This technique relies on averaging position data resulting from a propagation model implemented on the platform and the data acquired by robotic platforms at the disaster site. That allows us to calculate the approximate position of radio sources buried under the rubble. Based on measurements, a radio map of the disaster site is made, very useful for locating victims and for guiding specific rubble lifting machinery, by assuming that there is a victim next to a mobile device detected by the robotic platform; by knowing the approximate position, the lifting machinery does not risk to further hurt the victims. Moreover, by knowing the positions of the victims, the reaction time is decreased, and the chances of survival for the victims buried under the rubble, are obviously increased.

  6. Locating and Quantifying Broadband Fan Sources Using In-Duct Microphones

    NASA Technical Reports Server (NTRS)

    Dougherty, Robert P.; Walker, Bruce E.; Sutliff, Daniel L.

    2010-01-01

    In-duct beamforming techniques have been developed for locating broadband noise sources on a low-speed fan and quantifying the acoustic power in the inlet and aft fan ducts. The NASA Glenn Research Center's Advanced Noise Control Fan was used as a test bed. Several of the blades were modified to provide a broadband source to evaluate the efficacy of the in-duct beamforming technique. Phased arrays consisting of rings and line arrays of microphones were employed. For the imaging, the data were mathematically resampled in the frame of reference of the rotating fan. For both the imaging and power measurement steps, array steering vectors were computed using annular duct modal expansions, selected subsets of the cross spectral matrix elements were used, and the DAMAS and CLEAN-SC deconvolution algorithms were applied.

  7. Preserving Source Location Privacy for Energy Harvesting WSNs.

    PubMed

    Huang, Changqin; Ma, Ming; Liu, Yuxin; Liu, Anfeng

    2017-03-30

    Fog (From cOre to edGe) computing employs a huge number of wireless embedded devices to enable end users with anywhere-anytime-to-anything connectivity. Due to their operating nature, wireless sensor nodes often work unattended, and hence are exposed to a variety of attacks. Preserving source-location privacy plays a key role in some wireless sensor network (WSN) applications. In this paper, a redundancy branch convergence-based preserved source location privacy scheme (RBCPSLP) is proposed for energy harvesting sensor networks, with the following advantages: numerous routing branches are created in non-hotspot areas with abundant energy, and those routing branches can merge into a few routing paths before they reach the hotspot areas. The generation time, the duration of routing, and the number of routing branches are then decided independently based on the amount of energy obtained, so as to maximize network energy utilization, greatly enhance privacy protection, and provide long network lifetimes. Theoretical analysis and experimental results show that the RBCPSLP scheme allows a several-fold improvement of the network energy utilization as well as the source location privacy preservation, while maximizing network lifetimes.

  8. Functional delay and sum beamforming for three-dimensional acoustic source identification with solid spherical arrays

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Chu, Zhigang; Shen, Linbang; Xu, Zhongming

    2016-07-01

    Solid spherical arrays have become particularly attractive tools for doing acoustic sources identification in cabin environments. Spherical harmonics beamforming (SHB) is the popular conventional algorithm. Regrettably, its results suffer from severe sidelobe contaminations and the existing solutions are incapable of removing these contaminations both significantly and efficiently. This paper focuses on conquering these problems by creating a novel functional delay and sum (FDAS) algorithm. First and foremost, a new delay and sum (DAS) algorithm is established, and for which, the point spread function (PSF) is derived, the determination principle of the truncated upper limit of the spherical harmonics degree is explored, and the performance is examined as well as compared with that of SHB. Next, the FDAS algorithm is created by combining DAS and the functional beamforming (FB) approach initially suggested for planar arrays, and its merits are demonstrated. Additionally, performances of DAS and FDAS are probed into under the situation that the source is not at the focus point. Several interesting results have emerged: (1) the truncated upper limit of the spherical harmonics degree, capable of making DAS meet FB's requirement, exists and its minimum value depends only on the wave number and the array radius. (2) DAS can accurately locate and quantify the single source and the incoherent or coherent sources, and its comprehensive performance is not inferior to that of SHB. (3) For single source or incoherent sources, FDAS can not only accurately locate and quantify the source, but also significantly and efficiently attenuate sidelobes, effectively detect weak sources and acquire somewhat better spatial resolution. In contrast to that, for coherent sources, FDAS is not available. (4) DAS can invariably quantify the source accurately, irrespectively of the focus distance, whereas FDAS is burdened with a quantification deviation growing with the increase of the exponent

  9. Sound source localization by hearing preservation patients with and without symmetrical low-frequency acoustic hearing.

    PubMed

    Loiselle, Louise H; Dorman, Michael F; Yost, William A; Gifford, René H

    2015-01-01

    The aim of this article was to study sound source localization by cochlear implant (CI) listeners with low-frequency (LF) acoustic hearing in both the operated ear and in the contralateral ear. Eight CI listeners had symmetrical LF acoustic hearing and 4 had asymmetrical LF acoustic hearing. The effects of two variables were assessed: (i) the symmetry of the LF thresholds in the two ears and (ii) the presence/absence of bilateral acoustic amplification. Stimuli consisted of low-pass, high-pass, and wideband noise bursts presented in the frontal horizontal plane. Localization accuracy was 23° of error for the symmetrical listeners and 76° of error for the asymmetrical listeners. The presence of a unilateral CI used in conjunction with bilateral LF acoustic hearing does not impair sound source localization accuracy, but amplification for acoustic hearing can be detrimental to sound source localization accuracy.

  10. Validation of an acoustic location system to monitor Bornean orangutan (Pongo pygmaeus wurmbii) long calls.

    PubMed

    Spillmann, Brigitte; van Noordwijk, Maria A; Willems, Erik P; Mitra Setia, Tatang; Wipfli, Urs; van Schaik, Carel P

    2015-07-01

    The long call is an important vocal communication signal in the widely dispersed, semi-solitary orangutan. Long calls affect individuals' ranging behavior and mediate social relationships and regulate encounters between dispersed individuals in a dense rainforest. The aim of this study was to test the utility of an Acoustic Location System (ALS) for recording and triangulating the loud calls of free-living primates. We developed and validated a data extraction protocol for an ALS used to record wild orangutan males' long calls at the Tuanan field site (Central Kalimantan). We installed an ALS in a grid of 300 ha, containing 20 SM2+ recorders placed in a regular lattice at 500 m intervals, to monitor the distribution of calling males in the area. The validated system had the following main features: (i) a user-trained software algorithm (Song Scope) that reliably recognized orangutan long calls from sound files at distances up to 700 m from the nearest recorder, resulting in a total area of approximately 900 ha that could be monitored continuously; (ii) acoustic location of calling males up to 200 m outside the microphone grid, which meant that within an area of approximately 450 ha, call locations could be calculated through triangulation. The mean accuracy was 58 m, an error that is modest relative to orangutan mobility and average inter-individual distances. We conclude that an ALS is a highly effective method for detecting long-distance calls of wild primates and triangulating their position. In combination with conventional individual focal follow data, an ALS can greatly improve our knowledge of orangutans' social organization, and is readily adaptable for studying other highly vocal animals.

  11. Acoustic Sensor Planning for Gunshot Location in National Parks: A Pareto Front Approach

    PubMed Central

    González-Castaño, Francisco Javier; Alonso, Javier Vales; Costa-Montenegro, Enrique; López-Matencio, Pablo; Vicente-Carrasco, Francisco; Parrado-García, Francisco J.; Gil-Castiñeira, Felipe; Costas-Rodríguez, Sergio

    2009-01-01

    In this paper, we propose a solution for gunshot location in national parks. In Spain there are agencies such as SEPRONA that fight against poaching with considerable success. The DiANa project, which is endorsed by Cabaneros National Park and the SEPRONA service, proposes a system to automatically detect and locate gunshots. This work presents its technical aspects related to network design and planning. The system consists of a network of acoustic sensors that locate gunshots by hyperbolic multi-lateration estimation. The differences in sound time arrivals allow the computation of a low error estimator of gunshot location. The accuracy of this method depends on tight sensor clock synchronization, which an ad-hoc time synchronization protocol provides. On the other hand, since the areas under surveillance are wide, and electric power is scarce, it is necessary to maximize detection coverage and minimize system cost at the same time. Therefore, sensor network planning has two targets, i.e., coverage and cost. We model planning as an unconstrained problem with two objective functions. We determine a set of candidate solutions of interest by combining a derivative-free descent method we have recently proposed with a Pareto front approach. The results are clearly superior to random seeding in a realistic simulation scenario. PMID:22303135

  12. Acoustic sensor planning for gunshot location in national parks: a pareto front approach.

    PubMed

    González-Castaño, Francisco Javier; Alonso, Javier Vales; Costa-Montenegro, Enrique; López-Matencio, Pablo; Vicente-Carrasco, Francisco; Parrado-García, Francisco J; Gil-Castiñeira, Felipe; Costas-Rodríguez, Sergio

    2009-01-01

    In this paper, we propose a solution for gunshot location in national parks. In Spain there are agencies such as SEPRONA that fight against poaching with considerable success. The DiANa project, which is endorsed by Cabaneros National Park and the SEPRONA service, proposes a system to automatically detect and locate gunshots. This work presents its technical aspects related to network design and planning. The system consists of a network of acoustic sensors that locate gunshots by hyperbolic multi-lateration estimation. The differences in sound time arrivals allow the computation of a low error estimator of gunshot location. The accuracy of this method depends on tight sensor clock synchronization, which an ad-hoc time synchronization protocol provides. On the other hand, since the areas under surveillance are wide, and electric power is scarce, it is necessary to maximize detection coverage and minimize system cost at the same time. Therefore, sensor network planning has two targets, i.e., coverage and cost. We model planning as an unconstrained problem with two objective functions. We determine a set of candidate solutions of interest by combining a derivative-free descent method we have recently proposed with a Pareto front approach. The results are clearly superior to random seeding in a realistic simulation scenario.

  13. Accurate source location from waves scattered by surface topography

    NASA Astrophysics Data System (ADS)

    Wang, Nian; Shen, Yang; Flinders, Ashton; Zhang, Wei

    2016-06-01

    Accurate source locations of earthquakes and other seismic events are fundamental in seismology. The location accuracy is limited by several factors, including velocity models, which are often poorly known. In contrast, surface topography, the largest velocity contrast in the Earth, is often precisely mapped at the seismic wavelength (>100 m). In this study, we explore the use of P coda waves generated by scattering at surface topography to obtain high-resolution locations of near-surface seismic events. The Pacific Northwest region is chosen as an example to provide realistic topography. A grid search algorithm is combined with the 3-D strain Green's tensor database to improve search efficiency as well as the quality of hypocenter solutions. The strain Green's tensor is calculated using a 3-D collocated-grid finite difference method on curvilinear grids. Solutions in the search volume are obtained based on the least squares misfit between the "observed" and predicted P and P coda waves. The 95% confidence interval of the solution is provided as an a posteriori error estimation. For shallow events tested in the study, scattering is mainly due to topography in comparison with stochastic lateral velocity heterogeneity. The incorporation of P coda significantly improves solution accuracy and reduces solution uncertainty. The solution remains robust with wide ranges of random noises in data, unmodeled random velocity heterogeneities, and uncertainties in moment tensors. The method can be extended to locate pairs of sources in close proximity by differential waveforms using source-receiver reciprocity, further reducing errors caused by unmodeled velocity structures.

  14. Acoustic emission source localization in thin metallic plates: A single-sensor approach based on multimodal edge reflections.

    PubMed

    Ebrahimkhanlou, A; Salamone, S

    2017-03-14

    This paper presents a new acoustic emission (AE) source localization for isotropic plates with reflecting boundaries. This approach that has no blind spot leverages multimodal edge reflections to identify AE sources with only a single sensor. The implementation of the proposed approach involves three main steps. First, the continuous wavelet transform (CWT) and the dispersion curves of the fundamental Lamb wave modes are utilized to estimate the distance between an AE source and a sensor. This step uses a modal acoustic emission approach. Then, an analytical model is proposed that uses the estimated distances to simulate the edge-reflected waves. Finally, the correlation between the experimental and the simulated waveforms is used to estimate the location of AE sources. Hsu-Nielsen pencil lead break (PLB) tests were performed on an aluminum plate to validate this algorithm and promising results were achieved. Based on these results, the paper reports the statistics of the localization errors.

  15. Nonlinear Kalman Filtering for acoustic emission source localization in anisotropic panels.

    PubMed

    Dehghan Niri, E; Farhidzadeh, A; Salamone, S

    2014-02-01

    Nonlinear Kalman Filtering is an established field in applied probability and control systems, which plays an important role in many practical applications from target tracking to weather and climate prediction. However, its application for acoustic emission (AE) source localization has been very limited. In this paper, two well-known nonlinear Kalman Filtering algorithms are presented to estimate the location of AE sources in anisotropic panels: the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). These algorithms are applied to two cases: velocity profile known (CASE I) and velocity profile unknown (CASE II). The algorithms are compared with a more traditional nonlinear least squares method. Experimental tests are carried out on a carbon-fiber reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers to validate the proposed approaches. AE sources are simulated using an instrumented miniature impulse hammer. In order to evaluate the performance of the algorithms, two metrics are used: (1) accuracy of the AE source localization and (2) computational cost. Furthermore, it is shown that both EKF and UKF can provide a confidence interval of the estimated AE source location and can account for uncertainty in time of flight measurements.

  16. Measurement of Turbulence with Acoustic Doppler Current Profilers - Sources of Error and Laboratory Results

    USGS Publications Warehouse

    Nystrom, E.A.; Oberg, K.A.; Rehmann, C.R.; ,

    2002-01-01

    Acoustic Doppler current profilers (ADCPs) provide a promising method for measuring surface-water turbulence because they can provide data from a large spatial range in a relatively short time with relative ease. Some potential sources of errors in turbulence measurements made with ADCPs include inaccuracy of Doppler-shift measurements, poor temporal and spatial measurement resolution, and inaccuracy of multi-dimensional velocities resolved from one-dimensional velocities measured at separate locations. Results from laboratory measurements of mean velocity and turbulence statistics made with two pulse-coherent ADCPs in 0.87 meters of water are used to illustrate several of inherent sources of error in ADCP turbulence measurements. Results show that processing algorithms and beam configurations have important effects on turbulence measurements. ADCPs can provide reasonable estimates of many turbulence parameters; however, the accuracy of turbulence measurements made with commercially available ADCPs is often poor in comparison to standard measurement techniques.

  17. Locating tritium sources in a research reactor building.

    PubMed

    Fukui, Masami

    2005-10-01

    Despite renovation of the D2O facility, tritium concentrations in the condensates of reactor room air showed tens of Bq mL before venting resumption on July 1997. This suggested the presence of tritium sources in the research reactor-containment building. An investigation was therefore initiated to locate the source and determine the distribution of tritium in the containment building. Air monitoring in the working area using a dish of water placed in the building suggested that the source of tritium was near the reactor core. Monitoring exhaust air from the two facilities (a cold neutron source and a D(2)O tank) showed high specific activity on the order of 10 Bq mL(-1), suggesting the presence of tritium in condensates near the reactor core. The major concern was whether the leakage of liquid deuterium (4 L) and heavy water (2 x 10(3) L) used as a moderator had occurred. The concentration of tritium in condensates has not increased over the past few years in either the exhaust line or working area, and the deuterium itself has not been found in the surrounding environment. The concentration of tritium measured using an ionization chamber after Ar decay was dependent on the thermal output of the research reactor, indicating that the tritium was produced by the irradiation process within shielding/moderator materials or cover gas with neutrons.

  18. Simultaneous head tissue conductivity and EEG source location estimation

    PubMed Central

    Acar, Can E.; Makeig, Scott

    2015-01-01

    Accurate electroencephalographic (EEG) source localization requires an electrical head model incorporating accurate geometries and conductivity values for the major head tissues. While consistent conductivity values have been reported for scalp, brain, and cerebrospinal fluid, measured brain-to-skull conductivity ratio (BSCR) estimates have varied between 8 and 80, likely reflecting both inter-subject and measurement method differences. In simulations, mis-estimation of skull conductivity can produce source localization errors as large as 3 cm. Here, we describe an iterative gradient-based approach to Simultaneous tissue Conductivity And source Location Estimation (SCALE). The scalp projection maps used by SCALE are obtained from near-dipolar effective EEG sources found by adequate independent component analysis (ICA) decomposition of sufficient high-density EEG data. We applied SCALE to simulated scalp projections of 15 cm2-scale cortical patch sources in an MR image-based electrical head model with simulated BSCR of 30. Initialized either with a BSCR of 80 or 20, SCALE estimated BSCR as 32.6. In Adaptive Mixture ICA (AMICA) decompositions of (45-min, 128-channel) EEG data from two young adults we identified sets of 13 independent components having near-dipolar scalp maps compatible with a single cortical source patch. Again initialized with either BSCR 80 or 25, SCALE gave BSCR estimates of 34 and 54 for the two subjects respectively. The ability to accurately estimate skull conductivity non-invasively from any well-recorded EEG data in combination with a stable and non-invasively acquired MR imaging-derived electrical head model could remove a critical barrier to using EEG as a sub-cm2-scale accurate 3-D functional cortical imaging modality. PMID:26302675

  19. Experimental Characterization of Centrifugal Pumps as AN Acoustic Source at the Blade-Passing Frequency

    NASA Astrophysics Data System (ADS)

    Rzentkowski, G.; Zbroja, S.

    2000-05-01

    Centrifugal pumps represent the primary source of acoustic energy in industrial piping. For hydraulically similar pumps, the amount of emitted energy may vary significantly between different designs and it is generally not known. The available information, typically presented as a magnitude of pressure pulsations measured at the pump discharge, is not free of resonance effects associated with the piping acoustics and, in some aspects, may be seriously misleading. In this paper, we formulate an experimental method to examine the pump acoustic characteristics at the blade-passing frequency. First, we assess the resonance effects in the test-loop. Next, we decompose the measured signal into the components associated with the pump action and with the loop acoustics by means of a simple pump model which is based on a linear superposition of pressure wave transmission and excitation. We apply this technique to examine the acoustics of a single-stage, double-volute centrifugal pump. We estimate the strength of source variables and establish the pump characteristics as an acoustic source. The results indicate that (i) the source variables represent a jump in the acoustic field and are nearly free of resonance effects in the test-loop and that (ii) the pump may act either as a pressure or as a velocity source. Based on this analysis, we postulate that the pressure wave traveling in the direction of pump discharge should be used to define the pump pulsation level for valid comparison between different designs and for acoustic modelling of piping systems.

  20. Possible Source Location of the Terrestrial Myriametric Radio Burst

    NASA Astrophysics Data System (ADS)

    Fung, S. F.; Shao, X.; Frey, H. U.; Garcia, L. N.

    2013-12-01

    Fung et al. [2013] reported recently the identification of a terrestrial myriametric radio burst (TMRB) that was possibly a result from a dayside high latitude reconnection process. The TMRB was observed simultaneously by the IMAGE and Geotail satellites when the satellites were located at widely different latitudes on opposite sides of the Earth in nearly the same meridional plane. The TMRB was observed when the interplanetary field was northward. Its intensity seemed to be modulated by the IMF Bz component while the source directions (relative to the Geotail positions over the TMRB interval) also seemed to respond to the changes in the IMF By component. In this paper, we will present further observations from the IMAGE FUV data during the TMRB interval, revealing the presence of a bright proton aurora spot at the cusp foot print and thus confirming the presence of high-latitude dayside reconnection at the time. We have also performed a CCMC run-on-request of a global magnetospheric simulation for a time period over the TMRB interval. We will present the CCMC results and discuss the possible identification of the location of the TMRB source. Fung, S. F., K. Hashimoto, H. Kojima, S. A. Boardsen, L. N. Garcia, H. Matsumoto, J. L. Green, and B. W. Reinisch (2013), Terrestrial myriametric radio burst observed by IMAGE and Geotail satellites, J. Geophys. Res. Space Physics, 118, 1101-1111, doi:10.1002/jgra.50149.

  1. Nearfield Acoustical Holography

    NASA Astrophysics Data System (ADS)

    Hayek, Sabih I.

    Nearfield acoustical holography (NAH) is a method by which a set of acoustic pressure measurements at points located on a specific surface (called a hologram) can be used to image sources on vibrating surfaces on the acoustic field in three-dimensional space. NAH data are processed to take advantage of the evanescent wavefield to image sources that are separated less that one-eighth of a wavelength.

  2. Passive Acoustic Source Localization at a Low Sampling Rate Based on a Five-Element Cross Microphone Array

    PubMed Central

    Kan, Yue; Wang, Pengfei; Zha, Fusheng; Li, Mantian; Gao, Wa; Song, Baoyu

    2015-01-01

    Accurate acoustic source localization at a low sampling rate (less than 10 kHz) is still a challenging problem for small portable systems, especially for a multitasking micro-embedded system. A modification of the generalized cross-correlation (GCC) method with the up-sampling (US) theory is proposed and defined as the US-GCC method, which can improve the accuracy of the time delay of arrival (TDOA) and source location at a low sampling rate. In this work, through the US operation, an input signal with a certain sampling rate can be converted into another signal with a higher frequency. Furthermore, the optimal interpolation factor for the US operation is derived according to localization computation time and the standard deviation (SD) of target location estimations. On the one hand, simulation results show that absolute errors of the source locations based on the US-GCC method with an interpolation factor of 15 are approximately from 1/15- to 1/12-times those based on the GCC method, when the initial same sampling rates of both methods are 8 kHz. On the other hand, a simple and small portable passive acoustic source localization platform composed of a five-element cross microphone array has been designed and set up in this paper. The experiments on the established platform, which accurately locates a three-dimensional (3D) near-field target at a low sampling rate demonstrate that the proposed method is workable. PMID:26057042

  3. Passive Acoustic Source Localization at a Low Sampling Rate Based on a Five-Element Cross Microphone Array.

    PubMed

    Kan, Yue; Wang, Pengfei; Zha, Fusheng; Li, Mantian; Gao, Wa; Song, Baoyu

    2015-06-05

    Accurate acoustic source localization at a low sampling rate (less than 10 kHz) is still a challenging problem for small portable systems, especially for a multitasking micro-embedded system. A modification of the generalized cross-correlation (GCC) method with the up-sampling (US) theory is proposed and defined as the US-GCC method, which can improve the accuracy of the time delay of arrival (TDOA) and source location at a low sampling rate. In this work, through the US operation, an input signal with a certain sampling rate can be converted into another signal with a higher frequency. Furthermore, the optimal interpolation factor for the US operation is derived according to localization computation time and the standard deviation (SD) of target location estimations. On the one hand, simulation results show that absolute errors of the source locations based on the US-GCC method with an interpolation factor of 15 are approximately from 1/15- to 1/12-times those based on the GCC method, when the initial same sampling rates of both methods are 8 kHz. On the other hand, a simple and small portable passive acoustic source localization platform composed of a five-element cross microphone array has been designed and set up in this paper. The experiments on the established platform, which accurately locates a three-dimensional (3D) near-field target at a low sampling rate demonstrate that the proposed method is workable.

  4. Neptune's non-thermal radio emissions - Phenomenology and source locations

    NASA Technical Reports Server (NTRS)

    Rabl, Gerald K. F.; Ladreiter, H.-P.; Rucker, Helmut O.; Kaiser, Michael L.

    1992-01-01

    During the inbound and the outbound leg of Voyager 2's encounter with Neptune, the Planetary Radio Astronomy (PRA) experiment aboard the spacecraft detected short radio bursts at frequencies within the range of about 500-1300 kHz, and broad-banded smoothly varying emission patterns within the frequency range from about 40-800 kHz. Both emissions can be described in terms of a period of 16.1 hours determining Neptune's rotation period. Furthermore, just near closest approach, a narrow-banded smoothly varying radio component was observed occurring between 600 and 800 kHz. After giving a brief overview about some general characteristics of Neptune's nonthermal radio emission, the source locations of Neptune's emission components are determined, using an offset tilted dipole model for Neptune's magnetic field. Assuming that the emission originates near the electron gyrofrequency a geometrical beaming model is developed in order to fit the observed emission episodes.

  5. Characterizing, synthesizing, and/or canceling out acoustic signals from sound sources

    DOEpatents

    Holzrichter, John F.; Ng, Lawrence C.

    2007-03-13

    A system for characterizing, synthesizing, and/or canceling out acoustic signals from inanimate and animate sound sources. Electromagnetic sensors monitor excitation sources in sound producing systems, such as animate sound sources such as the human voice, or from machines, musical instruments, and various other structures. Acoustical output from these sound producing systems is also monitored. From such information, a transfer function characterizing the sound producing system is generated. From the transfer function, acoustical output from the sound producing system may be synthesized or canceled. The systems disclosed enable accurate calculation of transfer functions relating specific excitations to specific acoustical outputs. Knowledge of such signals and functions can be used to effect various sound replication, sound source identification, and sound cancellation applications.

  6. Phase Velocity and Full-Waveform Analysis of Co-located Distributed Acoustic Sensing (DAS) Channels and Geophone Sensor

    NASA Astrophysics Data System (ADS)

    Parker, L.; Mellors, R. J.; Thurber, C. H.; Wang, H. F.; Zeng, X.

    2015-12-01

    A 762-meter Distributed Acoustic Sensing (DAS) array with a channel spacing of one meter was deployed at the Garner Valley Downhole Array in Southern California. The array was approximately rectangular with dimensions of 180 meters by 80 meters. The array also included two subdiagonals within the rectangle along which three-component geophones were co-located. Several active sources were deployed, including a 45-kN, swept-frequency, shear-mass shaker, which produced strong Rayleigh waves across the array. Both DAS and geophone traces were filtered in 2-Hz steps between 4 and 20 Hz to obtain phase velocities as a function of frequency from fitting the moveout of travel times over distances of 35 meters or longer. As an alternative to this traditional means of finding phase velocity, it is theoretically possible to find the Rayleigh-wave phase velocity at each point of co-location as the ratio of DAS and geophone responses, because DAS is sensitive to ground strain and geophones are sensitive to ground velocity, after suitable corrections for instrument response (Mikumo & Aki, 1964). The concept was tested in WPP, a seismic wave propagation program, by first validating and then using a 3D synthetic, full-waveform seismic model to simulate the effect of increased levels of noise and uncertainty as data go from ideal to more realistic. The results obtained from this study provide a better understanding of the DAS response and its potential for being combined with traditional seismometers for obtaining phase velocity at a single location. This analysis is part of the PoroTomo project (Poroelastic Tomography by Adjoint Inverse Modeling of Data from Seismology, Geodesy, and Hydrology, http://geoscience.wisc.edu/feigl/porotomo).

  7. The source of solar high-frequency acoustic modes - Theoretical expectations

    NASA Technical Reports Server (NTRS)

    Brown, Timothy M.

    1991-01-01

    The source exciting the solar p-modes is likely to be acoustic noise generated in the top part of the sun's convection zone. If so, then simple arguments suggest that most of the emitted energy may come from rare localized events that are well separated from one another in space and time. This note describes the acoustic emission that would be expected from such events, based on a ray-theory analysis. Most of the acoustic energy is found to emerge very close to the source, so that observations to identify emission events will require high spatial resolution.

  8. Source localization from an elevated acoustic sensor array in a refractive atmosphere.

    PubMed

    Ostashev, Vladimir E; Scanlon, Michael V; Wilson, D Keith; Vecherin, Sergey N

    2008-12-01

    Localization of sound sources on the ground from an acoustic sensor array elevated on a tethered aerostat is considered. To improve estimation of the source coordinates, one should take into account refraction of sound rays due to atmospheric stratification. Using a geometrical acoustics approximation for a stratified moving medium, formulas for the source coordinates are derived that account for sound refraction. The source coordinates are expressed in terms of the direction of sound propagation as measured by the sensor array, its coordinates, and the vertical profiles of temperature and wind velocity. Employing these formulas and typical temperature and wind velocity profiles in the atmosphere, it is shown numerically that sound refraction is important for accurate predictions of the source coordinates. Furthermore, it is shown that the effective sound speed approximation, which is widely used in atmospheric acoustics, fails to correctly predict the source coordinates if the grazing angle of sound propagation is relatively large.

  9. Acoustic imaging system

    NASA Technical Reports Server (NTRS)

    Kendall, J. M., Jr.

    1977-01-01

    Tool detects noise sources by scanning sound "scene" and displaying relative location of noise-producing elements in area. System consists of ellipsoidal acoustic mirror and microphone and a display device.

  10. Source fields reconstruction with 3D mapping by means of the virtual acoustic volume concept

    NASA Astrophysics Data System (ADS)

    Forget, S.; Totaro, N.; Guyader, J. L.; Schaeffer, M.

    2016-10-01

    This paper presents the theoretical framework of the virtual acoustic volume concept and two related inverse Patch Transfer Functions (iPTF) identification methods (called u-iPTF and m-iPTF depending on the chosen boundary conditions for the virtual volume). They are based on the application of Green's identity on an arbitrary closed virtual volume defined around the source. The reconstruction of sound source fields combines discrete acoustic measurements performed at accessible positions around the source with the modal behavior of the chosen virtual acoustic volume. The mode shapes of the virtual volume can be computed by a Finite Element solver to handle the geometrical complexity of the source. As a result, it is possible to identify all the acoustic source fields at the real surface of an irregularly shaped structure and irrespective of its acoustic environment. The m-iPTF method is introduced for the first time in this paper. Conversely to the already published u-iPTF method, the m-iPTF method needs only acoustic pressure and avoids particle velocity measurements. This paper is focused on its validation, both with numerical computations and by experiments on a baffled oil pan.

  11. Recovery of burner acoustic source structure from far-field sound spectra

    NASA Technical Reports Server (NTRS)

    Mahan, J. R.; Jones, J. D.

    1984-01-01

    A method is presented that permits the thermal-acoustic efficiency spectrum in a long turbulent burner to be recovered from the corresponding far-field sound spectrum. An acoustic source/propagation model is used based on the perturbation solution of the equations describing the unsteady one-dimensional flow of an inviscid ideal gas with a distributed heat source. The technique is applied to a long cylindrical hydrogen-flame burner operating over power levels of 4.5-22.3 kW. The results show that the thermal-acoustic efficiency at a given frequency, defined as the fraction of the total burner power converted to acoustic energy at that frequency, is rather insensitive to burner power, having a maximum value on the order of 10 to the -4th at 150 Hz and rolling off steeply with increasing frequency. Evidence is presented that acoustic agitation of the flame at low frequencies enhances the mixing of the unburned fuel and air with the hot products of combustion. The paper establishes the potential of the technique as a useful tool for characterizing the acoustic source structure in any burner, such as a gas turbine combustor, for which a reasonable acoustic propagation model can be postulated.

  12. Estimating uncertainty in subsurface glider position using transmissions from fixed acoustic tomography sources.

    PubMed

    Van Uffelen, Lora J; Nosal, Eva-Marie; Howe, Bruce M; Carter, Glenn S; Worcester, Peter F; Dzieciuch, Matthew A; Heaney, Kevin D; Campbell, Richard L; Cross, Patrick S

    2013-10-01

    Four acoustic Seagliders were deployed in the Philippine Sea November 2010 to April 2011 in the vicinity of an acoustic tomography array. The gliders recorded over 2000 broadband transmissions at ranges up to 700 km from moored acoustic sources as they transited between mooring sites. The precision of glider positioning at the time of acoustic reception is important to resolve the fundamental ambiguity between position and sound speed. The Seagliders utilized GPS at the surface and a kinematic model below for positioning. The gliders were typically underwater for about 6.4 h, diving to depths of 1000 m and traveling on average 3.6 km during a dive. Measured acoustic arrival peaks were unambiguously associated with predicted ray arrivals. Statistics of travel-time offsets between received arrivals and acoustic predictions were used to estimate range uncertainty. Range (travel time) uncertainty between the source and the glider position from the kinematic model is estimated to be 639 m (426 ms) rms. Least-squares solutions for glider position estimated from acoustically derived ranges from 5 sources differed by 914 m rms from modeled positions, with estimated uncertainty of 106 m rms in horizontal position. Error analysis included 70 ms rms of uncertainty due to oceanic sound-speed variability.

  13. A hybrid algorithm for robust acoustic source localization in noisy and reverberant environments

    NASA Astrophysics Data System (ADS)

    Rajagopalan, Ramesh; Dessonville, Timothy

    2014-09-01

    Acoustic source localization using microphone arrays is widely used in videoconferencing and surveillance systems. However, it still remains a challenging task to develop efficient algorithms for accurate estimation of source location using distributed data processing. In this work, we propose a new algorithm for efficient localization of a speaker in noisy and reverberant environments such as videoconferencing. We propose a hybrid algorithm that combines generalized cross correlation based phase transform method (GCC-PHAT) and Tabu search to obtain a robust and accurate estimate of the speaker location. The Tabu Search algorithm iteratively improves the time difference of arrival (TDOA) estimate of GCC-PHAT by examining the neighboring solutions until a convergence in the TDOA value is obtained. Experiments were performed based on real world data recorded from a meeting room in the presence of noise such as computer and fans. Our results demonstrate that the proposed hybrid algorithm outperforms GCC-PHAT especially when the noise level is high. This shows the robustness of the proposed algorithm in noisy and realistic videoconferencing systems.

  14. Characterization of Acoustic Emission Source to Identify Fracture in Concrete

    DTIC Science & Technology

    1993-04-01

    Hardy, "An Approach to Acoustic Emission Signal Analysis," Materials Evaluation, 35, 1977 , pp. 100-106. [5] Hsu, N.N. and F.R. Breckenridge...Measurements," Journal of Applied Mechanics, 53, 1986, pp. 61-68. [17] Mindess , S., "The Fracture Process Zone in Concrete," Toughening Mechanisms in

  15. System and method for investigating sub-surface features of a rock formation using compressional acoustic sources

    DOEpatents

    Vu, Cung Khac; Skelt, Christopher; Nihei, Kurt; Johnson, Paul A.; Guyer, Robert; Ten Cate, James A.; Le Bas, Pierre-Yves; Larmat, Carene S.

    2016-09-27

    A system and method for investigating rock formations outside a borehole are provided. The method includes generating a first compressional acoustic wave at a first frequency by a first acoustic source; and generating a second compressional acoustic wave at a second frequency by a second acoustic source. The first and the second acoustic sources are arranged within a localized area of the borehole. The first and the second acoustic waves intersect in an intersection volume outside the borehole. The method further includes receiving a third shear acoustic wave at a third frequency, the third shear acoustic wave returning to the borehole due to a non-linear mixing process in a non-linear mixing zone within the intersection volume at a receiver arranged in the borehole. The third frequency is equal to a difference between the first frequency and the second frequency.

  16. Source location of the narrowbanded radio bursts at Uranus - Evidence of a cusp source

    NASA Astrophysics Data System (ADS)

    Farrell, W. M.; Desch, M. D.; Kaiser, M. L.; Kurth, W. S.

    1990-03-01

    While Voyager 2 was inbound to Uranus, radio bursts of narrow bandwidth (less than 5 kHz) were detected between 17-116 kHz. These R-X mode bursts, designated n-bursts, were of short duration, tended to occur when the north magnetic pole tipped toward the spacecraft, and increased in occurrence with increasing solar wind density. An explicit determination of the burst source location is presented, based upon fitting the region of detection at high and low frequencies to field-aligned, symmetric cones. The region of good fits was located between the north magnetic pole and the rotational pole, corresponding approximately to the northern polar cusp.

  17. Spatiotemporal reconstruction of auditory steady-state responses to acoustic amplitude modulations: Potential sources beyond the auditory pathway.

    PubMed

    Farahani, Ehsan Darestani; Goossens, Tine; Wouters, Jan; van Wieringen, Astrid

    2017-03-01

    Investigating the neural generators of auditory steady-state responses (ASSRs), i.e., auditory evoked brain responses, with a wide range of screening and diagnostic applications, has been the focus of various studies for many years. Most of these studies employed a priori assumptions regarding the number and location of neural generators. The aim of this study is to reconstruct ASSR sources with minimal assumptions in order to gain in-depth insight into the number and location of brain regions that are activated in response to low- as well as high-frequency acoustically amplitude modulated signals. In order to reconstruct ASSR sources, we applied independent component analysis with subsequent equivalent dipole modeling to single-subject EEG data (young adults, 20-30 years of age). These data were based on white noise stimuli, amplitude modulated at 4, 20, 40, or 80Hz. The independent components that exhibited a significant ASSR were clustered among all participants by means of a probabilistic clustering method based on a Gaussian mixture model. Results suggest that a widely distributed network of sources, located in cortical as well as subcortical regions, is active in response to 4, 20, 40, and 80Hz amplitude modulated noises. Some of these sources are located beyond the central auditory pathway. Comparison of brain sources in response to different modulation frequencies suggested that the identified brain sources in the brainstem, the left and the right auditory cortex show a higher responsiveness to 40Hz than to the other modulation frequencies.

  18. Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines

    PubMed Central

    Lien, Fue-Sang

    2017-01-01

    This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz. PMID:28378012

  19. Toward a Nonlinear Acoustic Analogy: Turbulence as a Source of Sound and Nonlinear Propagation

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2015-01-01

    An acoustic analogy is proposed that directly includes nonlinear propagation effects. We examine the Lighthill acoustic analogy and replace the Green's function of the wave equation with numerical solutions of the generalized Burgers' equation. This is justified mathematically by using similar arguments that are the basis of the solution of the Lighthill acoustic analogy. This approach is superior to alternatives because propagation is accounted for directly from the source to the far-field observer instead of from an arbitrary intermediate point. Validation of a numerical solver for the generalized Burgers' equation is performed by comparing solutions with the Blackstock bridging function and measurement data. Most importantly, the mathematical relationship between the Navier- Stokes equations, the acoustic analogy that describes the source, and canonical nonlinear propagation equations is shown. Example predictions are presented for nonlinear propagation of jet mixing noise at the sideline angle

  20. Toward a Nonlinear Acoustic Analogy: Turbulence as a Source of Sound and Nonlinear Propagation

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2015-01-01

    An acoustic analogy is proposed that directly includes nonlinear propagation effects. We examine the Lighthill acoustic analogy and replace the Green's function of the wave equation with numerical solutions of the generalized Burgers' equation. This is justified mathematically by using similar arguments that are the basis of the solution of the Lighthill acoustic analogy. This approach is superior to alternatives because propagation is accounted for directly from the source to the far-field observer instead of from an arbitrary intermediate point. Validation of a numerical solver for the generalized Burgers' equation is performed by comparing solutions with the Blackstock bridging function and measurement data. Most importantly, the mathematical relationship between the Navier-Stokes equations, the acoustic analogy that describes the source, and canonical nonlinear propagation equations is shown. Example predictions are presented for nonlinear propagation of jet mixing noise at the sideline angle.

  1. Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines.

    PubMed

    Ma, Ping; Lien, Fue-Sang; Yee, Eugene

    2017-01-01

    This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz.

  2. Broadband asymmetric acoustic transmission in a single medium by an array of heat sources

    NASA Astrophysics Data System (ADS)

    Guan, Yi-Jun; Sun, Hong-Xiang; Xia, Jian-Ping; Yuan, Shou-Qi

    2017-04-01

    We report the realization of a broadband asymmetric acoustic transmission with six different-temperature heat sources in air. This exotic effect arises from the desired refractive index in propagation paths induced from heat sources of different temperatures and asymmetrical distribution, which avoids acoustic impedance differences between the heat sources and air and has no reflection energy loss. In addition, the influence of the viscosity of air, the thermal convection, and the temperature and length of the heat sources on the asymmetric transmission effect is investigated in detail. The results show that the proposed device has the advantages of broad bandwidth, high transmission contrast, and simple structure, which enable it to provide more schemes for sound manipulation. It has excellent potential applications in acoustic devices.

  3. Energy Source Study Technical Report for Deployable Acoustic Projector System (DAPS)

    DTIC Science & Technology

    1988-12-23

    S SPARTON"- AD-A278 879 7097-0001-1192 ENERGY SOURCE STUDY TECHNICAL REPORT FOR DEPLOYABLE ACOUSTIC PROJECTOR SYSTEM (DAPS) Contract N62190-88-M...SUBTITLE 5. FUNDING NUMBERS Energy Source Study Technical Report for Deployable C:N62190-88-q+0755 Acoustic Projector System (DAPS) 6. AUTHOR(S) 7...Rev 2-89) P~IýAIppd by ill* 164 it- IJs IL- 3 Fst’ rPAITON OWiENSE mac vrroNcS r 7097-0001-1192 ENERGY SOURCE STUDY TECHNICAL REPORT I FOR DEPLOYABLE

  4. An impulsive source with variable output and stable bandwidth for underwater acoustic experiments.

    PubMed

    McNeese, Andrew R; Wilson, Preston S; Sagers, Jason D; Knobles, David P

    2014-07-01

    The Combustive Sound Source (CSS) is being developed as an environmentally friendly source to be used in ocean acoustics research and surveys. It has the ability to maintain the same wide bandwidth signal over a 20 dB drop in source level. The CSS consists of a submersible combustion chamber filled with a fuel/oxidizer mixture. The mixture is ignited and the ensuing combustion and bubble activity radiates an impulsive, thus broadband, acoustic pulse. The ability to control pulse amplitude while maintaining bandwidth is demonstrated.

  5. Seismic Acoustic Ratio Estimates Using a Moving Vehicle Source

    DTIC Science & Technology

    1999-08-01

    Sabatier et al., 1986b). More complex models for the earth, such as incorporating layering and poroelastic material (e.g., Albert, 1993; Attenborough ...Richard Detsch, David Fisk, Stephen Decato, and Roger Berger for assistance in data collection, Dr. Donald G. Albert for several useful discussions...groundwater and bedrock in an area .of discontinuous permafrost,” Geophysics 63(5), 1573-1584. Attenborough , K. (1985). “Acoustical impedance models for

  6. Concurrent development of the head and pinnae and the acoustical cues to sound location in a precocious species, the chinchilla (Chinchilla lanigera).

    PubMed

    Jones, Heath G; Koka, Kanthaiah; Thornton, Jennifer L; Tollin, Daniel J

    2011-04-01

    Sounds are filtered in a spatial- and frequency-dependent manner by the head and pinna giving rise to the acoustical cues to sound source location. These spectral and temporal transformations are dependent on the physical dimensions of the head and pinna. Therefore, the magnitudes of binaural sound location cues-the interaural time (ITD) and level (ILD) differences-are hypothesized to systematically increase while the lower frequency limit of substantial ILD production is expected to decrease due to the increase in head and pinna size during development. The frequency ranges of the monaural spectral notch cues to source elevation are also expected to decrease. This hypothesis was tested here by measuring directional transfer functions (DTFs), the directional components of head-related transfer functions, and the linear dimensions of the head and pinnae for chinchillas from birth through adulthood. Dimensions of the head and pinna increased by factors of 1.8 and 2.42, respectively, reaching adult values by ~6 weeks. From the DTFs, the ITDs, ILDs, and spectral shape cues were computed. Maximum ITDs increased by a factor of 1.75, from ~160 μs at birth (P0-1, first postnatal day) to 280 μs in adults. ILDs depended on source location and frequency exhibiting a shift in the frequency range of substantial ILD (>10 dB) from higher to lower frequencies with increasing head and pinnae size. Similar trends were observed for the spectral notch frequencies which ranged from 14.7-33.4 kHz at P0-1 to 5.3-19.1 kHz in adults. The development of the spectral notch cues, the spatial- and frequency-dependent distributions of DTF amplitude gain, acoustic directionality, maximum gain, and the acoustic axis were systematically related to the dimensions of the head and pinnae. The dimension of the head and pinnae in the chinchilla as well as the acoustical properties associated with them are mature by ~6 weeks.

  7. Design of acoustic logging signal source of imitation based on field programmable gate array

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Ju, X. D.; Lu, J. Q.; Men, B. Y.

    2014-08-01

    An acoustic logging signal source of imitation is designed and realized, based on the Field Programmable Gate Array (FPGA), to improve the efficiency of examining and repairing acoustic logging tools during research and field application, and to inspect and verify acoustic receiving circuits and corresponding algorithms. The design of this signal source contains hardware design and software design,and the hardware design uses an FPGA as the control core. Four signals are made first by reading the Random Access Memory (RAM) data which are inside the FPGA, then dealing with the data by digital to analog conversion, amplification, smoothing and so on. Software design uses VHDL, a kind of hardware description language, to program the FPGA. Experiments illustrate that the ratio of signal to noise for the signal source is high, the waveforms are stable, and also its functions of amplitude adjustment, frequency adjustment and delay adjustment are in accord with the characteristics of real acoustic logging waveforms. These adjustments can be used to imitate influences on sonic logging received waveforms caused by many kinds of factors such as spacing and span of acoustic tools, sonic speeds of different layers and fluids, and acoustic attenuations of different cementation planes.

  8. Effects of individual sound sources on the subjective loudness and acoustic comfort in underground shopping streets.

    PubMed

    Kang, Jian; Meng, Qi; Jin, Hong

    2012-10-01

    Previous studies have demonstrated that human evaluation of subjective loudness and acoustic comfort depends on a series of factors in a particular situation rather than only on sound pressure levels. In the present study, a large-scale subjective survey has been undertaken on underground shopping streets in Harbin, China, to determine how individual sound sources influence subjective loudness and acoustic comfort evaluation. Based on the analysis of case study results, it has been shown that all individual sound sources can increase subjective loudness to a certain degree. However, their levels of influence on acoustic comfort are different. Background music and the public address system can increase acoustic comfort, with a mean difference of 0.18 to 0.32 and 0.21 to 0.27, respectively, where a five-point bipolar category scale is used. Music from shops and vendor shouts can decrease acoustic comfort, with a mean difference of -0.11 to -0.38 and -0.39 to -0.62, respectively. The feasibility of improving acoustic comfort by changing certain sound sources is thus demonstrated.

  9. Acoustic suspension system

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Wang, T. G. (Inventor)

    1983-01-01

    An acoustic levitation system is described, with single acoustic source and a small reflector to stably levitate a small object while the object is processed as by coating or heating it. The system includes a concave acoustic source which has locations on opposite sides of its axis that vibrate towards and away from a focal point to generate a converging acoustic field. A small reflector is located near the focal point, and preferably slightly beyond it, to create an intense acoustic field that stably supports a small object near the reflector. The reflector is located about one-half wavelength from the focal point and is concavely curved to a radius of curvature (L) of about one-half the wavelength, to stably support an object one-quarter wavelength (N) from the reflector.

  10. A Location Method Using Sensor Arrays for Continuous Gas Leakage in Integrally Stiffened Plates Based on the Acoustic Characteristics of the Stiffener

    PubMed Central

    Bian, Xu; Li, Yibo; Feng, Hao; Wang, Jiaqiang; Qi, Lei; Jin, Shijiu

    2015-01-01

    This paper proposes a continuous leakage location method based on the ultrasonic array sensor, which is specific to continuous gas leakage in a pressure container with an integral stiffener. This method collects the ultrasonic signals generated from the leakage hole through the piezoelectric ultrasonic sensor array, and analyzes the space-time correlation of every collected signal in the array. Meanwhile, it combines with the method of frequency compensation and superposition in time domain (SITD), based on the acoustic characteristics of the stiffener, to obtain a high-accuracy location result on the stiffener wall. According to the experimental results, the method successfully solves the orientation problem concerning continuous ultrasonic signals generated from leakage sources, and acquires high accuracy location information on the leakage source using a combination of multiple sets of orienting results. The mean value of location absolute error is 13.51 mm on the one-square-meter plate with an integral stiffener (4 mm width; 20 mm height; 197 mm spacing), and the maximum location absolute error is generally within a ±25 mm interval. PMID:26404316

  11. Source localization with acoustic sensor arrays using generative model based fitting with sparse constraints.

    PubMed

    Velasco, Jose; Pizarro, Daniel; Macias-Guarasa, Javier

    2012-10-15

    This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies.

  12. Source Localization with Acoustic Sensor Arrays Using Generative Model Based Fitting with Sparse Constraints

    PubMed Central

    Velasco, Jose; Pizarro, Daniel; Macias-Guarasa, Javier

    2012-01-01

    This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP) strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies. PMID:23202021

  13. Near- and Far-field Response to Compact Acoustic Sources in Stratified Convection Zones

    NASA Astrophysics Data System (ADS)

    Cally, Paul S.

    2013-05-01

    The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure—the so-called acoustic jacket—that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

  14. Deployable Acoustic Projector System (DAPS) Energy Source Study

    DTIC Science & Technology

    1988-12-01

    final, etc. If Statements on Technical applicable, enter inclusive report dates (e.g. 10 Documents. Jun 87 - 30 Jun 88). DOE - See authorities...aJIUILOI NG 20C WIII OCSR L[~,CONNETICUT 0 811 LT = LECT I -w L94 5 06 036 Form Appmv’ovd REPORT DOCUMENTATION PAGE C No. 0A,-0pov pull efa’, m a fm thi...ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED Dec 88 Final 4. TITLE AND SUBTITLE S. FUNDING NUMBERS Deployable Acoustic Projector

  15. Quad Cities Unit 2 Main Steam Line Acoustic Source Identification and Load Reduction

    SciTech Connect

    DeBoo, Guy; Ramsden, Kevin; Gesior, Roman

    2006-07-01

    The Quad Cities Units 1 and 2 have a history of steam line vibration issues. The implementation of an Extended Power Up-rate resulted in significant increases in steam line vibration as well as acoustic loading of the steam dryers, which led to equipment failures and fatigue cracking of the dryers. This paper discusses the results of extensive data collection on the Quad Cities Unit 2 replacement dryer and the Main Steam Lines. This data was taken with the intent of identifying acoustic sources in the steam system. Review of the data confirmed that vortex shedding coupled column resonance in the relief and safety valve stub pipes were the principal sources of large magnitude acoustic loads in the main steam system. Modifications were developed in sub-scale testing to alter the acoustic properties of the valve standpipes and add acoustic damping to the system. The modifications developed and installed consisted of acoustic side branches that were attached to the Electromatic Relief Valve (ERV) and Main Steam Safety Valve (MSSV) attachment pipes. Subsequent post-modification testing was performed in plant to confirm the effectiveness of the modifications. The modifications have been demonstrated to reduce vibration loads at full Extended Power Up-rate (EPU) conditions to levels below those at Original Licensed Thermal Power (OLTP). (authors)

  16. Use of beamforming for detecting an acoustic source inside a cylindrical shell filled with a heavy fluid

    NASA Astrophysics Data System (ADS)

    Moriot, J.; Maxit, L.; Guyader, J. L.; Gastaldi, O.; Périsse, J.

    2015-02-01

    The acoustic detection of defects or leaks inside a cylindrical shell containing a fluid is of prime importance in the industry, particularly in the nuclear field. This paper examines the beamforming technique which is used to detect and locate the presence of an acoustic monopole inside a cylindrical elastic shell by measuring the external shell vibrations. In order to study the effect of fluid-structure interactions and the distance of the source from the array of sensors, a vibro-acoustic model of the fluid-loaded shell is first considered for numerical experiments. The beamforming technique is then applied to radial velocities of the shell calculated with the model. Different parameters such as the distance between sensors, the radial position of the source, the damping loss factor of the shell, or of the fluid, and modifications of fluid properties can be considered without difficulty. Analysis of these different results highlight how the behaviour of the fluid-loaded shell influences the detection. Finally, a test in a water-filled steel pipe is achieved for confirming experimentally the interest of the presented approach.

  17. Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic-impedance measurements. [Patent application

    DOEpatents

    Not Available

    1981-06-10

    Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material are presented. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material.

  18. Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements

    DOEpatents

    Langlois, Gary N.

    1983-09-13

    Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material.

  19. Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements

    DOEpatents

    Langlois, G.N.

    1983-09-13

    Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material are disclosed. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material. 6 figs.

  20. Source location of the narrowbanded radio bursts at Uranus: Evidence of a cusp source

    SciTech Connect

    Farrell, W.M.; Desch, M.D.; Kaiser, M.L. ); Kurth, W.S. )

    1990-03-01

    While Voyager 2 was inbound to Uranus, radio bursts of narrow bandwidth (< 5 kHz) were detected between 17-116 kHz by both the Planetary Radio Astronomy (PRA) and Plasma Wave (PWS) experiments. These R-X mode bursts, designated n-bursts, were of short duration (about 250 msec), tended to occur when the north magnetic pole tipped toward the spacecraft, and increased in occurrence with increasing solar wind density. In this report, the authors present an explicit determination of the burst source location based upon fitting the region of detection at high and low frequencies to field-aligned, symmetric cones. The region of good fits was located between the north magnetic pole an the rotational pole, corresponding approximately to the northern polar cusp. Based upon the emission power, it is suspected that at certain times large amounts of auroral input power may originate in this cusp.

  1. A sparse equivalent source method for near-field acoustic holography.

    PubMed

    Fernandez-Grande, Efren; Xenaki, Angeliki; Gerstoft, Peter

    2017-01-01

    This study examines a near-field acoustic holography method consisting of a sparse formulation of the equivalent source method, based on the compressive sensing (CS) framework. The method, denoted Compressive-Equivalent Source Method (C-ESM), encourages spatially sparse solutions (based on the superposition of few waves) that are accurate when the acoustic sources are spatially localized. The importance of obtaining a non-redundant representation, i.e., a sensing matrix with low column coherence, and the inherent ill-conditioning of near-field reconstruction problems is addressed. Numerical and experimental results on a classical guitar and on a highly reactive dipole-like source are presented. C-ESM is valid beyond the conventional sampling limits, making wide-band reconstruction possible. Spatially extended sources can also be addressed with C-ESM, although in this case the obtained solution does not recover the spatial extent of the source.

  2. Impulse source versus dodecahedral loudspeaker for measuring parameters derived from the impulse response in room acoustics.

    PubMed

    San Martín, Ricardo; Arana, Miguel; Machín, Jorge; Arregui, Abel

    2013-07-01

    This study investigates the performance of dodecahedral and impulse sources when measuring acoustic parameters in enclosures according to ISO 3382-1 [Acoustics-Measurement of room acoustic parameters. Part 1: Performance spaces (International Organization for Standardization, Geneva, Switzerland, 2009)]. In general, methods using speakers as a sound source are limited by their frequency response and directivity. On the other hand, getting impulse responses from impulse sources typically involves a lack of repeatability, and it is usually necessary to average several measurements for each position. Through experiments in different auditoriums that recreate typical situations in which the measurement standard is applied, it is found that using impulse sources leads to greater variation in the results, especially at low frequencies. However, this prevents subsequent dispersions due to variables that this technique does not require, such as the orientation of the emitting source. These dispersions may be relevant at high frequencies exceeding the established tolerance criteria for certain parameters. Finally, a new descriptor for dodecahedral sources reflecting the influence their lack of omnidirectionality produces on measuring acoustic parameters is proposed.

  3. Acoustic sources in the low Mach number turbulent boundary layer

    NASA Technical Reports Server (NTRS)

    Hardin, Jay C.

    1991-01-01

    The sources of sound production in a low Mach number turbulent boundary layer are examined. The sources are shown to be quadrupole in nature and to result from supersonically convecting wave-number components of the fluctuating Reynolds' normal stresses. The primary Tollmien-Schlichting instability of the boundary layer is found to radiate no sound. Analysis of various vortical phenomena suggests that the primary source is the process of formation of horseshoe vortices, with viscous sublayer bursts a possible secondary source.

  4. Aero-acoustics source separation with sparsity inducing priors in the frequency domain

    NASA Astrophysics Data System (ADS)

    Schwander, Olivier; Picheral, José; Gac, Nicolas; Mohammad-Djafari, Ali; Blacodon, Daniel

    2015-01-01

    The characterization of acoustic sources is of great interest in many industrial applications, in particular for the aeronautic or automotive industry for the development of new products. While localization of sources using observations from a wind tunnel is a well-known subject, the characterization and separation of the sources still needs to be explored. We present here a Bayesian approach for sources separation. Two prior modeling of the sources are considered: a sparsity inducing prior in the frequency domain and an autoregressive model in the time domain. The proposed methods are evaluated on synthetic data simulating noise sources emitting from an airfoil inside a wind tunnel.

  5. Transient nearfield acoustic holography based on an interpolated time-domain equivalent source method.

    PubMed

    Zhang, Xiao-Zheng; Bi, Chuan-Xing; Zhang, Yong-Bin; Xu, Liang

    2011-09-01

    Transient nearfield acoustic holography based on an interpolated time-domain equivalent source method (ESM) is proposed to reconstruct transient acoustic fields directly in the time domain. Since the equivalent source strengths solved by the traditional time-domain ESM formulation cannot be used to reconstruct the pressure on the source surface directly, an interpolation function is introduced to develop an interpolated time-domain ESM formulation which permits one to deduce an iterative reconstruction process. As the reconstruction process is ill-conditioned and especially there exists a cumulative effect of errors, the Tikhonov regularization is used to stabilize the process. Numerical examples of reconstructing transient acoustic fields from a baffled planar piston, an impulsively accelerating sphere and a cube box, respectively, demonstrate that the proposed method not only can effectively reconstruct transient acoustic fields in the time domain, but also can visualize acoustic fields in the space domain. And, in the first numerical example, the cumulative effect of errors and the validity of using the Tikhonov regularization to suppress the errors are described.

  6. Acoustic source characterization of impulsive Strombolian eruptions from the Mount Erebus lava lake

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey; Aster, Richard; Jones, Kyle R.; Kyle, Philip; McIntosh, Bill

    2008-11-01

    We invert for acoustic source volume outflux and momentum imparted to the atmosphere using an infrasonic network distributed about the erupting lava lake at Mount Erebus, Ross Island, Antarctica. By modeling these relatively simple eruptions as monopole point sources we estimate explosively ejected gas volumes that range from 1,000 m 3 to 24,000 m 3 for 312 lava lake eruptions recorded between January 6 and April 13, 2006. Though these volumes are compatible with bubble volumes at rupture (as estimated from explosion video records), departures from isotropic radiation are evident in the recorded acoustic wavefield for many eruptions. A point-source acoustic dipole component with arbitrary axis orientation and strength provides precise fit to the recorded infrasound. This dipole source axis, corresponding to the axis of inferred short-duration material jetting, varies significantly between events. Physical interpretation of dipole orientation as being indicative of eruptive directivity is corroborated by directional emissions of ejecta observed in Erebus eruption video footage. Although three azimuthally distributed stations are insufficient to fully characterize the eruptive acoustic source we speculate that a monopole with a minor amount of oriented dipole radiation may reasonably model the primary features of the recorded infrasound for these eruptions.

  7. Elastic parabolic equation solutions for underwater acoustic problems using seismic sources.

    PubMed

    Frank, Scott D; Odom, Robert I; Collis, Jon M

    2013-03-01

    Several problems of current interest involve elastic bottom range-dependent ocean environments with buried or earthquake-type sources, specifically oceanic T-wave propagation studies and interface wave related analyses. Additionally, observed deep shadow-zone arrivals are not predicted by ray theoretic methods, and attempts to model them with fluid-bottom parabolic equation solutions suggest that it may be necessary to account for elastic bottom interactions. In order to study energy conversion between elastic and acoustic waves, current elastic parabolic equation solutions must be modified to allow for seismic starting fields for underwater acoustic propagation environments. Two types of elastic self-starter are presented. An explosive-type source is implemented using a compressional self-starter and the resulting acoustic field is consistent with benchmark solutions. A shear wave self-starter is implemented and shown to generate transmission loss levels consistent with the explosive source. Source fields can be combined to generate starting fields for source types such as explosions, earthquakes, or pile driving. Examples demonstrate the use of source fields for shallow sources or deep ocean-bottom earthquake sources, where down slope conversion, a known T-wave generation mechanism, is modeled. Self-starters are interpreted in the context of the seismic moment tensor.

  8. 43 CFR 3746.1 - Mining locations for fissionable source materials.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Mining locations for fissionable source... MINERAL DEVELOPMENT Fissionable Source Materials § 3746.1 Mining locations for fissionable source... (68 Stat. 921), it is clear that after enactment of said Act of August 13, 1954, valid...

  9. 43 CFR 3746.1 - Mining locations for fissionable source materials.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Mining locations for fissionable source... MINERAL DEVELOPMENT Fissionable Source Materials § 3746.1 Mining locations for fissionable source... (68 Stat. 921), it is clear that after enactment of said Act of August 13, 1954, valid...

  10. A comparative evaluation of piezoelectric sensors for acoustic emission-based impact location estimation and damage classification in composite structures

    NASA Astrophysics Data System (ADS)

    Uprety, Bibhisha; Kim, Sungwon; Mathews, V. John; Adams, Daniel O.

    2015-03-01

    Acoustic Emission (AE) based Structural Health Monitoring (SHM) is of great interest for detecting impact damage in composite structures. Within the aerospace industry the need to detect and locate these events, even when no visible damage is present, is important both from the maintenance and design perspectives. In this investigation, four commercially available piezoelectric sensors were evaluated for usage in an AE-based SHM system. Of particular interest was comparing the acoustic response of the candidate piezoelectric sensors for impact location estimations as well as damage classification resulting from the impact in fiber-reinforced composite structures. Sensor assessment was performed based on response signal characterization and performance for active testing at 300 kHz and steel-ball drop testing using both aluminum and carbon/epoxy composite plates. Wave mode velocities calculated from the measured arrival times were found to be in good agreement with predictions obtained using both the Disperse code and finite element analysis. Differences in the relative strength of the received wave modes, the overall signal strengths and signal-to-noise ratios were observed through the use of both active testing as well as passive steel-ball drop testing. Further comparative is focusing on assessing AE sensor performance for use in impact location estimation algorithms as well as detecting and classifying damage produced in composite structures due to impact events.

  11. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  12. Lamb waves from airborne explosion sources: Viscous effects and comparisons to ducted acoustic arrivals

    SciTech Connect

    Revelle, D.O.; Whitaker, R.W.

    1996-12-31

    Observations of large explosions in the atmosphere at long range are dominated by a leading pulse of large amplitude and long period that is often followed by a series of higher frequency impulses usually of smaller amplitude. This description can be interpreted using linearized acoustic-gravity wave theory in terms of a Lamb wave arrival followed by ducted acoustic and/or gravity waves. This pattern of arrivals is not the same at all ranges nor is it independent of the source energy or of the altitude of the source. Earlier, Pierce, using an isothermal, windless atmospheric model, theoretically formulated the distances beyond which the Lamb wave would just be discernible and also where it would dominate the arriving signals for a specified explosion source. In this work the authors have evaluated these distances for the cases of both an inviscid and a viscous fluid for the source energies of interest to the CTBT (Comprehensive Test Ban Treaty) R and D work at Los Alamos. Although the inviscid results are analytic, the fully viscous solutions are iterative. For the inviscid solutions, the authors find that the Lamb wave domination distance is proportional to wave frequency at frequencies large with respect to the acoustic waveguide cut-off frequency. Under similar conditions they also find that the computed distances are linearly proportional to the source height. At 1 Hz for example, the Lamb wave must propagate about 200 km before having a significant amplitude. For a viscous fluid they found slight increases in the distances compared to an inviscid fluid with the lower frequencies, near the acoustic cut-off frequency, exhibiting the greatest changes. During the period from 1981--1994 at Los Alamos, they have also observed infrasound from eight point source, near-surface ANFO explosions at White Sands Missile Range events even though the ducted acoustic waves were observed. In this work, they will compare the current theory against some of these observations.

  13. Numerical investigation and electro-acoustic modeling of measurement methods for the in-duct acoustical source parameters.

    PubMed

    Jang, Seung-Ho; Ih, Jeong-Guon

    2003-02-01

    It is known that the direct method yields different results from the indirect (or load) method in measuring the in-duct acoustic source parameters of fluid machines. The load method usually comes up with a negative source resistance, although a fairly accurate prediction of radiated noise can be obtained from any method. This study is focused on the effect of the time-varying nature of fluid machines on the output results of two typical measurement methods. For this purpose, a simplified fluid machine consisting of a reservoir, a valve, and an exhaust pipe is considered as representing a typical periodic, time-varying system and the measurement situations are simulated by using the method of characteristics. The equivalent circuits for such simulations are also analyzed by considering the system as having a linear time-varying source. It is found that the results from the load method are quite sensitive to the change of cylinder pressure or valve profile, in contrast to those from the direct method. In the load method, the source admittance turns out to be predominantly dependent on the valve admittance at the calculation frequency as well as the valve and load admittances at other frequencies. In the direct method, however, the source resistance is always positive and the source admittance depends mainly upon the zeroth order of valve admittance.

  14. Grey seals use anthropogenic signals from acoustic tags to locate fish: evidence from a simulated foraging task.

    PubMed

    Stansbury, Amanda L; Götz, Thomas; Deecke, Volker B; Janik, Vincent M

    2015-01-07

    Anthropogenic noise can have negative effects on animal behaviour and physiology. However, noise is often introduced systematically and potentially provides information for navigation or prey detection. Here, we show that grey seals (Halichoerus grypus) learn to use sounds from acoustic fish tags as an indicator of food location. In 20 randomized trials each, 10 grey seals individually explored 20 foraging boxes, with one box containing a tagged fish, one containing an untagged fish and all other boxes being empty. The tagged box was found after significantly fewer non-tag box visits across trials, and seals revisited boxes containing the tag more often than any other box. The time and number of boxes needed to find both fish decreased significantly throughout consecutive trials. Two additional controls were conducted to investigate the role of the acoustic signal: (i) tags were placed in one box, with no fish present in any boxes and (ii) additional pieces of fish, inaccessible to the seal, were placed in the previously empty 18 boxes, making possible alternative chemosensory cues less reliable. During these controls, the acoustically tagged box was generally found significantly faster than the control box. Our results show that animals learn to use information provided by anthropogenic signals to enhance foraging success.

  15. Grey seals use anthropogenic signals from acoustic tags to locate fish: evidence from a simulated foraging task

    PubMed Central

    Stansbury, Amanda L.; Götz, Thomas; Deecke, Volker B.; Janik, Vincent M.

    2015-01-01

    Anthropogenic noise can have negative effects on animal behaviour and physiology. However, noise is often introduced systematically and potentially provides information for navigation or prey detection. Here, we show that grey seals (Halichoerus grypus) learn to use sounds from acoustic fish tags as an indicator of food location. In 20 randomized trials each, 10 grey seals individually explored 20 foraging boxes, with one box containing a tagged fish, one containing an untagged fish and all other boxes being empty. The tagged box was found after significantly fewer non-tag box visits across trials, and seals revisited boxes containing the tag more often than any other box. The time and number of boxes needed to find both fish decreased significantly throughout consecutive trials. Two additional controls were conducted to investigate the role of the acoustic signal: (i) tags were placed in one box, with no fish present in any boxes and (ii) additional pieces of fish, inaccessible to the seal, were placed in the previously empty 18 boxes, making possible alternative chemosensory cues less reliable. During these controls, the acoustically tagged box was generally found significantly faster than the control box. Our results show that animals learn to use information provided by anthropogenic signals to enhance foraging success. PMID:25411449

  16. Large-region acoustic source mapping using a movable array and sparse covariance fitting.

    PubMed

    Zhao, Shengkui; Tuna, Cagdas; Nguyen, Thi Ngoc Tho; Jones, Douglas L

    2017-01-01

    Large-region acoustic source mapping is important for city-scale noise monitoring. Approaches using a single-position measurement scheme to scan large regions using small arrays cannot provide clean acoustic source maps, while deploying large arrays spanning the entire region of interest is prohibitively expensive. A multiple-position measurement scheme is applied to scan large regions at multiple spatial positions using a movable array of small size. Based on the multiple-position measurement scheme, a sparse-constrained multiple-position vectorized covariance matrix fitting approach is presented. In the proposed approach, the overall sample covariance matrix of the incoherent virtual array is first estimated using the multiple-position array data and then vectorized using the Khatri-Rao (KR) product. A linear model is then constructed for fitting the vectorized covariance matrix and a sparse-constrained reconstruction algorithm is proposed for recovering source powers from the model. The user parameter settings are discussed. The proposed approach is tested on a 30 m × 40 m region and a 60 m × 40 m region using simulated and measured data. Much cleaner acoustic source maps and lower sound pressure level errors are obtained compared to the beamforming approaches and the previous sparse approach [Zhao, Tuna, Nguyen, and Jones, Proc. IEEE Intl. Conf. on Acoustics, Speech and Signal Processing (ICASSP) (2016)].

  17. Localization of random acoustic sources in an inhomogeneous medium

    NASA Astrophysics Data System (ADS)

    Khazaie, Shahram; Wang, Xun; Sagaut, Pierre

    2016-12-01

    In this paper, the localization of a random sound source via different source localization methods is considered, the emphasis being put on the robustness and the accuracy of classical methods in the presence of uncertainties. The sound source position is described by a random variable and the sound propagation medium is assumed to have spatially varying parameters with known values. Two approaches are used for the source identification: time reversal and beamforming. The probability density functions of the random source position are estimated using both methods. The focal spot resolutions of the time reversal estimates are also evaluated. In the numerical simulations, two media with different correlation lengths are investigated to account for two different scattering regimes: one has a correlation length relatively larger than the wavelength and the other has a correlation length comparable to the wavelength. The results show that the required sound propagation time and source estimation robustness highly depend on the ratio between the correlation length and the wavelength. It is observed that source identification methods have different robustness in the presence of uncertainties. Advantages and weaknesses of each method are discussed.

  18. On Acoustic Source Specification for Rotor-Stator Interaction Noise Prediction

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Envia, Edmane; Burley, Caesy L.

    2010-01-01

    This paper describes the use of measured source data to assess the effects of acoustic source specification on rotor-stator interaction noise predictions. Specifically, the acoustic propagation and radiation portions of a recently developed coupled computational approach are used to predict tonal rotor-stator interaction noise from a benchmark configuration. In addition to the use of full measured data, randomization of source mode relative phases is also considered for specification of the acoustic source within the computational approach. Comparisons with sideline noise measurements are performed to investigate the effects of various source descriptions on both inlet and exhaust predictions. The inclusion of additional modal source content is shown to have a much greater influence on the inlet results. Reasonable agreement between predicted and measured levels is achieved for the inlet, as well as the exhaust when shear layer effects are taken into account. For the number of trials considered, phase randomized predictions follow statistical distributions similar to those found in previous statistical source investigations. The shape of the predicted directivity pattern relative to measurements also improved with phase randomization, having predicted levels generally within one standard deviation of the measured levels.

  19. Quantitative acoustic emission from localized sources in material fatigue processes

    NASA Astrophysics Data System (ADS)

    Shi, Zhiqiang; Jarzynski, Jacek; Jacobs, Laurence

    2000-05-01

    Fretting fatigue is the phenomenon where two contacting bodies undergoing a cyclic fatigue loading experience small amplitude oscillatory motion. Fretting fatigue is characterized by crack nucleation and the subsequent propagation of these cracks. The coupling of fatigue with fretting leads to the premature nucleation and acceleration of the early growth of fatigue cracks, resulting in a significant reduction in a structure's service life. A better understanding of the mechanics of fretting fatigue is needed to prevent and reduce the severe consequences of such damage. This research uses quantitative acoustic emission (AE) techniques to study the fretting fatigue of PH 13-8 stainless steel under different loading conditions. Specifically, this work correlates AE signals to specific fretting characteristics such as frictional force history and frictional force-displacement hysteresis loops. These results indicate a close correlation between the various stages of fretting fatigue with the frequency of AE events. For example, AE waveform characteristics (such as amplitude, energy, and frequency spectrum) enable the identification and characterization of the different stages of fatigue. As a result, it is possible to establish a relationship between AE observations and fretting crack initiation and growth.

  20. Australasian tektites: source parameters and crater location reviewed

    NASA Astrophysics Data System (ADS)

    Stecher, O.; Storey, M.; Hopper, J. R.

    2009-12-01

    Tektites of the Australasian strewn field cover an area from SE-Asia, through the Southwestern part of the Pacific Ocean and parts of the Indian Ocean, down to Australia. The impact crater has until now not been positively located, but it is generally assumed to be located somewhere in Indochina, where tektites also are more abundant and larger. 40Ar/39Ar dated Australasian tektites consistently give ages around 800 ka (1,2), and our new laser step-heating determinations on a Thailand tektite are in agreement. Australasian tektites show a marked coherence in physical, chemical and isotopic parameters. Refractive indices of tektite fragments, numbers of vesicles, abundance of relict minerals, tektite mass/m2, major elements compositions from tektites covering the whole strewn field can be contoured with more or less elliptical curves with slightly varying center positions, located within a few 100 km of the Cambodia, Laos, Vietnam junction. Isotope data suggest that sediments of the impact area consisted of ~1500 Ma old denudation material (Nd-isotope data (3,4)) and that this material was eroded within the last 170 Ma (Sr-isotope data (3,4)). Fine-grained minerals and particularly soils are effective scavengers of cosmogenic 10Be, and the high values reported for Australasian tektites (5) suggest that clay minerals are a significant and variable component in the target material. The highest 10Be-values are from tektites found furthest from the impact site. In the impact process, the top layer of the target - with its young sedimentation ages and higher 10Be values - will be projected the furthest away from the impact site. The next layer down consists of slightly older material with lower 10Be, and the impact process will propel these tektites to areas closer to the impact site. The 10Be distribution in tektites shows this variation and defines a broad center (~17°N, ~107°E) off the coast of Vietnam (5). La-ICPMS Pb/Pb-isotope data from tektites show small

  1. Mesospheric airglow and ionospheric responses to upward-propagating acoustic and gravity waves above tropospheric sources

    NASA Astrophysics Data System (ADS)

    Snively, J. B.; Zettergren, M. D.

    2013-12-01

    The existence of acoustic waves (periods ~1-5 minutes) and gravity waves (periods >4 minutes) in the ionosphere above active tropospheric convection has been appreciated for more than forty years [e.g., Georges, Rev. Geophys. and Space Phys., 11(3), 1973]. Likewise, gravity waves exhibiting cylindrical symmetry and curvature of phase fronts have been observed via imaging of the mesospheric airglow layers [e.g., Yue et al., JGR, 118(8), 2013], clearly associated with tropospheric convection; gravity wave signatures have also recently been detected above convection in ionospheric total electron content (TEC) measurements [Lay et al., GRL, 40, 2013]. We here investigate the observable features of acoustic waves, and their relationship to upward-propagating gravity waves generated by the same sources, as they arrive in the mesosphere, lower-thermosphere, and ionosphere (MLTI). Numerical simulations using a nonlinear, cylindrically-axisymmetric, compressible atmospheric dynamics model confirm that acoustic waves generated by transient tropospheric sources may produce "concentric ring" signatures in the mesospheric hydroxyl airglow layer that precede the arrival of gravity waves. As amplitudes increase with altitude and decreasing neutral density, the modeled acoustic waves achieve temperature and vertical wind perturbations on the order of ~10s of Kelvin and m/s throughout the E- and F-region. Using a coupled multi-fluid ionospheric model [Zettergren and Semeter, JGR, 117(A6), 2012], extended for low-latitudes using a 2D dipole magnetic field coordinate system, we investigate acoustic wave perturbations to the ionosphere in the meridional direction. Resulting perturbations are predicted to be detectable by ground-based radar and GPS TEC measurements, or via in situ instrumentation. Although transient and short-lived, the acoustic waves' airglow and ionospheric signatures are likely to in some cases be observable, and may provide important insight into the regional

  2. Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials

    NASA Astrophysics Data System (ADS)

    Wen, Jihong; Shen, Huijie; Yu, Dianlong; Wen, Xisen

    2013-11-01

    The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is “clear” and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM.

  3. Ultrasonic condition monitoring of composite structures using a low-profile acoustic source and an embedded optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Pierce, S. Gareth; Staszewski, Wieslaw J.; Gachagan, Anthony; James, I. R.; Philip, Wayne R.; Worden, Keith; Culshaw, Brian; McNab, Alistair; Tomlinson, Geoffrey R.; Hayward, Gordon

    1997-06-01

    The purpose of this paper is to provide a concise introduction to the developments and recent findings of a BRITE-EURAM program of work (BRE2.CT94-0990 , structurally integrated system for the comprehensive evaluation of composites). The aim of the program has been to develop an acoustic/ultrasonic based structural monitoring system for composite structures using material compatible sensors. Since plate-like structures have been investigated, it has been a requirement to utilize the propagation of ultrasonic Lamb waves through the sample materials. Preliminary investigations utilized conventional piezo-electric sources coupled to the sample via perspex wedges. The Lamb waves generated by these sources were monitored using either a fully embedded or surface mounted optical fiber sensors. The system was tested with a variety of different carbon and glass fiber reinforced panels, and the interaction of the lamb waves with different defects in these materials was monitored. Conventional signal processing allowed the location of defects such as impact damage sites, delaminations and holes. Subsequent investigations have endeavored to refine the system. This paper reports the development of advanced wavelet based signal processing techniques to enhance defect visibility, the optical connectorization of composite panels, and the development of flexible low profile acoustic sources for efficient Lamb wave generation.

  4. Time-domain delay-and-sum beamforming for time-reversal detection of intermittent acoustic sources in flows.

    PubMed

    Rakotoarisoa, Ifanila; Fischer, Jeoffrey; Valeau, Vincent; Marx, David; Prax, Christian; Brizzi, Laurent-Emmanuel

    2014-11-01

    This study focuses on the identification of intermittent aeroacoustic sources in flows by using the time-domain beamforming technique. It is first shown that this technique can be seen as a time-reversal (TR) technique, working with approximate Green functions in the case of a shear flow. Some numerical experiments investigate the case of an array measurement of a generic acoustic pulse emitted in a wind-tunnel flow, with a realistic multi-arm spiral array. The results of the time-domain beamforming successfully match those given by a numerical TR technique over a wide range of flow speeds (reaching the transonic regime). It is shown how the results should be analyzed in a focusing plane parallel to the microphone array in order to estimate the location and emission time of the pulse source. An experimental application dealing with the aeroacoustic radiation of a bluff body in a wind-tunnel flow is also considered, and shows that some intermittent events can be clearly identified in the noise radiation. Time-domain beamforming is then an efficient tool for analyzing intermittent acoustic sources in flows, and is a computationally cheaper alternative to the numerical TR technique, which should be used for complex configurations where the Green function is not available.

  5. Energy-Based Acoustic Source Localization Methods: A Survey

    PubMed Central

    Meng, Wei; Xiao, Wendong

    2017-01-01

    Energy-based source localization is an important problem in wireless sensor networks (WSNs), which has been studied actively in the literature. Numerous localization algorithms, e.g., maximum likelihood estimation (MLE) and nonlinear-least-squares (NLS) methods, have been reported. In the literature, there are relevant review papers for localization in WSNs, e.g., for distance-based localization. However, not much work related to energy-based source localization is covered in the existing review papers. Energy-based methods are proposed and specially designed for a WSN due to its limited sensor capabilities. This paper aims to give a comprehensive review of these different algorithms for energy-based single and multiple source localization problems, their merits and demerits and to point out possible future research directions. PMID:28212281

  6. Energy-Based Acoustic Source Localization Methods: A Survey.

    PubMed

    Meng, Wei; Xiao, Wendong

    2017-02-15

    Energy-based source localization is an important problem in wireless sensor networks (WSNs), which has been studied actively in the literature. Numerous localization algorithms, e.g., maximum likelihood estimation (MLE) and nonlinear-least-squares (NLS) methods, have been reported. In the literature, there are relevant review papers for localization in WSNs, e.g., for distance-based localization. However, not much work related to energy-based source localization is covered in the existing review papers. Energy-based methods are proposed and specially designed for a WSN due to its limited sensor capabilities. This paper aims to give a comprehensive review of these different algorithms for energy-based single and multiple source localization problems, their merits and demerits and to point out possible future research directions.

  7. Poynting-vector based method for determining the bearing and location of electromagnetic sources

    DOEpatents

    Simons, David J.; Carrigan, Charles R.; Harben, Philip E.; Kirkendall, Barry A.; Schultz, Craig A.

    2008-10-21

    A method and apparatus is utilized to determine the bearing and/or location of sources, such as, alternating current (A.C.) generators and loads, power lines, transformers and/or radio-frequency (RF) transmitters, emitting electromagnetic-wave energy for which a Poynting-Vector can be defined. When both a source and field sensors (electric and magnetic) are static, a bearing to the electromagnetic source can be obtained. If a single set of electric (E) and magnetic (B) sensors are in motion, multiple measurements permit location of the source. The method can be extended to networks of sensors allowing determination of the location of both stationary and moving sources.

  8. Fast Grid Search Algorithm for Seismic Source Location

    SciTech Connect

    ALDRIDGE,DAVID F.

    2000-07-01

    The spatial and temporal origin of a seismic energy source are estimated with a first grid search technique. This approach has greater likelihood of finding the global rninirnum of the arrival time misiit function compared with conventional linearized iterative methods. Assumption of a homogeneous and isotropic seismic velocity model allows for extremely rapid computation of predicted arrival times, but probably limits application of the method to certain geologic environments and/or recording geometries. Contour plots of the arrival time misfit function in the vicinity of the global minimum are extremely useful for (i) quantizing the uncertainty of an estimated hypocenter solution and (ii) analyzing the resolving power of a given recording configuration. In particular, simultaneous inversion of both P-wave and S-wave arrival times appears to yield a superior solution in the sense of being more precisely localized in space and time. Future research with this algorithm may involve (i) investigating the utility of nonuniform residual weighting schemes, (ii) incorporating linear and/or layered velocity models into the calculation of predicted arrival times, and (iii) applying it toward rational design of microseismic monitoring networks.

  9. Single- and Multiple- Track Location Shear Wave and Acoustic Radiation Force Impulse Imaging: Matched Comparison of Contrast, CNR, and Resolution

    PubMed Central

    Hollender, Peter J.; Rosenzweig, Stephen J.; Nightingale, Kathryn R.; Trahey, Gregg E.

    2014-01-01

    Acoustic radiation force impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) use the dynamic response of tissue to impulsive mechanical stimulus to characterize local elasticity. A variant of conventional, multiple track location SWEI (MTL-SWEI), denoted single track location SWEI (STL-SWEI) offers the promise of creating speckle-free shear wave images. This work compares the three imaging modalities using a high push and track beam density combined acquisition sequence to image inclusions of different sizes and contrasts. STL-SWEI is shown to have significantly higher CNR than MTL-SWEI, allowing for operation at higher resolution. ARFI and STL-SWEI perform similarly in the larger inclusions, with STL-SWEI providing better visualization of small targets ≤2.5 mm in diameter. The processing of each modality introduces different trade-offs between smoothness and resolution of edges and structures; these are discussed in detail. PMID:25701531

  10. Acoustic noise associated with the MOD-1 wind turbine: its source, impact, and control

    SciTech Connect

    Kelley, N.D.; McKenna, H.E.; Hemphill, R.R.; Etter, C.L.; Garrelts, R.L.; Linn, N.C.

    1985-02-01

    This report summarizes extensive research by staff of the Solar Energy Research Institute and its subcontractors conducted to establish the origin and possible amelioration of acoustic disturbances associated with the operation of the DOE/NASA MOD-1 wind turbine installed in 1979 near Boone, North Carolina. Results have shown that the source of this acoustic annoyance was the transient, unsteady aerodynamic lift imparted to the turbine blades as they passed through the lee wakes of the large, cylindrical tower supports. Nearby residents were annoyed by the low-frequency, acoustic impulses propagated into the structures in which the complainants lived. The situation was aggravated further by a complex sound propagation process controlled by terrain and atmospheric focusing. Several techniques for reducing the abrupt, unsteady blade load transients were researched and are discussed in the report.

  11. An evaluation of differences due to changing source directivity in room acoustic computer modeling

    NASA Astrophysics Data System (ADS)

    Vigeant, Michelle C.; Wang, Lily M.

    2001-05-01

    This project examines the effects of changing source directivity in room acoustic computer models on objective parameters and subjective perception. Acoustic parameters and auralizations calculated from omnidirectional versus directional sources were compared. Three realistic directional sources were used, measured in a limited number of octave bands from a piano, singing voice, and violin. A highly directional source that beams only within a sixteenth-tant of a sphere was also tested. Objectively, there were differences of 5% or more in reverberation time (RT) between the realistic directional and omnidirectional sources. Between the beaming directional and omnidirectional sources, differences in clarity were close to the just-noticeable-difference (jnd) criterion of 1 dB. Subjectively, participants had great difficulty distinguishing between the realistic and omnidirectional sources; very few could discern the differences in RTs. However, a larger percentage (32% vs 20%) could differentiate between the beaming and omnidirectional sources, as well as the respective differences in clarity. Further studies of the objective results from different beaming sources have been pursued. The direction of the beaming source in the room is changed, as well as the beamwidth. The objective results are analyzed to determine if differences fall within the jnd of sound-pressure level, RT, and clarity.

  12. Electromagnetic acoustic source (EMAS) for generating shock waves and cavitation in mercury

    NASA Astrophysics Data System (ADS)

    Wang, Qi

    In the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory a vessel of liquid mercury is subjected to a proton beam. The resulting nuclear interaction produces neutrons that can be used for materials research, among other things, but also launches acoustic waves with pressures in excess of 10 MPa. The acoustic waves have high enough tensile stress to generate cavitation in the mercury which results in erosion to the steel walls of the vessel. In order to study the cavitation erosion and develop mitigation schemes it would be convenient to have a way of generating similar pressures and cavitation in mercury, without the radiation concerns associated with a proton beam. Here an electromagnetic acoustic source (EMAS) has been developed which consisted of a coil placed close to a metal plate which is in turn is in contact with a fluid. The source is driven by discharging a capacitor through the coil and results in a repulsive force on the plate launching acoustic waves in the fluid. A theoretical model is presented to predict the acoustic field from the EMAS and compares favorably with measurements made in water. The pressure from the EMAS was reported as a function of capacitance, charging voltage, number of coils, mylar thickness, and properties of the plates. The properties that resulted in the highest pressure were employed for experiments in mercury and a maximum pressure recorded was 7.1 MPa. Cavitation was assessed in water and mercury by high speed camera and by detecting acoustic emissions. Bubble clouds with lifetimes on the order of 100 µs were observed in water and on the order of 600 µs in mercury. Based on acoustic emissions the bubble radius in mercury was estimated to be 0.98 mm. Experiments to produce damage to a stainless steel plate in mercury resulted in a minimal effect after 2000 shock waves at a rate of 0.33 Hz - likely because the pressure amplitude was not high enough. In order to replicate the conditions in the SNS it is

  13. A novel multi-segment path analysis based on a heterogeneous velocity model for the localization of acoustic emission sources in complex propagation media.

    PubMed

    Gollob, Stephan; Kocur, Georg Karl; Schumacher, Thomas; Mhamdi, Lassaad; Vogel, Thomas

    2017-02-01

    In acoustic emission analysis, common source location algorithms assume, independently of the nature of the propagation medium, a straight (shortest) wave path between the source and the sensors. For heterogeneous media such as concrete, the wave travels in complex paths due to the interaction with the dissimilar material contents and with the possible geometrical and material irregularities present in these media. For instance, cracks and large air voids present in concrete influence significantly the way the wave travels, by causing wave path deviations. Neglecting these deviations by assuming straight paths can introduce significant errors to the source location results. In this paper, a novel source localization method called FastWay is proposed. It accounts, contrary to most available shortest path-based methods, for the different effects of material discontinuities (cracks and voids). FastWay, based on a heterogeneous velocity model, uses the fastest rather than the shortest travel paths between the source and each sensor. The method was evaluated both numerically and experimentally and the results from both evaluation tests show that, in general, FastWay was able to locate sources of acoustic emissions more accurately and reliably than the traditional source localization methods.

  14. Source identification in acoustics and structural mechanics using Sierra/SD.

    SciTech Connect

    Walsh, Timothy Francis; Aquino, Wilkins; Ross, Michael

    2013-03-01

    In this report we derive both time and frequency-domain methods for inverse identification of sources in elastodynamics and acoustics. The inverse/design problem is cast in a PDE-constrained optimization framework with efficient computation of gradients using the adjoint method. The implementation of source inversion in Sierra/SD is described, and results from both time and frequency domain source inversion are compared to actual experimental data for a weapon store used in captive carry on a military aircraft. The inverse methodology is advantageous in that it provides a method for creating ground based acoustic and vibration tests that can reduce the actual number of flight tests, and thus, saving costs and time for the program.

  15. An eighth-scale speech source for subjective assessments in acoustic models

    NASA Astrophysics Data System (ADS)

    Orlowski, R. J.

    1981-08-01

    The design of a source is described which is suitable for making speech recordings in eighth-scale acoustic models of auditoria. An attempt was made to match the directionality of the source with the directionality of the human voice using data reported in the literature. A narrow aperture was required for the design which was provided by mounting an inverted conical horn over the diaphragm of a high frequency loudspeaker. Resonance problems were encountered with the use of a horn and a description is given of the electronic techniques adopted to minimize the effect of these resonances. Subjective and objective assessments on the completed speech source have proved satisfactory. It has been used in a modelling exercise concerned with the acoustic design of a theatre with a thrust-type stage.

  16. Acoustic source localization using a polyhedral microphone array and an improved generalized cross-correlation technique

    NASA Astrophysics Data System (ADS)

    Padois, Thomas; Sgard, Franck; Doutres, Olivier; Berry, Alain

    2017-01-01

    Millions of workers are exposed to excessive noise levels each day. Acoustic solutions have to be developed to protect workers from hearing loss. The first step of an acoustic diagnosis is the source localization which can be performed with a microphone array. Spherical microphone arrays can be used to detect the acoustic source positions in a workplace. In this study, a spherical microphone array, with polyhedral discretization, is proposed and compared with a spherical array with a slightly different geometry. The generalized cross-correlation technique is used to detect the source positions. Moreover, two criteria are introduced to improve the noise source map. The first is based on the geometric properties of the microphone array and the scan zone whereas the second is based on the energy of the spatial likelihood function. Numerical data are used to provide a systematic comparison of both geometries and criteria. Finally, experiments in a reverberant room reveal that the polyhedral microphone array associated with both criteria provides the best noise source map.

  17. Rapid estimation of tsunami source centroid location using a dense offshore observation network

    NASA Astrophysics Data System (ADS)

    Yamamoto, N.; Hirata, K.; Aoi, S.; Suzuki, W.; Nakamura, H.; Kunugi, T.

    2016-05-01

    This paper proposes a rapid method of estimating tsunami source locations using real-time ocean-bottom hydrostatic pressure data from a dense offshore observation network. We defined two characteristic locations representing the real-time tsunami disturbance and the initial sea surface height distribution. First, we defined the tsunami centroid location (TCL), which is the centroid location of the maximum absolute amplitude of the real-time ocean-bottom hydrostatic pressure changes. Second, we defined the centroid location of the absolute values of the initial sea surface height displacements. To determine whether the TCL can approximate the centroid location of the tsunami source, we examined approximately 1000 near-field synthetic tsunami scenarios and a realistic tsunami scenario of the 2011 Tohoku earthquake in the Japan Trench. From these examinations, it was confirmed that in most scenarios, the TCLs obtained within a few minutes after the occurrence of an earthquake were close to the actual corresponding tsunami source locations.

  18. The application of inverse methods to spatially-distributed acoustic sources

    NASA Astrophysics Data System (ADS)

    Holland, K. R.; Nelson, P. A.

    2013-10-01

    Acoustic inverse methods, based on the output of an array of microphones, can be readily applied to the characterisation of acoustic sources that can be adequately modelled as a number of discrete monopoles. However, there are many situations, particularly in the fields of vibroacoustics and aeroacoustics, where the sources are distributed continuously in space over a finite area (or volume). This paper is concerned with the practical problem of applying inverse methods to such distributed source regions via the process of spatial sampling. The problem is first tackled using computer simulations of the errors associated with the application of spatial sampling to a wide range of source distributions. It is found that the spatial sampling criterion for minimising the errors in the radiated far-field reconstructed from the discretised source distributions is strongly dependent on acoustic wavelength but is only weakly dependent on the details of the source field itself. The results of the computer simulations are verified experimentally through the application of the inverse method to the sound field radiated by a ducted fan. The un-baffled fan source with the associated flow field is modelled as a set of equivalent monopole sources positioned on the baffled duct exit along with a matrix of complimentary non-flow Green functions. Successful application of the spatial sampling criterion involves careful frequency-dependent selection of source spacing, and results in the accurate reconstruction of the radiated sound field. Discussions of the conditioning of the Green function matrix which is inverted are included and it is shown that the spatial sampling criterion may be relaxed if conditioning techniques, such as regularisation, are applied to this matrix prior to inversion.

  19. Similarity assessment of acoustic emission signals and its application in source localization.

    PubMed

    Chen, Shiwan; Yang, Chunhe; Wang, Guibin; Liu, Wei

    2017-03-01

    In conventional AE source localization acoustic emission (AE) signals are applied directly to localize the source without any waveform identification or quality evaluation, which always leads to large errors in source localization. To improve the reliability and accuracy of acoustic emission source localization, an identification procedure is developed to assess the similarity of AE signals to select signals with high quality to localize the AE source. Magnitude square coherence (MSC), wavelet coherence and dynamic timing warping (DTW) are successively applied for similarity assessment. Results show that cluster analysis based on DTW distance is effective to select AE signals with high similarity. Similarity assessment results of the proposed method are almost completely consistent with manual identification. A novel AE source localization procedure is developed combining the selected AE signals with high quality and a direct source localization algorithm. AE data from thermal-cracking tests in Beishan granite are analyzed to demonstrate the effectiveness of the proposed AE localization procedure. AE events are re-localized by the proposed AE localization procedure. And the accuracy of events localization has been improved significantly. The reliability and credibility of AE source localization will be improved by the proposed method.

  20. Metamaterials-based sensor to detect and locate nonlinear elastic sources

    SciTech Connect

    Gliozzi, Antonio S.; Scalerandi, Marco; Miniaci, Marco; Bosia, Federico; Pugno, Nicola M.

    2015-10-19

    In recent years, acoustic metamaterials have attracted increasing scientific interest for very diverse technological applications ranging from sound abatement to ultrasonic imaging, mainly due to their ability to act as band-stop filters. At the same time, the concept of chaotic cavities has been recently proposed as an efficient tool to enhance the quality of nonlinear signal analysis, particularly in the ultrasonic/acoustic case. The goal of the present paper is to merge the two concepts in order to propose a metamaterial-based device that can be used as a natural and selective linear filter for the detection of signals resulting from the propagation of elastic waves in nonlinear materials, e.g., in the presence of damage, and as a detector for the damage itself in time reversal experiments. Numerical simulations demonstrate the feasibility of the approach and the potential of the device in providing improved signal-to-noise ratios and enhanced focusing on the defect locations.

  1. Embedded Acoustic Sensor Array for Engine Fan Noise Source Diagnostic Test: Feasibility of Noise Telemetry via Wireless Smart Sensors

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz; Bauch, Matthew; Raible, Daniel

    2011-01-01

    Aircraft engines have evolved into a highly complex system to meet ever-increasing demands. The evolution of engine technologies has primarily been driven by fuel efficiency, reliability, as well as engine noise concerns. One of the sources of engine noise is pressure fluctuations that are induced on the stator vanes. These local pressure fluctuations, once produced, propagate and coalesce with the pressure waves originating elsewhere on the stator to form a spinning pressure pattern. Depending on the duct geometry, air flow, and frequency of fluctuations, these spinning pressure patterns are self-sustaining and result in noise which eventually radiate to the far-field from engine. To investigate the nature of vane pressure fluctuations and the resulting engine noise, unsteady pressure signatures from an array of embedded acoustic sensors are recorded as a part of vane noise source diagnostics. Output time signatures from these sensors are routed to a control and data processing station adding complexity to the system and cable loss to the measured signal. "Smart" wireless sensors have data processing capability at the sensor locations which further increases the potential of wireless sensors. Smart sensors can process measured data locally and transmit only the important information through wireless communication. The aim of this wireless noise telemetry task was to demonstrate a single acoustic sensor wireless link for unsteady pressure measurement, and thus, establish the feasibility of distributed smart sensors scheme for aircraft engine vane surface unsteady pressure data transmission and characterization.

  2. Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures.

    PubMed

    Martellotta, Francesco

    2013-09-01

    Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections.

  3. Locating the source of diffusion in complex networks by time-reversal backward spreading

    NASA Astrophysics Data System (ADS)

    Shen, Zhesi; Cao, Shinan; Wang, Wen-Xu; Di, Zengru; Stanley, H. Eugene

    2016-03-01

    Locating the source that triggers a dynamical process is a fundamental but challenging problem in complex networks, ranging from epidemic spreading in society and on the Internet to cancer metastasis in the human body. An accurate localization of the source is inherently limited by our ability to simultaneously access the information of all nodes in a large-scale complex network. This thus raises two critical questions: how do we locate the source from incomplete information and can we achieve full localization of sources at any possible location from a given set of observable nodes. Here we develop a time-reversal backward spreading algorithm to locate the source of a diffusion-like process efficiently and propose a general locatability condition. We test the algorithm by employing epidemic spreading and consensus dynamics as typical dynamical processes and apply it to the H1N1 pandemic in China. We find that the sources can be precisely located in arbitrary networks insofar as the locatability condition is assured. Our tools greatly improve our ability to locate the source of diffusion in complex networks based on limited accessibility of nodal information. Moreover, they have implications for controlling a variety of dynamical processes taking place on complex networks, such as inhibiting epidemics, slowing the spread of rumors, pollution control, and environmental protection.

  4. Locating the source of diffusion in complex networks by time-reversal backward spreading.

    PubMed

    Shen, Zhesi; Cao, Shinan; Wang, Wen-Xu; Di, Zengru; Stanley, H Eugene

    2016-03-01

    Locating the source that triggers a dynamical process is a fundamental but challenging problem in complex networks, ranging from epidemic spreading in society and on the Internet to cancer metastasis in the human body. An accurate localization of the source is inherently limited by our ability to simultaneously access the information of all nodes in a large-scale complex network. This thus raises two critical questions: how do we locate the source from incomplete information and can we achieve full localization of sources at any possible location from a given set of observable nodes. Here we develop a time-reversal backward spreading algorithm to locate the source of a diffusion-like process efficiently and propose a general locatability condition. We test the algorithm by employing epidemic spreading and consensus dynamics as typical dynamical processes and apply it to the H1N1 pandemic in China. We find that the sources can be precisely located in arbitrary networks insofar as the locatability condition is assured. Our tools greatly improve our ability to locate the source of diffusion in complex networks based on limited accessibility of nodal information. Moreover, they have implications for controlling a variety of dynamical processes taking place on complex networks, such as inhibiting epidemics, slowing the spread of rumors, pollution control, and environmental protection.

  5. Numerical investigation of the seismo-acoustic responses of the Source Physics Experiment underground explosions

    NASA Astrophysics Data System (ADS)

    Antoun, T.; Ezzedine, S. M.; Vorobiev, O.; Glenn, L. A.

    2015-12-01

    We have performed three-dimensional high resolution simulations of underground explosions conducted recently in jointed rock outcrop as part of the Source Physics Experiment (SPE) being conducted at the Nevada National Security Site (NNSS). The main goal of the current study is to investigate the effects of the structural and geomechanical properties on the spall phenomena due to underground explosions and its subsequent effect on the seismo-acoustic signature at far distances. Two parametric studies have been undertaken to assess the impact of different 1) conceptual geological models including a single layer and two layers model, with and without joints and with and without varying geomechanical properties, and 2) depth of bursts of the explosions and explosion yields. Through these investigations we have explored not only the near-field response of the explosions but also the far-field responses of the seismic and the acoustic signatures. The near-field simulations were conducted using the Eulerian and Lagrangian codes, GEODYN and GEODYN -L, respectively, while the far-field seismic simulations were conducted using the elastic wave propagation code, WPP, and the acoustic response using the Kirchhoff-Helmholtz-Rayleigh time-dependent approximation code, KHR. Though a series of simulations, we have recorded the velocity field histories a) at the ground surface on an acoustic-source-patch for the acoustic simulations, and 2) on a seismic-source-box for the seismic simulations. We first analyzed the SPE3 and SPE4-prime experimental data and simulated results, and then simulated SPE5, SPE6/7 to anticipate their seismo-acoustic responses given conditions of uncertainties. SPE experiments were conducted in a granitic formation; we have extended the parametric study to include other geological settings such dolomite and alluvial formations. These parametric studies enabled us 1) investigating the geotechnical and geophysical key parameters that impact the seismo-acoustic

  6. Neutron stars as sources of gamma-ray bursts: Constraints from X-ray observations of source locations

    NASA Technical Reports Server (NTRS)

    Pizzichini, G.; Cline, T. L.; Desai, U.; Teegarden, B. J.; Hurley, K.; Niel, M.; Vedrenne, G.; Evans, W. D.; Fenimore, E. E.; Klebesadel, R. W.

    1982-01-01

    Results for three burst locations observed with the imaging proportional counter of the Einstein Observatory are given. The observations are used to determine temperature and accretion constraints for the burst source.

  7. Spin reversal and orbital torques on a viscous fluid Rayleigh sphere located arbitrarily in acoustical Bessel vortex (spiraling) beams.

    PubMed

    Mitri, F G

    2016-12-01

    The goal of this work is to demonstrate the emergence of a spin torque singularity (i.e. zero spin torque) and a spin rotation reversal of a small Rayleigh lipid/fat viscous fluid sphere located arbitrarily in space in the field of an acoustical Bessel vortex beam. This counter-intuitive property of negative spin torque generation suggests a direction of spin rotation in opposite handedness of the angular momentum carried by the incident beam. Such effects may open new capabilities in methods of quantitative characterization to determine physical properties such as viscosity, viscoelasticity, compressibility, stiffness, etc., and other techniques for the rotation and positioning using acoustical tractor beams and tweezers, invisibility cloaks, and acoustically-engineered composite metamaterials to name a few examples. Based on the descriptions for the velocity potential of the incident beam and the scattering coefficients of the sphere in the long-wavelength approximation limit, simplified expressions for the spin and orbital radiation torque components are derived. For beams with (positive or negative) unit topological charge (m=±1), the axial spin torque component for a Rayleigh absorptive sphere is maximal at the center of the beam, while it vanishes for |m|>1 therein. Moreover, the longitudinal orbital torque component, causing the sphere to rotate around the center of the beam is evaluated based on the mathematical decomposition using the gradient, scattering and absorption transverse radiation force vector components. It is shown that there is no contribution of the gradient transverse force to the orbital torque, which is only caused by the scattering and absorption transverse force components. Though the incident acoustical vortex beam carrying angular momentum causes the sphere to rotate in the same orbital direction of the beam handedness, it induces a spin torque singularity (i.e. zero spin torque) and subsequent sign reversal. This phenomenon of

  8. Slow Temporal Integration Enables Robust Neural Coding and Perception of a Cue to Sound Source Location

    PubMed Central

    Tollin, Daniel J.

    2016-01-01

    In mammals, localization of sound sources in azimuth depends on sensitivity to interaural differences in sound timing (ITD) and level (ILD). Paradoxically, while typical ILD-sensitive neurons of the auditory brainstem require millisecond synchrony of excitatory and inhibitory inputs for the encoding of ILDs, human and animal behavioral ILD sensitivity is robust to temporal stimulus degradations (e.g., interaural decorrelation due to reverberation), or, in humans, bilateral clinical device processing. Here we demonstrate that behavioral ILD sensitivity is only modestly degraded with even complete decorrelation of left- and right-ear signals, suggesting the existence of a highly integrative ILD-coding mechanism. Correspondingly, we find that a majority of auditory midbrain neurons in the central nucleus of the inferior colliculus (of chinchilla) effectively encode ILDs despite complete decorrelation of left- and right-ear signals. We show that such responses can be accounted for by relatively long windows of bilateral excitatory-inhibitory interaction, which we explicitly measure using trains of narrowband clicks. Neural and behavioral data are compared with the outputs of a simple model of ILD processing with a single free parameter, the duration of excitatory-inhibitory interaction. Behavioral, neural, and modeling data collectively suggest that ILD sensitivity depends on binaural integration of excitation and inhibition within a ≳3 ms temporal window, significantly longer than observed in lower brainstem neurons. This relatively slow integration potentiates a unique role for the ILD system in spatial hearing that may be of particular importance when informative ITD cues are unavailable. SIGNIFICANCE STATEMENT In mammalian hearing, interaural differences in the timing (ITD) and level (ILD) of impinging sounds carry critical information about source location. However, natural sounds are often decorrelated between the ears by reverberation and background noise

  9. Improvement of the imaging of moving acoustic sources by the knowledge of their motion

    NASA Astrophysics Data System (ADS)

    Hay, J.

    1981-03-01

    An analytical and experimental study is presented showing that, due to a more precise definition of nonstationary noises of a certain class, and to the preprocessing of microphone signals (termed 'coherent dedopplerization'), one can obtain acoustic imaging for sources whose velocity is greater than may be processed by conventional methods without the generation of blurrs of the same order as the antenna field. A useful application of these techniques would be to two-dimensional antennas.

  10. Acoustic beam steering by light refraction: illustration with directivity patterns of a tilted volume photoacoustic source.

    PubMed

    Raetz, Samuel; Dehoux, Thomas; Perton, Mathieu; Audoin, Bertrand

    2013-12-01

    The symmetry of a thermoelastic source resulting from laser absorption can be broken when the direction of light propagation in an elastic half-space is inclined relatively to the surface. This leads to an asymmetry of the directivity patterns of both compressional and shear acoustic waves. In contrast to classical surface acoustic sources, the tunable volume source allows one to take advantage of the mode conversion at the surface to control the directivity of specific modes. Physical interpretations of the evolution of the directivity patterns with the increasing light angle of incidence and of the relations between the preferential directions of compressional- and shear-wave emission are proposed. In order to compare calculated directivity patterns with measurements of normal displacement amplitudes performed on plates, a procedure is proposed to transform the directivity patterns into pseudo-directivity patterns representative of the experimental conditions. The comparison of the theoretical with measured pseudo-directivity patterns demonstrates the ability to enhance bulk-wave amplitudes and to steer specific bulk acoustic modes by adequately tuning light refraction.

  11. Efficient source separation algorithms for acoustic fall detection using a microsoft kinect.

    PubMed

    Li, Yun; Ho, K C; Popescu, Mihail

    2014-03-01

    Falls have become a common health problem among older adults. In previous study, we proposed an acoustic fall detection system (acoustic FADE) that employed a microphone array and beamforming to provide automatic fall detection. However, the previous acoustic FADE had difficulties in detecting the fall signal in environments where interference comes from the fall direction, the number of interferences exceeds FADE's ability to handle or a fall is occluded. To address these issues, in this paper, we propose two blind source separation (BSS) methods for extracting the fall signal out of the interferences to improve the fall classification task. We first propose the single-channel BSS by using nonnegative matrix factorization (NMF) to automatically decompose the mixture into a linear combination of several basis components. Based on the distinct patterns of the bases of falls, we identify them efficiently and then construct the interference free fall signal. Next, we extend the single-channel BSS to the multichannel case through a joint NMF over all channels followed by a delay-and-sum beamformer for additional ambient noise reduction. In our experiments, we used the Microsoft Kinect to collect the acoustic data in real-home environments. The results show that in environments with high interference and background noise levels, the fall detection performance is significantly improved using the proposed BSS approaches.

  12. System and method for investigating sub-surface features of a rock formation with acoustic sources generating coded signals

    SciTech Connect

    Vu, Cung Khac; Nihei, Kurt; Johnson, Paul A; Guyer, Robert; Ten Cate, James A; Le Bas, Pierre-Yves; Larmat, Carene S

    2014-12-30

    A system and a method for investigating rock formations includes generating, by a first acoustic source, a first acoustic signal comprising a first plurality of pulses, each pulse including a first modulated signal at a central frequency; and generating, by a second acoustic source, a second acoustic signal comprising a second plurality of pulses. A receiver arranged within the borehole receives a detected signal including a signal being generated by a non-linear mixing process from the first-and-second acoustic signal in a non-linear mixing zone within the intersection volume. The method also includes-processing the received signal to extract the signal generated by the non-linear mixing process over noise or over signals generated by a linear interaction process, or both.

  13. Development of an impulsive noise source to study the acoustic reflection characteristics of hard-walled wind tunnels

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Burrin, R. H.; Ahuja, K. K.; Bartel, H. W.

    1986-01-01

    Two impulsive sound sources, one using multiple acoustic drivers and the other using a spark discharge were developed to study the acoustic reflection characteristics of hard-walled wind tunnels, and the results of laboratory tests are presented. The analysis indicates that though the intensity of the pulse generated by the spark source was higher than that obtained from the acoustic source, the number of averages needed for a particular test may require an unacceptibly long tunnel-run time due to the low spark generation repeat rate because of capacitor charging time. The additional hardware problems associated with the longevity of electrodes and electrode holders in sustaining the impact of repetitive spark discharges, show the multidriver acoustic source to be more suitable for this application.

  14. Output of acoustical sources. [effects of structural elements and background flow on immobile multipolar point radiation

    NASA Technical Reports Server (NTRS)

    Levine, H.

    1980-01-01

    Acoustic radiation from a source, here viewed as an immobile point singularity with periodic strength and a given multipolar nature, is affected by the presence of nearly structural elements (e.g., rigid or impedance surfaces) as well as that of a background flow in the medium. An alternative to the conventional manner of calculating the net source output by integrating the energy flux over a distant control surface is described; this involves a direct evaluation of the secondary wavefunction at the position of the primary source and obviates the need for a (prospectively difficult) flux integration. Various full and half-planar surface configurations with an adjacent source are analyzed in detail, and the explicit results obtained, in particular, for the power factor of a dipole brings out a substantial rise in its output as the source nears the sharp edge of a half-plane.

  15. Sequential Optimal Monitoring Network Design using Iterative Kriging for Identification of Unknown Groundwater Pollution Sources Location

    NASA Astrophysics Data System (ADS)

    Prakash, O.; Datta, B.

    2011-12-01

    Identification of unknown groundwater pollution source characteristics, in terms of location, magnitude and activity duration is important for designing an effective pollution remediation strategy. Precise source characterization also becomes very important to ascertain liability, and to recover the cost of remediation from parties responsible for the groundwater pollution. Due to the uncertainties in accurately predicting the aquifer response to source flux injection, generally encountered sparsity of concentration observation data in the field, and the non uniqueness in the aquifer response to the subjected hydraulic and chemical stresses, groundwater pollution source characterization remains a challenging task. A scientifically designed pollutant concentration monitoring network becomes imperative for accurate pollutant source characterization. The efficiency of the unknown source locations identification process is largely determined by locations of monitoring wells where the pollutant concentration is observed. The proposed method combines spatial interpolation of concentration measurements and Simulated Annealing as optimization algorithm to find the optimum locations for monitoring wells. Initially, the observed concentration data at few sparsely and arbitrarily distributed wells are used to interpolate the concentration data for the aquifer study area. The concentration information is passed to the optimization algorithm (decision model) as concentration gradient which in turn finds the optimum locations for implementing the next sequence of monitoring wells. Concentration measurement data from these designed monitoring wells and already implemented monitoring network are iteratively used as feedback information for potential groundwater pollution source locations identification. The potential applicability of the developed methodology is demonstrated for an illustrative study area.

  16. Perceptual factors contribute more than acoustical factors to sound localization abilities with virtual sources

    PubMed Central

    Andéol, Guillaume; Savel, Sophie; Guillaume, Anne

    2015-01-01

    Human sound localization abilities rely on binaural and spectral cues. Spectral cues arise from interactions between the sound wave and the listener's body (head-related transfer function, HRTF). Large individual differences were reported in localization abilities, even in young normal-hearing adults. Several studies have attempted to determine whether localization abilities depend mostly on acoustical cues or on perceptual processes involved in the analysis of these cues. These studies have yielded inconsistent findings, which could result from methodological issues. In this study, we measured sound localization performance with normal and modified acoustical cues (i.e., with individual and non-individual HRTFs, respectively) in 20 naïve listeners. Test conditions were chosen to address most methodological issues from past studies. Procedural training was provided prior to sound localization tests. The results showed no direct relationship between behavioral results and an acoustical metrics (spectral-shape prominence of individual HRTFs). Despite uncertainties due to technical issues with the normalization of the HRTFs, large acoustical differences between individual and non-individual HRTFs appeared to be needed to produce behavioral effects. A subset of 15 listeners then trained in the sound localization task with individual HRTFs. Training included either visual correct-answer feedback (for the test group) or no feedback (for the control group), and was assumed to elicit perceptual learning for the test group only. Few listeners from the control group, but most listeners from the test group, showed significant training-induced learning. For the test group, learning was related to pre-training performance (i.e., the poorer the pre-training performance, the greater the learning amount) and was retained after 1 month. The results are interpreted as being in favor of a larger contribution of perceptual factors than of acoustical factors to sound localization

  17. Resolving the source of the solar acoustic oscillations: What will be possible with DKIST?

    NASA Astrophysics Data System (ADS)

    Rast, Mark; Martinez Pillet, Valentin

    2016-05-01

    The solar p-modes are likely excited by small-scale convective dynamics in the solar photosphere, but the detailed source properties are not known. Theoretical models differ and observations are yet unable to differentiate between them. Resolving the underlying source events is more than a curiosity. It is important to the veracity of global helioseismic measurements (including local spectral methods such as ring diagram analysis) because global p-mode line shapes and thus accurate frequency determinations depend critically on the relationship between intensity and velocity during the excitation events. It is also fundamental to improving the accuracy of the local time-distance measurements because in these kernel calculations depend on knowledge of the source profile and the properties of the excitation noise. The Daniel K. Inouye Solar Telescope (DKIST) will have the spatial resolution and spectral range needed to resolve the solar acoustic excitation events in both time and space (horizontally and with height) using multi-wavelength observations. Inversions to determine the dynamic and thermodynamic evolution of the discrete small-scale convective events that serve as acoustic sources may also be possible, though determination of the pressure fluctuations associated with the sources is a challenge. We describe the DKIST capabilities anticipated and the preliminary work needed to prepare for them.

  18. Time-distance domain transformation for Acoustic Emission source localization in thin metallic plates.

    PubMed

    Grabowski, Krzysztof; Gawronski, Mateusz; Baran, Ireneusz; Spychalski, Wojciech; Staszewski, Wieslaw J; Uhl, Tadeusz; Kundu, Tribikram; Packo, Pawel

    2016-05-01

    Acoustic Emission used in Non-Destructive Testing is focused on analysis of elastic waves propagating in mechanical structures. Then any information carried by generated acoustic waves, further recorded by a set of transducers, allow to determine integrity of these structures. It is clear that material properties and geometry strongly impacts the result. In this paper a method for Acoustic Emission source localization in thin plates is presented. The approach is based on the Time-Distance Domain Transform, that is a wavenumber-frequency mapping technique for precise event localization. The major advantage of the technique is dispersion compensation through a phase-shifting of investigated waveforms in order to acquire the most accurate output, allowing for source-sensor distance estimation using a single transducer. The accuracy and robustness of the above process are also investigated. This includes the study of Young's modulus value and numerical parameters influence on damage detection. By merging the Time-Distance Domain Transform with an optimal distance selection technique, an identification-localization algorithm is achieved. The method is investigated analytically, numerically and experimentally. The latter involves both laboratory and large scale industrial tests.

  19. Identification of blasting sources in the Dobrogea seismogenic region, Romania using seismo-acoustic signals

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela Veronica; Grecu, Bogdan; Popa, Mihaela; Radulian, Mircea

    2016-10-01

    In order to discriminate between quarry blasts and earthquakes observed in the Dobrogea seismogenic region, a seismo-acoustic analysis was performed on 520 events listed in the updated Romanian seismic catalogue from January 2011 to December 2012. During this time interval, 104 seismo-acoustic events observed from a distance between 110 and 230 km and backazimuth interval of 110-160° from the IPLOR infrasound array were identified as explosions by associating with infrasonic signals. WinPMCC software for interactive analysis was applied to detect and characterize infrasonic signals in terms of backazimuth, speed and frequency content. The measured and expected values of both backazimuths and arrival times for the study events were compared in order to identify the sources of infrasound. Two predominant directions for seismo-acoustic sources' aligning were observed, corresponding to the northern and central parts of Dobrogea, and these directions are further considered as references in the process of discriminating explosions from earthquakes. A predominance of high-frequency detections (above 1 Hz) is also observed in the infrasound data. The strong influence of seasonally dependent stratospheric winds on the IPLOR detection capability limits the efficiency of the discrimination procedure, as proposed by this study.

  20. Location of volatile odor sources by ghost crabOcypode quadrata (Fabricius).

    PubMed

    Wellins, C A; Rittschof, D; Wachowiak, M

    1989-04-01

    The ghost crab,Ocypode quadrata, was tested in the field for its ability to locate sources of volatile cues. The pure compound skatole, 3-methylindole, was a potent attractant. Crabs also located sources of complex odors such as dead fish,Lutjanus campechanus, dead mole crabs,Emerita talpoida; and peeled bananas. Ghost crabs possess concealed and reduced antennules that may not be the primary olfactory organs. Chemosensory hairs borne on the dactyls may be the primary detection system.

  1. Detection and Location of Gamma-Ray Sources with a Modulating Coded Mask

    SciTech Connect

    Anderson, Dale N.; Stromswold, David C.; Wunschel, Sharon C.; Peurrung, Anthony J.; Hansen, Randy R.

    2006-01-31

    This paper presents methods of detecting and locating a concelaed nuclear gamma-ray source with a coded aperture mask. Energetic gamma rays readily penetrate moderate amounts of shielding material and can be detected at distances of many meters. The detection of high energy gamma-ray sources is vitally important to national security for several reasons, including nuclear materials smuggling interdiction, monitoring weapon components under treaties, and locating nuclear weapons and materials in the possession terrorist organizations.

  2. Establishing a Dynamic Database of Blue and Fin Whale Locations from Recordings at the IMS CTBTO hydro-acoustic network. The Baleakanta Project

    NASA Astrophysics Data System (ADS)

    Le Bras, R. J.; Kuzma, H.

    2013-12-01

    Falling as they do into the frequency range of continuously recording hydrophones (15-100Hz), blue and fin whale songs are a significant source of noise on the hydro-acoustic monitoring array of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). One researcher's noise, however, can be a very interesting signal in another field of study. The aim of the Baleakanta Project (www.baleakanta.org) is to flag and catalogue these songs, using the azimuth and slowness of the signal measured at multiple hydrophones to solve for the approximate location of singing whales. Applying techniques borrowed from human speaker identification, it may even be possible to recognize the songs of particular individuals. The result will be a dynamic database of whale locations and songs with known individuals noted. This database will be of great value to marine biologists studying cetaceans, as there is no existing dataset which spans the globe over many years (more than 15 years of data have been collected by the IMS). Current whale song datasets from other sources are limited to detections made on small, temporary listening devices. The IMS song catalogue will make it possible to study at least some aspects of the global migration patterns of whales, changes in their songs over time, and the habits of individuals. It is believed that about 10 blue whale 'cultures' exist with distinct vocal patterns; the IMS song catalogue will test that number. Results and a subset of the database (delayed in time to mitigate worries over whaling and harassment of the animals) will be released over the web. A traveling museum exhibit is planned which will not only educate the public about whale songs, but will also make the CTBTO and its achievements more widely known. As a testament to the public's enduring fascination with whales, initial funding for this project has been crowd-sourced through an internet campaign.

  3. Multiple concurrent sources localization based on a two-node distributed acoustic sensor network

    NASA Astrophysics Data System (ADS)

    Xu, Jiaxin; Zhao, Zhao; Chen, Chunzeng; Xu, Zhiyong

    2017-01-01

    In this work, we propose a new approach to localize multiple concurrent sources using a distributed acoustic sensor network. Only two node-arrays are required in this sensor network, and each node-array consists of only two widely spaced sensors. Firstly, direction-of-arrivals (DOAs) of multiple sources are estimated at each node-array by utilizing a new pooled angular spectrum proposed in this paper, which can implement the spatial aliasing suppression effectively. Based on minimum variance distortionless response (MVDR) beamforming and the DOA estimates of the sources, the time-frequency spectra containing the corresponding energy distribution features associated with those sources are reconstructed in each node-array. Then, scale invariant feature transform (SIFT) is employed to solve the DOA association problem. Performance evaluation is conducted with field recordings and experimental results prove the effectivity and feasibility of the proposed method.

  4. System and method for characterizing, synthesizing, and/or canceling out acoustic signals from inanimate sound sources

    DOEpatents

    Holzrichter, John F.; Burnett, Greg C.; Ng, Lawrence C.

    2007-10-16

    A system and method for characterizing, synthesizing, and/or canceling out acoustic signals from inanimate sound sources is disclosed. Propagating wave electromagnetic sensors monitor excitation sources in sound producing systems, such as machines, musical instruments, and various other structures. Acoustical output from these sound producing systems is also monitored. From such information, a transfer function characterizing the sound producing system is generated. From the transfer function, acoustical output from the sound producing system may be synthesized or canceled. The methods disclosed enable accurate calculation of matched transfer functions relating specific excitations to specific acoustical outputs. Knowledge of such signals and functions can be used to effect various sound replication, sound source identification, and sound cancellation applications.

  5. System and method for characterizing, synthesizing, and/or canceling out acoustic signals from inanimate sound sources

    SciTech Connect

    Holzrichter, John F; Burnett, Greg C; Ng, Lawrence C

    2013-05-21

    A system and method for characterizing, synthesizing, and/or canceling out acoustic signals from inanimate sound sources is disclosed. Propagating wave electromagnetic sensors monitor excitation sources in sound producing systems, such as machines, musical instruments, and various other structures. Acoustical output from these sound producing systems is also monitored. From such information, a transfer function characterizing the sound producing system is generated. From the transfer function, acoustical output from the sound producing system may be synthesized or canceled. The methods disclosed enable accurate calculation of matched transfer functions relating specific excitations to specific acoustical outputs. Knowledge of such signals and functions can be used to effect various sound replication, sound source identification, and sound cancellation applications.

  6. System and method for characterizing synthesizing and/or canceling out acoustic signals from inanimate sound sources

    DOEpatents

    Holzrichter, John F.; Burnett, Greg C.; Ng, Lawrence C.

    2003-01-01

    A system and method for characterizing, synthesizing, and/or canceling out acoustic signals from inanimate sound sources is disclosed. Propagating wave electromagnetic sensors monitor excitation sources in sound producing systems, such as machines, musical instruments, and various other structures. Acoustical output from these sound producing systems is also monitored. From such information, a transfer function characterizing the sound producing system is generated. From the transfer function, acoustical output from the sound producing system may be synthesized or canceled. The methods disclosed enable accurate calculation of matched transfer functions relating specific excitations to specific acoustical outputs. Knowledge of such signals and functions can be used to effect various sound replication, sound source identification, and sound cancellation applications.

  7. Locating and quantifying gas emission sources using remotely obtained concentration data

    NASA Astrophysics Data System (ADS)

    Hirst, Bill; Jonathan, Philip; González del Cueto, Fernando; Randell, David; Kosut, Oliver

    2013-08-01

    We describe a method for detecting, locating and quantifying sources of gas emissions to the atmosphere using remotely obtained gas concentration data; the method is applicable to gases of environmental concern. We demonstrate its performance using methane data collected from aircraft. Atmospheric point concentration measurements are modelled as the sum of a spatially and temporally smooth atmospheric background concentration, augmented by concentrations due to local sources. We model source emission rates with a Gaussian mixture model and use a Markov random field to represent the atmospheric background concentration component of the measurements. A Gaussian plume atmospheric eddy dispersion model represents gas dispersion between sources and measurement locations. Initial point estimates of background concentrations and source emission rates are obtained using mixed ℓ2 - ℓ1 optimisation over a discretised grid of potential source locations. Subsequent reversible jump Markov chain Monte Carlo inference provides estimated values and uncertainties for the number, emission rates and locations of sources unconstrained by a grid. Source area, atmospheric background concentrations and other model parameters, including plume model spreading and Lagrangian turbulence time scale, are also estimated. We investigate the performance of the approach first using a synthetic problem, then apply the method to real airborne data from a 1600 km2 area containing two landfills, then a 225 km2 area containing a gas flare stack.

  8. A series expansion of the acoustic power radiated from planar sources

    NASA Technical Reports Server (NTRS)

    Willams, E. G.

    1983-01-01

    A series expansion in ascending powers of the wavenumber k is derived for the acoustic power delivered by baffled or unbaffled planar sources. This series provides a relatively simple means of derving expressions for the power radiated by a baffled source with a known velocity distribution and can be used for unbaffled plates when the velocity field outside the plate is also known. The terms in the series are calculated from the moments of this velocity distribution in the plane containing the source. If these moments are written as derivaties in wavenumber space, it is shown that a MacLaurin expansion of the Fourier transformed velocity provides an easy technique for computing the first few terms of the acoustic power. Examples are provided for baffled, rectangular plates with various boundary conditions. The arbirarily shaped plate with free boundaries is particularly interesting. It is proven that the volume flow across it surface must be zero and as a result corner and edge mode radiation cannot exist for this kind of source.

  9. Three-dimensional localization of transient acoustic sources using an ice-mounted geophone.

    PubMed

    Dosso, Stan E

    2014-01-01

    This paper presents an approach to three-dimensional (3D) localization of ocean acoustic sources using a single three-component geophone on Arctic sea ice. Source bearing is estimated by maximizing the radial signal power as a function of horizontal look angle, applying seismic polarization filters to suppress shear waves with transverse particle motion. The inherent 180° ambiguity is resolved by requiring outgoing (prograde) particle motion in the radial-vertical plane. Source range and depth estimates and uncertainties are computed by Bayesian inversion of arrival-time differences of the water-borne acoustic wave and ice seismic waves, including the horizontally-polarized shear wave and longitudinal plate wave. The 3D localization is applied to geophone recordings of impulsive sources deployed in the water column at a series of ranges (200 to 1000 m) and bearings (0° to 90°) for three sites in the Lincoln Sea characterized by smooth annual ice, rough/ridged annual ice, and thick multi-year ice. Good bearing estimates are obtained in all cases. Range-depth localization is successful for ranges over which ice seismic arrivals could be reliably detected, approximately 200 m on rough ice, 500 m on smooth ice, and 800 m on multi-year ice. Effects of environmental uncertainty on localization are quantified by marginalizing over unknown environmental parameters.

  10. Novel in situ method for locating virtual source in high-rate electron-beam evaporation

    NASA Astrophysics Data System (ADS)

    Bhatia, M. S.

    1994-07-01

    The concept of virtual source simplifies calculation of thickness distribution on extended substrates in high rate vacuum coating employing electron-beam heating. The height of the point (virtual source), from which vapor can be assumed to emanate in accordance with Knudsen's cosine law, to yield the experimentally obtained thickness distribution, is calculated and this establishes the position of virtual source. Such as post facto determination is cumbersome as it is valid for the prescribed material evaporating at a certain rate in a specified geometry. A change in any of these entails a fresh measurement. Experimenters who use a large number of materials and deposit at different rates therefore have to carry out a number of trials before they can locate the virtual source at the desired deposition parameters. An in situ method for obtaining virtual source position can go a long way in reducing the labor of these experiments. A novel in situ method is described to locate the virtual source.

  11. Precise source location of the anomalous 1979 March 5 gamma ray transient

    NASA Technical Reports Server (NTRS)

    Cline, T. L.; Desai, U. D.; Teegarden, B. J.; Evans, W. D.; Klebesadel, R. W.; Laros, J. G.; Barat, C.; Hurley, K.; Niel, M.; Vedrenne, G.

    1981-01-01

    Refinements in the source direction analysis of the observations of the unusual gamma ray transient are presented. The final results from the interplanetary gamma ray burst network produce a 0.1 arc sq. min. error box. It is nested inside the initially determined 2 arc sq min. source region. This smaller source location is within both the optical and X-ray contours of N49 although not positioned at either contour center.

  12. Bayesian statistics applied to the location of the source of explosions at Stromboli Volcano, Italy

    USGS Publications Warehouse

    Saccorotti, G.; Chouet, B.; Martini, M.; Scarpa, R.

    1998-01-01

    We present a method for determining the location and spatial extent of the source of explosions at Stromboli Volcano, Italy, based on a Bayesian inversion of the slowness vector derived from frequency-slowness analyses of array data. The method searches for source locations that minimize the error between the expected and observed slowness vectors. For a given set of model parameters, the conditional probability density function of slowness vectors is approximated by a Gaussian distribution of expected errors. The method is tested with synthetics using a five-layer velocity model derived for the north flank of Stromboli and a smoothed velocity model derived from a power-law approximation of the layered structure. Application to data from Stromboli allows for a detailed examination of uncertainties in source location due to experimental errors and incomplete knowledge of the Earth model. Although the solutions are not constrained in the radial direction, excellent resolution is achieved in both transverse and depth directions. Under the assumption that the horizontal extent of the source does not exceed the crater dimension, the 90% confidence region in the estimate of the explosive source location corresponds to a small volume extending from a depth of about 100 m to a maximum depth of about 300 m beneath the active vents, with a maximum likelihood source region located in the 120- to 180-m-depth interval.

  13. Wideband spherically focused PVDF acoustic sources for calibration of ultrasound hydrophone probes.

    PubMed

    Selfridge, A; Lewin, P A

    2000-01-01

    Several broadband sources have been developed for the purpose of calibrating hydrophones. The specific configuration described is intended for the calibration of hydrophones In a frequency range of 1 to 40 MHz. All devices used 25 /spl mu/m film of PVDF bonded to a matched backing. Two had radii of curvatures (ROC) of 25.4 and 127 mm with f numbers of 3.8 and 19, respectively. Their active element diameter was 0.28 in (6.60 mm). The active diameter of the third source used was 25 mm, and it had an ROC of 254 mm and an f number of 10. The use of a focused element minimized frequency-dependent diffraction effects, resulting in a smooth variation of acoustic pressure at the focus from 1 to 40 MHz. Also, using a focused PVDF source permitted calibrations above 20 MHz without resorting to harmonic generation via nonlinear propagation.

  14. Acoustic Localization with Infrasonic Signals

    NASA Astrophysics Data System (ADS)

    Threatt, Arnesha; Elbing, Brian

    2015-11-01

    Numerous geophysical and anthropogenic events emit infrasonic frequencies (<20 Hz), including volcanoes, hurricanes, wind turbines and tornadoes. These sounds, which cannot be heard by the human ear, can be detected from large distances (in excess of 100 miles) due to low frequency acoustic signals having a very low decay rate in the atmosphere. Thus infrasound could be used for long-range, passive monitoring and detection of these events. An array of microphones separated by known distances can be used to locate a given source, which is known as acoustic localization. However, acoustic localization with infrasound is particularly challenging due to contamination from other signals, sensitivity to wind noise and producing a trusted source for system development. The objective of the current work is to create an infrasonic source using a propane torch wand or a subwoofer and locate the source using multiple infrasonic microphones. This presentation will present preliminary results from various microphone configurations used to locate the source.

  15. A contrast source method for nonlinear acoustic wave fields in media with spatially inhomogeneous attenuation.

    PubMed

    Demi, L; van Dongen, K W A; Verweij, M D

    2011-03-01

    Experimental data reveals that attenuation is an important phenomenon in medical ultrasound. Attenuation is particularly important for medical applications based on nonlinear acoustics, since higher harmonics experience higher attenuation than the fundamental. Here, a method is presented to accurately solve the wave equation for nonlinear acoustic media with spatially inhomogeneous attenuation. Losses are modeled by a spatially dependent compliance relaxation function, which is included in the Westervelt equation. Introduction of absorption in the form of a causal relaxation function automatically results in the appearance of dispersion. The appearance of inhomogeneities implies the presence of a spatially inhomogeneous contrast source in the presented full-wave method leading to inclusion of forward and backward scattering. The contrast source problem is solved iteratively using a Neumann scheme, similar to the iterative nonlinear contrast source (INCS) method. The presented method is directionally independent and capable of dealing with weakly to moderately nonlinear, large scale, three-dimensional wave fields occurring in diagnostic ultrasound. Convergence of the method has been investigated and results for homogeneous, lossy, linear media show full agreement with the exact results. Moreover, the performance of the method is demonstrated through simulations involving steered and unsteered beams in nonlinear media with spatially homogeneous and inhomogeneous attenuation.

  16. Classification of acoustic emission sources produced by carbon/epoxy composite based on support vector machine

    NASA Astrophysics Data System (ADS)

    Ding, Peng; Li, Qin; Huang, Xunlei

    2015-07-01

    Carbon/epoxy specimens were made and stretched to fracture. In the process, acoustic emission (AE) signals were collected and their parameters were set as the input parameters of the neural network. Results show that using support vector machine (SVM) network can recognize the difference of AE sources more accurately than using the BP neural network. In addition, the accuracy of the SVM increases when the number of the training set increases. It is proved that using AE signal parameters and SVM network can recognize the AE sources’ pattern well.

  17. Application of cylindrical near-field acoustical holography to the visualization of aeroacoustic sources.

    PubMed

    Lee, Moohyung; Bolton, J Stuart; Mongeau, Luc

    2003-08-01

    The purpose of this study was to develop methods for visualizing the sound radiation from aeroacoustic sources in order to identify their source strength distribution, radiation patterns, and to quantify the performance of noise control solutions. Here, cylindrical Near-field Acoustical Holography was used for that purpose. In a practical holographic measurement of sources comprising either partially correlated or uncorrelated subsources, it is necessary to use a number of reference microphones so that the sound field on the hologram surface can be decomposed into mutually incoherent partial fields before holographic projection. In this article, procedures are described for determining the number of reference microphones required when visualizing partially correlated aeroacoustic sources; performing source nonstationarity compensation; and applying regularization. The procedures have been demonstrated by application to a ducted fan. Holographic tests were performed to visualize the sound radiation from that source in its original form. The system was then altered to investigate the effect of two modifications on the fan's sound radiation pattern: first, leaks were created in the fan and duct assembly, and second, sound absorbing material was used to line the downstream duct section. Results in all three cases are shown at the blade passing frequency and for a broadband noise component. In the absence of leakage, both components were found to exhibit a dipole-like radiation pattern. Leakage was found to have a strong influence on the directivity of the blade passing tone. The increase of the flow resistance caused by adding the acoustical lining resulted in a nearly symmetric reduction of sound radiation.

  18. Characterization of Source and Wave Propagation Effects of Volcano-seismic Events and Tremor Using the Amplitude Source Location Method

    NASA Astrophysics Data System (ADS)

    Kumagai, H.; Londono, J. M.; López, C. M.; Ruiz, M. C.; Mothes, P. A.; Maeda, Y.

    2015-12-01

    We propose application of the amplitude source location (ASL) method to characterize source and wave propagation effects of volcano-seismic events and tremor observed at different volcanoes. We used this method to estimate the source location and source amplitude from high-frequency (5-10 Hz) seismic amplitudes under the assumption of isotropic S-wave radiation. We estimated the cumulative source amplitude (Is) as the offset value of the time-integrated envelope of the vertical seismogram corrected for geometrical spreading and medium attenuation in the 5-10 Hz band. We studied these parameters of tremor signals associated with eruptions and explosion events at Tungurahua volcano, Ecuador; long-period (LP) events at Cotopaxi volcano, Ecuador; and LP events at Nevado del Ruiz volcano, Colombia. We identified two types of eruption tremor at Tungurahua; noise-like inharmonic waveforms and harmonic oscillatory signals. We found that Is increased linearly with increasing source amplitude for explosion events and LP events, and that Is increased exponentially with increasing source amplitude for inharmonic eruption tremor signals. The source characteristics of harmonic eruption tremor signals differed from those of inharmonic tremor signals. The Is values we estimated for inharmonic eruption tremor were consistent with previous estimates of volumes of tephra fallout. The linear relationship between the source amplitude and Is for LP events can be explained by the wave propagation effects in the diffusion model for multiple scattering assuming a diffusion coefficient of 105 m2/s and an intrinsic Q factor of around 50. The resultant mean free path is approximately 100 m. Our results suggest that Cotopaxi and Nevado del Ruiz volcanoes have similar highly scattering and attenuating structures. Our approach provides a systematic way to compare the size of volcano-seismic signals observed at different volcanoes. The scaling relations among source parameters that we identified

  19. Measurement of Acoustic Intensity Distribution and Radiation Power of Flat-Plate Phased-Array Sound Source

    NASA Astrophysics Data System (ADS)

    Yokoyama, Tomoki; Takahashi, Kumiko; Seki, Daizaburou; Hasegawa, Akio

    2002-05-01

    The acoustic intensity distribution and radiation power of a flat-plate phased-array sound source consisting of Tonpilz-type transducers were measured. This study shows that the active acoustic intensity is skewed in the direction of wave propagation. In addition, it clarifies that if the measurement is carried out in the immediate vicinity of the sound source, the reactive acoustic intensity distribution is effective for identifying the positions of the individual sound source elements. Experimental values of active radiation power agree well with theoretical values. Conversely, experimental values of reactive radiation power do not agree with theoretical values; it is clear that they fluctuate significantly with distance from the radiating surface. The reason for this is explained in the case of a point sound source.

  20. Underwater Source-Level Estimation using Sparsity-Cognizant Source-Location Mapping

    DTIC Science & Technology

    2014-12-01

    while being robust to environmental mismatch. Equation 3 can be cast as a convex optimization problem that forces sparsity and coherence, in the source...Baxley Pedro A. Forero SSC Pacific, 53560 Hull Street, San Diego, CA 92152–5001 TR 2060 Naval Innovative Science and...Engineering (NISE) Program (Basic Research) SSC Pacific, 53560 Hull Street, San Diego, CA 92152–5001 Approved for public release. This is work

  1. Quantification of Methane Source Locations and Emissions in AN Urban Setting

    NASA Astrophysics Data System (ADS)

    Crosson, E.; Richardson, S.; Tan, S. M.; Whetstone, J.; Bova, T.; Prasad, K. R.; Davis, K. J.; Phillips, N. G.; Turnbull, J. C.; Shepson, P. B.; Cambaliza, M. L.

    2011-12-01

    The regulation of methane emissions from urban sources such as landfills and waste-water treatment facilities is currently a highly debated topic in the US and in Europe. This interest is fueled, in part, by recent measurements indicating that urban emissions are a significant source of Methane (CH4) and in fact may be substantially higher than current inventory estimates(1). As a result, developing methods for locating and quantifying emissions from urban methane sources is of great interest to industries such as landfill and wastewater treatment facility owners, watchdog groups, and the governmental agencies seeking to evaluate or enforce regulations. In an attempt to identify major methane source locations and emissions in Boston, Indianapolis, and the Bay Area, systematic measurements of CH4 concentrations and meteorology data were made at street level using a vehicle mounted cavity ringdown analyzer. A number of discrete sources were detected at concentration levels in excess of 15 times background levels. Using Gaussian plume models as well as tomographic techniques, methane source locations and emission rates will be presented. In addition, flux chamber measurements of discrete sources such as those found in natural gas leaks will also be presented. (1) Wunch, D., P.O. Wennberg, G.C. Toon, G. Keppel-Aleks, and Y.G. Yavin, Emissions of Greenhouse Gases from a North American Megacity, Geophysical Research Letters, Vol. 36, L15810, doi:10.1029/2009GL)39825, 2009.

  2. A Novel Method for Separating and Locating Multiple Partial Discharge Sources in a Substation

    PubMed Central

    Li, Pengfei; Zhou, Wenjun; Yang, Shuai; Liu, Yushun; Tian, Yan; Wang, Yong

    2017-01-01

    To separate and locate multi-partial discharge (PD) sources in a substation, the use of spectrum differences of ultra-high frequency signals radiated from various sources as characteristic parameters has been previously reported. However, the separation success rate was poor when signal-to-noise ratio was low, and the localization result was a coordinate on two-dimensional plane. In this paper, a novel method is proposed to improve the separation rate and the localization accuracy. A directional measuring platform is built using two directional antennas. The time delay (TD) of the signals captured by the antennas is calculated, and TD sequences are obtained by rotating the platform at different angles. The sequences are separated with the TD distribution feature, and the directions of the multi-PD sources are calculated. The PD sources are located by directions using the error probability method. To verify the method, a simulated model with three PD sources was established by XFdtd. Simulation results show that the separation rate is increased from 71% to 95% compared with the previous method, and an accurate three-dimensional localization result was obtained. A field test with two PD sources was carried out, and the sources were separated and located accurately by the proposed method. PMID:28134812

  3. Quantitative and qualitative analyses of under-balcony acoustics with real and simulated arrays of multiple sources

    NASA Astrophysics Data System (ADS)

    Kwon, Youngmin

    The objective of this study was to quantitatively and qualitatively identify the acoustics of the under-balcony areas in music performance halls under realistic conditions that are close to an orchestral performance in consideration of multiple music instrumental sources and their diverse sound propagation patterns. The study executed monaural and binaural impulse response measurements with an array of sixteen directional sources (loudspeakers) for acoustical assessments. Actual measurements in a performance hall as well as computer simulations were conducted for the quantitative assessments. Psycho-acoustical listening tests were conducted for the qualitative assessments using the music signals binaurally recorded in the hall with the same source array. The results obtained from the multiple directional source tests were analyzed by comparing them to those obtained from the tests performed with a single omni-directional source. These two sets of results obtained in the under-balcony area were also compared to those obtained in the main orchestra area. The quantitative results showed that the use of a single source conforming to conventional measurement protocol seems to be competent for measurements of the room acoustical parameters such as EDTmid, RTmid, C80500-2k, IACCE3 and IACCL3. These quantitative measures, however, did not always agree with the results of the qualitative assessments. The primary reason is that, in many other acoustical analysis respects, the acoustical phenomena shown from the multiple source measurements were not similar to those shown from the single source measurements. Remarkable differences were observed in time-domain impulse responses, frequency content, spectral distribution, directional distribution of the early reflections, and in sound energy density over time. Therefore, the room acoustical parameters alone should not be the acoustical representative characterizing a performance hall or a specific area such as the under

  4. Ultrasonic power transfer from a spherical acoustic wave source to a free-free piezoelectric receiver: Modeling and experiment

    NASA Astrophysics Data System (ADS)

    Shahab, S.; Gray, M.; Erturk, A.

    2015-03-01

    Contactless powering of small electronic components has lately received growing attention for wireless applications in which battery replacement or tethered charging is undesired or simply impossible, and ambient energy harvesting is not a viable solution. As an alternative to well-studied methods of contactless energy transfer, such as the inductive coupling method, the use of ultrasonic waves transmitted and received by piezoelectric devices enables larger power transmission distances, which is critical especially for deep-implanted electronic devices. Moreover, energy transfer by means of acoustic waves is well suited in situations where no electromagnetic fields are allowed. The limited literature of ultrasonic acoustic energy transfer is mainly centered on proof-of-concept experiments demonstrating the feasibility of this method, lacking experimentally validated modeling efforts for the resulting multiphysics problem that couples the source and receiver dynamics with domain acoustics. In this work, we present fully coupled analytical, numerical, and experimental multiphysics investigations for ultrasonic acoustic energy transfer from a spherical wave source to a piezoelectric receiver bar that operates in the 33-mode of piezoelectricity. The fluid-loaded piezoelectric receiver under free-free mechanical boundary conditions is shunted to an electrical load for quantifying the electrical power output for a given acoustic source strength of the transmitter. The analytical acoustic-piezoelectric structure interaction modeling framework is validated experimentally, and the effects of system parameters are reported along with optimal electrical loading and frequency conditions of the receiver.

  5. Ultrasonic power transfer from a spherical acoustic wave source to a free-free piezoelectric receiver: Modeling and experiment

    SciTech Connect

    Shahab, S.; Gray, M.; Erturk, A.

    2015-03-14

    Contactless powering of small electronic components has lately received growing attention for wireless applications in which battery replacement or tethered charging is undesired or simply impossible, and ambient energy harvesting is not a viable solution. As an alternative to well-studied methods of contactless energy transfer, such as the inductive coupling method, the use of ultrasonic waves transmitted and received by piezoelectric devices enables larger power transmission distances, which is critical especially for deep-implanted electronic devices. Moreover, energy transfer by means of acoustic waves is well suited in situations where no electromagnetic fields are allowed. The limited literature of ultrasonic acoustic energy transfer is mainly centered on proof-of-concept experiments demonstrating the feasibility of this method, lacking experimentally validated modeling efforts for the resulting multiphysics problem that couples the source and receiver dynamics with domain acoustics. In this work, we present fully coupled analytical, numerical, and experimental multiphysics investigations for ultrasonic acoustic energy transfer from a spherical wave source to a piezoelectric receiver bar that operates in the 33-mode of piezoelectricity. The fluid-loaded piezoelectric receiver under free-free mechanical boundary conditions is shunted to an electrical load for quantifying the electrical power output for a given acoustic source strength of the transmitter. The analytical acoustic-piezoelectric structure interaction modeling framework is validated experimentally, and the effects of system parameters are reported along with optimal electrical loading and frequency conditions of the receiver.

  6. Acoustic emission monitoring system

    DOEpatents

    Romrell, Delwin M.

    1977-07-05

    Methods and apparatus for identifying the source location of acoustic emissions generated within an acoustically conductive medium. A plurality of acoustic receivers are communicably coupled to the surface of the medium at a corresponding number of spaced locations. The differences in the reception time of the respective sensors in response to a given acoustic event are measured among various sensor combinations prescribed by the monitoring mode employed. Acoustic reception response encountered subsequent to the reception by a predetermined number of the prescribed sensor combinations are inhibited from being communicated to the processing circuitry, while the time measurements obtained from the prescribed sensor combinations are translated into a position measurement representative of the location on the surface most proximate the source of the emission. The apparatus is programmable to function in six separate and five distinct operating modes employing either two, three or four sensory locations. In its preferred arrangement the apparatus of this invention will re-initiate a monitoring interval if the predetermined number of sensors do not respond to a particular emission within a given time period.

  7. All-Direction Random Routing for Source-Location Privacy Protecting against Parasitic Sensor Networks

    PubMed Central

    Wang, Na; Zeng, Jiwen

    2017-01-01

    Wireless sensor networks are deployed to monitor the surrounding physical environments and they also act as the physical environments of parasitic sensor networks, whose purpose is analyzing the contextual privacy and obtaining valuable information from the original wireless sensor networks. Recently, contextual privacy issues associated with wireless communication in open spaces have not been thoroughly addressed and one of the most important challenges is protecting the source locations of the valuable packages. In this paper, we design an all-direction random routing algorithm (ARR) for source-location protecting against parasitic sensor networks. For each package, the routing process of ARR is divided into three stages, i.e., selecting a proper agent node, delivering the package to the agent node from the source node, and sending it to the final destination from the agent node. In ARR, the agent nodes are randomly chosen in all directions by the source nodes using only local decisions, rather than knowing the whole topology of the networks. ARR can control the distributions of the routing paths in a very flexible way and it can guarantee that the routing paths with the same source and destination are totally different from each other. Therefore, it is extremely difficult for the parasitic sensor nodes to trace the packages back to the source nodes. Simulation results illustrate that ARR perfectly confuses the parasitic nodes and obviously outperforms traditional routing-based schemes in protecting source-location privacy, with a marginal increase in the communication overhead and energy consumption. In addition, ARR also requires much less energy than the cloud-based source-location privacy protection schemes. PMID:28304367

  8. All-Direction Random Routing for Source-Location Privacy Protecting against Parasitic Sensor Networks.

    PubMed

    Wang, Na; Zeng, Jiwen

    2017-03-17

    Wireless sensor networks are deployed to monitor the surrounding physical environments and they also act as the physical environments of parasitic sensor networks, whose purpose is analyzing the contextual privacy and obtaining valuable information from the original wireless sensor networks. Recently, contextual privacy issues associated with wireless communication in open spaces have not been thoroughly addressed and one of the most important challenges is protecting the source locations of the valuable packages. In this paper, we design an all-direction random routing algorithm (ARR) for source-location protecting against parasitic sensor networks. For each package, the routing process of ARR is divided into three stages, i.e., selecting a proper agent node, delivering the package to the agent node from the source node, and sending it to the final destination from the agent node. In ARR, the agent nodes are randomly chosen in all directions by the source nodes using only local decisions, rather than knowing the whole topology of the networks. ARR can control the distributions of the routing paths in a very flexible way and it can guarantee that the routing paths with the same source and destination are totally different from each other. Therefore, it is extremely difficult for the parasitic sensor nodes to trace the packages back to the source nodes. Simulation results illustrate that ARR perfectly confuses the parasitic nodes and obviously outperforms traditional routing-based schemes in protecting source-location privacy, with a marginal increase in the communication overhead and energy consumption. In addition, ARR also requires much less energy than the cloud-based source-location privacy protection schemes.

  9. A high intensity acoustic source for active attenuation of exhaust noise

    NASA Astrophysics Data System (ADS)

    Glendinning, A. G.; Elliott, S. J.; Nelson, P. A.

    1988-04-01

    An electropneumatic sound source was developed for active noise control systems applied in hostile environments such as the exhaust systems of gas turbines and internal combustion engines. It employs a gas bearing to support the friction free motion of a sliding plate which is used to modulate the supply of compressed air. The sliding plate is driven by an electrodynamic vibrator. Experimental results demonstrate that this arrangement reduces harmonic distortion to at least 20 dB below the fundamental driving frequency for most operating conditions. A theoretical analysis of the transducer enables predictions to be made of the acoustic volume velocity (source strength) produced by the transducer as a function of the upstream pressure and displacement of the sliding valve. Applicability of the transducer to gas turbine and internal combustion engine exhaust systems was tested, and net power consumption resulting from the operation of the device was estimated.

  10. Acoustic sniper localization system

    NASA Astrophysics Data System (ADS)

    Prado, Gervasio; Dhaliwal, Hardave; Martel, Philip O.

    1997-02-01

    Technologies for sniper localization have received increased attention in recent months as American forces have been deployed to various trouble spots around the world. Among the technologies considered for this task acoustics is a natural choice for various reasons. The acoustic signatures of gunshots are loud and distinctive, making them easy to detect even in high noise background environments. Acoustics provides a passive sensing technology with excellent range and non line of sight capabilities. Last but not least, an acoustic sniper location system can be built at a low cost with off the shelf components. Despite its many advantages, the performance of acoustic sensors can degrade under adverse propagation conditions. Localization accuracy, although good, is usually not accurate enough to pinpoint a sniper's location in some scenarios (for example which widow in a building or behind which tree in a grove). For these more demanding missions, the acoustic sensor can be used in conjunction with an infra red imaging system that detects the muzzle blast of the gun. The acoustic system can be used to cue the pointing system of the IR camera in the direction of the shot's source.

  11. On optimal retreat distance for the equivalent source method-based nearfield acoustical holography.

    PubMed

    Bai, Mingsian R; Chen, Ching-Cheng; Lin, Jia-Hong

    2011-03-01

    As a basic form of the equivalent source method (ESM) that is used to nearfield acoustical holography (NAH) problems, discrete monopoles are utilized to represent the sound field of interest. When setting up the virtual source distribution, it is vital to maintain a "retreat distance" between the virtual sources and the actual source surface such that reconstruction would not suffer from singularity problems. However, one cannot increase the distance without bound because of the ill-posedness inherent in the reconstruction process with large distance. In prior research, 1-2 times lattice spacing, or the inter-element distance of microphones, is generally recommended as retreat distance in using the ESM-based NAH. While this rule has shown to yield good results in many cases, the optimal choice is a complicated issue that depends on frequency, geometry of the physical source, content of evanescent waves, distribution of sensors and virtual sources, etc. This paper deals about attaining the best compromise between the reconstruction errors induced by the point source singularity; the reconstruction ill-posedness is an interesting problem in its own right. The paper revisits this issue, with the aid of an optimization algorithm based on the golden section search and parabolic interpolation. Numerical simulations were conducted for a baffled planar piston source and a spherically baffled piston source. The results revealed that the retreat distance appropriate for the ESM ranged from 0.4 to 0.5 times the spacing for the planar piston, while from 0.8 to 1.7 times average spacing for the spherical piston. Experiments carried out for a vibrating aluminum plate also revealed that the retreat distance with 0.5 times the spacing yielded better reconstructed velocity than those with 1/20 and 1 times the spacing.

  12. Source location of the smooth high-frequency radio emissions from Uranus

    SciTech Connect

    Farrell, W.M.; Calvert, W. )

    1989-05-01

    The source location of the smooth high-frequency (SHF) radio emissions from Uranus has been determined using a technique differing from those applied previously. Specifically, by fitting the signal dropouts which occurred as Voyager traversed the hollow center for the emission pattern to a symmetrical cone centered on the source magnetic field direction at the cyclotron frequency, a southern-hemisphere (nightside) source was found at approximately 56{degree} S, 219{degree} W. The half-angle for the hollow portion of the emission pattern was found to be 13{degree}.

  13. An Active Global Attack Model for Sensor Source Location Privacy: Analysis and Countermeasures

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Zhu, Sencun; Cao, Guohong; Laporta, Thomas

    Source locations of events are sensitive contextual information that needs to be protected in sensor networks. Previous work focuses on either an active local attacker that traces back to a real source in a hop-by-hop fashion, or a passive global attacker that eavesdrops/analyzes all network traffic to discover real sources. An active global attack model, which is more realistic and powerful than current ones, has not been studied yet. In this paper, we not only formalize this strong attack model, but also propose countermeasures against it.

  14. Wave field characterization for non-destructive assessment of elastic properties using laser-acoustic sources in fluids and eye related tissues

    NASA Astrophysics Data System (ADS)

    Windisch, T.; Schubert, F.; Köhler, B.; Spörl, E.

    2010-03-01

    The age-related changes in the visco-elastic properties of the human lens are discussed with respect to presbyopia for a long time. All known measurement techniques are based on extracted lenses or are damaging the tissue. Hence, in vivo studies of lens hardness are not possible at the moment. To close this gap in lens diagnostics this project deals with an approach for a non-contact laser-acoustic characterization technique. Laser-generated wave fronts are reflected by the tissue interfaces and are also affected by the visco-elastic properties of the lens tissue. After propagating through the eye, these waves are recorded as corneal vibrations by laser vibrometry. A systematic analysis of amplitude and phase of these signals and the wave generation process shall give information about the interface locations and the tissues viscoelastic properties. Our recent studies on extracted porcine eyes proved that laser-acoustic sources can be systematically used for non-contacting generation and recording of ultrasound inside the human eye. Furthermore, a specific numerical model provides important contributions to the understanding of the complex wave propagation process. Measurements of the acoustic sources support this approach. Future investigations are scheduled to answer the question, whether this novel technique can be directly used during a laser surgery for monitoring purposes and if a purely diagnostic approach, e.g. by excitation in the aqueous humor, is also possible. In both cases, this technique offers a promising approach for non-contact ultrasound based eye diagnostics.

  15. Building an open-source simulation platform of acoustic radiation force-based breast elastography

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Peng, Bo; Jiang, Jingfeng

    2017-03-01

    Ultrasound-based elastography including strain elastography, acoustic radiation force impulse (ARFI) imaging, point shear wave elastography and supersonic shear imaging (SSI) have been used to differentiate breast tumors among other clinical applications. The objective of this study is to extend a previously published virtual simulation platform built for ultrasound quasi-static breast elastography toward acoustic radiation force-based breast elastography. Consequently, the extended virtual breast elastography simulation platform can be used to validate image pixels with known underlying soft tissue properties (i.e. ‘ground truth’) in complex, heterogeneous media, enhancing confidence in elastographic image interpretations. The proposed virtual breast elastography system inherited four key components from the previously published virtual simulation platform: an ultrasound simulator (Field II), a mesh generator (Tetgen), a finite element solver (FEBio) and a visualization and data processing package (VTK). Using a simple message passing mechanism, functionalities have now been extended to acoustic radiation force-based elastography simulations. Examples involving three different numerical breast models with increasing complexity—one uniform model, one simple inclusion model and one virtual complex breast model derived from magnetic resonance imaging data, were used to demonstrate capabilities of this extended virtual platform. Overall, simulation results were compared with the published results. In the uniform model, the estimated shear wave speed (SWS) values were within 4% compared to the predetermined SWS values. In the simple inclusion and the complex breast models, SWS values of all hard inclusions in soft backgrounds were slightly underestimated, similar to what has been reported. The elastic contrast values and visual observation show that ARFI images have higher spatial resolution, while SSI images can provide higher inclusion-to-background contrast

  16. Building an open-source simulation platform of acoustic radiation force-based breast elastography.

    PubMed

    Wang, Yu; Peng, Bo; Jiang, Jingfeng

    2017-03-07

    Ultrasound-based elastography including strain elastography, acoustic radiation force impulse (ARFI) imaging, point shear wave elastography and supersonic shear imaging (SSI) have been used to differentiate breast tumors among other clinical applications. The objective of this study is to extend a previously published virtual simulation platform built for ultrasound quasi-static breast elastography toward acoustic radiation force-based breast elastography. Consequently, the extended virtual breast elastography simulation platform can be used to validate image pixels with known underlying soft tissue properties (i.e. 'ground truth') in complex, heterogeneous media, enhancing confidence in elastographic image interpretations. The proposed virtual breast elastography system inherited four key components from the previously published virtual simulation platform: an ultrasound simulator (Field II), a mesh generator (Tetgen), a finite element solver (FEBio) and a visualization and data processing package (VTK). Using a simple message passing mechanism, functionalities have now been extended to acoustic radiation force-based elastography simulations. Examples involving three different numerical breast models with increasing complexity-one uniform model, one simple inclusion model and one virtual complex breast model derived from magnetic resonance imaging data, were used to demonstrate capabilities of this extended virtual platform. Overall, simulation results were compared with the published results. In the uniform model, the estimated shear wave speed (SWS) values were within 4% compared to the predetermined SWS values. In the simple inclusion and the complex breast models, SWS values of all hard inclusions in soft backgrounds were slightly underestimated, similar to what has been reported. The elastic contrast values and visual observation show that ARFI images have higher spatial resolution, while SSI images can provide higher inclusion-to-background contrast. In

  17. Estimation of glottal source features from the spectral envelope of the acoustic speech signal

    NASA Astrophysics Data System (ADS)

    Torres, Juan Felix

    Speech communication encompasses diverse types of information, including phonetics, affective state, voice quality, and speaker identity. From a speech production standpoint, the acoustic speech signal can be mainly divided into glottal source and vocal tract components, which play distinct roles in rendering the various types of information it contains. Most deployed speech analysis systems, however, do not explicitly represent these two components as distinct entities, as their joint estimation from the acoustic speech signal becomes an ill-defined blind deconvolution problem. Nevertheless, because of the desire to understand glottal behavior and how it relates to perceived voice quality, there has been continued interest in explicitly estimating the glottal component of the speech signal. To this end, several inverse filtering (IF) algorithms have been proposed, but they are unreliable in practice because of the blind formulation of the separation problem. In an effort to develop a method that can bypass the challenging IF process, this thesis proposes a new glottal source information extraction method that relies on supervised machine learning to transform smoothed spectral representations of speech, which are already used in some of the most widely deployed and successful speech analysis applications, into a set of glottal source features. A transformation method based on Gaussian mixture regression (GMR) is presented and compared to current IF methods in terms of feature similarity, reliability, and speaker discrimination capability on a large speech corpus, and potential representations of the spectral envelope of speech are investigated for their ability represent glottal source variation in a predictable manner. The proposed system was found to produce glottal source features that reasonably matched their IF counterparts in many cases, while being less susceptible to spurious errors. The development of the proposed method entailed a study into the aspects

  18. Handbook for the identification, location and investigation of pollution sources affecting ground water

    SciTech Connect

    Oudijk, G.; Mujica, K.

    1989-01-01

    Due to environmental pollution associated with increased urbanization and industrial development in wellhead areas, many public and domestic supply wells are becoming polluted at an ever-increasing rate. To prevent continued pollution of underground drinking water supplies, investigations must be conducted to locate and identify the sources of pollution. To conduct such investigations requires a diverse knowledge of hydrogeology, chemistry, urban planning, industrial and commercial processes, environmental law, and many other disciplines. Groundwater pollution investigations can be subdivided into the following five phases: (1) the background investigation (historical land usage, aerial photographs, pollutant characteristics, local hydrogeology); (2) the field pollution survey (site inspections, initial waste characterization); (3) the site-specific groundwater pollution investigation (monitoring wells, groundwater sampling); (4) data analysis (groundwater elevation contour maps, statistical analysis); and (5) source identification. This process may be used by investigators in order to locate pollution sources affecting aquifers, potable wells, and/or well fields.

  19. A reliable acoustic path: Physical properties and a source localization method

    NASA Astrophysics Data System (ADS)

    Duan, Rui; Yang, Kun-De; Ma, Yuan-Liang; Lei, Bo

    2012-12-01

    The physical properties of a reliable acoustic path (RAP) are analysed and subsequently a weighted-subspace-fitting matched field (WSF-MF) method for passive localization is presented by exploiting the properties of the RAP environment. The RAP is an important acoustic duct in the deep ocean, which occurs when the receiver is placed near the bottom where the sound velocity exceeds the maximum sound velocity in the vicinity of the surface. It is found that in the RAP environment the transmission loss is rather low and no blind zone of surveillance exists in a medium range. The ray theory is used to explain these phenomena. Furthermore, the analysis of the arrival structures shows that the source localization method based on arrival angle is feasible in this environment. However, the conventional methods suffer from the complicated and inaccurate estimation of the arrival angle. In this paper, a straightforward WSF-MF method is derived to exploit the information about the arrival angles indirectly. The method is to minimize the distance between the signal subspace and the spanned space by the array manifold in a finite range-depth space rather than the arrival-angle space. Simulations are performed to demonstrate the features of the method, and the results are explained by the arrival structures in the RAP environment.

  20. Revision of earthquake hypocentre locations in global bulletin data sets using source-specific station terms

    NASA Astrophysics Data System (ADS)

    Nooshiri, Nima; Saul, Joachim; Heimann, Sebastian; Tilmann, Frederik; Dahm, Torsten

    2017-02-01

    Global earthquake locations are often associated with very large systematic travel-time residuals even for clear arrivals, especially for regional and near-regional stations in subduction zones because of their strongly heterogeneous velocity structure. Travel-time corrections can drastically reduce travel-time residuals at regional stations and, in consequence, improve the relative location accuracy. We have extended the shrinking-box source-specific station terms technique to regional and teleseismic distances and adopted the algorithm for probabilistic, nonlinear, global-search location. We evaluated the potential of the method to compute precise relative hypocentre locations on a global scale. The method has been applied to two specific test regions using existing P- and pP-phase picks. The first data set consists of 3103 events along the Chilean margin and the second one comprises 1680 earthquakes in the Tonga-Fiji subduction zone. Pick data were obtained from the GEOFON earthquake bulletin, produced using data from all available, global station networks. A set of timing corrections varying as a function of source position was calculated for each seismic station. In this way, we could correct the systematic errors introduced into the locations by the inaccuracies in the assumed velocity structure without explicitly solving for a velocity model. Residual statistics show that the median absolute deviation of the travel-time residuals is reduced by 40-60 per cent at regional distances, where the velocity anomalies are strong. Moreover, the spread of the travel-time residuals decreased by ˜20 per cent at teleseismic distances (>28°). Furthermore, strong variations in initial residuals as a function of recording distance are smoothed out in the final residuals. The relocated catalogues exhibit less scattered locations in depth and sharper images of the seismicity associated with the subducting slabs. Comparison with a high-resolution local catalogue reveals that

  1. Acoustic holography as a metrological tool for characterizing medical ultrasound sources and fields

    PubMed Central

    Sapozhnikov, Oleg A.; Tsysar, Sergey A.; Khokhlova, Vera A.; Kreider, Wayne

    2015-01-01

    Acoustic holography is a powerful technique for characterizing ultrasound sources and the fields they radiate, with the ability to quantify source vibrations and reduce the number of required measurements. These capabilities are increasingly appealing for meeting measurement standards in medical ultrasound; however, associated uncertainties have not been investigated systematically. Here errors associated with holographic representations of a linear, continuous-wave ultrasound field are studied. To facilitate the analysis, error metrics are defined explicitly, and a detailed description of a holography formulation based on the Rayleigh integral is provided. Errors are evaluated both for simulations of a typical therapeutic ultrasound source and for physical experiments with three different ultrasound sources. Simulated experiments explore sampling errors introduced by the use of a finite number of measurements, geometric uncertainties in the actual positions of acquired measurements, and uncertainties in the properties of the propagation medium. Results demonstrate the theoretical feasibility of keeping errors less than about 1%. Typical errors in physical experiments were somewhat larger, on the order of a few percent; comparison with simulations provides specific guidelines for improving the experimental implementation to reduce these errors. Overall, results suggest that holography can be implemented successfully as a metrological tool with small, quantifiable errors. PMID:26428789

  2. Acoustic holography as a metrological tool for characterizing medical ultrasound sources and fields.

    PubMed

    Sapozhnikov, Oleg A; Tsysar, Sergey A; Khokhlova, Vera A; Kreider, Wayne

    2015-09-01

    Acoustic holography is a powerful technique for characterizing ultrasound sources and the fields they radiate, with the ability to quantify source vibrations and reduce the number of required measurements. These capabilities are increasingly appealing for meeting measurement standards in medical ultrasound; however, associated uncertainties have not been investigated systematically. Here errors associated with holographic representations of a linear, continuous-wave ultrasound field are studied. To facilitate the analysis, error metrics are defined explicitly, and a detailed description of a holography formulation based on the Rayleigh integral is provided. Errors are evaluated both for simulations of a typical therapeutic ultrasound source and for physical experiments with three different ultrasound sources. Simulated experiments explore sampling errors introduced by the use of a finite number of measurements, geometric uncertainties in the actual positions of acquired measurements, and uncertainties in the properties of the propagation medium. Results demonstrate the theoretical feasibility of keeping errors less than about 1%. Typical errors in physical experiments were somewhat larger, on the order of a few percent; comparison with simulations provides specific guidelines for improving the experimental implementation to reduce these errors. Overall, results suggest that holography can be implemented successfully as a metrological tool with small, quantifiable errors.

  3. Evidence for opponent process analysis of sound source location in humans.

    PubMed

    Briley, Paul M; Kitterick, Pádraig T; Summerfield, A Quentin

    2013-02-01

    Research with barn owls suggested that sound source location is represented topographically in the brain by an array of neurons each tuned to a narrow range of locations. However, research with small-headed mammals has offered an alternative view in which location is represented by the balance of activity in two opponent channels broadly tuned to the left and right auditory space. Both channels may be present in each auditory cortex, although the channel representing contralateral space may be dominant. Recent studies have suggested that opponent channel coding of space may also apply in humans, although these studies have used a restricted set of spatial cues or probed a restricted set of spatial locations, and there have been contradictory reports as to the relative dominance of the ipsilateral and contralateral channels in each cortex. The current study used electroencephalography (EEG) in conjunction with sound field stimulus presentation to address these issues and to inform the development of an explicit computational model of human sound source localization. Neural responses were compatible with the opponent channel account of sound source localization and with contralateral channel dominance in the left, but not the right, auditory cortex. A computational opponent channel model reproduced every important aspect of the EEG data and allowed inferences about the width of tuning in the spatial channels. Moreover, the model predicted the oft-reported decrease in spatial acuity measured psychophysically with increasing reference azimuth. Predictions of spatial acuity closely matched those measured psychophysically by previous authors.

  4. Source location impact on relative tsunami strength along the U.S. West Coast

    NASA Astrophysics Data System (ADS)

    Rasmussen, L.; Bromirski, P. D.; Miller, A. J.; Arcas, D.; Flick, R. E.; Hendershott, M. C.

    2015-07-01

    Tsunami propagation simulations are used to identify which tsunami source locations would produce the highest amplitude waves on approach to key population centers along the U.S. West Coast. The reasons for preferential influence of certain remote excitation sites are explored by examining model time sequences of tsunami wave patterns emanating from the source. Distant bathymetric features in the West and Central Pacific can redirect tsunami energy into narrow paths with anomalously large wave height that have disproportionate impact on small areas of coastline. The source region generating the waves can be as little as 100 km along a subduction zone, resulting in distinct source-target pairs with sharply amplified wave energy at the target. Tsunami spectral ratios examined for transects near the source, after crossing the West Pacific, and on approach to the coast illustrate how prominent bathymetric features alter wave spectral distributions, and relate to both the timing and magnitude of waves approaching shore. To contextualize the potential impact of tsunamis from high-amplitude source-target pairs, the source characteristics of major historical earthquakes and tsunamis in 1960, 1964, and 2011 are used to generate comparable events originating at the highest-amplitude source locations for each coastal target. This creates a type of "worst-case scenario," a replicate of each region's historically largest earthquake positioned at the fault segment that would produce the most incoming tsunami energy at each target port. An amplification factor provides a measure of how the incoming wave height from the worst-case source compares to the historical event.

  5. Multiband array detection and location of seismic sources recorded by dense seismic networks

    NASA Astrophysics Data System (ADS)

    Poiata, Natalia; Satriano, Claudio; Vilotte, Jean-Pierre; Bernard, Pascal; Obara, Kazushige

    2016-06-01

    We present a new methodology for detection and space-time location of seismic sources based on multiscale, frequency-selective coherence of the wave field recorded by dense large-scale seismic networks and local antennas. The method is designed to enhance coherence of the signal statistical features across the array of sensors and consists of three steps: signal processing, space-time imaging, and detection and location. The first step provides, for each station, a simplified representation of seismic signal by extracting multiscale non-stationary statistical characteristics, through multiband higher-order statistics or envelopes. This signal processing scheme is designed to account for a priori unknown transients, potentially associated with a variety of sources (e.g. earthquakes, tremors), and to prepare data for a better performance in posterior steps. Following space-time imaging is carried through 3-D spatial mapping and summation of station-pair time-delay estimate functions. This step produces time-series of 3-D spatial images representing the likelihood that each pixel makes part of a source. Detection and location is performed in the final step by extracting the local maxima from the 3-D spatial images. We demonstrate the efficiency of the method in detecting and locating seismic sources associated with low signal-to-noise ratio on an example of the aftershock earthquake records from local stations of International Maule Aftershock Deployment in Central Chile. The performance and potential of the method to detect, locate and characterize the energy release associated with possibly mixed seismic radiation from earthquakes and low-frequency tectonic tremors is further tested on continuous data from southwestern Japan.

  6. A noninvasive method for locating a cardiac dipolar source in humans.

    PubMed

    Salu, Y; Bischof, C; Pandian, N

    1982-01-01

    A noninvasive method for locating isolated areas of cardiac electrical activity, such as an ectopic focus, is introduced and evaluated. Surface electric potentials due to the source are recorded at 20-25 points on the chest. Each chest is measured and its configuration is approximated by a grid of 126 points. A computer program utilizes these data to calculate the x, y, z coordinates of the cardiac source, and this calculated location is displayed on the bi-plane chest x-rays of the patient. Errors that may occur in other methods that utilize average torso shape and average heart position are eliminated in the proposed method. The method was evaluated by using it for locating the electrodes of implanted pacemakers from their "spikes" in the ECG's, and also from the potentials at the onset of the induced QRS complexes. The results were compared with bi-plane x-rays of the same patients. It was found that the average errors in locating the electrodes from their "spikes" in the ECG's were 1.3 cm in the frontal view and 1.4 cm in the lateral view. The errors in locating the paced myocardial area at the beginning of the QRS complex were similar. The errors in the lateral view are systematic and may be attributed to the effects of the intracavity blood volume (Brody's effect), which are neglected in this method.

  7. Source location and mechanism analysis of an earthquake triggered by the 2016 Kumamoto, southwestern Japan, earthquake

    NASA Astrophysics Data System (ADS)

    Nakamura, Takeshi; Aoi, Shin

    2017-01-01

    The 2016 Kumamoto earthquake ( Mw 7.0) occurred in the central part of Kyushu Island, southwestern Japan, on April 16, 2016. The mainshock triggered an event of maximum acceleration 700 gal that caused severe damage to infrastructure and thousands of homes. We investigate the source location of the triggered event, and the timing of large energy release, by employing the back-projection method for strong-motion network data. The optimal location is estimated to be [33.2750°, 131.3575°] (latitude, longitude) at a depth of 5 km, which is 80 km northeast of the epicenter of the mainshock. The timing is 33.5 s after the origin time of the mainshock. We also investigate the source mechanism by reproducing observed displacement waveforms at a near-source station. The waveforms at smaller-sized events, convolved with the source time function of a pulse width 1 s, are similar to the signature of the observed waveforms of the triggered event. The observations are also reproduced by synthetic waveforms for a normal-fault mechanism and a normal-fault with strike-slip components at the estimated locations. Although our approach does not constrain the strike direction well, our waveform analysis indicates that the triggered earthquake occurred near the station that observed the strong motions, primarily via a normal-fault mechanism or a normal-fault with strike-slip components.[Figure not available: see fulltext.

  8. Energy intakes of US children and adults by food purchase location and by specific food source

    PubMed Central

    2013-01-01

    Background To our knowledge, no studies have examined energy intakes by food purchase location and food source using a representative sample of US children, adolescents and adults. Evaluations of purchase location and food sources of energy may inform public health policy. Methods Analyses were based on the first day of 24-hour recall for 22,852 persons in the 2003-4, 2005-6, and 2007-8 National Health and Nutrition Examination Surveys (NHANES). The most common food purchase locations were stores (grocery store, supermarket, convenience store, or specialty store), quick-service restaurants/pizza (QSR), full-service restaurants (FSR), school cafeterias, or food from someone else/gifts. Specific food sources of energy were identified using the National Cancer Institute aggregation scheme. Separate analyses were conducted for children ages 6-11y, adolescents ages 12-19y, and adults aged 20-50y and ≥51y. Results Stores (grocery, convenience, and specialty) were the food purchase locations for between 63.3% and 70.3% of dietary energy in the US diet. Restaurants provided between 16.9% and 26.3% of total energy. Depending on the respondents’ age, QSR provided between 12.5% and 17.5% of energy, whereas FSR provided between 4.7% and 10.4% of energy. School meals provided 9.8% of energy for children and 5.5% for adolescents. Vending machines provided <1% of energy. Pizza from QSR, the top food away from home (FAFH) item, provided 2.2% of energy in the diets of children and 3.4% in the diets of adolescents. Soda, energy, and sports drinks from QSR provided approximately 1.2% of dietary energy. Conclusions Refining dietary surveillance approaches by incorporating food purchase location may help inform public health policy. Characterizing the important sources of energy, in terms of both purchase location and source may be useful in anticipating the population-level impacts of proposed policy or educational interventions. These data show that stores provide a majority of

  9. Quantifying uncertainties in location and source mechanism for Long-Period events at Mt Etna, Italy.

    NASA Astrophysics Data System (ADS)

    Cauchie, Léna; Saccorotti, Gilberto; Bean, Christopher

    2014-05-01

    The manifestation of Long-Period events is documented at many volcanoes worldwide. However the mechanism at their origin is still object of discussion. Models proposed so far involve (i) the resonance of fluid-filled cracks or conduits that are triggered by fluid instabilities or the brittle failure of high viscous magmas and (ii) the slow-rupture earthquakes in the shallow portion of volcanic edifices. Since LP activity usually precedes and accompanies volcanic eruption, the understanding of these sources is important in terms of hazard assessment and eruption early warning. The work is thus primarily aimed at the assessment of the uncertainties in the determination of LP source properties as a consequence of poor knowledge of the velocity structure and location errors. We used data from temporary networks deployed on Mt Etna in 2005. During August, 2005, about 13000 LP events were detected through a STA/LTA approach, and were classified into two families on the basis of waveform similarity. For each family of events, we located the source using three different approaches: (1) a single-station-location method based on the back-propagation of the polarization vector estimated from covariance analysis of three-component signals; (2) multi-channel analysis of data recorded by two seismic arrays; (3) relative locations based on inversion of differential times obtained through cross-correlation of similar waveforms. For all these three different methods, the solutions are very sensitive to the chosen velocity model. We thus iterated the location procedure for different medium properties; the preferred velocity is that for which the results obtained with the three different methods are consistent each other. For each family, we then defined a volume of possible source location and performed a full-waveform, moment tensor (MT) inversion for the entire catalog of events. In this manner, we obtained a MT solution for each grid node of the investigated volume. The MT

  10. Analysis of acoustic scattering from fluid bodies using a multipoint source model.

    PubMed

    Boag, A; Leviatan, Y

    1989-01-01

    A moment-method solution is presented for the problem of acoustic scattering from homogeneous fluid bodies. It uses fictitious isotropic point sources to simulate both the field scattered by the body and the field inside the body and, in turn, point-matches the continuity conditions for the normal component of the velocity and for the pressure across the surface of the body. The procedure is simple to execute and is general in that bodies of arbitrary smooth shape can be handled effectively. Perfectly rigid bodies are treated as reduced cases of the general procedure. Results are given and compared with available analytic solutions, which demonstrate the very good performance of the procedure.

  11. Cross-correlation function of acoustic fields generated by random high-frequency sources.

    PubMed

    Godin, Oleg A

    2010-08-01

    Long-range correlations of noise fields in arbitrary inhomogeneous, moving or motionless fluids are studied in the ray approximation. Using the stationary phase method, two-point cross-correlation function of noise is shown to approximate the sum of the deterministic Green's functions describing sound propagation in opposite directions between the two points. Explicit relations between amplitudes of respective ray arrivals in the noise cross-correlation function and the Green's functions are obtained and verified against specific problems allowing an exact solution. Earlier results are extended by simultaneously accounting for sound absorption, arbitrary distribution of noise sources in a volume and on surfaces, and fluid inhomogeneity and motion. The information content of the noise cross-correlation function is discussed from the viewpoint of passive acoustic characterization of inhomogeneous flows.

  12. Investigation of the Acoustic Source Characteristics of High Energy Laser Pulses: Models and Experiment

    DTIC Science & Technology

    2008-06-01

    consistent with the expected approximately 1/r relationship for pressure amplitudes under 100MPa. The modeling effort employed AUTODYN , a finite...agreed with Vogel’s measured values. The efficiency, pulse length, pulse shape, and variation of pressure amplitude with range achieved with AUTODYN ...Nonlinear Acoustics, AUTODYN , Acoustic Modeling, Shock Acoustics 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18. SECURITY

  13. 40 CFR 55.14 - Requirements that apply to OCS sources located within 25 miles of States' seaward boundaries, by...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... located within 25 miles of States' seaward boundaries, by State. 55.14 Section 55.14 Protection of... REGULATIONS § 55.14 Requirements that apply to OCS sources located within 25 miles of States' seaward... requirements. State and local requirements promulgated by EPA as applicable to OCS sources located within...

  14. Gravitational wave hotspots: Ranking potential locations of single-source gravitational wave emission

    SciTech Connect

    Simon, Joseph; Polin, Abigail; Lommen, Andrea; Christy, B; Stappers, Ben; Finn, Lee Samuel; Jenet, F. A.

    2014-03-20

    The steadily improving sensitivity of pulsar timing arrays (PTAs) suggests that gravitational waves (GWs) from supermassive black hole binary (SMBHB) systems in the nearby universe will be detectable sometime during the next decade. Currently, PTAs assume an equal probability of detection from every sky position, but as evidence grows for a non-isotropic distribution of sources, is there a most likely sky position for a detectable single source of GWs? In this paper, a collection of Galactic catalogs is used to calculate various metrics related to the detectability of a single GW source resolvable above a GW background, assuming that every galaxy has the same probability of containing an SMBHB. Our analyses of these data reveal small probabilities that one of these sources is currently in the PTA band, but as sensitivity is improved regions of consistent probability density are found in predictable locations, specifically around local galaxy clusters.

  15. Experimental validation of a method for the prediction of the acoustic field produced by an acoustic source and the reflected field produced by a solid interface

    NASA Astrophysics Data System (ADS)

    Diaz, Sandra; Chopra, Rajiv; Pichardo, Samuel

    2012-11-01

    In this work we present a model to calculate the acoustic pressure generated by the interaction of forward and reflected waves in the vicinity of a solid interface and compare it to experimental data. An experimental setup was designed to measure the forward and the combined forward-reflected acoustic fields produced by a solid interface. A 0.785mm-needle hydrophone was used to characterize the acoustic field produced by a 7.29MHz-ultrasound transducer focused at 6cm. The hydrophone was positioned perpendicularly to the sound propagation direction and moved between the transducer and a 9mm-thick acrylic sample using a robotic arm. Simulations were carried out using a modified Rayleigh-Sommerfeld integral that calculates the particle displacement over a reflecting surface. This particle displacement at the boundary of the interface is then used as an acoustic source to obtain the reflected particle displacement. The complex sum of the forward and reflected fields was compared to the experimental measurements. The measurements showed an interference pattern that increased the pressure amplitude in average 10.4% with peaks of up to 25.8%. The proposed model is able to represent the interference pattern produced by the reflected wave with an average absolute error of 3.4+/-0.54% and a maximal error of 5.6%. The comparison between the experimental measurements and the simulations indicates that the presented model predicts with good accuracy the acoustic field generated by ultrasound transducers facing a solid interface. This model can be used to foresee the outcome of therapeutic applications where the devices are used in proximity to a bone interface.

  16. A Numerical Investigation of Turbine Noise Source Hierarchy and Its Acoustic Transmission Characteristics

    NASA Technical Reports Server (NTRS)

    VanZante, Dale; Envia, Edmane

    2008-01-01

    Understanding the relative importance of the various turbine noise generation mechanisms and the characteristics of the turbine acoustic transmission loss are essential ingredients in developing robust reduced-order models for predicting the turbine noise signature. A computationally based investigation has been undertaken to help guide the development of a turbine noise prediction capability that does not rely on empiricism. The investigation relies on highly detailed numerical simulations of the unsteady flowfield inside a modern high-pressure turbine (HPT). The simulations are developed using TURBO, which is an unsteady Reynolds-averaged Navier-Stokes (URANS) code capable of multi-stage simulations. The purpose of this study is twofold. First, to determine an estimate of the relative importance of the contributions to the coherent part of the acoustic signature of a turbine from the three potential sources of turbine noise generation, namely, blade-row viscous interaction, potential field interaction, and entropic source associated with the interaction of the blade rows with the temperature nonuniformities caused by the incomplete mixing of the hot fluid and the cooling flow. Second, to develop an understanding of the turbine acoustic transmission characteristics and to assess the applicability of existing empirical and analytical transmission loss models to realistic geometries and flow conditions for modern turbine designs. The investigation so far has concentrated on two simulations: (1) a single-stage HPT and (2) a two-stage HPT and the associated inter-turbine duct/strut segment. The simulations are designed to resolve up to the second harmonic of the blade passing frequency tone in accordance with accepted rules for second order solvers like TURBO. The calculations include blade and vane cooling flows and a radial profile of pressure and temperature at the turbine inlet. The calculation can be modified later to include the combustor pattern factor at the

  17. Hard X-ray and microwave sources located around the apex of a solar flare loop

    NASA Astrophysics Data System (ADS)

    Masuda, S.; Shimojo, M.; Watanabe, K.; Minoshima, T.; Yaji, K.

    2010-12-01

    The apex of a flare loop is one of important regions to understand particle acceleration in solar flares, under the framework of the flare model based on magnetic reconnection. At that portion, nonthermal emissions are observed in hard X-rays and microwave. These two emissions are originated from electrons accelerated/energized in different energy ranges. Hard X-rays (~ 50 - 100 keV ) are emitted by relatively lower-energy (~ 100 keV) accelerated electrons. On the other hand, microwaves (17 GHz) are emitted by relatively higher-energy (~ 1 MeV) electrons. The locations (heights) of these two emitting regions impose considerable constraints on the acceleration/transport/loss processes of electrons in solar flares. To compare hard X-ray and microwave sources, we chose twenty-three events among all events detected by Nobeyama Radio Heliograph (NoRH) during the almost whole period of its operation (1992 - 2008). The criteria are (1) limb event, (2) simultaneous observation with Yohkoh/HXT or RHESSI, (3) enough number of photons in the energy range of 33 - 53 keV, and (4) microwave source large enough to resolve the flare loop into footpoint and looptop sources. However, only seven events among them can be used for this study. The remaining sixteen events are displaced from the list due to no hard X-ray looptop source, too complex structure of multiple loops, and so force. Among the seven events, six events show that the looptop hard X-ray source is located at a higher altitude than the looptop microwave source. This result suggests that lower-energy accelerated electrons (~ 100 keV) are located at a higher altitude than higher-energy (~ 1 MeV) electrons. What makes this height difference? We discuss the cause of it from various kinds of viewpoints, e.g. emission mechanism, trapping effect, transport process, loss process.

  18. The use of a global index of acoustic assessment for predicting noise in industrial rooms and optimizing the location of machinery and workstations.

    PubMed

    Pleban, Dariusz

    2014-01-01

    This paper describes the results of a study aimed at developing a tool for optimizing the location of machinery and workstations. A global index of acoustic assessment of machines was developed for this purpose. This index and a genetic algorithm were used in a computer tool for predicting noise emission of machines as well as optimizing the location of machines and workstations in industrial rooms. The results of laboratory and simulation tests demonstrate that the developed global index and the genetic algorithm support measures aimed at noise reduction at workstations.

  19. Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source.

    NASA Astrophysics Data System (ADS)

    Averbuch, Gil; Price, Colin

    2015-04-01

    Lithosphere-Atmosphere coupling: Spectral element modeling of the evolution of acoustic waves in the atmosphere from an underground source. G. Averbuch, C. Price Department of Geosciences, Tel Aviv University, Israel Infrasound is one of the four Comprehensive Nuclear-Test Ban Treaty technologies for monitoring nuclear explosions. This technology measures the acoustic waves generated by the explosions followed by their propagation through the atmosphere. There are also natural phenomena that can act as an infrasound sources like sprites, volcanic eruptions and earthquakes. The infrasound waves generated from theses phenomena can also be detected by the infrasound arrays. In order to study the behavior of these waves, i.e. the physics of wave propagation in the atmosphere, their evolution and their trajectories, numerical methods are required. This presentation will deal with the evolution of acoustic waves generated by underground sources (earthquakes and underground explosions). A 2D Spectral elements formulation for lithosphere-atmosphere coupling will be presented. The formulation includes the elastic wave equation for the seismic waves and the momentum, mass and state equations for the acoustic waves in a moving stratified atmosphere. The coupling of the two media is made by boundary conditions that ensures the continuity of traction and velocity (displacement) in the normal component to the interface. This work has several objectives. The first is to study the evolution of acoustic waves in the atmosphere from an underground source. The second is to derive transmission coefficients for the energy flux with respect to the seismic magnitude and earth density. The third will be the generation of seismic waves from acoustic waves in the atmosphere. Is it possible?

  20. Source characterization of a subsonic jet by using near-field acoustical holography.

    PubMed

    Lee, Moohyung; Bolton, J Stuart

    2007-02-01

    In the present study, patch near-field acoustical holography was used in conjunction with a multireference, cross-spectral sound pressure measurement to visualize the sound field emitted by a subsonic jet and to predict its farfield radiation pattern. A strategy for microphone array design is described that accounts for the low spatial coherence of aeroacoustic sources and for microphone self-noise resulting from entrained flow near the jet. In the experiments, a 0.8-cm-diameter burner was used to produce a subsonic, turbulent jet with a Mach number of 0.26. Six fixed, linear arrays holding eight reference microphones apiece were disposed circumferentially around the jet, and a circular array holding sixteen, equally spaced field microphones was traversed along the jet axis to measure the sound field on a 30-cm-diameter cylindrical surface enclosing the jet. The results revealed that the jet could be modeled as a combination of eleven uncorrelated dipole-, quadrupole-, and octupole-like sources, and the contribution of each source type to the total radiated sound power could be identified. Both the total sound field reconstructed in a three-dimensional space and the farfield radiation directivity obtained by using the latter model were successfully validated by comparisons to directly measured results.

  1. Precise tremor source locations and amplitude variations along the lower-crustal central San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Shelly, David R.; Hardebeck, Jeanne L.

    2010-07-01

    We precisely locate 88 tremor families along the central San Andreas Fault using a 3D velocity model and numerous P and S wave arrival times estimated from seismogram stacks of up to 400 events per tremor family. Maximum tremor amplitudes vary along the fault by at least a factor of 7, with by far the strongest sources along a 25 km section of the fault southeast of Parkfield. We also identify many weaker tremor families, which have largely escaped prior detection. Together, these sources extend 150 km along the fault, beneath creeping, transitional, and locked sections of the upper crustal fault. Depths are mostly between 18 and 28 km, in the lower crust. Epicenters are concentrated within 3 km of the surface trace, implying a nearly vertical fault. A prominent gap in detectible activity is located directly beneath the region of maximum slip in the 2004 magnitude 6.0 Parkfield earthquake.

  2. Precise tremor source locations and amplitude variations along the lower-crustal central San Andreas Fault

    USGS Publications Warehouse

    Shelly, David R.; Hardebeck, Jeanne L.

    2010-01-01

    We precisely locate 88 tremor families along the central San Andreas Fault using a 3D velocity model and numerous P and S wave arrival times estimated from seismogram stacks of up to 400 events per tremor family. Maximum tremor amplitudes vary along the fault by at least a factor of 7, with by far the strongest sources along a 25 km section of the fault southeast of Parkfield. We also identify many weaker tremor families, which have largely escaped prior detection. Together, these sources extend 150 km along the fault, beneath creeping, transitional, and locked sections of the upper crustal fault. Depths are mostly between 18 and 28 km, in the lower crust. Epicenters are concentrated within 3 km of the surface trace, implying a nearly vertical fault. A prominent gap in detectible activity is located directly beneath the region of maximum slip in the 2004 magnitude 6.0 Parkfield earthquake.

  3. Integration of Acoustical Information in the Perception of Impacted Sound Sources: The Role of Information Accuracy and Exploitability

    ERIC Educational Resources Information Center

    Giordano, Bruno L.; Rocchesso, Davide; McAdams, Stephen

    2010-01-01

    Sound sources are perceived by integrating information from multiple acoustical features. The factors influencing the integration of information are largely unknown. We measured how the perceptual weighting of different features varies with the accuracy of information and with a listener's ability to exploit it. Participants judged the hardness of…

  4. Acoustic Scattering by Three-Dimensional Stators and Rotors Using the SOURCE3D Code. Volume 2; Scattering Plots

    NASA Technical Reports Server (NTRS)

    Meyer, Harold D.

    1999-01-01

    This second volume of Acoustic Scattering by Three-Dimensional Stators and Rotors Using the SOURCE3D Code provides the scattering plots referenced by Volume 1. There are 648 plots. Half are for the 8750 rpm "high speed" operating condition and the other half are for the 7031 rpm "mid speed" operating condition.

  5. Travel-time source-specific station correction improves location accuracy

    NASA Astrophysics Data System (ADS)

    Giuntini, Alessandra; Materni, Valerio; Chiappini, Stefano; Carluccio, Roberto; Console, Rodolfo; Chiappini, Massimo

    2013-04-01

    Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty (CTBT). Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. The consequences of large mislocations of seismic events in the context of the CTBT verification is particularly critical in order to trigger a possible On Site Inspection (OSI). In fact, the Treaty establishes that an OSI area cannot be larger than 1000 km2, and its larger linear dimension cannot be larger than 50 km. Moreover, depth accuracy is crucial for the application of the depth event screening criterion. In the present study, we develop a method of source-specific travel times corrections based on a set of well located events recorded by dense national seismic networks in seismically active regions. The applications concern seismic sequences recorded in Japan, Iran and Italy. We show that mislocations of the order of 10-20 km affecting the epicenters, as well as larger mislocations in hypocentral depths, calculated from a global seismic network and using the standard IASPEI91 travel times can be effectively removed by applying source-specific station corrections.

  6. Acoustic Source Characteristics, Across-Formant Integration, and Speech Intelligibility Under Competitive Conditions

    PubMed Central

    2015-01-01

    An important aspect of speech perception is the ability to group or select formants using cues in the acoustic source characteristics—for example, fundamental frequency (F0) differences between formants promote their segregation. This study explored the role of more radical differences in source characteristics. Three-formant (F1+F2+F3) synthetic speech analogues were derived from natural sentences. In Experiment 1, F1+F3 were generated by passing a harmonic glottal source (F0 = 140 Hz) through second-order resonators (H1+H3); in Experiment 2, F1+F3 were tonal (sine-wave) analogues (T1+T3). F2 could take either form (H2 or T2). In some conditions, the target formants were presented alone, either monaurally or dichotically (left ear = F1+F3; right ear = F2). In others, they were accompanied by a competitor for F2 (F1+F2C+F3; F2), which listeners must reject to optimize recognition. Competitors (H2C or T2C) were created using the time-reversed frequency and amplitude contours of F2. Dichotic presentation of F2 and F2C ensured that the impact of the competitor arose primarily through informational masking. In the absence of F2C, the effect of a source mismatch between F1+F3 and F2 was relatively modest. When F2C was present, intelligibility was lowest when F2 was tonal and F2C was harmonic, irrespective of which type matched F1+F3. This finding suggests that source type and context, rather than similarity, govern the phonetic contribution of a formant. It is proposed that wideband harmonic analogues are more effective informational maskers than narrowband tonal analogues, and so become dominant in across-frequency integration of phonetic information when placed in competition. PMID:25751040

  7. Evidence for Different Reactive Hg Sources and Chemical Compounds at Adjacent Valley and High Elevation Locations.

    PubMed

    Sexauer Gustin, Mae; Pierce, Ashley M; Huang, Jiaoyan; Miller, Matthieu B; Holmes, Heather A; Loria-Salazar, S Marcela

    2016-11-15

    The spatial distribution of chemical compounds and concentration of reactive mercury (RM), defined as the sum of gaseous oxidized mercury (GOM) and <3 μm particulate bound mercury (PBM), are poorly characterized. The objective of this study was to understand the chemistry, concentration, and spatial and temporal distribution of GOM at adjacent locations (12 km apart) with a difference in elevation of ∼1000 m. Atmospheric GOM measurements were made with passive and active samplers using membranes, and at one location, a Tekran mercury measurement system was used. The chemistry of GOM varied across time and location. On the basis of data collected, chemistry at the low elevation site adjacent to a highway was primarily influenced by pollutants generated by mobile sources (GOM = nitrogen and sulfur-based compounds), and the high elevation site (GOM = halogen-based compounds) was affected by long-range transport in the free troposphere over the marine boundary layer into Nevada. Data collected at these two locations demonstrate that different GOM compounds exist depending on the oxidants present in the air. Measurements of GOM made by the KCl denuder in the Tekran instrument located at the low elevation site were lower than that measured using membranes by 1.7-13 times. Accurate measurements of atmospheric concentrations and chemistry of RM are necessary for proper assessment of environmental impacts, and field measurements are essential for atmospheric models, which in turn influence policy decisions.

  8. Locating and estimating air emissions from sources of perchloroethylene and trichloroethylene. Final report

    SciTech Connect

    Most, C.C.

    1989-08-01

    To assist groups interested in inventorying air emissions of various potentially toxic substances, EPA is preparing a series of documents to compile available information on sources and emissions of these substances. This document deals specifically with perchloroethylene and trichloroethylene. Its intended audience includes Federal, State, and local air-pollution personnel and others in locating potential emitters of perchloroethylene and trichloroethylene and in making gross estimates of air emissions therefrom. The document presents information on the types of sources that may emit perchloroethylene and trichloroethylene, process variations and release points that may be expected within these sources, and available emissions information indicating the potential for trichloroethylene and perchloroethylene releases into the air from each operation.

  9. Periodic shock-emission from acoustically driven cavitation clouds: a source of the subharmonic signal.

    PubMed

    Johnston, Keith; Tapia-Siles, Cecilia; Gerold, Bjoern; Postema, Michiel; Cochran, Sandy; Cuschieri, Alfred; Prentice, Paul

    2014-12-01

    Single clouds of cavitation bubbles, driven by 254kHz focused ultrasound at pressure amplitudes in the range of 0.48-1.22MPa, have been observed via high-speed shadowgraphic imaging at 1×10(6) frames per second. Clouds underwent repetitive growth, oscillation and collapse (GOC) cycles, with shock-waves emitted periodically at the instant of collapse during each cycle. The frequency of cloud collapse, and coincident shock-emission, was primarily dependent on the intensity of the focused ultrasound driving the activity. The lowest peak-to-peak pressure amplitude of 0.48MPa generated shock-waves with an average period of 7.9±0.5μs, corresponding to a frequency of f0/2, half-harmonic to the fundamental driving. Increasing the intensity gave rise to GOC cycles and shock-emission periods of 11.8±0.3, 15.8±0.3, 19.8±0.2μs, at pressure amplitudes of 0.64, 0.92 and 1.22MPa, corresponding to the higher-order subharmonics of f0/3, f0/4 and f0/5, respectively. Parallel passive acoustic detection, filtered for the fundamental driving, revealed features that correlated temporally to the shock-emissions observed via high-speed imaging, p(two-tailed) < 0.01 (r=0.996, taken over all data). Subtracting the isolated acoustic shock profiles from the raw signal collected from the detector, demonstrated the removal of subharmonic spectral peaks, in the frequency domain. The larger cavitation clouds (>200μm diameter, at maximum inflation), that developed under insonations of peak-to-peak pressure amplitudes >1.0MPa, emitted shock-waves with two or more fronts suggesting non-uniform collapse of the cloud. The observations indicate that periodic shock-emissions from acoustically driven cavitation clouds provide a source for the cavitation subharmonic signal, and that shock structure may be used to study intra-cloud dynamics at sub-microsecond timescales.

  10. Sources and characteristics of acoustic emissions from mechanically stressed geologic granular media — A review

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Cohen, Denis; Or, Dani

    2012-05-01

    The formation of cracks and emergence of shearing planes and other modes of rapid macroscopic failure in geologic granular media involve numerous grain scale mechanical interactions often generating high frequency (kHz) elastic waves, referred to as acoustic emissions (AE). These acoustic signals have been used primarily for monitoring and characterizing fatigue and progressive failure in engineered systems, with only a few applications concerning geologic granular media reported in the literature. Similar to the monitoring of seismic events preceding an earthquake, AE may offer a means for non-invasive, in-situ, assessment of mechanical precursors associated with imminent landslides or other types of rapid mass movements (debris flows, rock falls, snow avalanches, glacier stick-slip events). Despite diverse applications and potential usefulness, a systematic description of the AE method and its relevance to mechanical processes in Earth sciences is lacking. This review is aimed at providing a sound foundation for linking observed AE with various micro-mechanical failure events in geologic granular materials, not only for monitoring of triggering events preceding mass mobilization, but also as a non-invasive tool in its own right for probing the rich spectrum of mechanical processes at scales ranging from a single grain to a hillslope. We review first studies reporting use of AE for monitoring of failure in various geologic materials, and describe AE generating source mechanisms in mechanically stressed geologic media (e.g., frictional sliding, micro-crackling, particle collisions, rupture of water bridges, etc.) including AE statistical features, such as frequency content and occurrence probabilities. We summarize available AE sensors and measurement principles. The high sampling rates of advanced AE systems enable detection of numerous discrete failure events within a volume and thus provide access to statistical descriptions of progressive collapse of systems

  11. Ultra-directional source of longitudinal acoustic waves based on a two-dimensional solid/solid phononic crystal

    SciTech Connect

    Morvan, B.; Tinel, A.; Sainidou, R.; Rembert, P.; Vasseur, J. O.; Hladky-Hennion, A.-C.; Swinteck, N.; Deymier, P. A.

    2014-12-07

    Phononic crystals (PC) can be used to control the dispersion properties of acoustic waves, which are essential to direct their propagation. We use a PC-based two-dimensional solid/solid composite to demonstrate experimentally and theoretically the spatial filtering of a monochromatic non-directional wave source and its emission in a surrounding water medium as an ultra-directional beam with narrow angular distribution. The phenomenon relies on square-shaped equifrequency contours (EFC) enabling self-collimation of acoustic waves within the phononic crystal. Additionally, the angular width of collimated beams is controlled via the EFC size-shrinking when increasing frequency.

  12. Statistical study of coronal mass ejection source locations: Understanding CMEs viewed in coronagraphs

    NASA Astrophysics Data System (ADS)

    Wang, Yuming; Chen, Caixia; Gui, Bin; Shen, Chenglong; Ye, Pinzhong; Wang, S.

    2011-04-01

    How to properly understand coronal mass ejections (CMEs) viewed in white light coronagraphs is crucial to many relative researches in solar and space physics. The issue is now particularly addressed in this paper through studying the source locations of all the 1078 Large Angle and Spectrometric Coronagraph (LASCO) CMEs listed in Coordinated Data Analysis Workshop (CDAW) CME catalog during 1997-1998 and their correlation with CMEs' apparent parameters. By manually checking LASCO and Extreme Ultraviolet Imaging Telescope (EIT) movies of these CMEs, we find that, except 231 CMEs whose source locations cannot be identified due to poor data, there are 288 CMEs with location identified on the frontside solar disk, 234 CMEs appearing above solar limb, and 325 CMEs without evident eruptive signatures in the field of view of EIT. On the basis of the statistical results of CMEs' source locations, there are four physical issues: (1) the missing rate of CMEs by SOHO LASCO and EIT, (2) the mass of CMEs, (3) the causes of halo CMEs, and (4) the deflections of CMEs in the corona, are exhaustively analyzed. It is found that (1) about 32% frontside CMEs cannot be recognized by SOHO, (2) the brightness of a CME at any heliocentric distance is roughly positively correlated with its speed, and the CME mass derived from the brightness is probably overestimated, (3) both projection effect and violent eruption are the major causes of halo CMEs, and especially for limb halo CMEs the latter is the primary one, and (4) most CMEs deflected toward equator near the solar minimum; these deflections can be classified into three types: the asymmetrical expansion, the nonradial ejection, and the deflected propagation.

  13. An Improved Source-Scanning Algorithm for Locating Earthquake Clusters or Aftershock Sequences

    NASA Astrophysics Data System (ADS)

    Liao, Y.; Kao, H.; Hsu, S.

    2010-12-01

    The Source-scanning Algorithm (SSA) was originally introduced in 2004 to locate non-volcanic tremors. Its application was later expanded to the identification of earthquake rupture planes and the near-real-time detection and monitoring of landslides and mud/debris flows. In this study, we further improve SSA for the purpose of locating earthquake clusters or aftershock sequences when only a limited number of waveform observations are available. The main improvements include the application of a ground motion analyzer to separate P and S waves, the automatic determination of resolution based on the grid size and time step of the scanning process, and a modified brightness function to utilize constraints from multiple phases. Specifically, the improved SSA (named as ISSA) addresses two major issues related to locating earthquake clusters/aftershocks. The first one is the massive amount of both time and labour to locate a large number of seismic events manually. And the second one is to efficiently and correctly identify the same phase across the entire recording array when multiple events occur closely in time and space. To test the robustness of ISSA, we generate synthetic waveforms consisting of 3 separated events such that individual P and S phases arrive at different stations in different order, thus making correct phase picking nearly impossible. Using these very complicated waveforms as the input, the ISSA scans all model space for possible combination of time and location for the existence of seismic sources. The scanning results successfully associate various phases from each event at all stations, and correctly recover the input. To further demonstrate the advantage of ISSA, we apply it to the waveform data collected by a temporary OBS array for the aftershock sequence of an offshore earthquake southwest of Taiwan. The overall signal-to-noise ratio is inadequate for locating small events; and the precise arrival times of P and S phases are difficult to

  14. Extension of the angular spectrum method to calculate pressure from a spherically curved acoustic source.

    PubMed

    Vyas, Urvi; Christensen, Douglas A

    2011-11-01

    The angular spectrum method is an accurate and computationally efficient method for modeling acoustic wave propagation. The use of the typical 2D fast Fourier transform algorithm makes this a fast technique but it requires that the source pressure (or velocity) be specified on a plane. Here the angular spectrum method is extended to calculate pressure from a spherical transducer-as used extensively in applications such as magnetic resonance-guided focused ultrasound surgery-to a plane. The approach, called the Ring-Bessel technique, decomposes the curved source into circular rings of increasing radii, each ring a different distance from the intermediate plane, and calculates the angular spectrum of each ring using a Fourier series. Each angular spectrum is then propagated to the intermediate plane where all the propagated angular spectra are summed to obtain the pressure on the plane; subsequent plane-to-plane propagation can be achieved using the traditional angular spectrum method. Since the Ring-Bessel calculations are carried out in the frequency domain, it reduces calculation times by a factor of approximately 24 compared to the Rayleigh-Sommerfeld method and about 82 compared to the Field II technique, while maintaining accuracies of better than 96% as judged by those methods for cases of both solid and phased-array transducers.

  15. Noise disturbance in open-plan study environments: a field study on noise sources, student tasks and room acoustic parameters.

    PubMed

    Braat-Eggen, P Ella; van Heijst, Anne; Hornikx, Maarten; Kohlrausch, Armin

    2017-04-03

    The aim of this study is to gain more insight in the assessment of noise in open-plan study environments and to reveal correlations between noise disturbance experienced by students and the noise sources they perceive, the tasks they perform and the acoustic parameters of the open-plan study environment they work in. Data were collected in five open-plan study environments at universities in the Netherlands. A questionnaire was used to investigate student tasks, perceived sound sources and their perceived disturbance, and sound measurements were performed to determine the room acoustic parameters. This study shows that 38% of the surveyed students are disturbed by background noise in an open-plan study environment. Students are mostly disturbed by speech when performing complex cognitive tasks like studying for an exam, reading and writing. Significant but weak correlations were found between the room acoustic parameters and noise disturbance of students. Practitioner Summary: A field study was conducted to gain more insight in the assessment of noise in open-plan study environments at universities in the Netherlands. More than one third of the students was disturbed by noise. An interaction effect was found for task type, source type and room acoustic parameters.

  16. Transport of perfluoroalkyl substances (PFAS) from an arctic glacier to downstream locations: implications for sources.

    PubMed

    Kwok, Karen Y; Yamazaki, Eriko; Yamashita, Nobuyoshi; Taniyasu, Sachi; Murphy, Margaret B; Horii, Yuichi; Petrick, Gert; Kallerborn, Roland; Kannan, Kurunthachalam; Murano, Kentaro; Lam, Paul K S

    2013-03-01

    Perfluoroalkyl substances (PFAS) have been globally detected in various environmental matrices, yet their fate and transport to the Arctic is still unclear, especially for the European Arctic. In this study, concentrations of 17 PFAS were quantified in two ice cores (n=26), surface snow (n=9) and surface water samples (n=14) collected along a spatial gradient in Svalbard, Norway. Concentrations of selected ions (Na(+), SO4(2-), etc.) were also determined for tracing the origins and sources of PFAS. Perfluorobutanoate (PFBA), perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) were the dominant compounds found in ice core samples. Taking PFOA, PFNA and perfluorooctane-sulfonate (PFOS) as examples, higher concentrations were detected in the middle layers of the ice cores representing the period of 1997-2000. Lower concentrations of C8-C12 perfluorocarboxylates (PFCAs) were detected in comparison with concentrations measured previously in an ice core from the Canadian Arctic, indicating that contamination levels in the European Arctic are lower. Average PFAS concentrations were found to be lower in surface snow and melted glacier water samples, while increased concentrations were observed in river water downstream near the coastal area. Perfluorohexanesulfonate (PFHxS) was detected in the downstream locations, but not in the glacier, suggesting existence of local sources of this compound. Long-range atmospheric transport of PFAS was the major deposition pathway for the glaciers, while local sources (e.g., skiing activities) were identified in the downstream locations.

  17. Sequential optimal monitoring network design and iterative spatial estimation of pollutant concentration for identification of unknown groundwater pollution source locations.

    PubMed

    Prakash, Om; Datta, Bithin

    2013-07-01

    One of the difficulties in accurate characterization of unknown groundwater pollution sources is the uncertainty regarding the number and the location of such sources. Only when the number of source locations is estimated with some degree of certainty that the characterization of the sources in terms of location, magnitude, and activity duration can be meaningful. A fairly good knowledge of source locations can substantially decrease the degree of nonuniqueness in the set of possible aquifer responses to subjected geochemical stresses. A methodology is developed to use a sequence of dedicated monitoring network design and implementation and to screen and identify the possible source locations. The proposed methodology utilizes a combination of spatial interpolation of concentration measurements and simulated annealing as optimization algorithm for optimal design of the monitoring network. These monitoring networks are to be designed and implemented sequentially. The sequential design is based on iterative pollutant concentration measurement information from the sequentially designed monitoring networks. The optimal monitoring network design utilizes concentration gradient information from the monitoring network at previous iteration to define the objective function. The capability of the feedback information based iterative methodology is shown to be effective in estimating the source locations when no such information is initially available. This unknown pollution source locations identification methodology should be very useful as a screening model for subsequent accurate estimation of the unknown pollution sources in terms of location, magnitude, and activity duration.

  18. Honeybees perform optimal scale-free searching flights when attempting to locate a food source.

    PubMed

    Reynolds, Andrew M; Smith, Alan D; Reynolds, Don R; Carreck, Norman L; Osborne, Juliet L

    2007-11-01

    The foraging strategies used by animals are key to their success in spatially and temporally heterogeneous environments. We hypothesise that when a food source at a known location ceases to be available, flying insects will exhibit search patterns that optimise the rediscovery of such resources. In order to study these searching patterns, foraging honeybees were trained to an artificial feeder that was then removed, and the subsequent flight patterns of the bees were recorded using harmonic radar. We show that the flight patterns have a scale-free (Lévy-flight) characteristic that constitutes an optimal searching strategy for the location of the feeder. It is shown that this searching strategy would remain optimal even if the implementation of the Lévy-flights was imprecise due, for example, to errors in the bees' path integration system or difficulties in responding to variable wind conditions. The implications of these findings for animal foraging in general are discussed.

  19. Acoustic concentration of particles in fluid flow

    DOEpatents

    Ward, Michael D.; Kaduchak, Gregory

    2010-11-23

    An apparatus for acoustic concentration of particles in a fluid flow includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.

  20. Affective attitudes to face images associated with intracerebral EEG source location before face viewing.

    PubMed

    Pizzagalli, D; Koenig, T; Regard, M; Lehmann, D

    1999-01-01

    We investigated whether different, personality-related affective attitudes are associated with different brain electric field (EEG) sources before any emotional challenge (stimulus exposure). A 27-channel EEG was recorded in 15 subjects during eyes-closed resting. After recording, subjects rated 32 images of human faces for affective appeal. The subjects in the first (i.e., most negative) and fourth (i.e., most positive) quartile of general affective attitude were further analyzed. The EEG data (mean=25+/-4. 8 s/subject) were subjected to frequency-domain model dipole source analysis (FFT-Dipole-Approximation), resulting in 3-dimensional intracerebral source locations and strengths for the delta-theta, alpha, and beta EEG frequency band, and for the full range (1.5-30 Hz) band. Subjects with negative attitude (compared to those with positive attitude) showed the following source locations: more inferior for all frequency bands, more anterior for the delta-theta band, more posterior and more right for the alpha, beta and 1.5-30 Hz bands. One year later, the subjects were asked to rate the face images again. The rating scores for the same face images were highly correlated for all subjects, and original and retest affective mean attitude was highly correlated across subjects. The present results show that subjects with different affective attitudes to face images had different active, cerebral, neural populations in a task-free condition prior to viewing the images. We conclude that the brain functional state which implements affective attitude towards face images as a personality feature exists without elicitors, as a continuously present, dynamic feature of brain functioning.

  1. Efficient modeling of flat and homogeneous acoustic treatments for vibroacoustic finite element analysis. Finite size correction by image sources

    NASA Astrophysics Data System (ADS)

    Alimonti, L.; Atalla, N.

    2017-02-01

    This work is concerned with the hybrid finite element-transfer matrix methodology recently proposed by the authors. The main assumption behind this hybrid method consists in neglecting the actual finite lateral extent of the acoustic treatment. Although a substantial increase of the computational efficiency can be achieved, the effect of the reflected field (i.e. finite size effects) may be sometimes important, preventing the hybrid model from giving quantitative meaningful results. For this reason, a correction to account for wave reflections at the lateral boundaries of the acoustic treatment is sought. It is shown in the present paper that the image source method can be successfully employed to retrieve such finite size effects. Indeed, such methodology is known to be effective when the response of the system is a smooth function of the frequency, like in the case of highly dissipative acoustic treatments. The main concern of this paper is to assess accuracy and feasibility of the image source method in the context of acoustic treatments modeling. Numerical examples show that the performance of the standard hybrid model can be substantially improved by the proposed correction without deteriorating excessively the computational efficiency.

  2. Lightning source locations from VHF radiation data for a flash at Kennedy Space Center

    NASA Astrophysics Data System (ADS)

    Rustan, P. L.; Uman, M. A.; Childers, D. G.; Beasley, W. H.; Lennon, C. L.

    1980-09-01

    A comprehensive study of a three-stroke lightning flash that struck the 150-m weather tower at Kennedy Space Center (KSC) was recently reported by Uman et al. (1978). Here we supplement that study by presenting three-dimensional locations of the sources of VHF (30-50 MHz) radiation generated by the KSC flash. These locations were obtained by measuring with the KSC lightning detection and ranging (LDAR) system the difference in the time of arrival (DTOA) of radiated pulses at four ground stations and then by calculating the locations from the DTOA data. The DTOA data were obtained via a newly developed computer-implemented multiple time series analysis which uses cross-correlation and pattern recognition techniques. About 48,000 sequential VHF sources were located during the flash. We compared these locations with correlated wide band electric field records to provide a better understanding of the physics of the following discharge phases: preliminary breakdown, stepped leader, return strokes, dart leader, stepped-dart leader, J changes, solitary pulses, and intracloud discharge. Some of the more interesting new results obtained follow: before the stepped leader preceding the first return stroke, there was a primarily vertical discharge in the cloud between a height of 7.2 and 5.1 km. This preliminary breakdown has uniquely different VHF characteristics from those of the stepped leader which followed and was not accompanied by significant electric field change as was the stepped leader. The stepped leader propagated downward from the bottom of the preliminary breakdown. The only significant VHF radiation during the dart leader preceding the second return stroke came from within the cloud. The third return stroke was initiated by a stepped leader which propagated from about 8 km height, the bottom of the previous J process, down to about 3.3 km where it apparently joined the channel of the previous return stroke and became a dart leader. The VHF source locations

  3. Characterization and Simulation of an Acoustic Source Moving through an Oceanic Waveguide

    DTIC Science & Technology

    1994-09-01

    algorithms, classical spectrum estimation methods are employed [1, 2] to estimate the auto- and cross-spectra of data received at the array of...Acoust. Soc. Am., 65(3):675-681 (March). [4] Rao, Kodali V., Thomas M. Michaud, and Henrik Schmidt. 1991. "Doppler shifts in underwater acoustics using

  4. Reconstruction of source location in a network of gravitational wave interferometric detectors

    SciTech Connect

    Cavalier, Fabien; Barsuglia, Matteo; Bizouard, Marie-Anne; Brisson, Violette; Clapson, Andre-Claude; Davier, Michel; Hello, Patrice; Kreckelbergh, Stephane; Leroy, Nicolas; Varvella, Monica

    2006-10-15

    This paper deals with the reconstruction of the direction of a gravitational wave source using the detection made by a network of interferometric detectors, mainly the LIGO and Virgo detectors. We suppose that an event has been seen in coincidence using a filter applied on the three detector data streams. Using the arrival time (and its associated error) of the gravitational signal in each detector, the direction of the source in the sky is computed using a {chi}{sup 2} minimization technique. For reasonably large signals (SNR>4.5 in all detectors), the mean angular error between the real location and the reconstructed one is about 1 deg. . We also investigate the effect of the network geometry assuming the same angular response for all interferometric detectors. It appears that the reconstruction quality is not uniform over the sky and is degraded when the source approaches the plane defined by the three detectors. Adding at least one other detector to the LIGO-Virgo network reduces the blind regions and in the case of 6 detectors, a precision less than 1 deg. on the source direction can be reached for 99% of the sky.

  5. Measurement of Jovian decametric Io-related source location and beam shape

    NASA Technical Reports Server (NTRS)

    Maeda, K.; Carr, T. D.

    1992-01-01

    The paper presents new information on the locations of the Io-related sources A and C (i.e., Io-A and Io-C) and on the shapes of their emission beams on the basis of measurements of the Jovian decametric activity that was recorded by Voyager 1 and 2. In two instances, the same dynamic spectral arc event in the recorded data of the two spacecraft was recorded, providing in each case an opportunity to observe the same emission beam over a wide range of frequencies from two considerably different directions. The propagation-corrected centroid times of each of the Voyager-1 arcs are found to be coincident with those of the corresponding Voyager-2 arc in a particular frequency range, but not at other frequencies. The hypothesis that emission beams are in the form of thin, almost conical sheets, the cone opening angle decreasing with increasing frequency, is confirmed. It is demonstrated that both the Io-A and Io-C sources were located near the northern foot of the magnetic flux tube that was connected to Io.

  6. Using physics-based priors in a Bayesian algorithm to enhance infrasound source location

    NASA Astrophysics Data System (ADS)

    Marcillo, Omar; Arrowsmith, Stephen; Whitaker, Rod; Anderson, Dale; Nippress, Alexandra; Green, David N.; Drob, Douglas

    2014-01-01

    We show improvements in the precision of the Bayesian infrasound source localization (BISL) method by incorporating semi-empirical model-based prior information. Given a set of backazimuths and delay times at ≥2 arrays, BISL scans a parameter space (that comprises the horizontal coordinates, celerity and origin time) for the most likely solution. A key element of BISL is its flexibility; the method allows the incorporation of prior information to constrain the parameters. Our research focuses on generating model-based propagation catalogues using a comprehensive set of atmospheric scenarios, extracting celerity distributions based on range and azimuth from the catalogues and using these distributions as prior probability density functions to enhance the location solution from BISL. To illustrate the improvements in source location precision, we compare the BISL results computed using uniform celerity distribution priors with those using enhanced priors; as applied to: (1) a set of events recorded across a regional network and (2) a large accidental chemical explosion recorded by six infrasound arrays in Eurasia. Finally, we discuss efforts to improve the numerical implementation of BISL by expanding the parameter space to cover a richer set of parameters that can include station-specific celerity distributions.

  7. Solving seismological problems using SGRAPH program: I-source parameters and hypocentral location

    SciTech Connect

    Abdelwahed, Mohamed F.

    2012-09-26

    SGRAPH program is considered one of the seismological programs that maintain seismic data. SGRAPH is considered unique for being able to read a wide range of data formats and manipulate complementary tools in different seismological subjects in a stand-alone Windows-based application. SGRAPH efficiently performs the basic waveform analysis and solves advanced seismological problems. The graphical user interface (GUI) utilities and the Windows facilities such as, dialog boxes, menus, and toolbars simplified the user interaction with data. SGRAPH supported the common data formats like, SAC, SEED, GSE, ASCII, and Nanometrics Y-format, and others. It provides the facilities to solve many seismological problems with the built-in inversion and modeling tools. In this paper, I discuss some of the inversion tools built-in SGRAPH related to source parameters and hypocentral location estimation. Firstly, a description of the SGRAPH program is given discussing some of its features. Secondly, the inversion tools are applied to some selected events of the Dahshour earthquakes as an example of estimating the spectral and source parameters of local earthquakes. In addition, the hypocentral location of these events are estimated using the Hypoinverse 2000 program operated by SGRAPH.

  8. Solving seismological problems using SGRAPH program: I-source parameters and hypocentral location

    NASA Astrophysics Data System (ADS)

    Abdelwahed, Mohamed F.

    2012-09-01

    SGRAPH program [1] is considered one of the seismological programs that maintain seismic data. SGRAPH is considered unique for being able to read a wide range of data formats and manipulate complementary tools in different seismological subjects in a stand-alone Windows-based application. SGRAPH efficiently performs the basic waveform analysis and solves advanced seismological problems. The graphical user interface (GUI) utilities and the Windows facilities such as, dialog boxes, menus, and toolbars simplified the user interaction with data. SGRAPH supported the common data formats like, SAC, SEED, GSE, ASCII, and Nanometrics Y-format, and others. It provides the facilities to solve many seismological problems with the built-in inversion and modeling tools. In this paper, I discuss some of the inversion tools built-in SGRAPH related to source parameters and hypocentral location estimation. Firstly, a description of the SGRAPH program is given discussing some of its features. Secondly, the inversion tools are applied to some selected events of the Dahshour earthquakes as an example of estimating the spectral and source parameters of local earthquakes. In addition, the hypocentral location of these events are estimated using the Hypoinverse 2000 program [2] operated by SGRAPH.

  9. Investigation of source location determination from Magsat magnetic anomalies: The Euler method approach

    NASA Technical Reports Server (NTRS)

    Ravat, Dhananjay

    1996-01-01

    The applicability of the Euler method of source location determination was investigated on several model situations pertinent to satellite-data scale situations as well as Magsat data of Europe. Our investigations enabled us to understand the end-member cases for which the Euler method will work with the present satellite magnetic data and also the cases for which the assumptions implicit in the Euler method will not be met by the present satellite magnetic data. These results have been presented in one invited lecture at the Indo-US workshop on Geomagnetism in Studies of the Earth's Interior in August 1994 in Pune, India, and at one presentation at the 21st General Assembly of the IUGG in July 1995 in Boulder, CO. A new method, called Anomaly Attenuation Rate (AAR) Method (based on the Euler method), was developed during this study. This method is scale-independent and is appropriate to locate centroids of semi-compact three dimensional sources of gravity and magnetic anomalies. The method was presented during 1996 Spring AGU meeting and a manuscript describing this method is being prepared for its submission to a high-ranking journal. The grant has resulted in 3 papers and presentations at national and international meetings and one manuscript of a paper (to be submitted shortly to a reputable journal).

  10. Relation Between Sprite Distribution and Source Locations of VHF Pulses Derived From JEM- GLIMS Measurements

    NASA Astrophysics Data System (ADS)

    Sato, Mitsuteru; Mihara, Masahiro; Ushio, Tomoo; Morimoto, Takeshi; Kikuchi, Hiroshi; Adachi, Toru; Suzuki, Makoto; Yamazaki, Atsushi; Takahashi, Yukihiro

    2015-04-01

    JEM-GLIMS is continuing the comprehensive nadir observations of lightning and TLEs using optical instruments and electromagnetic wave receivers since November 2012. For the period between November 20, 2012 and November 30, 2014, JEM-GLIMS succeeded in detecting 5,048 lightning events. A total of 567 events in 5,048 lightning events were TLEs, which were mostly elves events. To identify the sprite occurrences from the transient optical flash data, it is necessary to perform the following data analysis: (1) a subtraction of the appropriately scaled wideband camera data from the narrowband camera data; (2) a calculation of intensity ratio between different spectrophotometer channels; and (3) an estimation of the polarization and CMC for the parent CG discharges using ground-based ELF measurement data. From a synthetic comparison of these results, it is confirmed that JEM-GLISM succeeded in detecting sprite events. The VHF receiver (VITF) onboard JEM-GLIMS uses two patch-type antennas separated by a 1.6-m interval and can detect VHF pulses emitted by lightning discharges in the 70-100 MHz frequency range. Using both an interferometric technique and a group delay technique, we can estimate the source locations of VHF pulses excited by lightning discharges. In the event detected at 06:41:15.68565 UT on June 12, 2014 over central North America, sprite was distributed with a horizontal displacement of 20 km from the peak location of the parent lightning emission. In this event, a total of 180 VHF pulses were simultaneously detected by VITF. From the detailed data analysis of these VHF pulse data, it is found that the majority of the source locations were placed near the area of the dim lightning emission, which may imply that the VHF pulses were associated with the in-cloud lightning current. At the presentation, we will show detailed comparison between the spatiotemporal characteristics of sprite emission and source locations of VHF pulses excited by the parent lightning

  11. Long Period (LP) volcanic earthquake source location at Merapi volcano by using dense array technics

    NASA Astrophysics Data System (ADS)

    Metaxian, Jean Philippe; Budi Santoso, Agus; Laurin, Antoine; Subandriyo, Subandriyo; Widyoyudo, Wiku; Arshab, Ghofar

    2015-04-01

    Since 2010, Merapi shows unusual activity compared to last decades. Powerful phreatic explosions are observed; some of them are preceded by LP signals. In the literature, LP seismicity is thought to be originated within the fluid, and therefore to be representative of the pressurization state of the volcano plumbing system. Another model suggests that LP events are caused by slow, quasi-brittle, low stress-drop failure driven by transient upper-edifice deformations. Knowledge of the spatial distribution of LP events is fundamental for better understanding the physical processes occurring in the conduit, as well as for the monitoring and the improvement of eruption forecasting. LP events recorded at Merapi have a spectral content dominated by frequencies between 0.8 and 3 Hz. To locate the source of these events, we installed a seismic antenna composed of 4 broadband CMG-6TD Güralp stations. This network has an aperture of 300 m. It is located on the site of Pasarbubar, between 500 and 800 m from the crater rim. Two multi-parameter stations (seismic, tiltmeter, S-P) located in the same area, equipped with broadband CMG-40T Güralp sensors may also be used to complete the data of the antenna. The source of LP events is located by using different approaches. In the first one, we used a method based on the measurement of the time delays between the early beginnings of LP events for each array receiver. The observed differences of time delays obtained for each pair of receivers are compared to theoretical values calculated from the travel times computed between grid nodes, which are positioned in the structure, and each receiver. In a second approach, we estimate the slowness vector by using MUSIC algorithm applied to 3-components data. From the slowness vector, we deduce the back-azimuth and the incident angle, which give an estimation of LP source depth in the conduit. This work is part of the Domerapi project funded by French Agence Nationale de la Recherche (https

  12. Comparisons of radial plume mapping algorithms for locating gaseous emission sources

    NASA Astrophysics Data System (ADS)

    Wu, Chang-fu; Chang, Shih-ying

    2011-03-01

    This paper presents the simulation and field evaluation results for two mathematical algorithms applied in the horizontal radial plume mapping (HRPM) technique with optical remote sensing instruments. In the simulation study, 450 test maps with skewed distributions (i.e., bivariate lognormal distribution) were generated in a two-dimensional domain. The HRPM techniques with the smooth basis function minimization (SBFM) algorithm and non-negative least square (NNLS) algorithm were then applied to reconstruct the plumes, assuming a nine-beam scanning beam geometry. The SBFM algorithm was able to identify the peak locations better than the NNLS algorithm when the plumes were near the origin. On the other hand, the NNLS performed better when the plumes were away from the origin. In the field validation study, four experiments were conducted in an open space with the same nine-beam geometry. In each experiment, two tracer gases were released simultaneously at two different locations, and an OP-FTIR was set up to collect the IR spectra. The collected path-integrated concentration data were then used to reconstruct the source locations. The results confirm the conclusions obtained in the simulation study of a better performance from the SBFM algorithm than from the NNLS algorithm for plumes near the origin. We also developed a screening criterion to determine which algorithm results should be chosen as the final estimates in future field applications.

  13. Induced seismicity during the construction of the Gotthard Base Tunnel, Switzerland: hypocenter locations and source dimensions

    NASA Astrophysics Data System (ADS)

    Husen, Stephan; Kissling, Edi; von Deschwanden, Angela

    2013-01-01

    A series of 112 earthquakes was recorded between October 2005 and August 2007 during the excavation of the MFS Faido, the southernmost access point of the new Gotthard Base Tunnel. Earthquakes were recorded at a dense network of 11 stations, including 2 stations in the tunnel. Local magnitudes computed from Wood-Anderson-filtered horizontal component seismograms ranged from -1.0 to 2.4; the largest earthquake was strongly felt at the surface and caused considerable damage in the tunnel. Hypocenter locations obtained routinely using a regional 3-D P-wave velocity model and a constant Vp/Vs ratio 1.71 were about 2 km below the tunnel. The use of seismic velocities calibrated from a shot in the tunnel revealed that routinely obtained hypocenter locations were systematically biased to greater depth and are now relocated to be on the tunnel level. Relocation of the shot using these calibrated velocities yields a location accuracy of 25 m in longitude, 70 m in latitude, and 250 m in focal depth. Double-difference relative relocations of two clusters with highly similar waveforms showed a NW-SE striking trend that is consistent with the strike of mapped faults in the MFS Faido. Source dimensions computed using the quasidynamic model of Madariaga (Bull Seismo Soc Am 66(3):639-666, 1976) range from 50 to 170 m. Overlapping source dimensions for earthquakes within the two main clusters suggests that the same fault patch was ruptured repeatedly. The observed seismicity was likely caused by stress redistribution due to the excavation work in the MFS Faido.

  14. Atmospheric Transport Modelling confining potential source location of East-Asian radionuclide detections in May 2010

    NASA Astrophysics Data System (ADS)

    Ross, J. Ole; Ceranna, Lars

    2016-04-01

    The radionuclide component of the International Monitoring System (IMS) to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is in place to detect tiny traces of fission products from nuclear explosions in the atmosphere. The challenge for the interpretation of IMS radionuclide data is to discriminate radionuclide sources of CTBT relevance against emissions from nuclear facilities. Remarkable activity concentrations of Ba/La-140 occurred at the IMS radionuclide stations RN 37 (Okinawa) and RN 58 (Ussurysk) mid of May 2010. In those days also an elevated Xe-133 level was measured at RN 38 (Takasaki). Additional regional measurements of radioxenon were reported in the press and further analyzed in various publications. The radionuclide analysis gives evidence for the presence of a nuclear fission source between 10 and 12 May 2010. Backward Atmospheric Transport Modelling (ATM) with HYSPLIT driven by 0.2° ECMWF meteorological data for the IMS samples indicates that, assuming a single source, a wide range of source regions is possible including the Korean Peninsula, the Sea of Japan (East Sea), and parts of China and Russia. Further confinement of the possible source location can be provided by atmospheric backtracking for the assumed sampling periods of the reported regional xenon measurements. New studies indicate a very weak seismic event at the DPRK test site on early 12 May 2010. Forward ATM for a pulse release caused by this event shows fairly good agreement with the observed radionuclide signature. Nevertheless, the underlying nuclear fission scenario remains quite unclear and speculative even if assuming a connection between the waveform and the radionuclide event.

  15. Earthquake Source Process from a Tide-Gauge and Hydro-Acoustic Station

    NASA Astrophysics Data System (ADS)

    Barrientos, S. E.

    2013-12-01

    A nearly 450-km-long rupture along the Nazca - South America plate interface, between Pichilemu (33.8°S) and the Arauco Peninsula (37.8°S) was responsible for the large earthquake (Mw=8.8) that took place in south-central Chile on 27 February 2010 at 03:34 (local time). Because of the location of the activated fault, a significant tsunami was generated which caused 156 deaths and 25 missing. Maximum run-ups of the generated tsunami reached 28 m in the neighborhood of Constitución. The most unusual feature of this tsunami was its long duration, it lasted more than 4 and a half hours at tide gages located close to the source region. A triad of hydrophone sensors, part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization, recorded the complete source process and later phases until the arrival of the tsunami that destroyed the facility. The hydroacoustic station at Juan Fernandez Island, placed around 500-600 km away from the rupture region together with a tide gauge recorder, captured some characteristics of the source processes as well as later arrivals, which have been interpreted as T phases generated by the rupture itself. The possibility of an induced landslide producing an anomalous signal is being investigated.

  16. Comments on inferring the properties of the solar acoustic sources by modeling the velocity and/or intensity fluctuations

    NASA Astrophysics Data System (ADS)

    Jefferies, Stuart M.; Moretti, Pier-Francesco; Oliviero, Maurizio; Giebink, Cynthia

    2003-02-01

    We model the observed velocity and intensity power spectra and the intensity-velocity cross-spectrum using an updated version of the Severino et al. (2001) model that includes the effects of the acoustic source. We find that in order to accurately describe the data it is necessary to include a correlated background component in both the V and I signals at low frequencies, and in the I signal at high frequencies. Preliminary results show that even using the new model we can not uniquely determine the phase that is related to the acoustic source depth at low frequencies, or the amplitudes and phases of the individual correlated background signals. It appears that further physical or observational constraints are needed before we can obtain this information.

  17. The impact of runoff generation mechanisms on the location of critical source areas

    USGS Publications Warehouse

    Lyon, S.W.; McHale, M.R.; Walter, M.T.; Steenhuis, T.S.

    2006-01-01

    Identifying phosphorus (P) source areas and transport pathways is a key step in decreasing P loading to natural water systems. This study compared the effects of two modeled runoff generation processes - saturation excess and infiltration excess - on total phosphorus (TP) and soluble reactive phosphorus (SRP) concentrations in 10 catchment streams of a Catskill mountain watershed in southeastern New York. The spatial distribution of runoff from forested land and agricultural land was generated for both runoff processes; results of both distributions were consistent with Soil Conservation Service-Curve Number (SCS-CN) theory. These spatial runoff distributions were then used to simulate stream concentrations of TP and SRP through a simple equation derived from an observed relation between P concentration and land use; empirical results indicate that TP and SRP concentrations increased with increasing percentage of agricultural land. Simulated TP and SRP stream concentrations predicted for the 10 catchments were strongly affected by the assumed runoff mechanism. The modeled TP and SRP concentrations produced by saturation excess distribution averaged 31 percent higher and 42 percent higher, respectively, than those produced by the infiltration excess distribution. Misrepresenting the primary runoff mechanism could not only produce erroneous concentrations, it could fail to correctly locate critical source areas for implementation of best management practices. Thus, identification of the primary runoff mechanism is critical in selection of appropriate models in the mitigation of nonpoint source pollution. Correct representation of runoff processes is also critical in the future development of biogeochemical transport models, especially those that address nutrient fluxes.

  18. Development and validation of a combined phased acoustical radiosity and image source model for predicting sound fields in rooms.

    PubMed

    Marbjerg, Gerd; Brunskog, Jonas; Jeong, Cheol-Ho; Nilsson, Erling

    2015-09-01

    A model, combining acoustical radiosity and the image source method, including phase shifts on reflection, has been developed. The model is denoted Phased Acoustical Radiosity and Image Source Method (PARISM), and it has been developed in order to be able to model both specular and diffuse reflections with complex-valued and angle-dependent boundary conditions. This paper mainly describes the combination of the two models and the implementation of the angle-dependent boundary conditions. It furthermore describes how a pressure impulse response is obtained from the energy-based acoustical radiosity by regarding the model as being stochastic. Three methods of implementation are proposed and investigated, and finally, recommendations are made for their use. Validation of the image source method is done by comparison with finite element simulations of a rectangular room with a porous absorber ceiling. Results from the full model are compared with results from other simulation tools and with measurements. The comparisons of the full model are done for real-valued and angle-independent surface properties. The proposed model agrees well with both the measured results and the alternative theories, and furthermore shows a more realistic spatial variation than energy-based methods due to the fact that interference is considered.

  19. Closed-form analytical solutions of the time difference of arrival source location problem for minimal element monitoring arrays.

    PubMed

    Spencer, Steven J

    2010-05-01

    Closed-form analytical solutions are found for the time difference of arrival (TDOA) source location problem. Solutions are found for both two-dimensional (2D) and three-dimensional (3D) source location by formulating the TDOA equations in, respectively, polar and spherical coordinate systems, with the radial direction coincident with the assumed geodesic path of signal propagation to a reference sensor. Quadratic equations for TDOA 2D and 3D source location based on the spherical intersection (SX) scheme, in some cases permitting dual physical solutions, are found for three and four sensor element monitoring arrays, respectively. A method of spherical intersection subarrays (SXSAs) is developed to derive from these quadratic equations globally unique closed-form analytical solutions for TDOA 2D and 3D source location, for four and five sensor element monitoring arrays, respectively. Errors in 2D source location for introduced bias in time differences of arrival are shown to have a strong geometrical dependence. The SXSA and SX methods perform well in terms of accuracy and precision at high levels of arrival time bias for both 2D and 3D source location and are much more efficient than nonlinear least-squares schemes. The SXSA scheme may have particular applicability to accurately solving source location problems in demanding real-time situations.

  20. Concurrent identification of aero-acoustic scattering and noise sources at a flow duct singularity in low Mach number flow

    NASA Astrophysics Data System (ADS)

    Sovardi, Carlo; Jaensch, Stefan; Polifke, Wolfgang

    2016-09-01

    A numerical method to concurrently characterize both aeroacoustic scattering and noise sources at a duct singularity is presented. This approach combines Large Eddy Simulation (LES) with techniques of System Identification (SI): In a first step, a highly resolved LES with external broadband acoustic excitation is carried out. Subsequently, time series data extracted from the LES are post-processed by means of SI to model both acoustic propagation and noise generation. The present work studies the aero-acoustic characteristics of an orifice placed in a duct at low flow Mach numbers with the "LES-SI" method. Parametric SI based on the Box-Jenkins mathematical structure is employed, with a prediction error approach that utilizes correlation analysis of the output residuals to avoid overfitting. Uncertainties of model parameters due to the finite length of times series are quantified in terms of confidence intervals. Numerical results for acoustic scattering matrices and power spectral densities of broad-band noise are validated against experimental measurements over a wide range of frequencies below the cut-off frequency of the duct.

  1. Investigation of acoustic gravity waves created by anomalous heat sources: experiments and theoretical analysis

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Lee, M. C.

    2013-07-01

    We have been investigating high-power radio wave-induced acoustic gravity waves (AGWs) at Gakona, Alaska, using the High-frequency Active Aurora Research Program (HAARP) heating facility (i.e. HF heater) and extensive diagnostic instruments. This work was aimed at performing a controlled study of the space plasma turbulence triggered by the AGWs originating from anomalous heat sources, as observed in our earlier experiments at Arecibo, Puerto Rico (Pradipta 2007 MS Thesis MIT Press, Cambridge, MA). The HF heater operated in continuous wave (CW) O-mode can heat ionospheric plasmas effectively to yield a depleted magnetic flux tube as rising plasma bubbles (Lee et al 1998 Geophys. Res. Lett. 25 579). Two processes are responsible for the depletion of the magnetic flux tube: (i) thermal expansion and (ii) chemical reactions caused by heated ions. The depleted plasmas create large density gradients that can augment spread F processes via generalized Rayleigh-Taylor instabilities (Lee et al 1999 Geophys. Res. Lett. 26 37). It is thus expected that the temperature of neutral particles in the heated ionospheric region can be increased. Such a heat source in the neutral atmosphere may potentially generate AGWs in the form of traveling ionospheric plasma disturbances (TIPDs). We should point out that these TIPDs have features distinctively different from electric and magnetic field (ExB) drifts of HF wave-induced large-scale non-propagating plasma structures. Moreover, it was noted in our recent study of naturally occurring AGW-induced TIDs that only large-scale AGWs can propagate upward to reach higher altitudes. Thus, in our Gakona experiments we select optimum heating schemes for HF wave-induced AGWs that can be distinguished from the naturally occurring ones. The generation and propagation of AGWs are monitored by MUIR (Modular Ultra high-frequency Ionospheric Radar), Digisonde and GPS/low-earth-orbit satellites. Our theoretical and experimental studies have shown that

  2. Outbreaks source: A new mathematical approach to identify their possible location

    NASA Astrophysics Data System (ADS)

    Buscema, Massimo; Grossi, Enzo; Breda, Marco; Jefferson, Tom

    2009-11-01

    Classical epidemiology has generally relied on the description and explanation of the occurrence of infectious diseases in relation to time occurrence of events rather than to place of occurrence. In recent times, computer generated dot maps have facilitated the modeling of the spread of infectious epidemic diseases either with classical statistics approaches or with artificial “intelligent systems”. Few attempts, however, have been made so far to identify the origin of the epidemic spread rather than its evolution by mathematical topology methods. We report on the use of a new artificial intelligence method (the H-PST Algorithm) and we compare this new technique with other well known algorithms to identify the source of three examples of infectious disease outbreaks derived from literature. The H-PST algorithm is a new system able to project a distances matrix of points (events) into a bi-dimensional space, with the generation of a new point, named hidden unit. This new hidden unit deforms the original Euclidean space and transforms it into a new space (cognitive space). The cost function of this transformation is the minimization of the differences between the original distance matrix among the assigned points and the distance matrix of the same points projected into the bi-dimensional map (or any different set of constraints). For many reasons we will discuss, the position of the hidden unit shows to target the outbreak source in many epidemics much better than the other classic algorithms specifically targeted for this task. Compared with main algorithms known in the location theory, the hidden unit was within yards of the outbreak source in the first example (the 2007 epidemic of Chikungunya fever in Italy). The hidden unit was located in the river between the two village epicentres of the spread exactly where the index case was living. Equally in the second (the 1967 foot and mouth disease epidemic in England), and the third (1854 London Cholera epidemic

  3. Stress Tolerance Variations in Saccharomyces cerevisiae Strains from Diverse Ecological Sources and Geographical Locations

    PubMed Central

    Zheng, Yan-Lin; Wang, Shi-An

    2015-01-01

    The budding yeast Saccharomyces cerevisiae is a platform organism for bioethanol production from various feedstocks and robust strains are desirable for efficient fermentation because yeast cells inevitably encounter stressors during the process. Recently, diverse S. cerevisiae lineages were identified, which provided novel resources for understanding stress tolerance variations and related shaping factors in the yeast. This study characterized the tolerance of diverse S. cerevisiae strains to the stressors of high ethanol concentrations, temperature shocks, and osmotic stress. The results showed that the isolates from human-associated environments overall presented a higher level of stress tolerance compared with those from forests spared anthropogenic influences. Statistical analyses indicated that the variations of stress tolerance were significantly correlated with both ecological sources and geographical locations of the strains. This study provides guidelines for selection of robust S. cerevisiae strains for bioethanol production from nature. PMID:26244846

  4. Source location of long period seismicity at Volcàn de Colima, México

    NASA Astrophysics Data System (ADS)

    Petrosino, Simona; Cusano, Paola; La Rocca, Mario; Galluzzo, Danilo; Orozco-Rojas, Justo; Bretón, Mauricio; Ibáñez, Jesus; Del Pezzo, Edoardo

    2011-09-01

    This paper presents an analysis of seismicity associated with the volcanic activity of Volcàn de Colima (México) and recorded in the period November 2005-April 2006 during a field survey by the Istituto Nazionale di Geofisica e Vulcanologia (INGV)-Osservatorio Vesuviano, the Observatorio Vulcanologico de Colima of Colima University and the Instituto Andaluz de Geofisica, University of Granada. Three different types of volcanic earthquakes have been identified on the basis of their spectral properties: Type A (0.3-1 Hz), Type B (1-5 Hz) and Type C (3-4 Hz). Results of polarization analysis applied to Type A events show a predominance of radial motion, indicating that the wavefield comprises compressional waves (P) and shear waves polarized in the vertical plane (SV), while the signal always begins with a negative polarity. Type A, B and C earthquakes have been located using both a flat layered model and a 3D model including topography. Hypocentre distributions indicate that the source of Type A signals is very shallow and confined to a small volume lying about 1 km below the crater. In contrast, the source of Type B and C events is significantly deeper, with most hypocentres located in a volume of about 1 km3 centred at 2.5-3 km depth. A cluster analysis based on the cross-correlation among the waveforms of different events recorded at the same station was applied to Type A earthquakes. Only two clusters, which include only a small percentage of events were found, indicating that earthquake families were uncommon during the period of our survey.

  5. True location and orientation of fractures logged with the acoustic televiewer (including programs to correct fracture orientation)

    USGS Publications Warehouse

    Kierstein, R.A.

    1984-01-01

    The attitude of fractures measured on acoustic-televiewer logs may be misorientated by as much as 180 degrees in a drill hole that is deviated significantly from vertical, because of the effect of the vertical component of the magnetic field on the tilted magnetometer that is used to orient the log. A method has been developed to correct for the misorientation by analyzing the orientation of the magnetometer with respect to the magnetic-field vector acting at the magnetometer 's center. Computer programs were written to correct the attitude of fractures for both magnetic effects and hole deviation. For the reorientation of a single fracture, a stereographic solution is illustrated. Test results suggest that the fracture orientation can be corrected to plus or minus five degrees of true orientation, provided there are no other magnetic effects, such as magnetite in the rocks. (USGS)

  6. A seismic field test with a Low-level Acoustic Combustion Source and Pseudo-Noise codes

    NASA Astrophysics Data System (ADS)

    Askeland, Bjørn; Ruud, Bent Ole; Hobæk, Halvor; Mjelde, Rolf

    2009-01-01

    The Low-level Acoustic Combustion Source (LACS) which can fire its pulses at a high rate, has been tested successfully as a seismic marine source on shallow ice-age sediments in Byfjorden at Bergen, Norway. Pseudo-Noise pulsed signals with spiky autocorrelation functions were used to detect the sediments. Each transmitted sequence lasted 10 s and contained 43 pulses. While correlation gave a blurry result, deconvolution between the near-field recordings and the streamer recordings gave a clear seismic section. Compared to the section acquired with single air-gun shots along the same profile, the LACS gave a more clear presentation of the sediments and basement.

  7. Assessing Acoustic Sound Levels Associated with Active Source Seismic Surveys in Shallow Marine Environments

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, D. R.; Tolstoy, M.; Thode, A.; Diebold, J. B.; Webb, S. C.

    2004-12-01

    The potential effect of active source seismic research on marine mammal populations is a topic of increasing concern, and controversy surrounding such operations has begun to impact the planning and permitting of academic surveys [e.g., Malakoff, 2002 Science]. Although no causal relationship between marine mammal strandings and seismic exploration has been proven, any circumstantial evidence must be thoroughly investigated. A 2002 stranding of two beaked whales in the Gulf of California within 50 km of a R/V Ewing seismic survey has been a subject of concern for both marine seismologists and environmentalists. In order to better understand possible received levels for whales in the vicinity of these operations, modeling is combined with ground-truth calibration measurements. A wide-angle parabolic equation model, which is capable of including shear within the sediment and basement layers, is used to generate predictive models of low-frequency transmission loss within the Gulf of California. This work incorporates range-dependent bathymetry, sediment thickness, sound velocity structure and sub-bottom properties. Oceanic sounds speed profiles are derived from the U.S. Navy's seasonal GDEM model and sediment thicknesses are taken from NOAA's worldwide database. The spectral content of the Ewing's 20-airgun seismic array is constrained by field calibration in the spring of 2003 [Tolstoy et al., 2004 GRL], indicating peak energies at frequencies below a few hundred Hz, with energy spectral density showing an approximate power-law decrease at higher frequencies (being ~40 dB below peak at 1 kHz). Transmission loss is estimated along a series of radials extending from multiple positions along the ship's track, with the directivity of the array accounted for by phase-shifting point sources that are scaled by the cube root of the individual airgun volumes. This allows the time-space history of low-frequency received levels to be reconstructed within the Gulf of California

  8. Integration of acoustical information in the perception of impacted sound sources: the role of information accuracy and exploitability.

    PubMed

    Giordano, Bruno L; Rocchesso, Davide; McAdams, Stephen

    2010-04-01

    Sound sources are perceived by integrating information from multiple acoustical features. The factors influencing the integration of information are largely unknown. We measured how the perceptual weighting of different features varies with the accuracy of information and with a listener's ability to exploit it. Participants judged the hardness of two objects whose interaction generates an impact sound: a hammer and a sounding object. In a first discrimination experiment, trained listeners focused on the most accurate information, although with greater difficulty when perceiving the hammer. We inferred a limited exploitability for the most accurate hammer-hardness information. In a second rating experiment, listeners focused on the most accurate information only when estimating sounding-object hardness. In a third rating experiment, we synthesized sounds by independently manipulating source properties that covaried in Experiments 1 and 2: sounding-object hardness and impact properties. Sounding-object hardness perception relied on the most accurate acoustical information, whereas impact-properties influenced more strongly hammer hardness perception. Overall, perceptual weight increased with the accuracy of acoustical information, although information that was not easily exploited was perceptually secondary, even if accurate.

  9. A "looming bias" in spatial hearing? Effects of acoustic intensity and spectrum on categorical sound source localization.

    PubMed

    McCarthy, Lisa; Olsen, Kirk N

    2017-01-01

    Continuous increases of acoustic intensity (up-ramps) can indicate a looming (approaching) sound source in the environment, whereas continuous decreases of intensity (down-ramps) can indicate a receding sound source. From psychoacoustic experiments, an "adaptive perceptual bias" for up-ramp looming tonal stimuli has been proposed (Neuhoff, 1998). This theory postulates that (1) up-ramps are perceptually salient because of their association with looming and potentially threatening stimuli in the environment; (2) tonal stimuli are perceptually salient because of an association with single and potentially threatening biological sound sources in the environment, relative to white noise, which is more likely to arise from dispersed signals and nonthreatening/nonbiological sources (wind/ocean). In the present study, we extrapolated the "adaptive perceptual bias" theory and investigated its assumptions by measuring sound source localization in response to acoustic stimuli presented in azimuth to imply looming, stationary, and receding motion in depth. Participants (N = 26) heard three directions of intensity change (up-ramps, down-ramps, and steady state, associated with looming, receding, and stationary motion, respectively) and three levels of acoustic spectrum (a 1-kHz pure tone, the tonal vowel /ә/, and white noise) in a within-subjects design. We first hypothesized that if up-ramps are "perceptually salient" and capable of eliciting adaptive responses, then they would be localized faster and more accurately than down-ramps. This hypothesis was supported. However, the results did not support the second hypothesis. Rather, the white-noise and vowel conditions were localized faster and more accurately than the pure-tone conditions. These results are discussed in the context of auditory and visual theories of motion perception, auditory attentional capture, and the spectral causes of spatial ambiguity.

  10. Acoustic Database for Turbofan Engine Core-Noise Sources. I; Volume

    NASA Technical Reports Server (NTRS)

    Gordon, Grant

    2015-01-01

    were processed using software that accounts for the effects of convective and conductive heat transfer. The software was developed under previous NASA sponsored programs. Compensated temperature spectra and compensated time histories corresponding to the dynamic temperature of the gas stream were generated. Auto-spectral and cross-spectral analyses of the data were performed to investigate spectral features, acoustic circumferential mode content, signal coherence, and time delays. The dynamic temperature data exhibit a wideband and fairly flat spectral content. The temperature spectra do not change substantially with operating speed. The pressure spectra in the combustor and ITD exhibit generally similar shapes and amplitudes, making it difficult to identify any features that suggest the presence of indirect combustion noise. Cross-spectral analysis reveal a strong correlation between pressure and temperature fluctuations in the ITD, but little correlation between temperature fluctuations at the entrance of the HPT and pressure fluctuations downstream of it. Temperature fluctuations at the entrance of the low pressure turbine were an order of magnitude smaller than those at the entrance to the high pressure turbine. Time delay analysis of the temperature fluctuations in the combustor was inconclusive, perhaps due to the substantial mixing that occurs between the upstream and downstream locations. Time delay analysis of the temperature fluctuations in the ITD indicate that they convect at the mean flow speed. Analysis of the data did not reveal any convincing indications of the presence of indirect combustion noise. However, this analysis has been preliminary and additional exploration of the data is recommended including the use of more sophisticated signal processing to explore subtle issues that have been revealed but which are not yet fully understood or explained.

  11. Virtual acoustic prototyping

    NASA Astrophysics Data System (ADS)

    Johnson, Marty

    2003-10-01

    In this paper the re-creation of 3-D sound fields so the full psycho-acoustic impact of sound sources can be assessed before the manufacture of a product or environment is examined. Using head related transfer functions (HRTFs) coupled with a head tracked set of headphones the sound field at the left and right ears of a listener can be re-created for a set of sound sources. However, the HRTFs require that sources have a defined location and this is not the typical output from numerical codes which describe the sound field as a set of distributed modes. In this paper a method of creating a set of equivalent sources is described such that the standard set of HRTFs can be applied in real time. A structural-acoustic model of a cylinder driving an enclosed acoustic field will be used as an example. It will be shown that equivalent sources can be used to recreate all of the reverberation of the enclosed space. An efficient singular value decomposition technique allows the large number of sources required to be simulated in real time. An introduction to the requirements necessary for 3-D virtual prototyping using high frequency Statistical Energy Analysis models will be presented. [Work supported by AuSim and NASA.

  12. Location, Location, Location!

    ERIC Educational Resources Information Center

    Ramsdell, Kristin

    2004-01-01

    Of prime importance in real estate, location is also a key element in the appeal of romances. Popular geographic settings and historical periods sell, unpopular ones do not--not always with a logical explanation, as the author discovered when she conducted a survey on this topic last year. (Why, for example, are the French Revolution and the…

  13. Test of acoustic tone source and propulsion performance of C8A Buffalo suppressor nozzle

    NASA Technical Reports Server (NTRS)

    Marrs, C. C.; Harkonen, D. L.; Okeefe, J. V.

    1974-01-01

    Results are presented for a static acoustic and propulsion performance ground test conducted at the Boeing hot nozzle facility on the C8A Buffalo noise suppressor nozzle. Various methods to remove a nozzle-associated 2000-Hz tone are evaluated. Results of testing this rectangular-array lobed nozzle for propulsion performance and acoustic directivity are reported. Recommendations for future nozzle modifications and further testing are included. Appendix A contains the test plan. Appendix B presents the test log. Appendix C contains plots of the one-third octave sound pressure levels recorded during the test. Appendix D describes the acoustic data recording and reduction systems. The performance data is tabulated in Appendix E.

  14. Volumetric Acoustic Vector Intensity Probe

    NASA Technical Reports Server (NTRS)

    Klos, Jacob

    2006-01-01

    A new measurement tool capable of imaging the acoustic intensity vector throughout a large volume is discussed. This tool consists of an array of fifty microphones that form a spherical surface of radius 0.2m. A simultaneous measurement of the pressure field across all the microphones provides time-domain near-field holograms. Near-field acoustical holography is used to convert the measured pressure into a volumetric vector intensity field as a function of frequency on a grid of points ranging from the center of the spherical surface to a radius of 0.4m. The volumetric intensity is displayed on three-dimensional plots that are used to locate noise sources outside the volume. There is no restriction on the type of noise source that can be studied. The sphere is mobile and can be moved from location to location to hunt for unidentified noise sources. An experiment inside a Boeing 757 aircraft in flight successfully tested the ability of the array to locate low-noise-excited sources on the fuselage. Reference transducers located on suspected noise source locations can also be used to increase the ability of this device to separate and identify multiple noise sources at a given frequency by using the theory of partial field decomposition. The frequency range of operation is 0 to 1400Hz. This device is ideal for the study of noise sources in commercial and military transportation vehicles in air, on land and underwater.

  15. Seismic precursors of vulcanian explosions at Ubinas volcano (Peru) : Statistical analysis and source locations

    NASA Astrophysics Data System (ADS)

    Métaxian, J.-P.; Macedo, O.; Lengline, O.; Monteiller, V.; Taipe, E.

    2009-04-01

    Ubinas stratovolcano (5672 m), located 60 km east from Arequipa city is historically the most active volcano in Peru. The present eruption began on March 25th 2006. A lava plug has been observed at the bottom of the pit crater situated in the south part of the caldeira. The eruptive activity involves very brought closer exhalations rising a few hundred meters above the crater rim to larger plumes produced by explosions that may reach up to 3 kilometers. The seismic activity is characterized by high rates of long-period (LP) event production accompanying eruptive activity and very long period (VLP) events observed at the same time as vulcanian explosions. The LP and VLP events have a spectral content respectively dominated by frequencies between 2-5 Hz and 0.3-0.9 Hz. The vulcanian explosive activity is characterized by the occurrence of LP swarm preceding most of the VLPs by about 2 hours. In some occasions, the LP swarm merges into tremor about half an hour before the explosion. LPs belonging to the same swarm have similar waveform suggesting a unique source area, which could be the conduit and/or the lava plug surface. The monitoring system includes 4 seismic stations, among which one is equipped with a broadband sensor and 2 tiltmeters. In this work we analyzed a catalogue of data including more than 40000 LP events and 130 VLP events recorded between May 2006 and December 2008. The evolution of the average number of LP events preceding explosions was computed. The variation of the LP rate is clearly diverging from the background rate ~ 0.1 days before explosions. In particular, the most energetic explosions are correlated with the biggest increases of seismicity. However this general behavior is not observed for every single explosion. A direct test is now under study in order to check if the earthquake rate can be used as an alert tool for future explosions. To locate the source of LP events belonging to the swarms, we used a method based on the measurement of

  16. Locating Groundwater Pollution Source using Breakthrough Curve Characteristics and Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Kumar, J.; Jain, A.; Srivastava, R.

    2005-12-01

    are peak concentration, time to peak concentration, the widths of the breakthrough curves at 50% and 75% of the peak concentration, and the time base of the breakthrough curve. The second ANN model employs only the first four parameters leaving out the time base. The measurement of breakthrough curve at an observation well involves very high costs in sample collection at suitable time intervals and analysis for various contaminants. The receding portions of the breakthrough curves are normally very long and excluding the time base from modeling would result in considerable cost savings. The feed-forward multi-layer perceptron (MLP) type neural networks trained using the back-propagation algorithm, are employed in this study. The ANN models for the two approaches were developed using simulated data generated for conservative pollutant transport through a homogeneous aquifer. A new approach for ANN training using back-propagation is employed that considers two different error statistics to prevent over-training and under-training of the ANNs. The preliminary results indicate that the ANNs are able to identify the location of the pollution source very efficiently from both the methods of the breakthrough curves characterization.

  17. A Review of Advancements in Particulate Matter Sampling and Analysis and its Application to Identifying Source Impacts at Receptor Locations

    EPA Science Inventory

    Time-integrated (typically 24-hr) filter-based methods (historical methods) form the underpinning of our understanding of the fate, impact of source emissions at receptor locations (source impacts), and potential health and welfare effects of particulate matter (PM) in air. Over...

  18. Locating non-volcanic tremor along the San Andreas Fault using a multiple array source imaging technique

    USGS Publications Warehouse

    Ryberg, T.; Haberland, C.H.; Fuis, G.S.; Ellsworth, W.L.; Shelly, D.R.

    2010-01-01

    Non-volcanic tremor (NVT) has been observed at several subduction zones and at the San Andreas Fault (SAF). Tremor locations are commonly derived by cross-correlating envelope-transformed seismic traces in combination with source-scanning techniques. Recently, they have also been located by using relative relocations with master events, that is low-frequency earthquakes that are part of the tremor; locations are derived by conventional traveltime-based methods. Here we present a method to locate the sources of NVT using an imaging approach for multiple array data. The performance of the method is checked with synthetic tests and the relocation of earthquakes. We also applied the method to tremor occurring near Cholame, California. A set of small-aperture arrays (i.e. an array consisting of arrays) installed around Cholame provided the data set for this study. We observed several tremor episodes and located tremor sources in the vicinity of SAF. During individual tremor episodes, we observed a systematic change of source location, indicating rapid migration of the tremor source along SAF. ?? 2010 The Authors Geophysical Journal International ?? 2010 RAS.

  19. How drone flies (Eristalis tenax L., Syrphidae, Diptera) use floral guides to locate food sources.

    PubMed

    Dinkel, T; Lunau, K

    2001-09-01

    In this study we show how inexperienced syrphid flies, Eristalis tenax, orient on artificial flowers by means of floral guides. To test the effect of floral guides such as line and ring markings on the probability and speed of the location of a potential food source, we exploited the spontaneous proboscis reaction triggered by yellow colour stimuli. We tested whether and how fast the flies, when placed on the edge of a circular dummy flower, found a small central yellow spot and touched it with the proboscis extended. The flies found the central yellow spot more often and faster if guide lines from the margin to the yellow spot were present. The effect of guide lines was dependent on the colour of the dummy flower, and independent of the colour of the guide lines, except for yellow guide lines releasing the proboscis reaction. The effect of guide lines was stronger if the yellow spot was hidden in a 2 mm deep depression and thus not as easily visible to the flies. Ring guides had a significant effect on performance only when the intensity of the central yellow spot was low.

  20. Location of the Norma transient with the HEAO 1 scanning modulation collimator. [X ray source in Norma Constellation

    NASA Technical Reports Server (NTRS)

    Fabbiano, G.; Gursky, H.; Schwartz, D. A.; Schwarz, J.; Bradt, H. V.; Doxsey, R. E.

    1978-01-01

    A precise position has been obtained for an X-ray transient source in Norma. The location uncertainty includes a variable star previously suggested to be the optical counterpart. This transient is associated with the steady X-ray source MX 1608-52 and probably with an X-ray burst source. A binary system containing a low-mass primary and a neutron-star or black-hole secondary of a few solar masses is consistent with the observations.

  1. Acoustic emissions of digital data video projectors- Investigating noise sources and their change during product aging

    NASA Astrophysics Data System (ADS)

    White, Michael Shane

    2005-09-01

    Acoustic emission testing continues to be a growing part of IT and telecommunication product design, as product noise is increasingly becoming a differentiator in the marketplace. This is especially true for digital/video display companies, such as InFocus Corporation, considering the market shift of these products to the home entertainment consumer as retail prices drop and performance factors increase. Projectors and displays using Digital Light Processing(tm) [DLP(tm)] technology incorporate a device known as a ColorWheel(tm) to generate the colors displayed at each pixel in the image. These ColorWheel(tm) devices spin at very high speeds and can generate high-frequency tones not typically heard in liquid crystal displays and other display technologies. Also, acoustic emission testing typically occurs at the beginning of product life and is a measure of acoustic energy emitted at this point in the lifecycle. Since the product is designed to be used over a long period of time, there is concern as to whether the acoustic emissions change over the lifecycle of the product, whether these changes will result in a level of nuisance to the average customer, and does this nuisance begin to develop prior to the intended lifetime of the product.

  2. West Texas array experiment: Noise and source characterization of short-range infrasound and acoustic signals, along with lab and field evaluation of Intermountain Laboratories infrasound microphones

    NASA Astrophysics Data System (ADS)

    Fisher, Aileen

    spatial wind noise filtering hoses or pipes. The grid was within the distance limits of a single gauge's normal hose array, and data were used to perform a spatial noise correlation study. The highest correlation values were not found in the lower frequencies as anticipated, owing to a lack of sources in the lower range and the uncorrelated nature of wind noise. The highest values, with cross-correlation averages between 0.4 and 0.7 from 3 to 17 m between gauges, were found at night from 10 and 20 Hz due to a continuous local noise source and low wind. Data from the larger array were used to identify continuous and impulsive signals in the area that comprise the ambient noise field. Ground truth infrasound and acoustic, time and location data were taken for a highway site, a wind farm, and a natural gas compressor. Close-range sound data were taken with a single IML "traveler" gauge. Spectrograms and spectrum peaks were used to identify their source signatures. Two regional location techniques were also tested with data from the large array by using a propane cannon as a controlled, impulsive source. A comparison is presented of the Multiple Signal Classification Algorithm (MUSIC) to a simple, quadratic, circular wavefront algorithm. MUSIC was unable to effectively separate noise and source eignenvalues and eigenvectors due to spatial aliasing of the propane cannon signal and a lack of incoherent noise. Only 33 out of 80 usable shots were located by MUSIC within 100 m. Future work with the algorithm should focus on location of impulsive and continuous signals with development of methods for accurate separation of signal and noise eigenvectors in the presence of coherent noise and possible spatial aliasing. The circular wavefront algorithm performed better with our specific dataset and successfully located 70 out of 80 propane cannon shots within 100 m of the original location, 66 of which were within 20 m. This method has low computation requirements, making it well

  3. Characterization and applications of VLF/LF source locations from lightning using the Huntsville Alabama Marx Meter Array

    NASA Astrophysics Data System (ADS)

    Bitzer, Phillip M.; Christian, Hugh J.; Stewart, Mike; Burchfield, Jeff; Podgorny, Scott; Corredor, David; Hall, John; Kuznetsov, Evgeny; Franklin, Veronica

    2013-04-01

    Arrays that detect and locate the four-dimensional spacetime positions of radiation sources from lightning have largely utilized sensors sensitive to the very high frequency (VHF) regime with ˜ 15 km baselines or very low frequency/low frequency (VLF/LF) regime with ˜ 100 km baselines. This paper details initial results from the newly developed Huntsville Alabama Marx Meter Array (HAMMA), consisting of Marx meters (electric field change meters) sensitive to a frequency band ˜ 1 Hz to 400 kHz. The arrival time of HAMMA waveforms due to radiation sources from lightning are used to determine the spacetime position of these sources. The locations are compared with two well-documented and operational arrays, the National Lightning Detection Network (NLDN) and the North Alabama Lightning Mapping Array (NALMA). The standard deviation of the difference between HAMMA and NLDN locations of return strokes is 305 and 266 m in x and y, respectively, while the standard deviation of the difference between HAMMA and NALMA sources is 237, 226, and 688 m in x, y and z, respectively. We further show that NLDN intracloud locations differ in horizontal distance from the corresponding HAMMA locations by a median value of 479 m. In addition, we use HAMMA source locations to map several lightning flashes in the VLF/LF and show HAMMA sources largely map out the same electrical extent as VHF sources and provide unique insights to the properties of the discharges occurring. Finally, we show that VLF/LF sources can determine the leader polarity in several example flashes but not necessarily whether a flash comes to ground. Copyright 2013 American Geophysical Union. All rights reserved.

  4. Fan Noise Prediction System Development: Source/Radiation Field Coupling and Workstation Conversion for the Acoustic Radiation Code

    NASA Technical Reports Server (NTRS)

    Meyer, H. D.

    1993-01-01

    The Acoustic Radiation Code (ARC) is a finite element program used on the IBM mainframe to predict far-field acoustic radiation from a turbofan engine inlet. In this report, requirements for developers of internal aerodynamic codes regarding use of their program output an input for the ARC are discussed. More specifically, the particular input needed from the Bolt, Beranek and Newman/Pratt and Whitney (turbofan source noise generation) Code (BBN/PWC) is described. In a separate analysis, a method of coupling the source and radiation models, that recognizes waves crossing the interface in both directions, has been derived. A preliminary version of the coupled code has been developed and used for initial evaluation of coupling issues. Results thus far have shown that reflection from the inlet is sufficient to indicate that full coupling of the source and radiation fields is needed for accurate noise predictions ' Also, for this contract, the ARC has been modified for use on the Sun and Silicon Graphics Iris UNIX workstations. Changes and additions involved in this effort are described in an appendix.

  5. Study on the Non-contact Acoustic Inspection Method for Concrete Structures by using Strong Ultrasonic Sound source

    NASA Astrophysics Data System (ADS)

    Sugimoto, Tsuneyoshi; Uechi, Itsuki; Sugimoto, Kazuko; Utagawa, Noriyuki; Katakura, Kageyoshi

    Hammering test is widely used to inspect the defects in concrete structures. However, this method has a major difficulty in inspect at high-places, such as a tunnel ceiling or a bridge girder. Moreover, its detection accuracy is dependent on a tester's experience. Therefore, we study about the non-contact acoustic inspection method of the concrete structure using the air borne sound wave and a laser Doppler vibrometer. In this method, the concrete surface is excited by air-borne sound wave emitted with a long range acoustic device (LRAD), and the vibration velocity on the concrete surface is measured by a laser Doppler vibrometer. A defect part is detected by the same flexural resonance as the hammer method. It is already shown clearly that detection of a defect can be performed from a long distance of 5 m or more using a concrete test object. Moreover, it is shown that a real concrete structure can also be applied. However, when the conventional LRAD was used as a sound source, there were problems, such as restrictions of a measurement angle and the surrounding noise. In order to solve these problems, basic examination which used the strong ultrasonic wave sound source was carried out. In the experiment, the concrete test object which includes an imitation defect from 5-m distance was used. From the experimental result, when the ultrasonic sound source was used, restrictions of a measurement angle become less severe and it was shown that circumference noise also falls dramatically.

  6. Source motion detection, estimation, and compensation for underwater acoustics inversion by wideband ambiguity lag-Doppler filtering.

    PubMed

    Josso, Nicolas F; Ioana, Cornel; Mars, Jérôme I; Gervaise, Cédric

    2010-12-01

    Acoustic channel properties in a shallow water environment with moving source and receiver are difficult to investigate. In fact, when the source-receiver relative position changes, the underwater environment causes multipath and Doppler scale changes on the transmitted signal over low-to-medium frequencies (300 Hz-20 kHz). This is the result of a combination of multiple paths propagation, source and receiver motions, as well as sea surface motion or water column fast changes. This paper investigates underwater acoustic channel properties in a shallow water (up to 150 m depth) and moving source-receiver conditions using extracted time-scale features of the propagation channel model for low-to-medium frequencies. An average impulse response of one transmission is estimated using the physical characteristics of propagation and the wideband ambiguity plane. Since a different Doppler scale should be considered for each propagating signal, a time-warping filtering method is proposed to estimate the channel time delay and Doppler scale attributes for each propagating path. The proposed method enables the estimation of motion-compensated impulse responses, where different Doppler scaling factors are considered for the different time delays. It was validated for channel profiles using real data from the BASE'07 experiment conducted by the North Atlantic Treaty Organization Undersea Research Center in the shallow water environment of the Malta Plateau, South Sicily. This paper provides a contribution to many field applications including passive ocean tomography with unknown natural sources position and movement. Another example is active ocean tomography where sources motion enables to rapidly cover one operational area for rapid environmental assessment and hydrophones may be drifting in order to avoid additional flow noise.

  7. Tracking the MSL-SAM methane detection source location Through Mars Regional Atmospheric Modeling System (MRAMS)

    NASA Astrophysics Data System (ADS)

    Pla-García, Jorge

    2016-04-01

    1. Introduction: The putative in situ detection of methane by Sample Analysis at Mars (SAM) instrument suite on Curiosi-ty at Gale crater has garnered significant attention because of the potential implications for the presence of geological methane sources or indigenous Martian organisms [1, 2]. SAM reported detection of back-ground levels of atmospheric methane of mean value 0.69±0.25 parts per billion by volume (ppbv) at the 95% confidence interval (CI). Additionally, in four sequential measurements spanning a 60-sol period, SAM observed elevated levels of methane of 7.2±2.1 ppbv (95% CI), implying that Mars is episodically producing methane from an additional unknown source. There are many major unresolved questions regard-ing this detection: 1) What are the potential sources of the methane release? 2) What causes the rapid decrease in concentration? and 3) Where is the re-lease location? 4) How spatially extensive is the re-lease? 5) For how long is CH4 released? Regarding the first question, the source of methane, is so far not identified. It could be related with geo-logical process like methane release from clathrates [3], serpentinisation [4] and volcanism [5]; or due to biological activity from methanogenesis [6]. To answer the second question, the rapid decrease in concentration, it is important to note that the photo-chemical lifetime of methane is of order 100 years, much longer than the atmospheric mixing time scale, and thus the gas should tend to be well mixed except near a source or shortly after an episodic release. The observed spike of 7 ppb from the background of <1 ppb, and then the rapid return to the background lev-el could be due to a sink (destruction) or due to at-mospheric mixing. A wind mediated erosion process of ordinary quartz crystals was proposed to produce activated quartz grains, which sequester methane by forming covalent Si-C bonds. If this process is op-erational on Mars today, which some recent prelimi-nary studies on

  8. Surveillance of nasal and bladder cancer to locate sources of exposure to occupational carcinogens.

    PubMed Central

    Teschke, K; Morgan, M S; Checkoway, H; Franklin, G; Spinelli, J J; van Belle, G; Weiss, N S

    1997-01-01

    OBJECTIVE: To locate sources of occupational exposure to nasal and bladder carcinogens for surveillance follow up in British Columbia, Canada. METHODS: Incident cases of nasal cancer (n = 48), bladder cancer (n = 105), and population based controls (n = 159) matched for sex and age, were interviewed about their jobs, exposures, and smoking histories. Odds ratios (ORs) were calculated for 57 occupational groups with stratified exact methods to control for age, sex, and smoking. RESULTS: Occupational groups at increased risk of nasal cancer included: textile workers (six cases, OR 7.6); miners, drillers, and blasters (six cases, OR 3.5); welders (two cases, OR 3.5); pulp and paper workers (three cases, OR 3.1); and plumbers and pipefitters (two cases, OR 3.0). Nasal cancer ORs were not increased in occupations exposed to wood dust, possibly due to low exposures in local wood industries. Strongly increased risks of bladder cancer were found for sheet metal workers (four cases, OR 5.3), miners (19 cases, OR 4.5), gardeners (six cases, OR 3.7), and hairdressers (three cases, OR 3.2). Among occupations originally considered at risk, the following had increased risks of bladder cancer: painters (four cases, OR 2.8); laundry workers (five cases, OR 2.3); chemical and petroleum workers (15 cases, OR 1.8); machinists (eight cases, OR 1.6); and textile workers (three cases, OR 1.5). CONCLUSIONS: Occupational groups with increased risks and three or more cases with similar duties were selected for surveillance follow up. For nasal cancer, these included textile workers (five were garment makers) and pulp and paper workers (three performed maintenance tasks likely to entail stainless steel welding). For bladder cancer, these included miners (12 worked underground), machinists (five worked in traditional machining), hairdressers (three had applied hair dyes), and laundry workers (three were drycleaners). PMID:9245952

  9. Source Population and Acceleration Location of Suprathermal Heavy Ions in Corotating Interaction Regions

    NASA Astrophysics Data System (ADS)

    Filwett, R. J.; Desai, M. I.; Dayeh, M. A.; Broiles, T. W.

    2017-03-01

    We have analyzed the ∼20–320 keV nucleon‑1 suprathermal (ST) heavy ion abundances in 41 corotating interaction regions (CIRs) observed by the Wind spacecraft from 1995 January to 2008 December. Our results are: (1) the CIR Fe/CNO and NeS/CNO ratios vary with the sunspot number, with values being closer to average solar energetic particle event values during solar maxima and lower than nominal solar wind values during solar minima. The physical mechanism responsible for the depleted abundances during solar minimum remains an open question. (2) The Fe/CNO increases with energy in the 6 events that occurred during solar maximum, while no such trends are observed for the 35 events during solar minimum. (3) The Fe/CNO shows no correlation with the average solar wind speed. (4) The Fe/CNO is well correlated with the corresponding upstream ∼20–320 keV nucleon‑1 Fe/CNO and not with the solar wind Fe/O measured by ACE in 31 events. Using the correlations between the upstream ∼20–40 keV nucleon‑1 Fe/CNO and the ∼20–320 keV nucleon‑1 Fe/CNO in CIRs, we estimate that, on average, the ST particles traveled ∼2 au along the nominal Parker spiral field line, which corresponds to upper limits for the radial distance of the source or acceleration location of ∼1 au beyond Earth orbit. Our results are consistent with those obtained from recent surveys, and confirm that CIR ST heavy ions are accelerated more locally, and are at odds with the traditional viewpoint that CIR ions seen at 1 au are bulk solar wind ions accelerated between 3 and 5 au.

  10. Nature and location of the source of plasma sheet boundary layer ion beams

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Onsager, T. G.; Thomsen, M. F.; Gosling, J. T.

    1995-01-01

    Onsager et al. (1991) have put forward a model of the formation of the plasma sheet boundary layer (PSBL) which relies on a steady source of plasma from a spatially extended plasma sheet, together with steady equatorward and earthward ExB convection of field lines due to reconnection at a downtail neutral line. This model is a synthesis of earlier proposals and it explains such features as an electron layer exterior to the ion boundary layer, ion velocity dispersion, counter streaming beams, low-speed cutoffs in the beams. It also explains the apparent evolution of the ion beams through 'kidney bean' shaped velocity-space distributions toward quasi-isotropic shells without invoking pitch angle scattering or energy diffusion. In this paper we explore two ramifications of the model. In principle we can map, as a function of time, the downtail neutral line distance and establish whether or not it is retreating during substorm recovery. We can also reconstruct the plasma distribution function near the neutral line to see if it is most consistent with mantle or plasma sheet plasma. We perform this analysis using International Sun Earth Explorer (ISEE) Fast Plasma Experiment (FPE) data for two plasma sheet recovery events, one on March 1, 1978, and the other on April 18, 1978. On March 1, 1978, we find evidence for an initial retreat from around 110 to 160 R(sub E) in the first 15 min; little further retreat occurs thereafter. On April 18, 1978, the neutral line location ranges from as little as 40 R(sub E) tailward of the satellite to as much as 200 R(sub E), but there is no evidence for a systematic retreat. The reconstructed ion distributions for these events are most consistent with a plasma sheet origin for the March 1 case and possibly plasma mantle or low-latitude boundary layer for the April 18 case.

  11. Numerical method to compute acoustic scattering effect of a moving source.

    PubMed

    Song, Hao; Yi, Mingxu; Huang, Jun; Pan, Yalin; Liu, Dawei

    2016-01-01

    In this paper, the aerodynamic characteristic of a ducted tail rotor in hover has been numerically studied using CFD method. An analytical time domain formulation based on Ffowcs Williams-Hawkings (FW-H) equation is derived for the prediction of the acoustic velocity field and used as Neumann boundary condition on a rigid scattering surface. In order to predict the aerodynamic noise, a hybrid method combing computational aeroacoustics with an acoustic thin-body boundary element method has been proposed. The aerodynamic results and the calculated sound pressure levels (SPLs) are compared with the known method for validation. Simulation results show that the duct can change the value of SPLs and the sound directivity. Compared with the isolate tail rotor, the SPLs of the ducted tail rotor are smaller at certain azimuth.

  12. Discrete-Mode Source Development and Testing for New Seismo-Acoustic Sonar

    DTIC Science & Technology

    1998-03-01

    the English scientist, Lord Rayleigh (J.W. Strutt ) [Ref. 6] demonstrated theoretically that there exist waves that can propagate over the planar...and T.G. Muir, Aug. 1994. 6. Rayleigh , Lord (J.W. Strutt ), "On Waves Propagated along the Plane Surface of an Elastic Solid," Proceedings London...13. ABSTRACT (maximum 200 words) A seismo-acoustic sonar concept that uses guided interface waves ( Rayleigh or Schölte) is being developed to

  13. Application of Acoustic Signal Processing Techniques for Improved Underwater Source Detection and Localization

    DTIC Science & Technology

    1988-08-31

    Systems Center, San Diego; the Electric Boat Division of General ambiguities in the beam patterns, provided the bearmforming is done with Dynamics. ] the...Am. Suppl. 1. Vol. 60. Fall 1986 112th Meeting: Acoustical Socity of America A wearable multichannel signal processor for stimulation of single... electrical dynamic range 1Hi4 & Channel interaction measured by forward-masked "pla of the patient. Several processor configurations with different resonator

  14. Analogies between the measurement of acoustic impedance via the reaction on the source method and the automatic microwave vector network analyzer technique

    NASA Astrophysics Data System (ADS)

    McLean, James; Sutton, Robert; Post, John

    2003-10-01

    One useful method of acoustic impedance measurement involves the measurement of the electrical impedance ``looking into'' the electrical port of a reciprocal electroacoustic transducer. This reaction on the source method greatly facilitates the measurement of acoustic impedance by borrowing highly refined techniques to measure electrical impedance. It is also well suited for in situ acoustic impedance measurements. In order to accurately determine acoustic impedance from the measured electrical impedance, the characteristics of the transducer must be accurately known, i.e., the characteristics of the transducer must be ``removed'' completely from the data. The measurement of acoustic impedance via the measurement of the reaction on the source is analogous to modern microwave measurements made with an automatic vector network analyzer. The action of the analyzer is described as de-embedding the desired data (such as acoustic impedance) from the raw data. Such measurements are fundamentally substitution measurements in that the transducer's characteristics are determined by measuring a set of reference standards. The reaction on the source method is extended to take advantage of improvements in microwave measurement techniques which allow calibration via imperfect standard loads. This removes one of the principal weaknesses of the method in that the requirement of high-quality reference standards is relaxed.

  15. Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away

    PubMed Central

    Risch, Denise; Corkeron, Peter J.; Ellison, William T.; Van Parijs, Sofie M.

    2012-01-01

    The effect of underwater anthropogenic sound on marine mammals is of increasing concern. Here we show that humpback whale (Megaptera novaeangliae) song in the Stellwagen Bank National Marine Sanctuary (SBNMS) was reduced, concurrent with transmissions of an Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiment approximately 200 km away. We detected the OAWRS experiment in SBNMS during an 11 day period in autumn 2006. We compared the occurrence of song for 11 days before, during and after the experiment with song over the same 33 calendar days in two later years. Using a quasi-Poisson generalized linear model (GLM), we demonstrate a significant difference in the number of minutes with detected song between periods and years. The lack of humpback whale song during the OAWRS experiment was the most substantial signal in the data. Our findings demonstrate the greatest published distance over which anthropogenic sound has been shown to affect vocalizing baleen whales, and the first time that active acoustic fisheries technology has been shown to have this effect. The suitability of Ocean Acoustic Waveguide Remote Sensing technology for in-situ, long term monitoring of marine ecosystems should be considered, bearing in mind its possible effects on non-target species, in particular protected species. PMID:22253769

  16. Properties of the Solar Acoustic Source Inferred from Nonadiabatic Oscillation Spectra

    NASA Astrophysics Data System (ADS)

    Wachter, R.; Kosovichev, A. G.

    2005-07-01

    Severino et al. suggested in 2001 that observed power and cross spectra of medium-degree p-modes in velocity and intensity can be described by splitting the solar background noise into correlated, coherent, and uncoherent components. We account for the nonadiabatic nature of solar oscillations by including the perturbations of the radiative energy flux in our model for the oscillations. Our calculations show the potential to explain the observations without the ad hoc phase differences between velocity and intensity oscillations introduced in the model of Severino et al. The phases and amplitudes of the correlated noise components are obtained by fitting our nonadiabatic model to the SOHO MDI power and cross spectra. These parameters provide information about the p-mode excitation process. We show that the type and location of the source can not be uniquely determined by the properties of the resonant p-modes in power and cross spectra of velocity and intensity oscillations. However, we obtain estimates for the phases and amplitudes of the correlated noise, which we interpret in terms of isolated rapid downdrafts in intergranular lanes. This idea is supported by three-dimensional simulations of the upper solar convection zone.

  17. Controlled and in situ target strengths of the jumbo squid Dosidicus gigas and identification of potential acoustic scattering sources.

    PubMed

    Benoit-Bird, Kelly J; Gilly, William F; Au, Whitlow W L; Mate, Bruce

    2008-03-01

    This study presents the first target strength measurements of Dosidicus gigas, a large squid that is a key predator, a significant prey, and the target of an important fishery. Target strength of live, tethered squid was related to mantle length with values standardized to the length squared of -62.0, -67.4, -67.9, and -67.6 dB at 38, 70, 120, and 200 kHz, respectively. There were relatively small differences in target strength between dorsal and anterior aspects and none between live and freshly dead squid. Potential scattering mechanisms in squid have been long debated. Here, the reproductive organs had little effect on squid target strength. These data support the hypothesis that the pen may be an important source of squid acoustic scattering. The beak, eyes, and arms, probably via the sucker rings, also play a role in acoustic scattering though their effects were small and frequency specific. An unexpected source of scattering was the cranium of the squid which provided a target strength nearly as high as that of the entire squid though the mechanism remains unclear. Our in situ measurements of the target strength of free-swimming squid support the use of the values presented here in D. gigas assessment studies.

  18. Analysis and modeling of 255 source levels of merchant ships from an acoustic observatory along St. Lawrence Seaway.

    PubMed

    Simard, Yvan; Roy, Nathalie; Gervaise, Cédric; Giard, Samuel

    2016-09-01

    An ensemble of 255 spectral source levels (SSLs) of merchant ships were measured with an opportunistic seaway acoustic observatory adhering to the American National Standards Institute/Acoustical Society of America S12.64-2009 standard as much as possible, and deployed in the 350-m deep lower St. Lawrence Seaway in eastern Canada. The estimated SSLs were sensitive to the transmission loss model. The best transmission loss model at the three measuring depths was an empirical in situ function for ranges larger than 300 m, fused with estimates from a wavenumber integration propagation model fed with inverted local geoacoustic properties for [300 to 1 m] ranges. Resulting SSLs still showed a high variability. Uni- and multi-variate analyses showed weak intermingled relations with ship type, length, breadth, draught, speed, age, and other variables. Cluster analyses distinguished six different SSL patterns, which did not correspond to distinctive physical characteristics of the ships. The broadband [20-500 Hz] source levels varied by 30 dB or more within all four 50-m length categories. Common SSL models based on frequency, length and speed failed to unbiasly replicate the observations. This article presents unbiased SSL models that explain 75%-88% of the variance using frequency, ship speed, and three other automatic identification system ship characteristics.

  19. Identifying elements of the plumbing system beneath Kilauea Volcano, Hawaii, from the source locations of very-long-period signals

    USGS Publications Warehouse

    Almendros, J.; Chouet, B.; Dawson, P.; Bond, T.

    2002-01-01

    We analyzed 16 seismic events recorded by the Hawaiian broad-band seismic network at Kilauca Volcano during the period September 9-26, 1999. Two distinct types of event are identified based on their spectral content, very-long-period (VLP) waveform, amplitude decay pattern and particle motion. We locate the VLP signals with a method based on analyses of semblance and particle motion. Different source regions are identified for the two event types. One source region is located at depths of ~1 km beneath the northeast edge of the Halemaumau pit crater. A second region is located at depths of ~8 km below the northwest quadrant of Kilauea caldera. Our study represents the first time that such deep sources have been identified in VLP data at Kilauea. This discovery opens the possibility of obtaining a detailed image of the location and geometry of the magma plumbing system beneath this volcano based on source locations and moment tensor inversions of VLP signals recorded by a permanent, large-aperture broad-band network.

  20. Numerical wave modelling for seismo-acoustic noise sources: wave model accuracy issues and evidence for variable seismic attenuation

    NASA Astrophysics Data System (ADS)

    Ardhuin, F.; Lavanant, T.; Obrebski, M. J.; Marié, L.; Royer, J.

    2012-12-01

    Nonlinear wave-wave interactions generate noise that numerical ocean wave models may simulate. The accuracy of the noise source predicted by the theory of Longuet-Higgins (1950) and Hasselmann (1963) depends on the realism of the directional wave distribution, which is generally not very well known. Numerical noise models developed by Kedar et al. (2008) and Ardhuin et al. (2010) also suffer from poorly known seismic wave propagation and attenuation properties. Here, several seismic and ocean pressure records are used here to assess the effects of wave modelling errors on the magnitude of noise sources. Measurements within 200~m from the sea surface are dominated by acoustic-gravity modes, for which bottom effects are negligible. These data show that directional wave spectra are well enough reproduced to estimate seismo-acoustic noise sources at frequencies below 0.3~Hz, whith an underestimation of the noise level by about 50%. In larger water depths, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and Kerguelen islands reveal that a) deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the Rayleigh wave theory, and is well predicted up to 0.4~Hz. b) In particular, evidence of the vertical modes expected theoretically is given by the local maxima in the noise spectrum. c) noise above 0.6 Hz is not well modeled probably due to a poor estimate of the directional properties of high frequency wind-waves, d) the noise level is strongly influenced by bottom properties, in particular the presence of sediments. Further, for continental coastal seismic stations, an accurate model of noise level variability near the noise spectral peak requires an accurate modelling of coastal reflection (Ardhuin and Roland JGR 2012). In cases where noise sources are confined to a small area (e.g. Obrebski et al. GRL 2012), the source amplitude may be factored out, allowing an estimate of seismic attenuation rates

  1. 40 CFR Table 2c to Subpart Zzzz of... - Requirements for Existing Compression Ignition Stationary RICE Located at a Major Source of HAP...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Ignition Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE â¤500 HP Located at a Major Source of HAP Emissions 2c Table 2c to Subpart ZZZZ of Part 63... Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE...

  2. 40 CFR Table 2c to Subpart Zzzz of... - Requirements for Existing Compression Ignition Stationary RICE Located at a Major Source of HAP...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Ignition Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE ⤠500 HP Located at a Major Source of HAP Emissions 2c Table 2c to Subpart ZZZZ of Part 63... Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE ≤...

  3. 40 CFR Table 2c to Subpart Zzzz of... - Requirements for Existing Compression Ignition Stationary RICE Located at a Major Source of HAP...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Ignition Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE â¤500 HP Located at a Major Source of HAP Emissions 2c Table 2c to Subpart ZZZZ of Part 63... Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE...

  4. 40 CFR Table 2c to Subpart Zzzz of... - Requirements for Existing Compression Ignition Stationary RICE Located at a Major Source of HAP...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Ignition Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE ⤠500 HP Located at a Major Source of HAP Emissions 2c Table 2c to Subpart ZZZZ of Part 63... Stationary RICE Located at a Major Source of HAP Emissions and Existing Spark Ignition Stationary RICE ≤...

  5. Acoustic emission linear pulse holography

    DOEpatents

    Collins, H. Dale; Busse, Lawrence J.; Lemon, Douglas K.

    1985-01-01

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  6. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. D.; Busse, L. J.; Lemon, D. K.

    1985-07-30

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  7. Relation between near field and far field acoustic measurements

    NASA Technical Reports Server (NTRS)

    Bies, D. A.; Scharton, T. D.

    1974-01-01

    Several approaches to the problem of determining the far field directivity of an acoustic source located in a reverberant environment, such as a wind tunnel, are investigated analytically and experimentally. The decrease of sound pressure level with distance is illustrated; and the spatial extent of the hydrodynamic and geometric near fields, the far field, and the reverberant field are described. A previously-prosposed analytical technique for predicting the far field directivity of the acoustic source on the basis of near field data is investigated. Experiments are conducted with small acoustic sources and an analysis is performed to determine the variation with distance from the source of the directionality of the sound field. A novel experiment is conducted in which the sound pressure measured at various distances from an acoustic driver located in the NASA Ames 40 x 80 ft wind tunnel is crosscorrelated with the driver excitation voltage.

  8. Vibro-Acoustic Analysis of Computer Disk Drive Components with Emphasis on Electro-Mechanical Noise Sources.

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Ran

    Vibro-acoustic characteristics of compact electro -mechanical devices are not well understood. This study examines fundamental research issues in this area through the example case of a 3.5" personal computer hard disk drive. In particular, a narrow band mathematical model of the drive has been developed to predict prominent pure tones over the high frequency range (1-6.5 KHz). Through detailed analytical studies, it has been found that the motor torque pulsation of the brushless d.c. motor is the source for this noise problem. Accordingly, a simplified disk drive model consisting of motor driving a single disk is used to investigate key components, with emphasis on the development of new mathematical models to describe the source, path and radiator characteristics. Two different mathematical models have been developed for brushless d.c. motor to predict the torque spectrum associated with invertor switching logic, pulse width modulation control scheme, eccentricity, and magnetic saturation. Frequency contents of predicted variables are identified and matched with measured sound data. Additionally, the Galerkin's method (or modified harmonic balance) is also employed successfully to develop an efficient computational scheme which predicts the Fourier coefficients of torque pulsations directly including various effects associated with inductance harmonics and the fluctuation of rotor angular velocity. For the radiator (annular disk), modal base formulations of sound radiation have been developed by approximating disk eigen-functions. Specifically, the effects of modal coupling and source rotation on radiated sound are investigated. Analytical predictions match well with numerical results obtained by using a boundary element program. New mobility transfer functions (path) are derived to couple the source and radiator formulations in order to construct an overall vibro-acoustic model. Potential areas of further research including experimental validation are discussed.

  9. A comparison of summertime secondary organic aerosol source contributions at contrasting urban locations.

    PubMed

    Stone, Elizabeth A; Zhou, Jiabin; Snyder, David C; Rutter, Andrew P; Mieritz, Mark; Schauer, James J

    2009-05-15

    Primary and secondary sources contributing to atmospheric organic aerosol during the months of July and August were quantitatively assessed in three North American urban areas: Cleveland, Ohio, and Detroit, Michigan, in the Midwest region and Riverside, California, in the Los Angeles Air Basin. Organic molecular marker species unique to primary aerosol sources and secondarytracers derived from isoprene, alpha-pinene, beta-caryophyllene, and toluene were measured using gas chromatography-mass spectrometry. Source contributions from motor vehicles, biomass burning, vegetative detritus, and secondary organic aerosol (SOA) were estimated using chemical mass balance (CMB) modeling. In Cleveland, primary sources accounted for 37 +/- 2% of ambient organic carbon, measured biogenic and anthropogenic secondary sources contributed 46 +/- 6%, and other unknown sources contributed 17 +/- 4%. Similarly, Detroit aerosol was determined to be 44 +/- 5% primary and 37 +/- 3% secondary, while 19 +/- 7% was unaccounted for by measured sources. In Riverside, 21 +/- 3% of organic carbon came from primary sources, 26 +/- 5% was attributed to measured secondary sources, and 53 +/- 3% came from other sources that were expected to be secondary in nature. The comparison of samples across these two regions demonstrated that summertime SOA in the Midwestern United States was substantially different from the summertime SOA in the Los Angeles Air Basin and indicated the need to exert caution when generalizing about the sources and nature of SOA across different urban areas. Furthermore, the results of this study suggestthatthe contemporary understanding of SOA sources and formation mechanisms is satisfactory to explainthe majority of SOA in the Midwest Additional SOA sources and mechanisms of formation are needed to explain the majority of SOA in the Los Angeles Air Basin.

  10. Estimation of source location and ground impedance using a hybrid multiple signal classification and Levenberg-Marquardt approach

    NASA Astrophysics Data System (ADS)

    Tam, Kai-Chung; Lau, Siu-Kit; Tang, Shiu-Keung

    2016-07-01

    A microphone array signal processing method for locating a stationary point source over a locally reactive ground and for estimating ground impedance is examined in detail in the present study. A non-linear least square approach using the Levenberg-Marquardt method is proposed to overcome the problem of unknown ground impedance. The multiple signal classification method (MUSIC) is used to give the initial estimation of the source location, while the technique of forward backward spatial smoothing is adopted as a pre-processer of the source localization to minimize the effects of source coherence. The accuracy and robustness of the proposed signal processing method are examined. Results show that source localization in the horizontal direction by MUSIC is satisfactory. However, source coherence reduces drastically the accuracy in estimating the source height. The further application of Levenberg-Marquardt method with the results from MUSIC as the initial inputs improves significantly the accuracy of source height estimation. The present proposed method provides effective and robust estimation of the ground surface impedance.

  11. Deconvolution of acoustic emissions for source localization using time reverse modeling

    NASA Astrophysics Data System (ADS)

    Kocur, Georg Karl

    2017-01-01

    Impact experiments on small-scale slabs made of concrete and aluminum were carried out. Wave motion radiated from the epicenter of the impact was recorded as voltage signals by resonant piezoelectric transducers. Numerical simulations of the elastic wave propagation are performed to simulate the physical experiments. The Hertz theory of contact is applied to estimate the force impulse, which is subsequently used for the numerical simulation. Displacements at the transducer positions are calculated numerically. A deconvolution function is obtained by comparing the physical (voltage signal) and the numerical (calculated displacement) experiments. Acoustic emission signals due to pencil-lead breaks are recorded, deconvolved and applied for localization using time reverse modeling.

  12. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  13. Efficient Location of Research Reference Sources in the Field of Dance.

    ERIC Educational Resources Information Center

    Kissinger, Pat; Jay, Danielle

    More than 45 basic dance reference research sources that would be useful to students, scholars, teachers, historians, and therapists are discussed in this bibliographic essay. Aspects of dance covered include choreography, criticism, teaching principles, aesthetic theory, dance therapy, and history. Sources are grouped by type: dictionaries and…

  14. Wave field synthesis of a virtual source located in proximity to a loudspeaker array.

    PubMed

    Lee, Jung-Min; Choi, Jung-Woo; Kim, Yang-Hann

    2013-09-01

    For the derivation of 2.5-dimensional operator in wave field synthesis, a virtual source is assumed to be positioned far from a loudspeaker array. However, such far-field approximation inevitably results in a reproduction error when the virtual source is placed adjacent to an array. In this paper, a method is proposed to generate a virtual source close to and behind a continuous line array of loudspeakers. A driving function is derived by reducing a surface integral (Rayleigh integral) to a line integral based on the near-field assumption. The solution is then combined with the far-field formula of wave field synthesis by introducing a weighting function that can adjust the near- and far-field contribution of each driving function. This enables production of a virtual source anywhere in relation to the array. Simulations show the proposed method can reduce the reproduction error to below -18 dB, regardless of the virtual source position.

  15. Measurement of Insertion Loss of an Acoustic Treatment in the Presence of Additional Uncorrelated Sound Sources

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Palumbo, Daniel L.

    2003-01-01

    A method to intended for measurement of the insertion loss of an acoustic treatment applied to an aircraft fuselage in-situ is documented in this paper. Using this method, the performance of a treatment applied to a limited portion of an aircraft fuselage can be assessed even though the untreated fuselage also radiates into the cabin, corrupting the intensity measurement. This corrupting noise in the intensity measurement incoherent with the panel vibration of interest is removed by correlating the intensity to reference transducers such as accelerometers. Insertion loss of the acoustic treatments is estimated from the ratio of correlated intensity measurements with and without a treatment applied. In the case of turbulent boundary layer excitation of the fuselage, this technique can be used to assess the performance of noise control methods without requiring treatment of the entire fuselage. Several experimental studies and numerical simulations have been conducted, and results from three case studies are documented in this paper. Conclusions are drawn about the use of this method to study aircraft sidewall treatments.

  16. Source estimates for MEG/EEG visual evoked responses constrained by multiple, retinotopically-mapped stimulus locations.

    PubMed

    Hagler, Donald J; Halgren, Eric; Martinez, Antigona; Huang, Mingxiong; Hillyard, Steven A; Dale, Anders M

    2009-04-01

    Studying the human visual system with high temporal resolution is a significant challenge due to the limitations of the available, noninvasive measurement tools. MEG and EEG provide the millisecond temporal resolution necessary for answering questions about intracortical communication involved in visual processing, but source estimation is ill-posed and unreliable when multiple; simultaneously active areas are located close together. To address this problem, we have developed a retinotopy-constrained source estimation method to calculate the time courses of activation in multiple visual areas. Source estimation was disambiguated by: (1) fixing MEG/EEG generator locations and orientations based on fMRI retinotopy and surface tessellations constructed from high-resolution MRI images; and (2) solving for many visual field locations simultaneously in MEG/EEG responses, assuming source current amplitudes to be constant or varying smoothly across the visual field. Because of these constraints on the solutions, estimated source waveforms become less sensitive to sensor noise or random errors in the specification of the retinotopic dipole models. We demonstrate the feasibility of this method and discuss future applications such as studying the timing of attentional modulation in individual visual areas.

  17. Alignment of leading-edge and peak-picking time of arrival methods to obtain accurate source locations

    SciTech Connect

    Roussel-Dupre, R.; Symbalisty, E.; Fox, C.; and Vanderlinde, O.

    2009-08-01

    The location of a radiating source can be determined by time-tagging the arrival of the radiated signal at a network of spatially distributed sensors. The accuracy of this approach depends strongly on the particular time-tagging algorithm employed at each of the sensors. If different techniques are used across the network, then the time tags must be referenced to a common fiducial for maximum location accuracy. In this report we derive the time corrections needed to temporally align leading-edge, time-tagging techniques with peak-picking algorithms. We focus on broadband radio frequency (RF) sources, an ionospheric propagation channel, and narrowband receivers, but the final results can be generalized to apply to any source, propagation environment, and sensor. Our analytic results are checked against numerical simulations for a number of representative cases and agree with the specific leading-edge algorithm studied independently by Kim and Eng (1995) and Pongratz (2005 and 2007).

  18. Acoustic attenuation, phase and group velocities in liquid-filled pipes II: simulation for Spallation Neutron Sources and planetary exploration.

    PubMed

    Jiang, Jian; Baik, Kyungmin; Leighton, Timothy G

    2011-08-01

    This paper uses a finite element method (FEM) to compare predictions of the attenuation and sound speeds of acoustic modes in a fluid-filled pipe with those of the analytical model presented in the first paper in this series. It explains why, when the predictions of the earlier paper were compared with experimental data from a water-filled PMMA pipe, the uncertainties and agreement for attenuation data were worse than those for sound speed data. Having validated the FEM approach in this way, the versatility of FEM is thereafter demonstrated by modeling two practical applications which are beyond the analysis of the earlier paper. These applications model propagation in the mercury-filled steel pipework of the Spallation Neutron Source at the Oak Ridge National Laboratory (Tennessee), and in a long-standing design for acoustic sensors for use on planetary probes. The results show that strong coupling between the fluid and the solid walls means that erroneous interpretations are made of the data if they assume that the sound speed and attenuation in the fluid in the pipe are the same as those that would be measured in an infinite volume of identical fluid, assumptions which are common when such data have previously been interpreted.

  19. Acoustics Research of Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Gao, Ximing; Houston, Janice

    2014-01-01

    The liftoff phase induces high acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are used in the prediction of the internal vibration responses of the vehicle and components. Present liftoff vehicle acoustic environment prediction methods utilize stationary data from previously conducted hold-down tests to generate 1/3 octave band Sound Pressure Level (SPL) spectra. In an effort to update the accuracy and quality of liftoff acoustic loading predictions, non-stationary flight data from the Ares I-X were processed in PC-Signal in two flight phases: simulated hold-down and liftoff. In conjunction, the Prediction of Acoustic Vehicle Environments (PAVE) program was developed in MATLAB to allow for efficient predictions of sound pressure levels (SPLs) as a function of station number along the vehicle using semi-empirical methods. This consisted of generating the Dimensionless Spectrum Function (DSF) and Dimensionless Source Location (DSL) curves from the Ares I-X flight data. These are then used in the MATLAB program to generate the 1/3 octave band SPL spectra. Concluding results show major differences in SPLs between the hold-down test data and the processed Ares I-X flight data making the Ares I-X flight data more practical for future vehicle acoustic environment predictions.

  20. Location of odor sources and the affected population in Imperial County, California

    SciTech Connect

    Hahn, J.L.

    1981-08-01

    This report is divided into four sections. The first two sections contain general background information on Imperial County. The third section is a general discussion of odor sources in Imperial County, and the fourth maps the specific odor sources, the expected areas of perception, and the affected populations. this mapping is done for the Imperial Valley and each of the four Imperial County KGRA's (Known Geothermal Resource Areas) where odor from the development of the geothermal energy may affect population.

  1. Source location determination of Uranian kilometric radiation from ray tracing and emission lobe modelling

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    1991-01-01

    We use an analytical fit to an emission lobe profile together with three-dimensional ray tracing to model the broad-banded smooth Uranian kilometric radiation (UKR). We assume the radiation is gyroemission from sources along magnetic field lines. Using an iterative technique that modifies the lobe function and source region, the results are compared to observations at a frequency of 481 kHz. The best-fit calculations are compared to previously published models and to recent ultraviolet (UV) observations.

  2. Acoustic Scattering by Three-Dimensional Stators and Rotors Using the SOURCE3D Code. Volume 1; Analysis and Results

    NASA Technical Reports Server (NTRS)

    Meyer, Harold D.

    1999-01-01

    This report provides a study of rotor and stator scattering using the SOURCE3D Rotor Wake/Stator Interaction Code. SOURCE3D is a quasi-three-dimensional computer program that uses three-dimensional acoustics and two-dimensional cascade load response theory to calculate rotor and stator modal reflection and transmission (scattering) coefficients. SOURCE3D is at the core of the TFaNS (Theoretical Fan Noise Design/Prediction System), developed for NASA, which provides complete fully coupled (inlet, rotor, stator, exit) noise solutions for turbofan engines. The reason for studying scattering is that we must first understand the behavior of the individual scattering coefficients provided by SOURCE3D, before eventually understanding the more complicated predictions from TFaNS. To study scattering, we have derived a large number of scattering curves for vane and blade rows. The curves are plots of output wave power divided by input wave power (in dB units) versus vane/blade ratio. Some of these plots are shown in this report. All of the plots are provided in a separate volume. To assist in understanding the plots, formulas have been derived for special vane/blade ratios for which wavefronts are either parallel or normal to rotor or stator chords. From the plots, we have found that, for the most part, there was strong transmission and weak reflection over most of the vane/blade ratio range for the stator. For the rotor, there was little transmission loss.

  3. 43 CFR 3746.1 - Mining locations for fissionable source materials.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... said Atomic Energy Act, would have been locatable under such mining laws, shall, insofar as adversely...) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) PUBLIC LAW 585; MULTIPLE... materials. (a) In view of the amendment of section 5(b)(7) of the Atomic Energy Act of 1946 by section...

  4. Experimental study of noise sources and acoustic propagation in a turbofan model

    NASA Astrophysics Data System (ADS)

    Lewy, S.; Canard-Caruana, S.; Julliard, J.

    1990-10-01

    Experimental studies of the acoustic radiation of subsonic fans mainly due to blade and vane presure fluctuations were performed in the SNECMA 5C2 compressor anechoic facility. A brief description of the test rig is presented noting that the CA5 turbojet engine model fan has a diameter of 47 cm, 48 blades, and a nominal rotation speed of 12,600 rpm. The two chief experiments discussed are the measurement of blade and vane pressure fluctuations by thin-film transducers and the spinning mode analysis of the sound field propagating in the intake duct. Several examples of applications are discussed, and it is shown that an inflow control device, as expected, reduces the aerodynamic disturbances by about 10 dB. Rotor-stator interaction tones are determined by the modal analysis, and it is found that a duct lining with a length of one duct radius could give an insertion loss up to 20 dB in flight.

  5. Acoustic source localization using time-difference of arrival and neural-network analysis

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Dong, Jiancheng; Ying, Ren D.

    2013-03-01

    The developing embedded technology requires revolutions in human-machine interaction. In this paper, we propose a novel method using localization of the taping sound on the table to replace the keyboard as manual input device. The method is applicable with a quad-channel-array collection of acoustic signals, from which the time-of-arrival differences and the position information could be estimated. In practice, as our table is in a limited size and the material properties are complex, the traditional localization algorithm based on time-of-arrival differences contains a sizable margin for error. Furthermore, we use neural-network analysis to improve recognition accuracy. Then experiments and simulations are carried out to verify this signal processing algorithm.

  6. Growth and optimization of piezoelectric single crystal transducers for energy harvesting from acoustic sources

    NASA Astrophysics Data System (ADS)

    Dhar, Romit

    Low power requirements of modern sensors and electronics have led to the examination of the feasibility of several energy harvesting schemes. This thesis describes the fabrication and performance of an acoustic energy harvester with single crystal piezoelectric unimorph. The unimorphs were fabricated from single crystal relaxor ferroelectric (1-x)PMN - xPT grown with x = 0.3 and 0.32 as the starting composition. It is demonstrated that significant power can be harvested using unimorph structures from an acoustic field at resonance. Passive circuit components were used for output circuit with a resistive load in series with a tunable inductor. A tuning capacitor connected in parallel to the device further increased the power output by matching the impedance of the unimorph. The power harvested can be either used directly for running low-power devices or can be stored in a rechargeable battery. A comparison of the performance of PMN-PT and PZT unimorphs at the resonance of the coupled structure under identical excitation conditions was done. For a certain optimized thickness ratio and circuit parameters, the single crystal PMN-PT unimorph generated 30 mW of power while a PZT unimorph generated 7.5 mW at resonance and room temperature. The harvested output power from the single crystal PMN-PT unimorphs depends on several material properties, physical and ambient parameters and an effort has been made to study their effect on the performance. A self-seeding high pressure Bridgman (HPB) technique was used to grow the PMN-PT single crystal ingots in a cost-effective way in our laboratories. Several techniques of material processing were developed to fabricate the PMN-PT single crystal unimorphs from as grown bulk ingots. This growth technique produced good quality single crystals for our experiments, with a k33 = 0.91 for a <001> oriented bar.

  7. Differentiation between sources of mechanoluminescence and acoustic emission in impact-loaded ZnSe and ZnS ceramics.

    PubMed

    Chmel, Alexandre; Dunaev, Anatolij; Shcherbakov, Igor

    2017-03-09

    Ductile semiconductor ceramics ZnSe and ZnS were damaged by a falling weight, and the time series of mechanoluminescence (ML) and acoustic emission (AE) pulses were recorded with the nanosecond resolution. The ML lighting appeared in the instance of shock but the AE generation emerged with a delay of 50-100 μsec; however, the maxima of the light and sound emissions coincided in time. This difference in temporal profiles was explained by the difference in prevailing sources of emissions of two types. The detected luminescence in A2 B6 compounds was excited, mainly, by moving and multiplying dislocations, while the sound was generated by nucleating and growing cracks. The statistical analysis showed that at the stage of pre-failure deformation, the ensemble of dislocations exhibited a trend to self-organizing; the cracking was fully random. The effect of intergranular boundaries on the dislocation motion manifested itself in the statistics of mechanoluminescence generation.

  8. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  9. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  10. Fuel from wastewater : harnessing a potential energy source in Canada through the co-location of algae biofuel production to sources of effluent, heat and CO2.

    SciTech Connect

    Passell, Howard David; Whalen, Jake; Pienkos, Philip P.; O'Leary, Stephen J.; Roach, Jesse Dillon; Moreland, Barbara D.; Klise, Geoffrey Taylor

    2010-12-01

    Sandia National Laboratories is collaborating with the National Research Council (NRC) Canada and the National Renewable Energy Laboratory (NREL) to develop a decision-support model that will evaluate the tradeoffs associated with high-latitude algae biofuel production co-located with wastewater, CO2, and waste heat. This project helps Canada meet its goal of diversifying fuel sources with algae-based biofuels. The biofuel production will provide a wide range of benefits including wastewater treatment, CO2 reuse and reduction of demand for fossil-based fuels. The higher energy density in algae-based fuels gives them an advantage over crop-based biofuels as the 'production' footprint required is much less, resulting in less water consumed and little, if any conversion of agricultural land from food to fuel production. Besides being a potential source for liquid fuel, algae have the potential to be used to generate electricity through the burning of dried biomass, or anaerobically digested to generate methane for electricity production. Co-locating algae production with waste streams may be crucial for making algae an economically valuable fuel source, and will certainly improve its overall ecological sustainability. The modeling process will address these questions, and others that are important to the use of water for energy production: What are the locations where all resources are co-located, and what volumes of algal biomass and oil can be produced there? In locations where co-location does not occur, what resources should be transported, and how far, while maintaining economic viability? This work is being funded through the U.S. Department of Energy (DOE) Biomass Program Office of Energy Efficiency and Renewable Energy, and is part of a larger collaborative effort that includes sampling, strain isolation, strain characterization and cultivation being performed by the NREL and Canada's NRC. Results from the NREL / NRC collaboration including specific

  11. 40 CFR Table 2d to Subpart Zzzz of... - Requirements for Existing Stationary RICE Located at Area Sources of HAP Emissions

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... RICE Located at Area Sources of HAP Emissions 2d Table 2d to Subpart ZZZZ of Part 63 Protection of... 2d Table 2d to Subpart ZZZZ of Part 63—Requirements for Existing Stationary RICE Located at Area... requirements for existing stationary RICE located at area sources of HAP emissions: For each . . . You...

  12. 40 CFR Table 2d to Subpart Zzzz of... - Requirements for Existing Stationary RICE Located at Area Sources of HAP Emissions

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... RICE Located at Area Sources of HAP Emissions 2d Table 2d to Subpart ZZZZ of Part 63 Protection of... 2d Table 2d to Subpart ZZZZ of Part 63—Requirements for Existing Stationary RICE Located at Area... requirements for existing stationary RICE located at area sources of HAP emissions: For each . . . You...

  13. 40 CFR Table 2d to Subpart Zzzz of... - Requirements for Existing Stationary RICE Located at Area Sources of HAP Emissions

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... RICE Located at Area Sources of HAP Emissions 2d Table 2d to Subpart ZZZZ of Part 63 Protection of... 2d Table 2d to Subpart ZZZZ of Part 63—Requirements for Existing Stationary RICE Located at Area... requirements for existing stationary RICE located at area sources of HAP emissions: For each . . . You...

  14. 40 CFR Table 2d to Subpart Zzzz of... - Requirements for Existing Stationary RICE Located at Area Sources of HAP Emissions

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... RICE Located at Area Sources of HAP Emissions 2d Table 2d to Subpart ZZZZ of Part 63 Protection of... 2d Table 2d to Subpart ZZZZ of Part 63—Requirements for Existing Stationary RICE Located at Area... requirements for existing stationary RICE located at area sources of HAP emissions: For each . . . You...

  15. Lithospheric Models of the Middle East to Improve Seismic Source Parameter Determination/Event Location Accuracy

    DTIC Science & Technology

    2012-09-01

    structure of Saudi Arabia through data collection from broadband stations. Figure 2. (Left) Map of Arabian Plate showing major tectonic ...State Award Nos. DE-AC52-07NA27344/24.2.3.2 and DOS_SIAA-11-AVC/NMA-1 ABSTRACT The Middle East is a tectonically complex and seismically...active region. The ability to accurately locate earthquakes and other seismic events in this region is complicated by tectonics , the uneven

  16. Fast 3D elastic micro-seismic source location using new GPU features

    NASA Astrophysics Data System (ADS)

    Xue, Qingfeng; Wang, Yibo; Chang, Xu

    2016-12-01

    In this paper, we describe new GPU features and their applications in passive seismic - micro-seismic location. Locating micro-seismic events is quite important in seismic exploration, especially when searching for unconventional oil and gas resources. Different from the traditional ray-based methods, the wave equation method, such as the method we use in our paper, has a remarkable advantage in adapting to low signal-to-noise ratio conditions and does not need a person to select the data. However, because it has a conspicuous deficiency due to its computation cost, these methods are not widely used in industrial fields. To make the method useful, we implement imaging-like wave equation micro-seismic location in a 3D elastic media and use GPU to accelerate our algorithm. We also introduce some new GPU features into the implementation to solve the data transfer and GPU utilization problems. Numerical and field data experiments show that our method can achieve a more than 30% performance improvement in GPU implementation just by using these new features.

  17. Hybrid CFD/CAA Modeling for Liftoff Acoustic Predictions

    NASA Technical Reports Server (NTRS)

    Strutzenberg, Louise L.; Liever, Peter A.

    2011-01-01

    This paper presents development efforts at the NASA Marshall Space flight Center to establish a hybrid Computational Fluid Dynamics and Computational Aero-Acoustics (CFD/CAA) simulation system for launch vehicle liftoff acoustics environment analysis. Acoustic prediction engineering tools based on empirical jet acoustic strength and directivity models or scaled historical measurements are of limited value in efforts to proactively design and optimize launch vehicles and launch facility configurations for liftoff acoustics. CFD based modeling approaches are now able to capture the important details of vehicle specific plume flow environment, identifY the noise generation sources, and allow assessment of the influence of launch pad geometric details and sound mitigation measures such as water injection. However, CFD methodologies are numerically too dissipative to accurately capture the propagation of the acoustic waves in the large CFD models. The hybrid CFD/CAA approach combines the high-fidelity CFD analysis capable of identifYing the acoustic sources with a fast and efficient Boundary Element Method (BEM) that accurately propagates the acoustic field from the source locations. The BEM approach was chosen for its ability to properly account for reflections and scattering of acoustic waves from launch pad structures. The paper will present an overview of the technology components of the CFD/CAA framework and discuss plans for demonstration and validation against test data.

  18. Identifying constituent spectra sources in multispectral images to quantify and locate cervical neoplasia

    NASA Astrophysics Data System (ADS)

    Baker, Kevin C.; Bambot, Shabbir

    2011-02-01

    Optical spectroscopy has been shown to be an effective method for detecting neoplasia. Guided Therapeutics has developed LightTouch, a non invasive device that uses a combination of reflectance and fluorescence spectroscopy for identifying early cancer of the human cervix. The combination of the multispectral information from the two spectroscopic modalities has been shown to be an effective method to screen for cervical cancer. There has however been a relative paucity of work in identifying the individual spectral components that contribute to the measured fluorescence and reflectance spectra. This work aims to identify the constituent source spectra and their concentrations. We used non-negative matrix factorization (NNMF) numerical methods to decompose the mixed multispectral data into the constituent spectra and their corresponding concentrations. NNMF is an iterative approach that factorizes the measured data into non-negative factors. The factors are chosen to minimize the root-mean-squared residual error. NNMF has shown promise for feature extraction and identification in the fields of text mining and spectral data analysis. Since both the constituent source spectra and their corresponding concentrations are assumed to be non-negative by nature NNMF is a reasonable approach to deconvolve the measured multispectral data. Supervised learning methods were then used to determine which of the constituent spectra sources best predict the amount of neoplasia. The constituent spectra sources found to best predict neoplasia were then compared with spectra of known biological chromophores.

  19. Technique to determine location of radio sources from measurements taken on spinning spacecraft

    NASA Technical Reports Server (NTRS)

    Fainberg, J.

    1979-01-01

    The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.

  20. Location of usual source of care among children and adolescents in the US, 1997–2013

    PubMed Central

    Simon, Alan E.; Rossen, Lauren; Schoendorf, Kenneth C.; Larson, Kandyce; Olson, Lynn M.

    2016-01-01

    Objectives To examine national trends in the percentage of children whose usual source of care is at a clinic, health center, or hospital outpatient department (hereafter “clinics”) and whether trends differ by sociodemographic subpopulations. Clinics have a greater percentage of patients from vulnerable populations than do physician’s offices and trends in their use as a usual source of care have not previously been described. Study design Analysis of serial, cross-sectional, nationally representative in-person household surveys, the 1997–2013 National Health Interview Surveys, was conducted to identify children with a usual source of care (n=190,571), and the percentage receiving that care in a clinic. We used Joinpoint regression to identify changes in linear trends, and logistic regression with predictive margins to obtain per-year changes in percentages, both unadjusted and adjusted for sociodemographic factors. Interaction terms in logistic regressions were used to assess whether trends varied by sociodemographic subgroups. Results Of all children with a usual source of care, the percentage receiving that care in a clinic declined 0.44 percentage points per year (p<0.001) from 22.97% in 1997 to 19.31% in 2002. Thereafter, it increased approximately 0.57 percentage points per year (p<0.001), reaching 26.1% in 2013. Trends for some sociodemographic subgroups varied from these overall trends. No changes were observed between 2003 and 2013 for non-Hispanic black and Medicaid/SCHIP insured children. Conclusions This study shows that, although the percentage of children with a usual source of care in a clinic declined between 1997 and 2002, it has steadily increased since that time. PMID:26454575

  1. Normalization and source separation of acoustic emission signals for condition monitoring and fault detection of multi-cylinder diesel engines

    NASA Astrophysics Data System (ADS)

    Wu, Weiliang; Lin, Tian Ran; Tan, Andy C. C.

    2015-12-01

    A signal processing technique is presented in this paper to normalize and separate the source of non-linear acoustic emission (AE) signals of a multi-cylinder diesel engine for condition monitoring applications and fault detection. The normalization technique presented in the paper overcomes the long-existing non-linearity problem of AE sensors so that responses measured by different AE sensors can be quantitatively analysed and compared. A source separation algorithm is also developed in the paper to separate the mixture of the normalized AE signals produced by a multi-cylinder diesel engine by utilising the system parameters (i.e., wave attenuation constant and the arrival time delay) of AE wave propagation determined by a standard pencil lead break test on the engine cylinder head. It is shown that the source separation algorithm is able to separate the signal interference of adjacent cylinders from the monitored cylinder once the wave attenuation constant and the arrival time delay along the propagation path are known. The algorithm is particularly useful in the application of AE technique for condition monitoring of small-size diesel engines where signal interference from the neighbouring cylinders is strong.

  2. Acoustic Source Localization via Time Difference of Arrival Estimation for Distributed Sensor Networks Using Tera-Scale Optical Core Devices

    DOE PAGES

    Imam, Neena; Barhen, Jacob

    2009-01-01

    For real-time acoustic source localization applications, one of the primary challenges is the considerable growth in computational complexity associated with the emergence of ever larger, active or passive, distributed sensor networks. These sensors rely heavily on battery-operated system components to achieve highly functional automation in signal and information processing. In order to keep communication requirements minimal, it is desirable to perform as much processing on the receiver platforms as possible. However, the complexity of the calculations needed to achieve accurate source localization increases dramatically with the size of sensor arrays, resulting in substantial growth of computational requirements that cannot bemore » readily met with standard hardware. One option to meet this challenge builds upon the emergence of digital optical-core devices. The objective of this work was to explore the implementation of key building block algorithms used in underwater source localization on the optical-core digital processing platform recently introduced by Lenslet Inc. This demonstration of considerably faster signal processing capability should be of substantial significance to the design and innovation of future generations of distributed sensor networks.« less

  3. Acoustics Research of Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Gao, Ximing; Houston, Janice D.

    2014-01-01

    The liftoff phase induces some of the highest acoustic loading over a broad frequency for a launch vehicle. These external acoustic environments are used in the prediction of the internal vibration responses of the vehicle and components. Thus, predicting these liftoff acoustic environments is critical to the design requirements of any launch vehicle but there are challenges. Present liftoff vehicle acoustic environment prediction methods utilize stationary data from previously conducted hold-down tests; i.e. static firings conducted in the 1960's, to generate 1/3 octave band Sound Pressure Level (SPL) spectra. These data sets are used to predict the liftoff acoustic environments for launch vehicles. To facilitate the accuracy and quality of acoustic loading, predictions at liftoff for future launch vehicles such as the Space Launch System (SLS), non-stationary flight data from the Ares I-X were processed in PC-Signal in two forms which included a simulated hold-down phase and the entire launch phase. In conjunction, the Prediction of Acoustic Vehicle Environments (PAVE) program was developed in MATLAB to allow for efficient predictions of sound pressure levels (SPLs) as a function of station number along the vehicle using semiempirical methods. This consisted, initially, of generating the Dimensionless Spectrum Function (DSF) and Dimensionless Source Location (DSL) curves from the Ares I-X flight data. These are then used in the MATLAB program to generate the 1/3 octave band SPL spectra. Concluding results show major differences in SPLs between the hold-down test data and the processed Ares IX flight data making the Ares I-X flight data more practical for future vehicle acoustic environment predictions.

  4. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor; Hearing loss - acoustic; Tinnitus - acoustic ... Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are uncommon.

  5. Acoustic emission monitoring of structural perturbations with serially multiplexed optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Liang, Yujin; Sun, Changsen; Ansari, Farhad

    2005-05-01

    Damage location and damage state identification of a hybrid Carbon-glass FRP rod was performed by means of a serially multiplexed fiber optic acoustic emission sensor. The detection and identification of acoustic emission signals along a single data stream reduces the data acquisition rigor and provides for rapid real time damage location detection in materials. Linear source location method and signature frequency spectra energy of acoustic emission signals were employed for locating the fiber breakage and distinguishing the damage state in the hybrid FRP rod, respectively.

  6. Bayesian hindcast of acoustic transmission loss in the western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Palmsten, Margaret; Paquin Fabre, J.

    2016-09-01

    A Bayesian network is developed to demonstrate the feasibility of using environmental acoustic feature vectors (EAFVs) to predict underwater acoustic transmission loss (TL) versus range at two locations for a single acoustic source depth and frequency. Features for the networks are chosen based on a sensitivity analysis. The final network design resulted in a well-trained network, with high skill, little gain error, and low bias. The capability presented here shows promise for expansion to a more generalized approach, which could be applied at varying locations, depths and frequencies to estimate acoustic performance over a highly variable oceanographic area in real-time or near-real-time.

  7. Planetary surface research with acoustic sounding

    NASA Astrophysics Data System (ADS)

    Krause, C.; Seidensticker, K. J.

    2007-08-01

    Planetary space missions like Rosetta and ExoMars put more and more emphasis on the in-situ investigation of planetary surfaces. The use of mechanical vibrations in the audible frequency range provide a new means to study the structure and properties of the surface layers of terrestrial planets and minor bodies like comets. As the first of this new type of instruments, the Comet Acoustic Surface Sounding Experiment (CASSE) on the Rosetta Lander Philae intends to determine elastic parameters and the structure of the surface layer of the target comet. One drawback of CASSE is unknown possibly weak coupling to the cometary surface. A DFG project is being conducted at the DLR - Deutsches Zentrum für Luft- und Raumfahrt - to test the applicability of planetary penetration instruments like PLUTO, planetary sampling tool, developed for the Mars Express lander Beagle 2, or MUPUS, a heat probe instrument also on Philae, as stronger acoustic sources as well as to develop new methods for the analysis of acoustic data. From the analysis of the polarisation of the recorded acoustic signals it is possible to separate the mixture of different propagating wave types. These identified waves can be used for the determination of mechanical soil properties and near-surface layering. We also will present how acoustic receivers can be used to locate acoustic penetrators or nearby seismic sources using the travel time and/or the polarisation of the acoustic waves.

  8. Beamforming for directional sources: additional estimator and evaluation of performance under different acoustic scenarios.

    PubMed

    Bouchard, Christian; Havelock, David I; Bouchard, Martin

    2011-04-01

    Beamforming is done with an array of sensors to achieve a directional or spatially-specific response by using a model of the arriving wavefront. Conventionally, a plane wave or point source model is used and this can cause decreased array gain or even total breakdown of beamforming when the source is directional. To avoid this, the authors proposed in recent work an alternative beamforming method which defines a set of "sub-beamformers," each designed to respond to a different spatial mode of the source. The outputs of the individual sub-beamformers are combined in a weighted sum to give an overall output of better quality than that of a monopole beamformer. This paper extends the previous work by introducing an additional estimator for the weighted sum and by presenting simulation results to demonstrate the relative performance of the proposed method and the different estimators for a directional source in the presence of diffuse noise, reverberation, and an interfering source. Gain optimization subject to a constraint on the white-noise gain with the proposed beamforming method is also introduced. Generally, when beamforming on directional sources, the proposed method outperforms beamforming with a point source model when the input signal-to-noise ratio (SNR) is 0 dB or higher.

  9. Locating very high energy gamma ray sources with arc minute accuracy

    NASA Technical Reports Server (NTRS)

    Akerlof, C. W.; Cawley, M. F.; Chantell, M.; Fegan, D. J.; Harris, K.; Hillas, A. M.; Jennings, D. G.; Lamb, R. C.; Lawrence, M. A.; Lang, M. J.

    1992-01-01

    The angular accuracy of gamma-ray detectors is intrinsically limited by the physical processes involved in photon detection. Although a number of point-like sources were detected by the COS-B satellite, only two were unambiguously identified by time signature with counterparts at longer wavelengths. By taking advantage of the extended longitudinal structure of Very High Energy gamma-ray showers, measurements in the TeV energy range can pinpoint source coordinates to arc minute accuracy. This was demonstrated using Cerenkov air shower imaging techniques. With two telescopes in coincidence, the individual event circular probable error will be 0.13 deg. The half-cone angle of the field of view is effectively 1 deg.

  10. Can Handheld Plastic Detectors Do Both Gamma and Neutron Isotopic Identification with Directional Source Location?

    SciTech Connect

    Robert Hayes

    2008-04-18

    This paper demonstrates, through MCNPX simulations, that a compact hexagonal array of detectors can be utilized to do both gamma isotopic identification (ID) along with neutron identification while simultaneously finding the direction of the source relative to the detector array. The detector array itself is composed of seven borated polyvinyl toluene (PVT) hexagonal light pipes approximately 4 inches long and with a 1.25 inch face-to-face thickness assembled in a tight configuration. The gamma ID capability is realized through judicious windowing algorithms as is the neutron spectral unfolding. By having multiple detectors in different relative positions, directional determination of the source can be realized. By further adding multiplicity counters to the neutron counts, fission events can be measured.

  11. Improvements in mining induced microseismic source locations at the Lucky Friday mine using an automated whole-waveform analysis system

    NASA Astrophysics Data System (ADS)

    Dodge, Douglas A.; Sprenke, Kenneth F.

    1992-09-01

    For years, severe rockburst problems at the Lucky Friday mine in northern Idaho have been a persistent safety hazard and an impediment to production. An MP250 based microseismic monitoring system, which uses simple voltage threshold picking of first arrivals, has been used in this mine since 1973 to provide source locations and energy estimates of seismic events. Recently, interest has been expressed in developing a whole waveform microseismic monitoring system for the mine to provide more accurate source locations and information about source characteristics. For this study, we have developed a prototype whole-waveform microseismic monitoring system based on a 80386 computer equipped with a 50 kHz analog-digital convertor board. The software developed includes a data collection program, a data analysis program, and an event detection program. Whole-waveform data collected and analyzed using this system during a three-day test have been employed to investigate sources of error in the hypocenter location process and to develop an automatic phase picker appropriate for microseismic events. Comparison of hypocenter estimates produced by the MP250 system to those produced by the whole-waveform system shows that significant timing errors are common in the MP250 system and that these errors caused a large part of the scatter evident in the daily activity plots produced at the mine. Simulations and analysis of blast data show that analytical control over the solutions is strongly influenced by the array geometry. Within the geophone array, large errors in the velocity model or moderate timing errors may result in small changes in the solution, but outside the array, the solution is very sensitive to small changes in the data. Our whole-waveform detection program picks event onset times and determines event durations by analysis of a segmented envelope function (SEF) derived from the microseismic signal. The detection program has been tested by comparing its arrival time

  12. [Discrimination of the dynamic properties of sound source spatial location in humans (electrophysiology and psychophysics)].

    PubMed

    Al'tman, Ia A; Vaĭtulevich, S F; Petropavlovskaia, E A; Shestopalova, L B

    2010-01-01

    The spatial resolution of human auditory system has been studied while the localization of sound source has been changed according to the different temporal patterns of interaural time delay. Two experimental procedures have been run in the same group of subjects: psychophysical procedure (the transformed staircase method) and electrophysiological one (which requires recording of mismatch negativity, the auditory evoked response component). It has been established that 1) the magnitude of the mismatch negativity reflects the extent of spatial deviance of the sound source 2) the mismatch negativity is elicited even at minimal (20 micros) interaural time delays under both temporal patterns (abrupt azimuth change and gradual sound movement at various velocities) 3) the abrupt change of the sound source azimuth results in greater mismatch negativity than the gradual sound movement does, if the interaural time delay exceeds 40 micros 4) the discrimination threshold values of the interaural delay obtained in the psychophysical procedure are greater than the minimal interaural delays that elicit the mismatch negativity, with the exception of the expert listeners who has shown no significant difference.

  13. Source Apportionment of Particle Bound Polycyclic Aromatic Hydrocarbons at an Industrial Location in Agra, India

    PubMed Central

    Lakhani, Anita

    2012-01-01

    16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) were quantified in total suspended ambient particulate matter (TSPM) collected from an industrial site in Agra (India) using gas chromatography. The major industrial activities in Agra are foundries that previously used coal and coke as fuel in cupola furnaces. These foundries have now switched over to natural gas. In addition, use of compressed natural gas has also been promoted and encouraged in automobiles. This study attempts to apportion sources of PAH in the ambient air and the results reflect the advantages associated with the change of fuel. The predominant PAHs in TSPM include high molecular weight (HMW) congeners BghiP, DbA, IP, and BaP. The sum of 16 priority PAHs had a mean value of 72.7 ± 4.7 ng m−3. Potential sources of PAHs in aerosols were identified using diagnostic ratios and principal component analysis. The results reflect a blend of emissions from diesel and natural gas as the major sources of PAH in the city along with contribution from emission of coal, coke, and gasoline. PMID:22606062

  14. Source apportionment of particle bound polycyclic aromatic hydrocarbons at an industrial location in Agra, India.

    PubMed

    Lakhani, Anita

    2012-01-01

    16 U.S. EPA priority polycyclic aromatic hydrocarbons (PAHs) were quantified in total suspended ambient particulate matter (TSPM) collected from an industrial site in Agra (India) using gas chromatography. The major industrial activities in Agra are foundries that previously used coal and coke as fuel in cupola furnaces. These foundries have now switched over to natural gas. In addition, use of compressed natural gas has also been promoted and encouraged in automobiles. This study attempts to apportion sources of PAH in the ambient air and the results reflect the advantages associated with the change of fuel. The predominant PAHs in TSPM include high molecular weight (HMW) congeners BghiP, DbA, IP, and BaP. The sum of 16 priority PAHs had a mean value of 72.7 ± 4.7 ng m(-3). Potential sources of PAHs in aerosols were identified using diagnostic ratios and principal component analysis. The results reflect a blend of emissions from diesel and natural gas as the major sources of PAH in the city along with contribution from emission of coal, coke, and gasoline.

  15. Surface Properties Associated With Dust Storm Plume's Point-Source Locations In The Border Region Of The US And Mexico

    NASA Astrophysics Data System (ADS)

    Bleiweiss, M. P.; DuBois, D. W.; Flores, M. I.

    2013-12-01

    Dust storms in the border region of the Southwest US and Northern Mexico are a serious problem for air quality (PM10 exceedances), health (Valley Fever is pandemic in the region) and transportation (road closures and deadly traffic accidents). In order to better understand the phenomena, we are attempting to identify critical characteristics of dust storm sources so that, possibly, one can perform more accurate predictions of events and, thus, mitigate some of the deleterious effects. Besides the emission mechanisms for dust storm production that are tied to atmospheric dynamics, one must know those locations whose source characteristics can be tied to dust production and, therefore, identify locations where a dust storm is eminent under favorable atmospheric dynamics. During the past 13 years, we have observed, on satellite imagery, more than 500 dust events in the region and are in the process of identifying the source regions for the dust plumes that make up an event. Where satellite imagery exists with high spatial resolution (less than or equal to 250m), dust 'plumes' appear to be made up of individual and merged plumes that are emitted from a 'point source' (smaller than the resolution of the imagery). In particular, we have observed events from the ASTER sensor whose spatial resolution is 15m as well as Landsat whose spatial resolution is 30m. Tying these source locations to surface properties such as NDVI, albedo, and soil properties (percent sand, silt, clay, and gravel; soil moisture; etc.) will identify regions with enhanced capability to produce a dust storm. This, along with atmospheric dynamics, will allow the forecast of dust events. The analysis of 10 events from the period 2004-2013, for which we have identified 1124 individual plumes, will be presented.

  16. XMM-NEWTON OBSERVATIONS OF FIVE INTEGRAL SOURCES LOCATED TOWARD THE SCUTUM ARM

    SciTech Connect

    Bodaghee, A.; Tomsick, J. A.; Rodriguez, J.

    2012-07-01

    Results are presented for XMM-Newton observations of five hard X-ray sources discovered by INTEGRAL in the direction of the Scutum Arm. Each source received {approx}>20 ks of effective exposure time. We provide refined X-ray positions for all five targets enabling us to pinpoint the most likely counterpart in optical/infrared archives. Spectral and timing information (much of which is provided for the first time) allow us to give a firm classification for IGR J18462-0223 and to offer tentative classifications for the others. For IGR J18462-0223, we discovered a coherent pulsation period of 997 {+-} 1 s, which we attribute to the spin of a neutron star in a highly obscured (N{sub H} =2 Multiplication-Sign 10{sup 23} cm{sup -2}) high-mass X-ray binary (HMXB). This makes IGR J18462-0223 the seventh supergiant fast X-ray transient candidate with a confirmed pulsation period. IGR J18457+0244 is a highly absorbed (N{sub H} =8 Multiplication-Sign 10{sup 23} cm{sup -2}) source in which the possible detection of an iron line suggests an active galactic nucleus (AGN) of type Sey-2 situated at z = 0.07(1). A periodic signal at 4.4 ks could be a quasi-periodic oscillation which would make IGR J18457+0244 one of a handful of AGNs in which such features have been claimed, but a slowly rotating neutron star in an HMXB cannot be ruled out. IGR J18482+0049 represents a new obscured HMXB candidate with N{sub H} =4 Multiplication-Sign 10{sup 23} cm{sup -2}. We tentatively propose that IGR J18532+0416 is either an AGN or a pulsar in an HMXB system. The X-ray spectral properties of IGR J18538-0102 are consistent with the AGN classification that has been proposed for this source.

  17. Source locations for impulsive electric signals seen in the night ionosphere of Venus

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Von Dornum, M.; Scarf, F. L.

    1989-01-01

    A mapping of the rate of occurrence of impulsive VLF noise bursts in Venus' dark low altitude ionosphere, which increases rapidly with decreasing altitude, as a function of latitude and longitude indicates enhanced occurrence rates over Atla. In a 30-sec observing period, there are impulsive signals 70 percent of the time at 160 km in the region of maximum occurrence; the occurrence rates, moreover, increase with decreasing latitude, so that the equatorial rate is of the order of 1.6 times that at 30 deg latitude. These phenomena are in keeping with lightning-generated wave sources.

  18. Arcsec source location measurements in gamma-ray astronomy from a lunar observatory

    NASA Technical Reports Server (NTRS)

    Koch, David G.; Hughes, E. B.

    1990-01-01

    The physical processes typically used in the detection of high energy gamma-rays do not permit good angular resolution, which makes difficult the unambiguous association of discrete gamma-ray sources with objects emitting at other wavelengths. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For the purpose of discussion, this concept is examined for gamma rays above about 20 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.

  19. UTILIZING RESULTS FROM INSAR TO DEVELOP SEISMIC LOCATION BENCHMARKS AND IMPLICATIONS FOR SEISMIC SOURCE STUDIES

    SciTech Connect

    M. BEGNAUD; ET AL

    2000-09-01

    Obtaining accurate seismic event locations is one of the most important goals for monitoring detonations of underground nuclear teats. This is a particular challenge at small magnitudes where the number of recording stations may be less than 20. Although many different procedures are being developed to improve seismic location, most procedures suffer from inadequate testing against accurate information about a seismic event. Events with well-defined attributes, such as latitude, longitude, depth and origin time, are commonly referred to as ground truth (GT). Ground truth comes in many forms and with many different levels of accuracy. Interferometric Synthetic Aperture Radar (InSAR) can provide independent and accurate information (ground truth) regarding ground surface deformation and/or rupture. Relating surface deformation to seismic events is trivial when events are large and create a significant surface rupture, such as for the M{sub w} = 7.5 event that occurred in the remote northern region of the Tibetan plateau in 1997. The event, which was a vertical strike slip even appeared anomalous in nature due to the lack of large aftershocks and had an associated surface rupture of over 180 km that was identified and modeled using InSAR. The east-west orientation of the fault rupture provides excellent ground truth for latitude, but is of limited use for longitude. However, a secondary rupture occurred 50 km south of the main shock rupture trace that can provide ground truth with accuracy within 5 km. The smaller, 5-km-long secondary rupture presents a challenge for relating the deformation to a seismic event. The rupture is believed to have a thrust mechanism; the dip of the fimdt allows for some separation between the secondary rupture trace and its associated event epicenter, although not as much as is currently observed from catalog locations. Few events within the time period of the InSAR analysis are candidates for the secondary rupture. Of these, we have

  20. Beryllium-10 in Australasian tektites: Constraints on the location of the source crater

    NASA Astrophysics Data System (ADS)

    Ma, P.; Aggrey, K.; Tonzola, C.; Schnabel, C.; de Nicola, P.; Herzog, G. F.; Wasson, J. T.; Glass, B. P.; Brown, L.; Tera, F.; Middleton, R.; Klein, J.

    2004-10-01

    By using accelerator mass spectrometry we have measured the 10Be concentrations of 86 Australasian tektites. Corrected to the time of tektite production ˜0.8 My ago, the 10Be concentrations (10 6 atom/g) range from 59 for a layered tektite from Huai Sai, Thailand, to 280 for an australite from New South Wales, Australia. The average value is 143 ± 50. When tektites are sorted by country, their average measured 10Be concentrations increase slowly with increasing distance from Southeast Asia, the probable location of the tektite producing event, from 59 ± 9 for 6 layered tektites from Laos to 136 ± 20 for 20 splash-form tektites from Australia. The lowest 10Be concentrations for tektites fall on or within a contour centered off the shore of Vietnam, south of the Gulf of Tonkin (107°E; 17°N), but also encompassing two other locations in the area of northeastern Thailand previously proposed for the site of a single tektite-producing impact. The 10Be concentrations of layered tektites show only a weak anticorrelation (R ˜ -0.3) with the numbers of relict crystalline inclusions. Loosely consolidated, fine-grained terrestrial sediments or recently consolidated sedimentary rocks are the most likely precursor materials. Dilution of sediments with other kinds of rock raises problems in mixing and is not supported by petrographic data. Sedimentary columns that have the right range of 10Be concentrations occur off the coasts of places where sedimentation rates are high relative to those in the deep sea. A single impact into such a region, 15 to 300 m thick, could have propelled near-surface, high- 10Be material farthest—to Australia—while keeping the deeper-lying, low- 10Be layers closer to home. We do not rule out, however, other proposed mechanisms for tektite formation.

  1. Location and release time identification of pollution point source in river networks based on the Backward Probability Method.

    PubMed

    Ghane, Alireza; Mazaheri, Mehdi; Mohammad Vali Samani, Jamal

    2016-09-15

    The pollution of rivers due to accidental spills is a major threat to environment and human health. To protect river systems from accidental spills, it is essential to introduce a reliable tool for identification process. Backward Probability Method (BPM) is one of the most recommended tools that is able to introduce information related to the prior location and the release time of the pollution. This method was originally developed and employed in groundwater pollution source identification problems. One of the objectives of this study is to apply this method in identifying the pollution source location and release time in surface waters, mainly in rivers. To accomplish this task, a numerical model is developed based on the adjoint analysis. Then the developed model is verified using analytical solution and some real data. The second objective of this study is to extend the method to pollution source identification in river networks. In this regard, a hypothetical test case is considered. In the later simulations, all of the suspected points are identified, using only one backward simulation. The results demonstrated that all suspected points, determined by the BPM could be a possible pollution source. The proposed approach is accurate and computationally efficient and does not need any simplification in river geometry and flow. Due to this simplicity, it is highly recommended for practical purposes.

  2. A new experimental method for the determination of the effective orifice area based on the acoustical source term

    NASA Astrophysics Data System (ADS)

    Kadem, L.; Knapp, Y.; Pibarot, P.; Bertrand, E.; Garcia, D.; Durand, L. G.; Rieu, R.

    2005-12-01

    The effective orifice area (EOA) is the most commonly used parameter to assess the severity of aortic valve stenosis as well as the performance of valve substitutes. Particle image velocimetry (PIV) may be used for in vitro estimation of valve EOA. In the present study, we propose a new and simple method based on Howe’s developments of Lighthill’s aero-acoustic theory. This method is based on an acoustical source term (AST) to estimate the EOA from the transvalvular flow velocity measurements obtained by PIV. The EOAs measured by the AST method downstream of three sharp-edged orifices were in excellent agreement with the EOAs predicted from the potential flow theory used as the reference method in this study. Moreover, the AST method was more accurate than other conventional PIV methods based on streamlines, inflexion point or vorticity to predict the theoretical EOAs. The superiority of the AST method is likely due to the nonlinear form of the AST. There was also an excellent agreement between the EOAs measured by the AST method downstream of the three sharp-edged orifices as well as downstream of a bioprosthetic valve with those obtained by the conventional clinical method based on Doppler-echocardiographic measurements of transvalvular velocity. The results of this study suggest that this new simple PIV method provides an accurate estimation of the aortic valve flow EOA. This new method may thus be used as a reference method to estimate the EOA in experimental investigation of the performance of valve substitutes and to validate Doppler-echocardiographic measurements under various physiologic and pathologic flow conditions.

  3. On the location of microseismic sources in instable rock slope areas: heterogeneous vs. homogenous 3D velocity models

    NASA Astrophysics Data System (ADS)

    Coviello, Velio; Manconi, Andrea; Occhiena, Cristina; Arattano, Massimo; Scavia, Claudio

    2013-04-01

    Rock-falls are one of the most common and hazardous phenomena occurring in mountainous areas. The formation of cracks in rocks is often accompanied by a sudden release of energy, which propagates in form of elastic waves and can be detected by a suitable transducer array. Therefore, geophones are among the most effective monitoring devices to investigate eventual precursors of rock-fall phenomena. However, the identification of an efficient procedure to forecast rock-fall occurrence in space and time is still an open challenge. In this study, we aim at developing an efficient procedure to locate microseismic sources relevant to cracking mechanisms, and thus gather indications on eventual precursors of rock-fall phenomena. Common seismic location tools usually implement homogeneous or multilayered velocity models but, in case of high slope gradients and heavily fractured rock masses, these simplifications may lead to errors on the correct estimation of the source location. Thus, we analyzed how the consideration of 3D material properties on the propagation medium may influence the location. In the framework of the Alcotra 2007-2013 Project MASSA (Medium And Small Size rock-fall hazard Assessment), a monitoring system composed by 8 triaxial geophones was installed in 2010 at the J.A. Carrel hut (3829 m a.s.l., Matterhorn, NW Italian Alps) and during the first year of operation the network recorded more than 600 natural events that exceeded a fixed threshold [1]. Despite the harsh environmental conditions of the study area, eighteen points distributed as uniformly as possible in space were selected for hammering. The artificial source dataset of known coordinates was used to constrain a 3D heterogeneous velocity model through a Simultaneous Iterative Reconstructive Technique. In order to mitigate the intrinsic uncertainties of the inversion procedure, bootstrapping was performed to extend the dataset and a statistical analysis was issued to improve the model

  4. Determining the seismic source mechanism and location for an explosive eruption with limited observational data: Augustine Volcano, Alaska

    USGS Publications Warehouse

    Dawson, P.B.; Chouet, B.A.; Power, J.

    2011-01-01

    Waveform inversions of the very-long-period components of the seismic wavefield produced by an explosive eruption that occurred on 11 January, 2006 at Augustine Volcano, Alaska constrain the seismic source location to near sea level beneath the summit of the volcano. The calculated moment tensors indicate the presence of a volumetric source mechanism. Systematic reconstruction of the source mechanism shows the source consists of a sill intersected by either a sub-vertical east-west trending dike or a sub-vertical pipe and a weak single force. The trend of the dike may be controlled by the east-west trending Augustine-Seldovia arch. The data from the network of broadband sensors is limited to fourteen seismic traces, and synthetic modeling confirms the ability of the network to recover the source mechanism. The synthetic modeling also provides a guide to the expected capability of a broadband network to resolve very-long-period source mechanisms, particularly when confronted with limited observational data. Copyright 2011 by the American Geophysical Union.

  5. Determining the seismic source mechanism and location for an explosive eruption with limited observational data: Augustine Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Dawson, Phillip B.; Chouet, Bernard A.; Power, John

    2011-02-01

    Waveform inversions of the very-long-period components of the seismic wavefield produced by an explosive eruption that occurred on 11 January, 2006 at Augustine Volcano, Alaska constrain the seismic source location to near sea level beneath the summit of the volcano. The calculated moment tensors indicate the presence of a volumetric source mechanism. Systematic reconstruction of the source mechanism shows the source consists of a sill intersected by either a sub-vertical east-west trending dike or a sub-vertical pipe and a weak single force. The trend of the dike may be controlled by the east-west trending Augustine-Seldovia arch. The data from the network of broadband sensors is limited to fourteen seismic traces, and synthetic modeling confirms the ability of the network to recover the source mechanism. The synthetic modeling also provides a guide to the expected capability of a broadband network to resolve very-long-period source mechanisms, particularly when confronted with limited observational data.

  6. Transmitted sound field due to an impulsive line acoustic source bounded by a plate followed by a vortex sheet

    NASA Technical Reports Server (NTRS)

    Miura, T.; Chao, C. C.

    1980-01-01

    The propagation of sound due to a line acoustic source in the moving stream across a semiinfinite vortex sheet which trails from a rigid plate is examined in a linear theory for the subsonic case. A solution for the transmitted sound field is obtained with the aid of multiple integral transforms and the Wiener-Hopf technique for both the steady state (time harmonic) and initial value (impulsive source) situations. The contour of inverse transform and hence the decomposition of the functions are determined through causality and radiation conditions. The solution obtained satisfies causality and the full Kutta conditions. The transmitted sound field is composed of two waves in both the stady state and initial value problems. One is the wave scattered from the edge of the plate which is associated with the bow wave and the instability wave. These waves exist in the downstream sectors. The other is the wave transmitted through the vortex sheet which is also associated with the instability wave. Regional divisions of the transmitted sound field are identified.

  7. Fourier method for recovering acoustic sources from multi-frequency far-field data

    NASA Astrophysics Data System (ADS)

    Wang, Xianchao; Guo, Yukun; Zhang, Deyue; Liu, Hongyu

    2017-03-01

    We consider an inverse source problem of determining a source term in the Helmholtz equation from multi-frequency far-field measurements. Based on the Fourier series expansion, we develop a novel non-iterative reconstruction method for solving the problem. A promising feature of this method is that it utilizes the data from only a few observation directions for each frequency. Theoretical uniqueness and stability analysis are provided. Numerical experiments are conducted to illustrate the effectiveness and efficiency of the proposed method in both two and three dimensions.

  8. Site Characterization of the Source Physics Experiment Phase II Location Using Seismic Reflection Data

    SciTech Connect

    Sexton, Emily; Snelson, Catherine M; Chipman, Veraun D; Emer, Dudley; White, Bob; Emmit, Ryan; Wright, Al; Drellack, Sigmund; Huckins-Gang, Heather; Mercadante, Jennifer; Floyd, Michael; McGowin, Chris; Cothrun, Chris; Bonal, Nedra

    2013-12-05

    An objective of the Source Physics Experiment (SPE) is to identify low-yield nuclear explosions from a regional distance. Low-yield nuclear explosions can often be difficult to discriminate among the clutter of natural and man-made explosive events (e.g., earthquakes and mine blasts). The SPE is broken into three phases. Phase I has provided the first of the physics-based data to test the empirical models that have been used to discriminate nuclear events. The Phase I series of tests were placed within a highly fractured granite body. The evolution of the project has led to development of Phase II, to be placed within the opposite end member of geology, an alluvium environment, thereby increasing the database of waveforms to build upon in the discrimination models. Both the granite and alluvium sites have hosted nearby nuclear tests, which provide comparisons for the chemical test data. Phase III of the SPE is yet to be determined.

  9. Source characteristics and locations of hectometric radio emissions from the northern Jovian hemisphere

    NASA Technical Reports Server (NTRS)

    Reiner, M. J.; Fainberg, J.; Stone, R. G.

    1993-01-01

    Northern Jovian hectometric (HOM) radio emissions, detected from high Jovian latitudes by the Unified Radio and Plasma Wave experiment on the Ulysses spacecraft, were observed at all Jovian longitudes. This emission was observed to be predominantly right-hand circularly polarized, but some left-hand circular polarization was observed implying the presence of O mode emissions from the northern Jovian hemisphere. Intense HOM emissions, with well-defined directions and polarizations, were often confined to similar longitudinal regions where intense HOM emissions were previously observed at low latitudes. The present analysis confirms that these northern HOM sources lie in the Jovian polar regions on magnetic field lines that pass through the Io plasma torus. The observations may be consistent with emission from either a filled cone beam or a longitudinal distribution of thin hollow cones.

  10. Effect of tides and source location on nearshore tsunami-induced currents

    NASA Astrophysics Data System (ADS)

    Ayca, Aykut; Lynett, Patrick J.

    2016-12-01

    Here we present the results of a numerical modeling study that investigates how event-maximum tsunami-induced currents vary due to the dynamic effects of tides and wave directivity. First, analyses of tide-tsunami interaction are presented in three harbors by coupling the tsunami with the tide, and allowing the initial tsunami wave to arrive at various tidal phases. We find that tsunami-tide interaction can change the event-maximum current speed experienced in a harbor by up to 25% for the events and harbors studied, and we note that this effect is highly site-specific. Second, to evaluate the effect of wave directionality on event-maximum currents, earthquakes sources were placed throughout the Pacific, with magnitudes tuned to create the same maximum near-coast amplitude at the harbor of study. Our analysis also shows that, for the harbor and sources examined, the effect of offshore directionality and tsunami frequency content has a weak effect on the event-maximum currents experienced in the harbor. The more important dependency of event-maximum currents is the near-harbor amplitude of the wave, indicating that event-maximum currents in a harbor from a tsunami generated by a large far-field earthquake may be reasonably well predicted with only information about the predicted local maximum tsunami amplitude. This study was motivated by the hope of constructing a basis for understanding the dynamic effects of tides and wave directivity on current-based tsunami hazards in a coastal zone. The consideration of these aspects is crucial and yet challenging in the modeling of tsunami currents.

  11. Directionality of Ambient Noise on the Juan de Fuca Plate: Implications for Source Locations of the Primary and Secondary Microseism

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Ritzwoller, M. H.

    2014-12-01

    Based on cross-correlations computed from 61 ocean bottom seismometers (OBSs) within the Juan de Fuca plate from the Cascadia Initiative experiment and 42 continental stations near the western US coast, we investigate the generation locations of the primary (11-20 sec period) and secondary (5-10 sec period) microseisms in the northern Pacific Ocean by analyzing the directionality of the microseism signals received in this region. (1) Ambient noise observed across the array is much different in the primary and secondary microseism bands, both in its azimuthal content and seasonal variation, indicating different source generation locations. (2) The principal secondary microseism signals propagate toward the east, consistent with source generation in deep water of the North Pacific, perhaps coincident with the region of body wave excitation observed by Gerstoft et al. [2008] and Landès et al. [2010]. (3) Local primary microseism sources within and near the Juan de Fuca plate are implied by observations of the azimuthal dependence of the fundamental mode Rayleigh wave amplitudes as well as observations of precursory arrivals in cross-correlations of ambient noise. The strongest local generation region is observed northwest of the Juan de Fuca plate near the coast of British Columbia perhaps near Graham Island. Weaker local sources appear to be oceanward of Vancouver Island and southern Oregon. (4) High quality Green's functions are derived from cross-correlations between deep water OBSs and continental stations proving that deep water generated signals can efficiently propagate onto the continent and are well recorded by continental seismic stations, at least at periods longer than about 5 sec.In conclusion, the primary and secondary microseisms are generated at different locations, with the secondary microseism dominantly coming from deep-water sources and the source of primary microseism having a significant component in the shallow waters of the eastern Pacific

  12. Characterizing and locating air pollution sources in a complex industrial district using optical remote sensing technology and multivariate statistical modeling.

    PubMed

    Chang, Pao-Erh Paul; Yang, Jen-Chih Rena; Den, Walter; Wu, Chang-Fu

    2014-09-01

    Emissions of volatile organic compounds (VOCs) are most frequent environmental nuisance complaints in urban areas, especially where industrial districts are nearby. Unfortunately, identifying the responsible emission sources of VOCs is essentially a difficult task. In this study, we proposed a dynamic approach to gradually confine the location of potential VOC emission sources in an industrial complex, by combining multi-path open-path Fourier transform infrared spectrometry (OP-FTIR) measurement and the statistical method of principal component analysis (PCA). Close-cell FTIR was further used to verify the VOC emission source by measuring emitted VOCs from selected exhaust stacks at factories in the confined areas. Multiple open-path monitoring lines were deployed during a 3-month monitoring campaign in a complex industrial district. The emission patterns were identified and locations of emissions were confined by the wind data collected simultaneously. N,N-Dimethyl formamide (DMF), 2-butanone, toluene, and ethyl acetate with mean concentrations of 80.0 ± 1.8, 34.5 ± 0.8, 103.7 ± 2.8, and 26.6 ± 0.7 ppbv, respectively, were identified as the major VOC mixture at all times of the day around the receptor site. As the toxic air pollutant, the concentrations of DMF in air samples were found exceeding the ambient standard despite the path-average effect of OP-FTIR upon concentration levels. The PCA data identified three major emission sources, including PU coating, chemical packaging, and lithographic printing industries. Applying instrumental measurement and statistical modeling, this study has established a systematic approach for locating emission sources. Statistical modeling (PCA) plays an important role in reducing dimensionality of a large measured dataset and identifying underlying emission sources. Instrumental measurement, however, helps verify the outcomes of the statistical modeling. The field study has demonstrated the feasibility of

  13. Modeling the Infrasound Acoustic Signal Generation of Underground Explosions at the Source Physics Experiment

    NASA Astrophysics Data System (ADS)

    Whitaker, R. W.; Jones, K. R.; Arrowsmith, S.

    2013-12-01

    One of the primary goals of the Source Physics Experiment is to improve upon and develop new physics based models for underground nuclear explosions using scaled, underground chemical explosions as proxies. Jones et. al, (AGU 2012) previously presented results describing the use of the Rayleigh integral (RI) to model the source region of the SPE explosions. While these results showed that the source region could be modeled using the RI, there were some complexities in the produced, synthetic waveforms that were unaccounted for when compared to the observed data. To gain insight into these complexities and to verify the results of the RI method, we used CAVEAT, a two-dimensional computational fluid dynamics, time-domain finite-difference code developed at Los Alamos National Labs (LANL). CAVEAT has been used in the solution of high speed and low speed fluid problems. While the RI uses the observed acceleration records from the 12 vertical surface accelerometers installed above ground zero, CAVEAT employs a synthetic source-time function, based on the acceleration records, that varies with range and time. This model provides a velocity boundary condition at the bottom boundary of the CAVEAT computation mesh that drives the atmospheric pressure wave into the atmosphere.

  14. Estimating colony sizes of emerging bats using acoustic recordings.

    PubMed

    Kloepper, Laura N; Linnenschmidt, Meike; Blowers, Zelda; Branstetter, Brian; Ralston, Joel; Simmons, James A

    2016-03-01

    The decline of bats demands more widespread monitoring of populations for conservation and management. Current censusing methods are either prone to bias or require costly equipment. Here, we report a new method using passive acoustics to determine bat count census from overall acoustic amplitude of the emerging bat stream. We recorded the video and audio of an emerging colony of Mexican free-tailed bats from two cave locations across multiple nights. Instantaneous bat counts were calculated from the video frames, and the bat stream's acoustic amplitude corresponding to each video frame was determined using three different methods for calculating acoustic intensity. We found a significant link between all three acoustic parameters and bat count, with the highest R (2) of 0.742 linking RMS pressure and bat count. Additionally, the relationship between acoustics and population size at one cave location could accurately predict the population size at another cave location. The data were gathered with low-cost, easy-to-operate equipment, and the data analysis can be easily accomplished using automated scripts or with open-source acoustic software. These results are a potential first step towards creating an acoustic model to estimate bat population at large cave colonies worldwide.

  15. Estimating colony sizes of emerging bats using acoustic recordings

    PubMed Central

    Kloepper, Laura N.; Linnenschmidt, Meike; Blowers, Zelda; Branstetter, Brian; Ralston, Joel; Simmons, James A.

    2016-01-01

    The decline of bats demands more widespread monitoring of populations for conservation and management. Current censusing methods are either prone to bias or require costly equipment. Here, we report a new method using passive acoustics to determine bat count census from overall acoustic amplitude of the emerging bat stream. We recorded the video and audio of an emerging colony of Mexican free-tailed bats from two cave locations across multiple nights. Instantaneous bat counts were calculated from the video frames, and the bat stream’s acoustic amplitude corresponding to each video frame was determined using three different methods for calculating acoustic intensity. We found a significant link between all three acoustic parameters and bat count, with the highest R2 of 0.742 linking RMS pressure and bat count. Additionally, the relationship between acoustics and population size at one cave location could accurately predict the population size at another cave location. The data were gathered with low-cost, easy-to-operate equipment, and the data analysis can be easily accomplished using automated scripts or with open-source acoustic software. These results are a potential first step towards creating an acoustic model to estimate bat population at large cave colonies worldwide. PMID:27069667

  16. Magneto-acoustic imaging by continuous-wave excitation.

    PubMed

    Shunqi, Zhang; Zhou, Xiaoqing; Tao, Yin; Zhipeng, Liu

    2017-04-01

    The electrical characteristics of tissue yield valuable information for early diagnosis of pathological changes. Magneto-acoustic imaging is a functional approach for imaging of electrical conductivity. This study proposes a continuous-wave magneto-acoustic imaging method. A kHz-range continuous signal with an amplitude range of several volts is used to excite the magneto-acoustic signal and improve the signal-to-noise ratio. The magneto-acoustic signal amplitude and phase are measured to locate the acoustic source via lock-in technology. An optimisation algorithm incorporating nonlinear equations is used to reconstruct the magneto-acoustic source distribution based on the measured amplitude and phase at various frequencies. Validation simulations and experiments were performed in pork samples. The experimental and simulation results agreed well. While the excitation current was reduced to 10 mA, the acoustic signal magnitude increased up to 10(-7) Pa. Experimental reconstruction of the pork tissue showed that the image resolution reached mm levels when the excitation signal was in the kHz range. The signal-to-noise ratio of the detected magneto-acoustic signal was improved by more than 25 dB at 5 kHz when compared to classical 1 MHz pulse excitation. The results reported here will aid further research into magneto-acoustic generation mechanisms and internal tissue conductivity imaging.

  17. Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: Earthquake locations and source parameters

    USGS Publications Warehouse

    Ruppert, N.A.; Prejean, S.; Hansen, R.A.

    2011-01-01

    An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field. Copyright ?? 2011 by the American Geophysical Union.

  18. Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: earthquake locations and source parameters

    USGS Publications Warehouse

    Ruppert, Natalia G.; Prejean, Stephanie G.; Hansen, Roger A.

    2011-01-01

    An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field.

  19. Locating the sources of an invasive pest, grape phylloxera, using a mitochondrial DNA gene genealogy.

    PubMed

    Downie, D A

    2002-10-01

    Range expansions through human introductions have increased with global commerce and have led to the extinction of native species, alterations in community structure and pest status of the invasive species. Inferring the evolutionary history of invasive species can help to build a firmer footing for management tactics. This study used mitochondrial DNA (mtDNA) sequence comparisons of samples collected from the native and introduced ranges of a pest herbivore of cultivated grapes, grape phylloxera (Daktulosphaira vitifoliae Fitch, Phylloxeridae) to infer the sources and pattern of introductions into worldwide viticulture. Introductions into viticulture from its native North American range first occurred in the mid-19th century. The pattern of spread has suggested a focus of introduction into France, but independent introductions may have occurred elsewhere. The results show that the introduced population represents a limited subsample of the native genetic diversity. The data suggest that most grape phylloxera in viticulture, including all European, have originated in the northeastern USA where the grape species Vitis riparia dominates. There was evidence for independent introductions into South Africa and California. Most California haplotypes were most closely related to native grape phylloxera from the Atlantic Coast on V. vulpina. It is likely that subsequent spread from California into Australia, New Zealand and Peru has occurred.

  20. Low frequency acoustic microscope

    DOEpatents

    Khuri-Yakub, Butrus T.

    1986-11-04

    A scanning acoustic microscope is disclosed for the detection and location of near surface flaws, inclusions or voids in a solid sample material. A focused beam of acoustic energy is directed at the sample with its focal plane at the subsurface flaw, inclusion or void location. The sample is scanned with the beam. Detected acoustic energy specularly reflected and mode converted at the surface of the sample and acoustic energy reflected by subsurface flaws, inclusions or voids at the focal plane are used for generating an interference signal which is processed and forms a signal indicative of the subsurface flaws, inclusions or voids.

  1. Fuel from Wastewater - Harnessing a Potential Energy Source in Canada through the Co-location of Algae Biofuel Production to Sources of Effluent, Heat and CO2

    NASA Astrophysics Data System (ADS)

    Klise, G. T.; Roach, J. D.; Passell, H. D.; Moreland, B. D.; O'Leary, S. J.; Pienkos, P. T.; Whalen, J.

    2010-12-01

    Sandia National Laboratories is collaborating with the National Research Council (NRC) Canada and the National Renewable Energy Laboratory (NREL) to develop a decision-support model that will evaluate the tradeoffs associated with high-latitude algae biofuel production co-located with wastewater, CO2, and waste heat. This project helps Canada meet its goal of diversifying fuel sources with algae-based biofuels. The biofuel production will provide a wide range of benefits including wastewater treatment, CO2 reuse and reduction of demand for fossil-based fuels. The higher energy density in algae-based fuels gives them an advantage over crop-based biofuels as the “production” footprint required is much less, resulting in less water consumed and little, if any conversion of agricultural land from food to fuel production. Besides being a potential source for liquid fuel, algae have the potential to be used to generate electricity through the burning of dried biomass, or anaerobically digested to generate methane for electricity production. Co-locating algae production with waste streams may be crucial for making algae an economically valuable fuel source, and will certainly improve its overall ecological sustainability. The modeling process will address these questions, and others that are important to the use of water for energy production: What are the locations where all resources are co-located, and what volumes of algal biomass and oil can be produced there? In locations where co-location does not occur, what resources should be transported, and how far, while maintaining economic viability? This work is being funded through the U.S. Department of Energy (DOE) Biomass Program Office of Energy Efficiency and Renewable Energy, and is part of a larger collaborative effort that includes sampling, strain isolation, strain characterization and cultivation being performed by the NREL and Canada’s NRC. Results from the NREL / NRC collaboration including specific

  2. Location and source mechanism of the Karlsruhe earthquake of 24 September 2014

    NASA Astrophysics Data System (ADS)

    Barth, Andreas

    2016-07-01

    On 24 September 2014, a ML 2.3 earthquake occurred southwest of the urban area of Karlsruhe, Germany, which was felt by a few people (maximum intensity I 0 = III). It was the first seismic event in this highly populated area since an I 0 = VII earthquake in 1948. Data of 35 permanent and temporary seismometers were analysed to localise the event and to determine the focal mechanism to compare it to previous seismicity. Restricting the data to P- and S-phases from 18 nearby stations and optimising the local earth model result in an epicentre in the southwest of the city at 48.986°N/8.302°E and in a hypocentral depth of 10 km. To calculate the focal mechanism, 22 P- and 5 SH-polarities were determined that constrain a stable left lateral strike-slip focal mechanism with a minor thrusting component and nodal planes striking NE-SW and NW-SE. The epicentre lies in the vicinity of the I 0 = VII earthquake of 1948. Both events are part of the graben-parallel flower structure beneath the Upper Rhine Graben, parallel to the active Rastatt source zone, which runs 5 km further east and included the epicentre of the 1933 Rastatt I 0 = VII earthquake. The focal mechanisms of the 2014 and 1948 earthquakes show NE-SW striking nodal planes that dip to the southeast. However, for the 1948 event, a normal faulting mechanism was determined earlier. Taking the uncertainty of the epicentre and focal mechanism in 1948 and its fault dimensions into account, both events might have happened on the same fault plane.

  3. Study of noise sources in a subsonic fan using measured blade pressures and acoustic theory

    NASA Technical Reports Server (NTRS)

    Hanson, D. B.

    1975-01-01

    Sources of noise in a 1.4 m (4.6 ft) diameter subsonic tip speed propulsive fan running statically outdoors are studied using a combination of techniques. Signals measured with pressure transducers on a rotor blade are plotted in a format showing the space-time history of inlet distortion. Study of these plots visually and with statistical correlation analysis confirms that the inlet flow contains long, thin eddies of turbulence. Turbulence generated in the boundary layer of the shroud upstream of the rotor tips was not found to be an important noise source. Fan noise is diagnosed by computing narrowband spectra of rotor and stator sound power and comparing these with measured sound power spectra. Rotor noise is computed from spectra of the measured blade pressures and stator noise is computed using the author's stator noise theory. It is concluded that the rotor and stator sources contribute about equally at frequencies in the vicinity of the first three harmonics of blade passing frequency. At higher frequencies, the stator contribution diminishes rapidly and the rotor/inlet turbulence mechanism dominates. Two parametric studies are performed by using the rotor noise calculation procedure which was correlated with test. In the first study, the effects on noise spectrum and directivity are calculated for changes in turbulence properties, rotational Mach number, number of blades, and stagger angle. In the second study the influences of design tip speed and blade number on noise are evaluated.

  4. openPSTD: The open source pseudospectral time-domain method for acoustic propagation

    NASA Astrophysics Data System (ADS)

    Hornikx, Maarten; Krijnen, Thomas; van Harten, Louis

    2016-06-01

    An open source implementation of the Fourier pseudospectral time-domain (PSTD) method for computing the propagation of sound is presented, which is geared towards applications in the built environment. Being a wave-based method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory usage as it allows to spatially sample close to the Nyquist criterion, thus keeping both the required spatial and temporal resolution coarse. In the implementation it has been opted to model the physical geometry as a composition of rectangular two-dimensional subdomains, hence initially restricting the implementation to orthogonal and two-dimensional situations. The strategy of using subdomains divides the problem domain into local subsets, which enables the simulation software to be built according to Object-Oriented Programming best practices and allows room for further computational parallelization. The software is built using the open source components, Blender, Numpy and Python, and has been published under an open source license itself as well. For accelerating the software, an option has been included to accelerate the calculations by a partial implementation of the code on the Graphical Processing Unit (GPU), which increases the throughput by up to fifteen times. The details of the implementation are reported, as well as the accuracy of the code.

  5. Indoor acoustic gain design

    NASA Astrophysics Data System (ADS)

    Concha-Abarca, Justo Andres

    2002-11-01

    The design of sound reinforcement systems includes many variables and usually some of these variables are discussed. There are criteria to optimize the performance of the sound reinforcement systems under indoor conditions. The equivalent acoustic distance, the necessary acoustic gain, and the potential acoustic gain are parameters which must be adjusted with respect to the loudspeaker array, electric power and directionality of loudspeakers, the room acoustics conditions, the distance and distribution of the audience, and the type of the original sources. The design and installation of front of the house and monitoring systems have individual criteria. This article is about this criteria and it proposes general considerations for the indoor acoustic gain design.

  6. The time-dependent inverse source problem for the acoustic and electromagnetic equations in the one- and three-dimensional cases

    NASA Astrophysics Data System (ADS)

    Moses, Harry E.

    1984-06-01

    The object of the time-dependent inverse source problem of electromagnetic theory and acoustics is to find time-dependent sources and currents, which are turned on at a given time and then off to give rise to prescribed radiation fields. In an early paper for the three-dimensional electromagnetic case, the present writer showed that the sources and currents are not unique and gave conditions which make them so. The ideas of that paper are reformulated for the three-dimensional electromagnetic case and extended to the acoustical three-dimensional case and the one-dimensional electromagnetic and acoustic cases. The one-dimensional cases show very explicitly the nature of the ambiguity of the choice of sources and currents. This ambiguity is closely related to one which occurs in inverse scattering theory. The ambiguity in inverse scattering theory arises when one wishes to obtain the off-shell elements of the T matrix from some of the on-shell elements (i.e., from the corresponding elements of the scattering operator). In inverse scattering theory prescribing of the representation in which the potential is to be diagonal removes the ambiguity. For the inverse source problem a partial prescription of the time dependence of the sources and currents removes the ambiguity. The inverse source problem is then solved explicitly for this prescribed time dependence. The direct source problems for the one- and three-dimensional acoustic and electromagnetic cases are also given to provide a contrast with the inverse source problem and for use in later papers. Moreover, the present author's earlier work on the eigenfunctions of the curl operator is reviewed and used to simplify drastically the three-dimensional direct and inverse source problems for electromagnetic theory by splitting off the radiation field and its currents from the longitudinal field and its sources and currents. Finally, for a prescribed time dependence, the inverse source problem is solved explicitly in

  7. Dynamic surface acoustic response to a thermal expansion source on an anisotropic half space.

    PubMed

    Zhao, Peng; Zhao, Ji-Cheng; Weaver, Richard

    2013-05-01

    The surface displacement response to a distributed thermal expansion source is solved using the reciprocity principle. By convolving the strain Green's function with the thermal stress field created by an ultrafast laser illumination, the complete surface displacement on an anisotropic half space induced by laser absorption is calculated in the time domain. This solution applies to the near field surface displacement due to pulse laser absorption. The solution is validated by performing ultrafast laser pump-probe measurements and showing very good agreement between the measured time-dependent probe beam deflection and the computed surface displacement.

  8. Shifting primary energy source and NOx emission location with plug-in hybrid vehicles

    NASA Astrophysics Data System (ADS)

    Karman, Deniz

    2011-06-01

    Plug-in hybrid vehicles (PHEVs) present an interesting technological opportunity for using non-fossil primary energy in light duty passenger vehicles, with the associated potential for reducing air pollutant and greenhouse gas emissions, to the extent that the electric power grid is fed by non-fossil sources. This perspective, accompanying the article by Thompson et al (2011) in this issue, will touch on two other studies that are directly related: the Argonne study (Elgowainy et al 2010) and a PhD thesis from Utrecht (van Vliet 2010). Thompson et al (2011) have examined air quality effects in a case where the grid is predominantly fossil fed. They estimate a reduction of 7.42 tons/day of NOx from motor vehicles as a result of substituting electric VMTs for 20% of the light duty gasoline vehicle miles traveled. To estimate the impact of this reduction on air quality they also consider the increases in NOx emissions due to the increased load on electricity generating units. The NOx emission increases are estimated as 4.0, 5.5 and 6.3 tons for the Convenience, Battery and Night charging scenarios respectively. The net reductions are thus in the 1.1-3.4 tons/day range. The air quality modelling results presented show that the air quality impact from a ground-level ozone perspective is favorable overall, and while the effect is stronger in some localities, the difference between the three scenarios is small. This is quite significant and suggests that localization of the NOx emissions to point sources has a more pronounced effect than the absolute reductions achieved. Furthermore it demonstrates that localization of NOx emissions to electricity generating units by using PHEVs in vehicle traffic has beneficial effects for air quality not only by minimizing direct human exposure to motor vehicle emissions, but also due to reduced exposure to secondary pollutants (i.e. ozone). In an electric power grid with a smaller share of fossil fired generating units, the beneficial

  9. A comparison of feed-forward networks and maximum likelihood on a point-source location problem

    NASA Astrophysics Data System (ADS)

    Webb, Andrew R.

    1991-04-01

    The problem of point source location using a multibeam focal plane staring array radar is considered. It is viewed as one in functional approximation in which the position of the source is regarded as a nonlinear function of the sampled radar image. An approximant is constructed, using a training set, which minimizes the mean square error in the position estimate. The problem of generalization is discussed. Two feed forward network architectures are considered: a particular radial basis function network which arises as a consequence of the minimum mean square error solution and is appropriate when the signal to noise ratio is 'small', and a multilayer perceptron, chosen for high signal to noise ratio approximation. The errors in the position estimates for each of these approaches are compared with a maximum likelihood position estimation method. The maximum likelihood method gives better overall performance and has the advantage that it is not dependent on the signal to noise ratio.

  10. Near-Infrared Image Reconstruction of Newborns' Brains: Robustness to Perturbations of the Source/Detector Location.

    PubMed

    Ahnen, L; Wolf, M; Hagmann, C; Sanchez, S

    2016-01-01

    The brain of preterm infants is the most vulnerable organ and can be severely injured by cerebral ischemia. We are working on a near-infrared imager to early detect cerebral ischemia. During imaging of the brain, movements of the newborn infants are inevitable and the near-infrared sensor has to be able to function on irregular geometries. Our aim is to determine the robustness of the near-infrared image reconstruction to small variations of the source and detector locations. In analytical and numerical simulations, the error estimations for a homogeneous medium agree well. The worst case estimates of errors in reduced scattering and absorption coefficient for distances of r=40 mm are acceptable for a single source-detector pair. The optical properties of an inhomogeneity representing an ischemia are reconstructed correctly within a homogeneous medium, if the error in placement is random.

  11. 40 CFR Table 2d to Subpart Zzzz of... - Requirements for Existing Compression Ignition Stationary RICE Located at Area Sources of HAP...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Ignition Stationary RICE Located at Area Sources of HAP Emissions 2d Table 2d to Subpart ZZZZ of Part 63... Stationary RICE Located at Area Sources of HAP Emissions As stated in §§ 63.6600 and 63.6640, you must comply with the following emission and operating limitations for existing compression ignition stationary...

  12. 40 CFR Table 2c to Subpart Zzzz of... - Requirements for Existing Compression Ignition Stationary Rice Located at Major Sources of HAP...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Ignition Stationary Rice Located at Major Sources of HAP Emissions 2c Table 2c to Subpart ZZZZ of Part 63... Stationary Rice Located at Major Sources of HAP Emissions As stated in §§ 63.6600 and 63.6640, you must comply with the following requirements for existing compression ignition stationary RICE: For...

  13. Virtual acoustics for music practice rooms

    NASA Astrophysics Data System (ADS)

    Freiheit, Ron

    2003-04-01

    The use of virtual acoustics has provided a new level of practice experience for the musician. By integrating the sound isolation of music practice rooms with the signal processing of an active acoustic system (with time variant-gain before feedback) musicians can now benefit from the experience of practicing in multiple acoustic environments. Musicians select from various acoustics environments from a typical small practice room to that of a large space such as a sports arena. The variability of the acoustic environment allows the musician to hear clearly their intonation and articulation, which may be difficult to discern in a small practice room. To effectively communicate the various acoustics environments, the musicians must be immersed in the sound field of the active acoustics without being able to discern source locations of the speakers. The system must also be able to support the dynamic range of the musicians without presenting artifacts of its own such as system noise or audible distortion. This paper deals with the design constraints needed to meet these requirements as well the antidotal responses from musicians who have used these environments for practice.

  14. Development of a Persistent Reactive Treatment Zone for Containment of Sources Located in Lower-Permeability Strata

    NASA Astrophysics Data System (ADS)

    Marble, J.; Carroll, K. C.; Brusseau, M. L.; Plaschke, M.; Brinker, F.

    2013-12-01

    Source zones located in relatively deep, low-permeability formations provide special challenges for remediation. Application of permeable reactive barriers, in-situ thermal, or electrokinetic methods would be expensive and generally impractical. In addition, the use of enhanced mass-removal approaches based on reagent injection (e.g., ISCO, enhanced-solubility reagents) is likely to be ineffective. One possible approach for such conditions is to create a persistent treatment zone for purposes of containment. This study examines the efficacy of this approach for containment and treatment of contaminants in a lower permeability zone using potassium permanganate (KMnO4) as the reactant. A localized 1,1-dichloroethene (DCE) source zone is present in a section of the Tucson International Airport Area (TIAA) Superfund Site. Characterization studies identified the source of DCE to be located in lower-permeability strata adjacent to the water table. Bench-scale studies were conducted using core material collected from boreholes drilled at the site to measure DCE concentrations and determine natural oxidant demand. The reactive zone was created by injecting ~1.7% KMnO4 solution into multiple wells screened within the lower-permeability unit. The site has been monitored for ~8 years to characterize the spatial distribution of DCE and permanganate. KMnO4 continues to persist at the site, demonstrating successful creation of a long-term reactive zone. Additionally, the footprint of the DCE contaminant plume in groundwater has decreased continuously with time. This project illustrates the application of ISCO as a reactive-treatment system for lower-permeability source zones, which appears to effectively mitigate persistent mass flux into groundwater.

  15. Locating sources of surf zone pollution: a mass budget analysis of fecal indicator bacteria at Huntington Beach, California.

    PubMed

    Kim, Joon Ha; Grant, Stanley B; McGee, Charles D; Sanders, Brett F; Largier, John L

    2004-05-01

    The surf zone is the unique environment where ocean meets land and a place of critical ecological, economic, and recreational importance. In the United States, this natural resource is increasingly off-limits to the public due to elevated concentrations of fecal indicator bacteria and other contaminants, the sources of which are often unknown. In this paper, we describe an approach for calculating mass budgets of pollutants in the surf zone from shoreline monitoring data. The analysis reveals that fecal indicator bacteria pollution in the surf zone at several contiguous beaches in Orange County, California, originates from well-defined locations along the shore, including the tidal outlets of the Santa Ana River and Talbert Marsh. Fecal pollution flows into the ocean from the Santa Ana River and Talbert Marsh outlets during ebb tides and from there is transported parallel to the shoreline by wave-driven surf zone currents and/or offshore tidal currents, frequently contaminating >5 km of the surf zone. The methodology developed here for locating and quantifying sources of surf zone pollution should be applicable to a wide array of contaminants and coastal settings.

  16. Spatial variability and source apportionment of PM2.5 across multiple sampling locations in southwest China

    NASA Astrophysics Data System (ADS)

    Shi, F.; Xie, S.

    2015-12-01

    The Chengdu Plain, which is located in the west of the Sichuan Basin, is the largest plain and the fastest-growing area in southwest China. The Chengdu Plain is considered one of the hotspot areas in China. The pollution pattern in this area is unique due to the hilly topography, humid and stagnant weather. To investigate the composition and major sources of the ambient PM2.5, a one-year observation was performed at five sites in the Chengdu Plain during August, 2013 to August, 2014. The five sites contained three urban background sites and two rural background sites. Samples were analyzed for major water-soluble ions, organic carbon (OC), element carbon (EC), and trace elements. The Posit