bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of ototoxic drugs on Rana catesbeiana tadpole orientation behavior and caspase-3 expression.
Authors: Alexander Erika , Schmidt Brian , Simmons Andrea
Published: March 2010

Treatment with the ototoxic antibiotic gentamicin results in specific damage to hair cells of the inner ear and possibly of the lateral line system. In amphibians, damaged hair cells may spontaneously recover. Rana catesbeiana tadpoles were treated with different dosages of gentamicin solution, including a nontreated control, for 24 h. Animals were tested behaviorally and then sacrificed either immediately or after a 7 day recovery period. Their brains were processed for immunohistofluorescent labeling of caspase-3, a marker for apoptosis. Behavioral changes associated with gentamicin treatment included a disruption of balance, altered swimming, and an inability to detect water currents. Animals treated with gentamicin showed increased caspase-3 expression in multiple brain areas compared to non-treated controls. Animals allowed a 7 day recovery period that showed lower caspase-3 label across brain areas than animals sacrificed immediately after treatment. These results suggest that ototoxic damage is associated with increased caspase-3 expression in the central nervous system. In tadpoles, affected behaviors undergo spontaneous recovery, which is itself correlated with decreases in caspase-3 expression. [Work supported by NSF GRFP, NIH, and RI Space Grants.]
Multi-emitters and multi-receivers probe for long cortical bone assessment.
Authors: Minonzio Jean-Gabriel , Talmant Maryline , Laugier Pascal
Published: March 2010

Different quantitative ultrasound techniques are currently developed for clinical assessment of human bone status. This paper is dedicated to axial transmission: emitter(s) and receiver(s) are linearly arranged on the same side of the skeletal site. A multiparameter approach might be relevant to improve bone diagnosis and this be could achieved by accurate measurement of guided wave phase velocities. Clinical requirements and bone/soft tissue heterogeneities constrain the length probe to about 10 mm. Thus efficiency of conventional spatio-temporal Fourier transform is reduced. Signal processing to obtain reliable guided wave velocities is a key point. Here the guided mode phase velocities are obtained using a projection in the singular vectors basis determined by the singular values decomposition of the transmission matrix between the two arrays. This method has been first validated on metallic plates. A set of excised human radius were then probed. Attention was paid to observation of cut-off frequencies because of their high power of discrimination of relevant bone properties (thickness and elasticity). The analysis of the whole spectrum including several branches of intermediate phase velocities is under progress. The so-called bi-directional correction of the soft tissue thickness variations under the probe is used for the in vivo measurements.
Discrimination of bone fractures by low-frequency axial transmission velocity in the radius and tibia.
Authors: Moilanen Petro , Määttä Mikko , Kilappa Vantte , Xu Leiting , Jämsä Timo , Timonen Jussi , Cheng Sulin
Published: March 2010

Low-frequency axial transmission velocity of the first arriving signal (VLF, 0.4 MHz) has a wavelength (8–10 mm) sufficient to probe osteoporotic changes in subcortical bone. Purpose of the present study was to evaluate VLF on retrospective fracture discrimination, using a custom-made ultrasonometer in the midshaft radius and tibia. Preliminary data for 49 non-fractured (NF; 45–87 years) and 16 fractured (F; 56–81 years) postmenopausal females were analyzed. The fractures included were caused by low or moderate trauma and mostly occurred in the forearms or lower legs. Subjects with disease or medication affecting bone metabolism were excluded. Areas under receiver operating characteristic curve were 0.76 for the radius and 0.60 for the tibia VLF. When adjusted for age and BMI, odds ratio for the radius VLF was 1.97 (95% CI: 1.11–3.48), while that for the tibia VLF was not statistically significant. In the contrary, dual-energy x-ray absorptiometry (DXA; whole-body, femoral neck, and L2–L4) was unable to differentiate between the F and NF groups. Despite the small study population, these results suggest that V𝔏𝔉 in the radius discriminates osteoporotic fractures in cases of peripheral fractures, in particular, for which DXA has a limited sensitivity.
Decomposition of two-component pulses: Simulation and phantom experiment.
Authors: Wear Keith A
Published: March 2010

Porous media often support propagation of two compressional waves. When cancellous bone samples are interrogated in through-transmission with broadband sources, these two waves often overlap in time. A method for measuring attenuation and velocity of the two component waves was developed. The method (1) assumes that the transfer function is the sum of two exponentially modulated sinusoids and (2) minimizes the sum of the squared error between a model fit and the data. The method was tested for decomposing a 500-kHz-center-frequency signal containing two overlapping components: one passing through a polycarbonate plate (fast wave) and another passing through a cancellous-bone-mimicking phantom (slow wave). The method yielded estimates of attenuation slopes accurate to within 7% (polycarbonate plate) and 2% (cancellous bone phantom). The method yielded estimates of phase velocities accurate to within 1.5% (both media). The method was tested on simulated data generated using attenuation slopes and phase velocities corresponding to bovine cancellous bone. Throughout broad ranges of signal-to-noise ratio and fast-slow-wave-velocity differential, the method yielded estimates of attenuation slope that were accurate to within 10% and estimates of phase velocity that were accurate to within 5% (fast wave) and 2% (slow wave).
Recovery of structural degradation indicators of human bones using elastic waves.
Authors: Ogam Erick , Fellah Zine El Abeddine , Groby Jean-Philippe , Gilbert Robert , Wirgin Armand
Published: March 2010

Non-ionizing techniques of bone characterization have mostly been based on ultrasonic wave propagation. In this study, bone is characterized via its linear response to vibratory solicitations. The analysis of the response of bones to transient mechanical excitation is made both theoretically and experimentally. An orthotropic three-dimensional finite element interaction model (FEIM) using computerized tomography scan image geometries of excised dry human tibiae bones is developed. The model parameters (nine elastic constants) are recovered by solving an inverse eigenvalue problem using resonance frequencies from vibration spectroscopy. Transient waves are excited and signals acquired along the diaphysis of the tibiae, experimentally by employing piezoelectric transducers and numerically using FEIM and a time integration scheme. The elastic waves propagating as guided modes in the bone are investigated using reassigned bilinear time-frequency distribution. To avoid ambiguity in determining the elastic wave phase velocities due to the dispersive nature of propagation in bone, the longitudinal L(0,1) and flexural F(1,1) phase velocities, measured at their asymptotes, i.e., the bar and Rayleigh velocities respectively, are proposed as indicators for assessing the strength of long bones. Their sensitivity to changes in bone state like the effect of cortical thickness variation due to aging and osteoporosis is examined.
On the relation between effective properties of cancellous bones and quantification of the microstructure.
Authors: Ou Miao-jung Yvonne , Lipton Robert
Published: March 2010

The effective properties of a two-phase composite depends both on the constituent materials and the microstructure. Starting from David J. Bergman’s work on the integral representation formula (IRF) approach for deriving bounds on dielectric properties of composites with isotropic constituents, followed by Golden & Papanicolaou’s work on establishing the link between IRF and spectral theory, the IRF is on now a firm mathematical background for further generalization from isotropic constituents to general constituents. The key feature we are looking for is the separation of information on material contrast from that of microstructure in the IRF. This is especially important for (visco)elastic composites because their current available IRFs do not have this feature, even when constituents are isotropic. In this talk, we will present a recently derived IRF for general (visco)elastic composites with the above feature. The relation between IRF and the quantification of microstructure (as spectrum of a generalized Helmholtz projection operator) will be explained. If time permits, numerical results will be presented and the connection between the IRF and the fabric tensor introduced by Stephen C. Cowin will also be discussed.
Role of absorption mechanisms for ultrasound attenuation in cancellous bone: Macroscopic modeling and experiment.
Authors: Pakula Michal , Kaczmarek Mariusz
Published: March 2010

Evaluation of the relative contribution of physical mechanisms responsible for attenuation of ultrasonic wave in cancellous bone is one of the crucial issues from the point of view of modeling elastic wave propagation and related model-based identification of the structural and mechanical properties of bone material. Considering trabecular bone as a porous material filled with fluid, the wave attenuation may stem from (i) intrinsic absorption in the fluid and solid phase, (ii) friction at the fluid-solid interface, as well as (iii) wave scattering by inhomogeneities (pores/trabeculaes). The commonly used for modeling ultrasound propagation in cancellous bone of the macroscopic Biot’s theory will be discussed in context of its potential applicability for prediction of wave parameters: phase velocity and attenuation coefficient as functions of frequency. Since the model was introduced for long wavelength range, the scattering effects are neglected, and the analysis will be focused on the absorption mechanisms responsible for attenuation of ultrasonic waves in bone material. The suitability of the model will be verified by comparison of results of sensitivity analysis of the model with in vitro experimental ultrasonic data obtained for cancellous bones filled with different fluids.
Characterization of cortical bone fracture with scanning confocal ultrasound and longitudinal acoustic velocity.
Authors: Qin Yi-Xian , Cheng Jiqi , Ferreri Suzanne , Lin Wei
Published: March 2010

Non-invasive assessment of fracture, particularly in non-typical fracture, is a critical health problem. As a promising alternative to the x-ray, ultrasound has demonstrated potentials in early fracture diagnosis. A real-time scanning confocal ultrasound image was developed to evaluate bone defect and bone loss. The objectives of this study were to evaluate the cortical fracture gap size using quantitative ultrasound imaging and the longitudinal ultrasound velocity in bone to predict the fracture gap size. The total fractures were created by MTE compression at the middle diaphysis, with gap size varied from 1–5 mm (N=4). Fractures were tested with the ultrasound scanning with 0.5-mm resolution. The measured ultrasound signals were analyzed to calculate BUA (dB/MHz), ATT (dB), and transverse velocity (m/s). The longitudinal wave velocity was tested using three surface transducers. Strong correlations were observed between ultrasound and x-ray images in fracture size (R2=0.91). High correlation was found between gap size and the longitudinal velocity from 4000 to 3000-m/s for 0–5-mm gaps (R2=0.93). These results suggest that ultrasound is capable to predict bone fracture and provide useful information for longitudinal assessment of complications, such as non-union fracture, and for evaluating healing. [Work supported by NSBRI/NASA and NIH.]
Dynamic acoustoelastic testing for noninvasive detection of microdamage in cortical tissue of long bones.
Authors: Renaud Guillaume , Talmant Maryline , Laugier Pascal
Published: March 2010

First developed for trabecular bone, dynamic acoustoelastic testing (DAT) is based on the measurement of ultrasound (US) pulses time of flight and energy modulations (TOFM and EMs) induced by a low-frequency (LF) acoustic wave, synchronously injected in the probed medium. The technique needs the LF wave to be quasi-uniform in the investigated region and quasi-static in time (compared with the US TOF). US TOFM and EM are related to elastic and dissipative nonlinearities, respectively. Here is presented the application of the technique to cortical tissue of long bones. A LF vibration is generated along the axis of the sample whose frequency corresponds to the first compressional resonance mode. Simultaneously, US pulses are emitted and received by a dedicated probe, after propagation along the axis of the sample. The emitter-receiver distance is chosen and the position of the US probe is adjusted so that the head wave arrives first in time. US TOFM and EM are thus computed using the head wave. After validation in an aluminum cylinder where no dissipative nonlinearity but weak quadratic elastic nonlinearity is observed, in vitro results are presented for bone. DAT is performed on diaphyseal bone sections before and after mechanical damage was induced.
Bone quality assessment at multiple skeletal sites using quantitative ultrasound imaging.
Authors: Serra-Hsu Frederick , Cheng Jiqi , Lin Wei , Qin Yi-Xian
Published: March 2010

Osteoporosis is responsible for nearly 1.5 × 106 fractures annually in U.S. with the most typical sites at the hip, spine, and wrist. Early diagnosis is essential for the prediction of fracture risk. While BMD only represents quantitative information of bone, current quantitative ultrasound (QUS) typically employs index using attenuation (BUA) and velocity (UV) measurements at the calcaneus. The objective of this study aims to develop an image based QUS technology for enhanced diagnostic readings at multiple anatomical sites. With a newly developed scanning confocal acoustic diagnosis system, five embalmed cadaver forearms were disarticulated from the wrist joint, cut at the mid shaft, leaving the interosseous membrane intact, and scanned by the ultrasound. Acoustic phantoms scanned with the new system and basic water coupling show low variation (<7% of mean BUA) with highly linear BUA curves (mean R2=0.96). BUA and UV were analyzed at the distal radius using existing algorithms; however, the distal radius geometry provides much different BUA and UV schemes than the calcaneous so site-specific calculation algorithms are needed. DXA, mCT, and mechanical testing are currently under evaluation. These preliminary data demonstrated feasibility of ultrasound imaging in critical skeletal site, i.e., wrist. [Work supported by NSBRI/NASA and NIH.]
Separating individual modes from multimodal guided wave signals in long cortical bones.
Authors: Xu K. L. , Ta D. A. , Moilanen P. , Wang W. Q.
Published: March 2010

Time-frequency representation (TFR) is one of the classical methods used for guided wave signal processing in assessment of long cortical bones. In this paper, we first used a crazy-climber ridge detection method to separate individual modes from multimodal guided wave signals in the time-frequency domain. Second, a penalization algorithm, based on spline smoothing, was employed to reconstruct the individual modes separately in the time domain. Robustness of these methods was evaluated by analyzing highly noisy simulated signals and experimental signals on bovine tibiae. It was found that the separated TFR ridges, provided by the crazy-climber algorithm, were clearer than using the TFR alone and these corresponding trajectories were in good agreement with theoretical dispersion curves. The penalization algorithm, on the other hand, showed promising performance by yielding good accordance between the reconstructed individual modes and the theoretical predictions. Both the crazy-climber and the penalization algorithms were thus useful for TFR analysis of multimodal signals, even under strongly noisy conditions, by separating and reconstructing the individual contributions in the time domain. These methods can thus significantly improve ultrasonic guided wave signal processing by providing a feasible quantitative assessment of individual modes in temporal multimode signals, recorded in long bones.
Stratified layer imaging using synthetic aperture processing.
Authors: Schock Steven , Ringle Victoria
Published: March 2010

Synthetic aperture processing is applied to seabed reflection data to improve images of stratified sediment layering. Vertical profiles of sediments are limited in dynamic range by sediment scattering. Synthetic aperture processing, which increases the effectiveness along track length of the sonar transmitter and receiver, suppresses scattering noise, thereby allowing detection of stratified layering with weaker reflection coefficients. The image improvement resulting from the application of synthetic aperture processing is determined by comparing reflection profiles generated with and without synthetic aperture processing. The processing algorithm used in the analyses is not the conventional synthetic aperture processing algorithm which is coherent for point scatterers, but is an algorithm that provides coherent processing for planar reflectors.
Fast array processor for the noiselet reverberation model.
Authors: Sullivan Edmund J. , Goddard Robert P. , Greenbaum Hyman A. , Godoy Carlos
Published: March 2010

The noiselet reverberation model, instead of transmitting the pulse itself, transmits a superposition of many copies of the pulse, each copy with a random amplitude and phase. This allows the simulation to mimic the point scatterer method without requiring a prohibitively large number of scatterers. It uses the GRAB ray model to introduce the propagation information. It provides a real-time high-fidelity simulation, providing element-level time series as an output for a planar array of receivers. However, it is presently limited by the phase shift calculations required by the frequency-domain beamformer to about 20 receivers without an unacceptable trimming of the number of rays used. Here, an approach is demonstrated that significantly improves the speed of this computation by identifying those receivers requiring the same phase shift to within a given specified error, such that only a single phase shift computation is required. These receivers fall onto a finite width strip, or quasi stave, that is not required to be parallel to element rows or columns. Along with providing a significant speed-up to the calculation, the approach becomes more efficient as the number of receivers increases, thereby allowing real time simulations using receiver arrays of over 100 elements.
Multidomain modeling of transducers and acoustical systems.
Authors: Thompson Stephen C.
Published: March 2010

Multidomain modeling, recently also called multiphysics modeling, is appropriate for systems in which different parts of the system are modeled using different equations and different modeling variables. Each such domain is modeled using the variables and equations that are appropriate for it, and the domains are coupled by additional equations at their boundaries and in regions of overlap. Acoustic transducers are an obvious example of multidomain systems. Historically, electrical circuit analog modeling was an approach for multidomain analysis. In addition, specific domain couplings have been hard-coded into particular FEA codes for the analysis of some kinds of coupled systems. Today there are FEA codes, as well as codes based on simpler ordinary differential and algebraic equation analysis, that provide a robust framework for this kind of modeling. This paper will discuss these anaylsis methods and provide computational examples from some simple multidomain systems that include acoustic transducers. [Work supported in part by the Office of Naval Research.]
Ducted propagation in the atmosphere, from audible sound to infrasound.
Authors: Waxler Roger , Talmadge Carrick , Gilbert Kenneth , Di Xiao , Blom Phillip , Assink Jelle , Hetzer Claus
Published: March 2010

Earth’s atmosphere supports complicated and highly variable winds and temperature gradients. Temperature inversions and wind jets provide ducts in which sound can propagate efficiently to great distances from the source. Due to the intrinsic variability of the atmospheric winds, these sound ducts are also quite variable, both temporally and spatially. Further, the direction of the atmospheric winds can change dramatically with increasing altitude so that the behavior of the propagated field can become quite complex as the range from the source increases. Despite this, some systematic behavior has been observed in long range sound propagation. An overview will be presented, with an emphasis on the systematic behavior. The current state of our understanding of the sources and consequences of the atmosphere’s variability will be discussed.
Atmospheric sound scattering model to test signal coding methods for acoustic wind profiling.
Authors: Kendrick Paul , Hünerbein Sabine von
Published: March 2010

This presentation concerns simulation of atmospheric sound propagation, including the backscatter of acoustic waves from moving temperature fluctuations. The model has been developed to evaluate the performance of acoustic wind speed profiling techniques, in particular, the use of pulse coding methods which aim to increase range resolution, accuracy, and data availability. Stepped frequency chirps are propagated through the model and the results used to optimize matched filtering algorithms. Results from simulations are presented and the performance of several different signal detection algorithms evaluated. This methodology provides insight into particular problems encountered by the signal detection algorithm and will be utilized to aid the design of an experimental acoustic wind speed profiler. [Work funded by the Engineering and Physical Sciences Research Council (EPSRC).]
A finite difference model for low frequency sound measurement in kraft recovery boilers.
Authors: Hildebrand Robert , Carroll Matthew , Jarvinen Ville , Miettinen Juha
Published: March 2010

Kraft recovery boilers greatly enhance the efficiency of paper pulp mills by burning the organic wastes recovered from the pulp making process and generating electricity, but significant smelt-water explosion hazards exist when steam is used as the working fluid due to sodium compounds in the sludge from the waste incineration process. Current practice is to use acoustic emission sensors to monitor for leaks in the bottom wall and to initiate an automatic shutdown sequence for the boiler once a leak is detected. A high-frequency model previously developed by the authors and verified by measurements performed in Skoghall, Sweden indicated strong attenuation in the sludge between the point of leakage and the detectors, but experimental results demonstrated a pass band at low frequencies (under 20 kHz). In this paper the authors develop a two-degree-of-freedom finite difference model for the prediction of acoustic attenuation at low frequencies. The bottom wall is modeled as a periodic tube and fin arrangement, and a time-domain finite difference method is used whereby the fin and tube are simple lumped elements. The model is then compared to previous experimental results, with which excellent agreement is obtained.
Analytical and finite element modeling of vibro-acoustic modes of a fluid-filled thick-walled hollow microcylinder and applications in low-power particle manipulation.
Authors: Araz Muhammet K. , Lal Amit
Published: March 2010

Nonlinear acoustic interactions such as acoustic radiation forces or acoustic streaming require high-amplitude acoustic pressure or velocity terms to generate observable effects. While at the macro-scale these effects are not widely used; due to the highly compliant microstructures, high-amplitude acoustic pressure and velocity terms have been reached in a microscopic cavity even at very low-voltage drives (1–10 Vpp). Here, vibrational and acoustic modes of a thick-walled fluid-filled hollow cylindrical glass capillary are introduced. Vibrations are coupled to the capillary through a laser cut, C-shaped lead zirconate titanate plate. Mode shapes and dispersion relationships are obtained both analytically and from finite element modeling in ANSYS. Analytical modeling of the microcavity resonator shows excellent agreement with the computational models developed in ANSYS and the experimental results. Coupling of the vibrational modes of the capillary to the fluid enclosed plays an essential role in manipulation and separation of micro- and nanoparticles and biological entities in acoustically excited portable microfluidic platforms. In this regard, proper modeling of the vibroacoustic modes enables calculation of acoustic radiation force field generated inside the microfluidic capillary. Experimental results on particle collection and separation will be presented at the meeting.
Shock wave formation on turbulent coanda surfaces.
Authors: Dowd Thomas
Published: March 2010

In the petroleum industry a procedure called flaring is used, which is the burning off of unwanted gas. Modern day flares use the Coanda effect,which states “when a jet of fluid is passed over a curved surface it bends to follow the surface entraining large amounts of air” to achieve smokeless combustion, increased combustion efficiency, and decreased thermal radiation due to the entrainment of large amounts of air. These advantages are at the cost of increased noise pollution, due to shock wave formation caused by the difference in the nozzle exit pressure and the ambient pressure. Sound called shock-associated noise is generated by the interaction of downstream propagating turbulent eddies and the stationary quasi-periodic shock-cell structure contained in the supersonic jet. A model of shock-associated noise near turbulent Coanda surfaces will be presented and compared with experimental data along with suggestions for reducing noise. Also a visualization of these shock wave formations and their intricacies will be presented if time allows.
Power analysis for decoding of the digital audio encoding format MP3: Decoding the central processing unit and the graphics processing unit.
Authors: Kang Seung Gu , Sun Pil Joung , Kim Cheol Hong , Kim Jong-Myon
Published: March 2010

Power consumption is one of the major design considerations for recent computing systems. MP3 players require MP3 decoding performed on the processor. We analyze the power consumption for MP3 decoding varying the processor type [central processing unit (CPU) and graphics processing unit (GPU)]. In general, the MP3 decoding is performed on CPU . GPU, which is a specialized processor that offloads three dimensional graphics rendering from the CPU, can be used for MP3 decoding since it is used for various computations as well as graphics rendering. At first, we analyze the power consumption for the MP3 decoding performed on CPU by using Inspector tool. And then, we analyze the power consumption for the MP3 decoding performed on GPU. To analyze the power efficiency of the GPU for MP3 decoding, we use CUDA for translating the MP3 decoding process from CPU to GPU. Computer unified device architecture (CUDA) is the computing engine in NVIDIA GPUs that is accessible to software developers through industry standard programming languages. According to our experimental results, the MP3 decoding performed on GPU saves power consumption by 23% compared to that on CPU. [Work supported by the MKE, Korea, under the ITRC supervised by the IITA (IITA-2009-(C1090-0903-0008).]
Ground effects in time-domain simulations of outdoor sound propagation.
Authors: Dragna Didier , Blanc-Benon Philippe , Poisson Franck
Published: March 2010

Finite-difference, time-domain (FDTD) methods are precise and powerful tools to solve linearized Euler equations. Interaction between the acoustic waves with local wind or temperature gradients as well as a complex topography can be taken into account. Recently, a time-domain boundary condition has been proposed [Cotté et al., AIAA J. 47, 2391–2403 (2009)] and has been implemented in a FDTD solver using methods developed in the computational aeroacoustics community [Bogey and Bailly, J. Comput. Phys. 194, 194–214 (2004)]. Propagation of an initial pulse over a distance of 500 m in a two-dimensional geometry is considered in a frequency band up to 1200 Hz. Surface waves which propagate close to and parallel to impedance grounds are exhibited. To validate the obtained results, a comparison is made in the time-domain with an analytical solution. Ground effects are discussed depending on the impedance of the ground. [This work was performed using HPC resources from GENCI-IDRIS (Grant 2009-022203).]
Metamodel predictions for long range speech intelligibility using parabolic equation calculations.
Authors: Hanford Amanda D. , Barnard Andrew R. , Jonson Michael L. , Martin Jay D.
Published: March 2010

The Crank–Nicholson parabolic equation (CNPE) method was used to calculate speech intelligibility for long range propagation of voice messages. How intelligible a voice message will be at long range is very sensitive to atmospheric conditions and parameters such as source height and background noise levels. In order to identify this sensitivity, four independent variables were identified and varied throughout the study. These independent variables are the atmospheric refraction index, which takes into account both temperature and wind gradients within the atmosphere, ambient temperature, source height, and background noise level. CNPE computations were performed for 31 optimally chosen cases where all four of the independent variables were random variables and were inputted into a metamodel. This allows for curve fitting and extrapolation of the existing data to determine intermediate results for any operation scenario defined within the bounds of the current study. Upon doing this, it was determined that the atmospheric refraction index is the most sensitive variable. In addition, there is virtually no dependence on ambient surface temperature.
Wind velocity measurements with acoustic daylight.
Authors: Godin Oleg A. , Irisov Vladimir G. , Charnotskii Mikhail I.
Published: March 2010

Ambient acoustic noise in ocean and atmosphere provides acoustic illumination, which can be used, akin to daylight, to visualize objects and characterize the environment [Buckingham et al., Nature(London) 356, 327–329 (1992)]. It has been shown theoretically [O. A. Godin, Phys. Rev. Lett. 97, 054301 (2006)] that deterministic travel times of acoustic waves propagating in opposite directions between two points in an inhomogeneous, moving, time-independent medium can be retrieved from the cross-correlation function of non-diffuse acoustic noise recorded at the two points. Thus, the noise cross-correlation function contains information on non-reciprocity of sound propagation, which can be utilized to measure flow velocities small compared to the sound speed. This paper presents an experimental verification of the theoretical predictions. Deterministic travel times have been retrieved from cross-correlations of noise recorded at three microphones about 20 m apart and inverted for the sound speed and two horizontal components of the wind velocity. Traffic noise served as the acoustic daylight in the experiment. Accuracy of the passive acoustic measurements of sound speed and wind velocity has been confirmed by comparison with contact measurements of wind, air temperature, and humidity. Possible uses of acoustic daylight for a low-cost environmental monitoring will be discussed.
Acoustic location under metal foam windscreens.
Authors: Webster Jeremy , Raspet Richard , Beam Jason , Dudziak Kelsey
Published: March 2010

Large wind noise reduction outdoors can be achieved by the use of metal foam layers mounted flush with the surface. In this research, a triangular array for source direction determination is mounted under different thickness metal foams. The performance of the array in locating a spark source is determined by measurements with and without metal foam covers. The performance is quantified by agreement with the actual direction and by the chi squared values of the fit to the direction and the speed of sound. Some geometries produced large errors in speed of sound but the corresponding directions were reasonably accurate. Relatively thin layers of metal foam produced accurate estimates for the direction and sound speed. With the microphones mounted just under a 0.5-in.-thick foam, the direction could be measured to within a few degrees. [This work is funded by the Armaments Research, Development, and Engineering Command (ARDEC)].
Gunshot localization using distributed acoustic sensors.
Authors: Di Xiao , Frazier W. Garth , Gilbert Kenneth E.
Published: March 2010

For detecting and localizing gunshot sound, distributed acoustic sensors with various baseline separations (several meters to dozens of meters) are used in our field experiments. The large baselines of the distributed sensor networks, based on the time difference of arrival method, provide improved localization accuracy and have distinct advantages over small arrays. Results are reported and compared for various baseline separations, detection distances, numbers of sensors, and weather conditions. The sound source used is a propane cannon. Several least squares methods are used in the data analysis and source localization. Results from the experiment are presented and discussed. The localization errors are analyzed as a function of combined error sources (GPS, timing, weather, etc.). Possible ways to improve the localization accuracy are suggested. [Research supported by the U. S. Army TACOM-ARDEC at Picatinny Arsenal, NJ.]
Acoustic response of rigid pipe wind-noise reducers for infrasound measurement.
Authors: Poese Matthew E. , Gabrielson Thomas B.
Published: March 2010

A network of rigid pipes with multiple inlets is one commonly employed strategy to filter out pressure fluctuations generated by wind when making infrasound measurements. This talk presents a model of the transfer function of such a rosette filter using a computer model (DeltaEC) that includes thermo-viscous effects at the walls of the pipes. Measurements of this transfer function have been made utilizing the coherence between a calibrated reference microphone and a calibrated microphone shielded by the wind-reduction rosette and these data will be compared to the model. Rosettes with pipes of varied lengths were tested and modeled. The response of the rosette as a function of the vertical arrival angle of the incident plane wave will also be presented. [Work supported by US Army Space and Missile Defense Command.]
Acoustical characterization of rigid porous materials.
Authors: Li Kai Ming , Liu Sheng
Published: March 2010

In an earlier study [K. M. Li, J. Acoust. Soc. Am. Soc. 123, 1352–1363 (2008)], an analytical expression has been derived to predict the penetration of sound into a rigid porous ground due to a monopole source. In the present study, this analytical formula has been exploited for a numerical method to characterize the acoustical properties of rigid porous materials. They can be obtained from a pair of excess attenuation spectra measured above and below a thick layer of the material. Specifically, its propagation constant and complex density ratio can be determined from the measured data by a downhill simplex method. A series of preliminary indoor measurements was conducted in an anechoic chamber for measuring the propagation of sound above and below a layer of glass beads of different sizes. Based on the measured excess attenuation spectra, the acoustical characteristics of two different sizes of glass beads were determined numerically. These acoustical parameters were compared with the predictions based on the classical impedance model.
Interaction of shear horizontal ultrasonic waves with a surface grating: Analytical and experimental results.
Authors: Valier-Brasier Tony , Leduc Damien , Potel Catherine , Morvan Bruno , Bruneau Michel , Izbicki Jean-Louis
Published: March 2010

This paper deals with the propagation of shear horizontal (SH) ultrasonic waves on a plate with one surface grating. The theoretical acoustic field in the corrugated plate is obtained from a linear combination of the Neumann eigenmodes of a plane plate waveguide which bounds outwardly the perturbed surface of the plate considered. Coupling of the eigenmodes with the rough walls is studied using the integral formulation. The effect of the roughness is expressed in such a way that two intermodal coupling mechanisms are highlighted: a bulk coupling and a surface coupling. The first one depends only on the depth of the roughness and the second one on both its depth and its slope. Moreover, the coupling between SH modes is studied experimentally. An electromagnetic acoustic transducer enables a non-contact emission of the SH waves. Notably, the energy transfer from a mode to others so appears to be strongest at frequencies where a relation between the period of the grating and the wavenumbers of the coupled SH modes is verified.
High-quality acoustic cavities based on radial sonic crystals.
Authors: Torrent Daniel , Snchez-Dehesa José
Published: March 2010

Radial sonic crystals are radially inhomogeneous systems that present a dispersion relation similar to one dimensional sonic crystals, with the peculiarity of having low-frequency band gaps. These structures are here employed to design high-quality circularly symmetric acoustic cavities. The presence of band gaps in their dispersion relation allows to localize sound in the cavity centers, leading to strong resonances whose frequency depends on the symmetry of the field. Therefore, it is possible to design cavities with monopolar, dipolar, quadrupolar, etc., symmetry. A proposal for its physical realization is also described, showing that radial sonic crystals are possible to build by using the concept of acoustic metamaterials. [Work supported by MCIIN of Spain and ONR.]
Ultrasonic characterization of fluid saturated absorbing polymethylacrylate porous plates.
Authors: Derible Serge , Campistron Pierre , Freiha Georges , Franklin Hervé , Nongaillard Bertrand
Published: March 2010

Experiments are led on five manufactured porous polymethylmethacrylate (PMMA) samples, numbered 1–5. Their constituting materials are packed beads whose diameters run from 200–300 μm for plate 1 up to 600–700 μm for plate 5. The plates are normally insonified by wide band transducers acting within the frequency range 100–800 kHz. The samples obey Biot’s theory taking into account the viscoelasticity of the solid frame. The reflection and transmission coefficients are measured and then added or subtracted to give the two transition terms, issued from S-matrix theory. They are connected to the symmetrical or asymmetrical motions of the faces of the plates. Those terms allow us a characterization of the porous media by means of a computer program that seeks the values of the Biot parameters giving the best agreement between theory and experiments.
Fiber based transduction.
Authors: Phung Ethan N. , Deschamp Barbara , Thompson Charles
Published: March 2010

In this work we will examine the conversion of mechanical vibration into electrical energy. This is done by using a conductive fiber in close proximity to a conductive plate. In this configuration it is shown that the fiber behaves as a square law detector. This observation may make it useful for mechanical power conversion for radio frequency demodulation. Based on the previous findings, the mechanical vibration of the fiber can be modeled by a simple damped oscillator with external applied source. The result indicated that the original signal can be recovered.
A novel algorithm for sparse classification.
Authors: Bharadwaj Sujeeth , Hasegawa-Johnson Mark
Published: March 2010

A recent result in compressed sensing (CS) makes it possible to perform non-parametric speech recognition that is robust to noise and that requires few training examples. By taking fixed length representations of training examples and stacking them in a matrix, a frame or an over-complete basis can be constructed. Gemmeke and Cranen showed that sparse projections onto this frame recover the correct transcription with 91% accuracy at -5-dB SNR. The goal of speech recognition is not sparse projection onto training tokens, but onto training types. Sparse projection onto types can be achieved by building a frame for each word in the dictionary and stacking the frames to form a rank 3 tensor. Speech recognition is performed by convex linear projection onto the tensor, with sparsity enforced only in the index that specifies type. A mixed L1/L2 relaxation was derived, leading to a Newton descent algorithm that converges to the global optimum.
Speech classification using penalized logistic regression with hidden Markov model log-likelihood regressors.
Authors: Birkenes Øystein , Matsui Tomoko , Tanabe Kunio , Johnsen Magne Hallstein
Published: March 2010

Penalized logistic regression (PLR) is a well-founded discriminative classifier with long roots in the history of statistics. Speech classification with PLR is possible with an appropriate choice of map from the space of feature vector sequences into the Euclidean space. In this talk, one such map is presented, namely, the one that maps into vectors consisting of log-likelihoods computed from a set of hidden Markov models (HMMs). The use of this map in PLR leads to a powerful discriminative classifier that naturally handles the sequential data arising in speech classification. In the training phase, the HMM parameters and the regression parameters are jointly estimated by maximizing a penalized likelihood. The proposed approach is shown to be a generalization of conditional maximum likelihood (CML) and maximum mutual information (MMI) estimation for speech classification, leading to more flexible decision boundaries and higher classification accuracy. The posterior probabilities resulting from classification with PLR allow for continuous speech recognition via N-best or lattice rescoring.
Integrating evidence over time: A look at conditional models for speech processing.
Authors: Fosler-Lussier Eric , Morris Jeremy , Heintz Ilana , Prabhavalkar Rohit
Published: March 2010

Many acoustic events, particularly those associated with speech events, can be thought of as events in a rich descriptive subspace where the dimensions of the subspace can be thought of as a sort of decomposition of the original event space. In phonetic terms, we can think of how phonological features can be integrated to determine phonetic identity; for auditory scene analysis we can look how features like harmonic energy and cross-channel correlation come together to determine whether a particular frequency corresponds to target speech versus background noise. Some success has been achieved by thinking of these problems as probabilistic detection of acoustic (sub-)events. However, event detectors are typically local in nature and need to be smoothed out by looking at neighboring events in time. This talk describes using conditional random fields models within the automatic speech recognition setting to combine bottom-up speech event detectors. The talk will explore some of the successes and limitations of this log-linear method which integrates local evidence over time sequences.
Machine learning strategies for recovering speech articulatory trajectories and gestures from speech.
Authors: Mitra Vikramjit , Nam Hosung , Espy-Wilson Carol Y. , Saltzman Elliot , Goldstein Louis
Published: March 2010

Articulatory information can improve the performance of automatic speech recognition systems. Unfortunately, since such information is not directly observable, it must be estimated from the acoustic signal using speech-inversion techniques. Here, we first compare five different machine learning techniques for inverting the speech acoustics generated using the Haskins Laboratories speech production model in combination with HLsyn. In particular, we compare the accuracies of estimating two forms of articulatory information (a) vocal tract constriction trajectories and (b) articulatory flesh-point pellet trajectories. We show that tract variable estimation can be performed more accurately than pellet estimation. Second, we also show that estimated tract variables can improve the performance of an autoregressive neural network model for recognizing speech gestures. We compare gesture recognition accuracy for three different input conditions: (1) generated acoustic signal and estimated tract variables, (2) acoustic signal and the original (or groundtruth) tract variables, and (3) acoustic signal only. Results show that gesture recognition accuracy was, not surprisingly, best for condition (2) and worst for condition (3). Importantly, however, condition (1) yielded better performance than (3), demonstrating that estimated tract-variable articulatory information is indeed helpful for automatic speech recognition.
Formulation for statistics of echoes due to a finite number of scatterers and patches of scatterers in a directional sonar beam.
Authors: Stanton Timothy K.
Published: March 2010

A general theoretical formulation is developed for echo statistics associated with a finite number of scatterers and patches of scatterers, each being randomly located in a directional sonar beam. This is the case of a direct-path sonar where there are no echoes from the seafloor and sea surface. The formulation is derived by combining the equations of Ehrenberg and colleagues (single scatterer randomly located in sonar beam) and Barakat (sum of finite number of random variables). Each scatterer or patch of scatterers is independent and can have its own echo probability density function (PDF) (before beampattern effects). Examples show that the PDF of the echo (as received by the sonar) is strongly non-Rayleigh due to beampattern effects and finite number of scatterers or patches. Numerical simulations are made for validation. [Work supported by ONR.]
Featureless classification for active sonar systems.
Authors: Soules Mary E. , Broadwater Joshua B.
Published: March 2010

Active sonar systems depend on classification algorithms to identify target echoes and suppress false alarms. Historically, classifiers use a set of empirically derived features that exhibit some statistical separation between background clutter and target echoes. In an ideal scenario, these features would form a sufficient set of statistics capturing all of the information required to classify an echo return. Unfortunately, due to their empirically derived nature, features are rarely provably sufficient. To overcome this drawback, a featureless classifier will be presented. Instead of features, the raw data samples, which form a trivial but provable set of sufficient statistics, are used. The adaptive cosine estimate algorithm has a history of success with featureless classification in other applications and is well suited for underwater acoustics. An in-depth look at the featureless algorithm that will include comparisons to several traditional active sonar classifiers will be provided.