bluuebunny/crossref_metadata_2025 huggingface dataset:
Artifact reduction in medical ultrasound
Authors: Schwartz Gary A.
Published: February 2014

Interpretation of medical ultrasound images is confounded by the presence of significant acoustic imaging artifacts. These artifacts result from diffraction, propagation, and scattering effects and regional variations in these effects. Commercial diagnostic imaging systems have taken various design approaches to mitigate the artifacts. Anatomic features widely vary in size relative to the imaging wavelengths, resulting in angular scattering variations and speckle-limited resolution. Tissue attenuation varies greatly resulting in shadowing and enhancement. This review will look at the origins of certain acoustic imaging artifacts and discuss methods that have been applied to address their contribution to image quality. Included in the discussion will be acoustic methods (such as spatial compounding), and signal processing methods (such as attenuation compensation and frequency compounding). Design approaches and clinical image examples will be presented.
Higher order nonlinear ultrasonic imaging
Authors: Haider Bruno , Chiao Richard Y.
Published: February 2014

The processing of second harmonic echoes from both biological tissue and contrast agents has generated new diagnostic methods in medical ultrasound. The work presented here demonstrates the extraction of higher order nonlinearities. The underlying idea is to model the nonlinear wave propagation or reflection from a contrast bubble by a polynomial expansion of some basis waveform. When this model is excited by a number of transmit pulses which only differ in their amplitude and phase then the coefficients of this polynomial model can be extracted through least squares inversion. The coefficients correspond to the individual nonlinear components. An important feature of the method is the evaluation of nonlinear components whose spectra are folded back into the transmission band. All odd order nonlinearities can create such echo components. The reception of these components eliminates the high bandwidth requirements encountered in second harmonic imaging. Higher-order even harmonics may also be detected by taking advantage of the harmonic fold-back process. Folded frequency components will be centered around DC and at two times the transmit frequency (2 f0). This still requires a bandwidth sufficient to detect signals at 2 f0 but eliminates the reception at higher multiples of f0.
B-mode blood flow (B-Flow) imaging
Authors: Chiao Richard Y.
Published: February 2014

B-Flow is a new technique that extends the resolution, frame rate, and dynamic range of B-mode to simultaneously image blood flow and tissue. B-Flow relies on coded excitation to boost weak signals from blood scatterers and on tissue equalization to simultaneously display flowing blood and tissue without threshold decision and overlay. Various classes of codes such as Barker and Golay may be used. Clinical B-Flow cineloops demonstrate 3× resolution and frame rate improvement over color flow, which, together with over 60 dB of display dynamic range, is able to image hemodynamics and vessel walls with unprecedented clarity.
Spatial sampling resolution study on BAI-mode imaging for defect detection
Authors: Yin Xiangtao , Nayfeh Osama , Morris Scott A. , O’Brien William D.
Published: February 2014

The principal concern with regard to defect detection in hermetically sealed flexible food packages is the safety and shelf life of the food. The spatial sampling issue of the pulse echo backscattered amplitude integral (BAI) mode imaging technique for defect detection is investigated. In our previous spatial sampling study, it has been shown that for channel defects, the contrast to noise ratio (CNR) degrades as a function of scanning step size on each dimension of the image. To further understand spatial sampling resolution of this method, BAI imaging technique is applied to rectilinear grided dot samples with different grid sizes (distance between adjacent dots). Data is collected with the transducer scanned in a zigzag raster pattern. Quantitatively, the CNR and ΔBAI values are assessed to evaluate the image quality versus the changing spatial interval between dots. At a given operating frequency and a fixed spatial grid size, the CNR and ΔBAI value degrade as a function of the scanning step size on each dimension. Not only the scanning step size, but also the ultrasound beam spot size affect the spatial sampling resolution in the BAI imaging technique for defect detection. [Work supported by the C-FAR program, University of Illinois.]
Spatial resolution performance of a one-dimensional linear amplitude-steered array in an attenuating medium
Authors: Hartleben Sarah A. , Lassale Virginia , O’Brien William D.
Published: February 2014

The amplitude-steered array concept [J. Acoust. Soc. Am. 59, 1040 (1976)] introduced the idea of steering the maximum response of a linear array by amplitude weighting the output signals of the elements. Recently, an evaluation of the linear amplitude-steered array assessed its performance such as lateral and axial resolution in a lossless medium [Frazier, Hughes, and O’Brien, J. Acoust. Soc. Am. 107, 2430 (2000)]. In the present work, the array’s performance is evaluated in an attenuating medium similar to biological tissue (1 dB/cmMHz). Similar to the array’s performance in a lossless medium, the length of the array limits the axial and lateral resolution in the attenuating medium. As the steering direction is decreased, which corresponds to increasing frequency, the array’s performance with attenuation has a worse resolution when compared with its performance without attenuation. For example, using a 10-cm-length array and a 6-deg steering direction (4.6 MHz), the axial resolution (−3-dB point spread function width) with attenuation was 7.9 mm, compared with 6.4 mm without attenuation. When the steering direction was increased to 12 deg (2.3 MHz), the axial resolution with attenuation was 12.8 mm compared with 11.5 mm without attenuation. In the attenuating medium there is increased importance on the steering direction or frequency. [Work supported by NIH CA09067.]
Elasticity imaging with time-resolved pulsed elastography
Authors: Sandrin Laurent , Tanter Micka , Catheline Stefan , Fink Mathias
Published: February 2014

Time-resolved pulsed elastography is a promising technique for imaging the shear modulus of soft tissues. It is based on the investigation of a low-frequency transient shear wave using an ultrafast ultrasonic imaging system (up to 10000 frames/s) composed of 128 channels sampled at 50 MHz and having 2 Mbytes. The system is connected to a linear array of transducers. Displacements induced by the propagating shear wave are measured using cross correlation of the ultrasonic signals. A low-frequency vibrating device was designed. The linear array of transducers is placed between two rods fixed to electromagnetic vibrators. The rods are either orthogonal or parallel to the active surface of the transducer array. The low-frequency shear waves are sent using the rods which are placed in such a way that the lobes of the induced shear waves superimpose in front of the transducer array. Large displacements are observed in the tissues which makes deeper investigations possible. Movies of the low-frequency (50–200 Hz) shear wave propagation through soft tissues can be used either to estimate the shear modulus distribution in the medium by direct local inversion, or to localize visually lesions of unexpected elasticity. In vivo measurements in human breast will be presented and discussed.
Quantitative elasticity imaging with ultrasound
Authors: Barbone Paul E. , Bamber Jeffrey C.
Published: February 2014

For the past 10 or so years, various researchers have proposed different ways to measure strain distributions in vivo. The measured strains result from various sources including external palpation, low frequency vibration, or internal motion. By examining the relative strains in adjacent tissues, it is thought that one can infer the relative distributions of tissue stiffness. In this presentation, we discuss the process of creating a quantitative stiffness image from a given measurement of tissue strain. We show that the strain image by itself is insufficient information to infer the elastic stiffness. By examining the well-posedness of the inverse problem, we determine what information is needed to supplement the strain image in order to quantitatively infer the elastic stiffness distribution. Methods for obtaining the required information in vivo are currently being developed. We show examples of incorrect and misleading stiffness reconstructions in the absence of the required data. [Work supported by BU, NIH, Fulbright Foundation, ICR, and NSF via CenSSIS ERC.]
Comparison of stiffness estimated with vibration elastography to dynamic mechanical analyzer results
Authors: Oliphant Travis , Kinnick Randy , Greenleaf James , Dresner Alex , Ehman Richard
Published: February 2014

Several pathological conditions induce altered tissue mechanical properties. The goal of elastography is to noninvasively generate images and/or measurements of tissue mechanical properties. Vibration elastography is a technique for measuring stiffness using low-frequency (10–1000 Hz) shear waves to vibrate a region of interest. Ultrasonic time-delay estimation techniques or phase-contrast magnetic resonance methods measure the amplitude and phase of one or more components of the harmonic vibration everywhere in the region. Under a linear, isotropic, and incompressible tissue model, the displacement field in a locally homogeneous region satisfies the vector-Helmholtz equation and stiffness estimation becomes an inverse-scattering problem where the field is known inside the region of interest. Using an optimal inversion algorithm recently developed by the authors and a data-dependent noise-model, an estimate of local stiffness along with its uncertainty is reported at frequencies from 200–600 Hz for three gels of varying concentrations. For each gel, the displacement is measured using either ultrasound or magnetic resonance. The vibration elastography estimate of stiffness for the three gels is less than the complex modulus measured over a frequency range of 10–250 Hz using the shear sandwich clamp on a dynamic mechanical analyzer (DMA 2980, TA Instruments) by an approximate factor of 3.
Experimental results of real-time freehand elasticity imaging
Authors: Hall Timothy , Zhu Yanning , Spalding Candace , Cook Larry
Published: February 2014

A system for high-speed calculation of tissue elastic properties using a clinical ultrasonic imaging system will be presented. The hypothesis driving this development is that real-time feedback of elasticity images is essential in obtaining high-quality data (consecutive images with high spatial coherence). Extensive experience with laboratory fixtures and off-line processing of elasticity data showed that problems occurring in data acquisition often resulted in poor elasticity image quality. The delay in observing the resulting images, due to off-line processing, resulted in slow progress in developing experimental techniques and signal processing strategies. When high-quality data were obtained, high contrast-to-noise images were available. Initial experience with real-time freehand elasticity imaging shows that images with similar high contrast to noise can be obtained. Results in volunteer patients have shown that high-quality elasticity images are easily obtained in vivo for a variety of breast pathologies, and the changes in breast tumor elasticity during the course of chemotherapy can be monitored. Video of real-time elasticity imaging will demonstrate the ease with which these results are obtained. [We are grateful for the support by USAMRAA DAMD17-00-1-0596, Siemens Medical Systems, and NSF BES-9708221.]
A trimodal directional transducer
Authors: Butler Alexander L. , Butler John L. , Rice Joe
Published: February 2014

A cylindrical transducer, which achieves a directional horizontal beam through the addition of the first three extensional modes of radial vibration is presented. The three modes are the omni, dipole, and quadrupole modes, related in resonant frequency by the formula fn=f0(1+n)1/2, where ∫n=0, 1, and 2, respectively. The addition of the quadrupole mode to the omni and dipole modes yields a frequency independent horizontal beam that has greater directionality than the commonly used two-mode scheme, first described by S. L. Ehrlich and P. D. Frelich [U. S. Patent 3,290,646 (1966)]. Theoretical and measured beam pattern results on two different trimodal cylindrical transducer designs are presented and compared. One of the transducers, fabricated from rings of the same diameter, operates in the vicinity of 20 kHz and combines modes with three different resonant frequencies. The second transducer, fabricated from rings of different diameters, operates in the vicinity of 10 kHz and combines modes with the same resonant frequency. It is shown that steered beamwidths of 90° and front to back ratios of 10 dB can be readily obtained from comparatively small diameter transducers. [SBIR work supported by ONR and SPAWAR.]
Development and validation of a computational process for pass-by noise simulation
Authors: Zhang Zhidong , Vlahopoulos Nickolas , Allen T. , Zhang K. Y.
Published: February 2014

The indirect boundary-element analysis is employed for developing a computational pass-by noise simulation capability. An acoustic field reconstruction process is developed in order to generate the definition of the main pass-by noise sources in a computational model. Numerical boundary-element models that characterize the individual sources are combined in order to develop a system model for the pass-by noise simulation. The acoustic field reconstruction process is validated initially by employing analytical solutions. The numerical techniques are also validated through comparison between numerical results and test data for component-level and system-level analyses. Specially, the source definition capability is validated by comparing the actual and the computationally reconstructed acoustic field for an engine intake manifold. The overall pass-by noise simulation capability is validated by computing the maximum overall sound-pressure level for a vehicle under two different driving conditions. [Research supported by the Ford University Research Program.]
Interior noise prediction using a broadband high-frequency boundary-element method based on energy and intensity variables
Authors: Franzoni Linda , Lussier Brett , Bliss Donald
Published: February 2014

The analysis of high-frequency broadband sound fields is computationally intensive if it is done on a frequency-by-frequency basis. In addition, traditional numerical methods require that the boundary-element or finite-element model be discretized into elements that are fractions of a wavelength in size. Despite the high-resolution numerics, in many cases the resulting broadband mean-square pressures are spatially fairly uniform. In this work a boundary element approach has been developed that uses uncorrelated broadband energy sources whose strength and directional properties satisfy certain conditions at the boundary. This method considers all frequencies at once and the element size is large compared to a typical wavelength in the frequency band. There is good agreement between the energy-based boundary-element method and exact solutions for a three-dimensional enclosure with an interior sound source. Spatial correlation effects, which are not in the current model, are also discussed. [Work sponsored by NSF.]
Modeling absorbent finite element for numerical disipation
Authors: Picard Lopez M. A. , Solana Quiros P. E. , Arizo Serrulla J. V.
Published: February 2014

The modeling of the absorbent materials is of great importance for accurate results of the sound field in irregular enclosures using different models by means of finite elements. In this paper different models of porous materials are proven, some already well known due to Craggs, for different geometries of enclosures. The computed results are compared with experimental results obtained demonstrating the reliability of the method and their precision, as well as the validity of the modelization for the absorbent elements by means of their placement in different positions inside the enclosure and for different frequencies. The physics properties used by the absorbent materials are the porosity, the mass density, the flow resistance, and the structure factor. The kinetics, potential, and dissipation energy were considered by the pattern variational used in the FEM. For the discrete distribution of points of the enclosure and the results obtained, averaging of the average residuals has been made. On the other hand, between computed and measured sound pressure values, a Pearsons correlation coefficients has been carried out. There are about 0.8 in numerous cases, an intermediate frequencies. With the absorbents and the numeric method employed, good approaches have been reached.
Simulating an audio beam: A second-generation wavelet collocation method to numerically solve the Khokhlov–Zabalotskaya–Kuznetsov equation
Authors: Lee Kelvin C. M. , Liew Yew-Hin , Gan Woon-Seng
Published: February 2014

The Khokhlov–Zabalotskaya–Kuznetsov (KZK) equation is a nonlinear parabolic wave equation which describes an intense finite-amplitude directional sound beam and accounts for the combined effects of diffraction, absorption, and the nonlinearity behavior of the sound beam in air. A general exact solution has not been found for the KZK equation. Nevertheless, it is usually solved by approximate methods or numerical techniques. A second-generation wavelet collocation method using a lifting scheme is used to numerically solve the KZK equation in a highly accurate and efficient manner and has been found to have significant improvements over the conventional finite-difference scheme. Using a new approach to construct wavelets on the interval in the spatial domain (independent of the Fourier transform), the method uses a computational grid which adapts dynamically in time to allow for solution refinement in local regions with sharp transitions, e.g., development of shocks. It is also found to be particularly effective in the treatment of nonlinear terms and general boundary conditions in the equation. Furthermore with a lifting scheme, the wavelet transform can be computed in place of the original signal without the need for auxiliary memory.
New woodwind instruments
Authors: Jones Lewis
Published: February 2014

Progress towards the development of woodwind instruments designed to play fluently in tuning systems other than 12-note equal temperament is described. The problems of closing many toneholes with only ten digits are outlined, and past solutions, depending chiefly on rod and lever keywork, are briefly reviewed. The alternative of largely keyless toneholes, as embodied in Jones and Armitage’s 19ET recorders (1999) is considered. The electromechanical means of tonehole closure introduced in Giles Brindley’s ‘‘logical bassoon’’ is taken as a point of departure for a range of woodwind instruments including flutes dividing the octave into as many as 36 steps, others of exceptionally deep pitch, and others, narrow but of great length which, by exploiting the higher harmonics of the air column can, without impossibly many toneholes, produce divisions of the octave into 72 or 96 steps. Softare mediates between practicable fingerings and at times complex patterns of tonehole movement. A scheme of fingering is proposed which is intended to enable a single player to learn to play in many alternative tuning systems while preserving as many essential parallels between fingering and sound as possible.
Conventional harmonic behavior associated with the equal tunings of 17 and 19 notes
Authors: Blackwood Easley
Published: February 2014

It will be demonstrated how diatonic behavior associated with the equal tunings of 17 and 19 notes is virtually identical to that of the standard 12-note equal tuning. However, levels of discordance are noticeably different among the three tunings. The reasons for this will be shown in detail. It will also be shown how the conventional musical notation—the five-line staff with treble and bass clef, as well as accidentals—is an accurate and comprehensible representation of the tunings of 17 and 19 notes. Musical illustrations in the form of brief (4-minute) compositions, electronically created, can be provided. Funding for this study was provided by a grant from the NEH, and administered through Webster College, St. Louis.
Customizing vehicle interior noise to reflect the brand image
Authors: Schedl Hans P.
Published: February 2014

Noise control engineers in their endeavors to make vehicles as quiet as possible have succeeded thanks to major strides in measurement techniques. The different noise sources in vehicles are now quite well known. Additionally, sounds may be simulated and easily modified on simple PCs. Through psychoacoustic means, we are able to evaluate and understand the effects of noise on human beings. A totally new approach to vehicle interior noise now exists. Engine noise conveys meaningful information to the driver, and thus, noise characteristics constitute a design attribute. Manufacturers are increasingly establishing design rules for the sound of their cars to meet special requirements and preferences of their potential customers. The design rules are meant to yield a vehicle brand-specific sound. This paper analyzes the positive and negative effects of noise on both driver and passengers in a vehicular environment and how sound is used as a marketing and public relations instrument. We also examine briefly the way sound-effect design affects a project’s progress, cost and time limits. An example will demonstrate how the interior noise of a basic car is modified to either sound like an upper-class luxury sedan or like a high-performance sports car.
Quantifying customer perceptions of impulsive vehicle noise
Authors: Blommer Mike , Amman Scott , Hoffman Deanna
Published: February 2014

Sounds such as spark and diesel knock, squeaks and rattles due to body and suspension components, gear rattle, and other impulsive events, can occur in vehicles and be a major source of customer dissatisfaction. It is desirable to not only know the detection thresholds of these impulsive events, but also the relative annoyance they impart on the customer once they become audible. This work describes research addressing both aspects. The first part of the paper presents a generalized detection model of impulsive events in common vehicle background noises (e.g., wind, road, and powertrain noise). Important properties of the model are the combination of impulsive event information across frequency and also the effect of overall background noise level on detection thresholds. Application of the model to predict detection thresholds for spark knock and also squeaks and rattles is presented. Comparisons are made to measured subjective thresholds. The second part of the paper presents research in objectively quantifying the relative annoyance of impulsive sounds as a function of their temporal and amplitude distributions, as well as their loudness. Comparisons are made to objective metrics used for characterizing single impulsive events.
Future trends in the automotive sound package industry
Authors: Saha Pranab
Published: February 2014

With various challenges in the automotive industry, there are enormous opportunities in sound package treatments. Although the fundamentals of the sound package practices have changed very little, the technology has changed significantly, and this has brought about new opportunities. More and more the supplier companies are asked to join OEM companies in actively assisting with the optimization of sound package treatments in vehicles. This environment encourages innovation and suppliers now can bring in new concepts and products that were not thought of before. This adds more value which is a combination of performance, cost, and weight. New products that are coming to the industry are products like fine fibers and barriers for airborne noise, and sprayable damping materials for structure-borne noise. In addition, there are new test methods that are intended to validate these products which will help acoustics in the vehicle. This paper discusses these trends, and associated opportunities and challenges in the automotive sound package industry in the years to come.
Computational methods for prediction and control of automotive interior noise
Authors: Raveendra S. T.
Published: February 2014

Prediction of noise and vibration characteristics is important to the automotive community. Typically, noise and vibration testing are performed on prototypes of vehicles during pre-production stages of the development. Although testing is an essential tool, it is not the most effective tool since it is done at the later stages of the development. As a result it is not possible to make major design modifications that may be necessary for the effective treatment of the noise and vibration problems. On the other hand, computational modeling and simulation is feasible at the early stages of the design and is thus effective for the management of noise and vibration problems. This presentation will demonstrate how boundary-element method based techniques can be used to predict and effectively control noise in the interior of an automobile. Initially, a technique based on acoustic contribution analysis that intuitively allows the reduction of noise in the interior of an automobile will be demonstrated. This will be followed by a demonstration of an integrated experimental/computational simulation technique based on the near-field acoustical holography that permits the identification of panel vibrations that contribute to the noise in the interior of an automobile.
An experimental investigation of techniques for reducing flow-induced cavity resonance
Authors: Zoccola Paul
Published: February 2014

Excitation of cavity resonance by flow over an aperture is often a source of unwanted noise in aerospace, automotive, and marine applications. An experimental investigation of three resonance reduction techniques was conducted. These were: a fence at the upstream edge, fluid injection, and a new technique developed by the author, in which fluid from the boundary layer is diverted into the cavity. Spectra of the pressure in the cavity were obtained for various flow speeds. Results show that the fence and the boundary-layer diversion technique have the effect of reducing the Strouhal number of the flow-excited sheartones, delaying resonance to higher speeds. Reduction at the resonant speed is also observed. The boundary layer diversion technique was much more effective than the fence. The Strouhal number reduction effect is not observed with fluid injection. The effect on resonance reduction by fluid injection as a function of several parameters, including the rate of fluid injection, is discussed.
Fiber optic sensor system for structural acoustics control
Authors: Yu Miao , Balachandran Balakumar
Published: February 2014

Recent work on acoustic measurements using a fiber-tip-based Fabry–Perot sensor system is presented. A single Fabry–Perot sensor using a path matched Mach–Zehnder interferometer is developed, and by taking advantage of an integrated optical circuit phase modulator, a digital demodulation scheme based on the phase stepping technique is developed. It has been determined that this system can be used to detect acoustic fields in the frequency range of 20 Hz–6 kHz with a sensitivity of 0.9 rad/Pa. This sensor is designed to be used in a multiplexed architecture to provide inputs to a structural acoustic control system. A series of experiments are performed to investigate the possibility and potential use of this sensor system for acoustic noise detection. In this study, initial test data from the prototype optical sensor microphone are presented and the envisioned multiplexed sensor scheme and control system are illustrated.
‘‘Sonoluminescence’’ from the early Universe
Authors: Turner Michael
Published: February 2014

The tens of microkelvin variations in the temperature of the cosmic microwave background (CMB) across the sky are snapshots of the Universe at 400000 years of age and a Rosetta Stone for unraveling its earliest history. During the first 400000 years the lumpy distribution of dark matter excited gravity-driven acoustic oscillations of the ordinary matter. Pressure provided by the photons in the CMB, which were tightly coupled to the ordinary matter, acted as the restoring force for these compressional modes. During an oscillation, photons were alternately compressed and heated, and rarefied and cooled. Ordinary matter and photons decoupled at 400000 years, and CMB photons streamed freely to us, creating a snapshot of modes caught at maximum compression (hot spots) and maximum rarefaction (cold spots) at this early time. The pattern of hot and cold spots on the CMB sky today is being used to determine the curvature of the Universe, the Hubble constant, the total amount of ordinary matter and of dark matter, and to test theories of the early Universe including inflation.
The other ocean: probing Europa’s interior with natural ambient noise sources
Authors: Thode Aaron M. , Zanolin Michele , Lee Sunwoong , Ratilal Purnima , Wilson Josh , Makris Nicholas C.
Published: February 2014

Jupiter’s moon, Europa, possesses a surface composed primarily of water ice. Gravity and magnetic data collected by the NASA Galileo Orbiter over the past five years have provided increasing evidence that an ocean exists underneath this layer, and that the combined ice/water layer thickness is 80–170 km, although the ice shell thickness remains unknown. The surface is covered by numerous fractures and ridges, believed to have formed in response to tidal deformations generated by Europa’s slightly eccentric 85-hour orbit around Jupiter. A recently published model [Hoppa et al., Science 285, 1899–1902] argues that certain cycloidal fractures must form during a single revolution, and propagate horizontally at an average speed of 3 km/h. Considerations from ice mechanics suggest that these propagating fractures would generate significant acoustic energy in the frequency range 0.5–4 Hz, where low attenuation in the ice/water environment is expected. In this presentation an acoustic sound speed profile for Europa is constructed, and standard ocean acoustic techniques are used to demonstrate how an array of geophones on the icy surface could simultaneously localize discrete events and invert for the ice-layer thickness.
Correlation of resonance spectra excited by acoustic waves on elongated elastic objects with elastic bulk parameters and object identification
Authors: Uberall H. , Werby M. F.
Published: February 2014

Acoustic resonance spectra are calculated for scattering of acoustic signals from elongated objects composed of six elastic materials with two aspect ratios of 3 and 6. The incident field is along the axis of symmetry and broadside. A comparison is made of the resonance locations of the six materials (brass, nickel, aluminum, steel, manganese, and tungsten carbide) representing a broad spectrum of elastic materials. For the principal resonances the ratios are seen to correspond exactly to the Rayleigh phase velocities on an evacuated half-space, or alternatively to the shear bulk velocity and are a function of the Poisson ratios of the material. Further, the resonance widths are related inversely to the density of the material and the shear velocity (the mechanical impedance of the shear wave). Time-domain calculations are also carried out and the resonance widths and travel times may be identified with the material properties of the target. Thus, the material properties of such objects including elongation may be distinguished for submerged objects, and this is a useful tool for inverse issues.
Gel formation monitoring by acoustic spectroscopy
Authors: Martinez Loïc , Serfaty Stéphane , Senouci Brahim , Giesmar Pascal , Gindre Marcel
Published: February 2014

An acoustic technique in the audible range has been developed to characterize the sol–gel process. Resonances appear at the sol to gel transition of a sol–gel matrix when submitted to an acoustic wave. The range of the associated resonance frequencies leads to a very low propagation speed of sound (about 20 m/s). The resonance frequencies versus time curves, corresponding to the harmonic propagation modes, converge to a unique intersection point with the time axis corresponding to the gelation time tg. The temporal evolution of the resonance frequencies features the formation of the network. Actually, the evolution of the matrix is independent of the initial conditions (precursor concentration, hydrolysis rate). Depicting the ‘‘reduced frequency’’ fi/fi(∞) [fi(∞) is the long-term resonance frequency for the harmonic mode i] versus the ‘‘reduced time’’ t/tg for various Si concentrations and hydrolysis rates results in a unique curve, revealing the insensitivity of the matrix formation process to the input parameters. A propagation model of an acoustic wave in a cylindrical cavity is proposed, to compute the resonance frequencies as a function of the longitudinal to transverse propagation velocity ratio CL/CT. The comparison with the experimental data is conclusive.
The influence of a strong acoustic cw wave on a weak signal in rock
Authors: Soustova Irina , Nazarov Veniamin , Sutin Alexander , Radostin Andrey
Published: February 2014

We are conducting studies of the effect of a strong pump wave on a probe wave in rock. Specifically, we are measuring resonance frequencies and quality factors (applying linear resonant ultrasound spectroscopy) for a relatively weak probe wave in the presence of a strong, cw pump wave. Experiments conducted in sandstone demonstrate a shift of the resonance frequency and increasing of Q factor in the presence of the low frequency pump wave. The model describing this phenomenon is based on including small hysteretic loops in the stress–strain dependence for the probe wave. The hysteretic loop parameters depend on the loop position on the stress–strain dependence for the pump wave. [Work was partially supported by International Science Technical Center, Grant No. 1369.]
Resonant ultrasound spectroscopy studies of clathrate thermoelectrics
Authors: McGuire Michael , Teklu Alem , Keppens Veerle , Mandrus David , Sales Brian
Published: February 2014

Resonant ultrasound spectroscopy (RUS) measurements have been carried out for 2 cubic clathrate materials, Eu8Ga16Ge30 and Ba8Ga16Ge30. In these materials, the Eu and Ba ions rattle in oversized atomic cages. They have attracted attention as promising thermoelectric materials, having thermal conductivities with a glasslike order of magnitude while maintaining crystalline electronic properties. RUS has proven to be useful for the study of similar cage-like materials [Keppens et al., Nature 395, 876–878 (1988)], identifying 2 local modes in the filled skutterudite La0.75Fe3CoSb12. The RUS measurements we present here were carried out as a function of temperature (2-300K) on single crystals, and allow the determination of the 3 elastic moduli. The results are compared to ultrasonic attenuation measurements on Sr8Ga16Ge30 and RUS measurements on filled and unfilled skutterudites. [Work supported in part by ONR. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.]
Fluid volume displacement at the stapes footplate and round window due to air and bone conduction stimulation
Authors: Stenfelt Stefan , Hato Naohito , Goode Richard L.
Published: February 2014

The fluid volume displacement of the two major in- and outlets of the cochlea, the stapes footplate and the round window, are normally considered equal but with opposite phase. However, other channels, such as the cochlear and vestibular aqueducts, may affect the fluid flow in the cochlea. To test this hypothesis, the volume displacement at the stapes footplate and the round window was measured with a laser Doppler vibrometer with air conduction stimulation in seven fresh human temporal bones and with bone conduction stimulation in eight temporal bones. The volume displacement was computed by measuring at five positions on the footplate and by scanning the motion of the round-window membrane at approximately thirty positions. With air conduction stimulation, the average volume displacement of the two windows was within 5 dB of each other and the phase difference was close to 180 deg within the frequency range 0.1–10 kHz. With bone conduction stimulation and below 1.5 kHz the volume displacement of the round window was about 10 dB greater than at the footplate with a phase difference of 150–200 deg. Above 1.5 kHz this difference rolled off with 6 dB/octave and 100 deg/octave.
Oxidative DNA damage associated with intense noise exposure in a rat
Authors: van Campen Luann E. , Murphy William J. , Toraason Mark A.
Published: February 2014

Increasing evidence suggests that noise-induced hearing loss may be prevented with antioxidant therapy. In order to appreciate treatment constraints, a biochemical marker(s) of reactive oxygen species (ROS)-induced damage is necessary. Without a marker, the timing of damage and biologically effective exposure(s) cannot be understood fully. This study examined the time course of ROS damage following noise exposure resulting in permanent threshold shift in a rat. Cochlea, brain, liver, serum and urine were analyzed. Oxidative DNA damage was assessed by measuring 8-hydroxy-2′-deoxyguanosine (8OHdG) by high performance liquid chromatography with electrochemical detection (HPLC-EC). Lipid peroxidation was measured via the thiobarbituric acid reactive substance’s (TBARS’s) colormetric assay for detection of aldehydes (e.g., malondialdehyde). Auditory brainstem response and distortion product otoacoustic emissions thresholds showed progressive elevation up to 3–8-h post-exposure, then notable recovery at 72 h, and some worsening at 672 h. 8OHdG/dG was significantly elevated in cochlea at 8-h post-exposure, and in the brain and liver at 72 h. TBARS were significantly elevated in serum at 72 h. This is the first evidence that oxidative DNA damage is present in cochlea following intense noise, and that the timing of damage corresponds to the timing of functional impairment.
Wideband reflectance measurement of the contralateral acoustic reflex threshold for broadband noise and 1000-Hz tones
Authors: Feeney M. Patrick , Marryott Lindsay
Published: February 2014

Recent work has suggested that wideband reflectance measures may provide a sensitive estimate of the acoustic reflex threshold [M. P. Feeney and D. H. Keefe, J. Speech, Lang. Hear. Res. 42, 1029–1041 (1999)]. This study examined contralateral reflex thresholds for broadband noise and 1000-Hz tones in 21 young adults. The acoustic reflex was detected with the reflectance system by assessing the correlation between pairs of wideband reflectance shifts for a given activator level. Reflex threshold estimates obtained with this method were compared with those obtained with a clinical admittance system. Reflex thresholds for the noise activator were around 10 dB lower for reflectance (M=77.4-dB SPL, Zwislocki coupler) than for the clinical measure [M=87.8-dB SPL, t (20)=6.2, p<0.001]. For the 1000-Hz activator, reflectance reflex thresholds averaged 5 dB lower (M=95.3-dB SPL) than for the clinical system [M=100.2-dB SPL, t (20)=8.2, p<0.001]. Moreover, the tone-noise reflex threshold difference was significantly larger for reflectance (M=17.9-dB SPL) than for the clinical measure [M=12.4-dB SPL, t (20)=6.2, p<0.001]. These results support the use of wideband reflectance as a sensitive measure of the acoustic reflex threshold. [Supported by NIH-R03DC04129.]
An auditory-nerve model with an instantaneous frequency glide and its application to modeling psychophysical results
Authors: Tan Qing , Carney Laurel
Published: February 2014

A computational model was developed to simulate the responses of auditory nerve (AN) fibers. The model consists of a time-varying band-pass filter with a nonlinear feed-forward control path, which changes the bandwidth and gain of the signal path. This model produces realistic response features to various stimuli, including pure tones, two-tone combinations, wide-band noise and clicks. The parameters of the band-pass filter were estimated by fitting the model revcor functions to revcor functions from experimental data of cat. The Marquardt method was used to minimize the difference between the model revcor function and the cat revcor function at various characteristic frequencies. Instantaneous frequency (IF) glides in the reverse correlation function of the models response to broad-band noise were achieved by simple configuration of the locations of the poles and zeros in the band-pass filter. The locations of the poles are continuously varied by the control signal to change the gain and bandwidth of the signal path, without affecting the IF profile, which is level independent. Other important properties, such as nonlinear compression, two-tone suppression and reasonable Q10 values are also included. Applications of this model for studying AN responses to speechlike signals will be discussed.
MLDs for signals placed in masker envelope minima and maxima
Authors: Buss Emily , Hall Joseph , Grose John
Published: February 2014

Previous data on the masking level difference (MLD) have suggested that NoSpi detection for a long-duration signal is dominated by signal energy occurring in masker envelope minima [Hall et al., J. Acoust. Soc. Am. 103, 2573–2577 (1998); Grose and Hall, ibid. 103, 2590–2594 (1998)]. This finding was expanded upon using a brief (30-ms) 500-Hz tonal signal that coincided with either the envelope maximum or envelope minimum of a 50-Hz wide bandpass Gaussian noise masker centered at 500 Hz. On each interval a masker band was digitally generated in the frequency domain, the envelope maximum (or minimum) was identified, and the sample was rotated until that maximum (or minimum) fell in the temporal center of the sample. Data were collected at a range of masker levels (25, 40, and 55 dB spectrum level) in order to assess the possible contributions of compression. Conditions employing frozen noise samples were included to assess the possible role of masker uncertainty. Results to date suggest substantially larger MLDs for signals coinciding with masker envelope minima as contrasted with envelope maxima. This result is primarily due to decreased NoSpi thresholds for signals coinciding with mimima. [Work supported by NIH NIDCD.]
Short-term adaptation to novel combinations of acoustic spatial cues
Authors: Streeter Timothy , Shinn-Cunningham Barbara G. , Brughera Andrew
Published: February 2014

Previous work demonstrates that a listener’s interpretation of spatial cues can change due to long- or short-term training. Results suggest that short-term training does not alter how spatial locations are computed, but how spatial percepts are interpreted. This series of experiments examines how subjects adapt to different rearrangements of auditory cues. In Experiment I, subjects were trained to identify the spatial cues normally associated with exocentric location x as coming from 2x (a pure linear remapping of space). In Experiment II, ITDs were remapped in the same way, but were paired with normal IID and spectral cues (i.e., the ITD normally associated with azimuth 2x was paired with IID and spectral cues associated with location x). Results examine how spatial resolution and bias are affected by unusual mappings between spatial cues and exocentric location as well as by combining spatial cues that normally do not correspond to one source location. These experiments test the hypothesis that listeners rapidly and subconsciously recalibrate a ‘‘gain’’ describing how to map an internal representation of auditory space to exocentric space, but cannot rapidly alter how the source positions in this internal representation are computed. [Work supported by a grant from the Whitaker Foundation.]
The minimum audible facing angle
Authors: Neuhoff John G. , Rodstrom Mary-Alice , Vaidya Tanaya
Published: February 2014

Many sound sources have a directional characteristic such that they project sound from one planar orientation at a time (e.g., talkers and loudspeakers). Yet, almost all localization studies employ a unidirectionally facing source aimed at the listener. Although there are good reasons for holding the facing direction of a loudspeaker constant relative to the listener when investigating localization, it is curious that the acoustic facing direction itself has received little or no attention. Here, blindfolded listeners heard pulsed noise from a loudspeaker facing a reference point of either 0 deg (directly facing the listener) or 30 deg. The loudspeaker was then rotated clockwise or counterclockwise to one of six facing angles (5, 10, 15, 20, 25, or 30 deg), and the stimulus was replayed. The listeners indicated perceived direction of rotation. The minimum threshold for detection, or in this case what is termed the minimum audible facing angle (mAFA), was 15 deg for the 0 deg reference point and 21 deg for the 30 deg reference point. Within the limitations of the current experimental conditions, listeners showed appreciable sensitivity to the facing angle of a unidirectionally facing sound source. Our results also show evidence for a maximum auditory facing angle (MAFA).
Effect of auditory cuing on azimuthal localization accuracy
Authors: Kopčo Norbert , Ler Albert , Shinn-Cunningham Barbara G.
Published: February 2014

Auditory localization in the horizontal plane was measured following the presentation of a cue in order to explore whether attentional focus could improve localization accuracy. Subjects pointed to the heard location of a broadband target source that was presented (at a delay of either 50 or 300 ms) after a cue source. In half of the blocks of trials, the cue source came from the same (left/right) hemifield as the target on most (75%) of the trials, and thus (on average) provided the listener with information about the target location. In the other half of the blocks of trials, the cue source location was equally likely to come from either the same or the opposite hemifield and provided no information to the subject regarding target position. The presence of a cue biased localization performance in both conditions rather than improving accuracy when the cue provided information about the target laterality, even for a delay of 300 ms between the cue and target. Results suggest that auditory cuing, which has been shown to decrease response times, degrades localization accuracy. [Work supported by a grant from the Air Force Office of Scientific Research.]
Localization of sound by binaural cochlear implant users
Authors: Preece John P. , Tyler Richard S. , Rubinstein Jay T. , Gantz Bruce J. , van Hoesel Richard J. M.
Published: February 2014

We examined the localization ability in five adult patients who were implanted bilaterally with the CI24M implant from Cochlear Corporation. These patients demonstrated a difference in either length of time deaf before implantation, preimplant thresholds, or both. Patients were tested in an anechoic room. Signals were four 200-ms bursts of broadband noise separated by 55 ms of silence. Stimuli were randomly presented from one of eight loudspeakers arrayed in an arc at ear level in front of the patient. The speakers were separated by 15 deg azimuth. The patient was seated 1.5 m from the speakers and responded orally with a speaker number. The level of individual stimuli was varied randomly over an 8-dB range with an average level of presentation of 65-dB SPL measured at the approximate location of the center of the patient’s head. Patients were tested with each ear separately and with both ears together. The results show a very good ability in all five patients to localize sounds with two cochlear implants. The monaural abilities varied considerably across patients, and often between ears for each patient, but were always worse than the binaural abilities. [Work supported by NIDC and CRC.]