bluuebunny/crossref_metadata_2025 huggingface dataset:
Therapeutic ultrasound induced cell death from a histological perspective
Authors: Brayman Andrew , Kaczkowski Peter , Wang Yak-Nam , Andrew Marilee , Crum Lawrence A. , Kargl Steven , Speyer Gavriel
Published: May 2008

High-power, short-exposure time, High Intensity Focused Ultrasound (HIFU) treatment protocols are under development that offer the potential to increase procedure throughput and optimize individual therapies. Histological examination and optical image analysis of tissues following dynamic HIFU exposure in ex vivo bovine liver have revealed that cells undergo a fundamentally different form of cell death. The rapid temperature rise due to the HIFU exposure leaves the cells structurally intact but no longer viable, similar to the cell "fixation" induced by snap-freezing. These results suggest that careful choice of both staining technique and metric for determining cell death are important in quantifying type and morphology of cell ablation, and more broadly, safety and efficacy of treatment. This finding is similar to those obtained and under discussion in the laser and RF ablation communities. Specifically, the NADH staining technique is superior to H&E for assessing cell viability, and an alternative measure of cell death may be preferable to the binary thermal dose threshold currently the standard for HIFU treatment. [Work supported by NIH.]
Ultrasound interstitial applicators for thermal ablation in liver
Authors: Lafon Cyril , Salomir Rares , Bouchoux Guillaume , Birer Alain , Owen Neil , Delabrousse Eric , Mithieux François , Chapelon Jean Yves
Published: May 2008

Aggressive treatment of localized hepatic metastases, by surgery or other means, was proven to be a viable strategy for improving the prognoses of many patients. In that context, thermal ablation by high intensity ultrasound was proposed and used in clinics. However, for treating deep-seated tumors and in most cases, radiofrequency and cryotherapy probes are applied interstitially. Interstitial ultrasound applicators were proposed as an intermediate solution. The treatment can be focused, deeper than with other physical agents, and the transducer can eventually both treat and image tissues. In our experience, two approaches were investigated: percutaneous and intratissular, or endo vascular. The active element was a miniature flat transducer operating at a frequency of 5 MHz, for a satisfactory tradeoff between beam penetration and energy absorption. In vivo trials on a porcine model demonstrated that both procedures are minimally invasive and that large thermal lesions, up to 20 mm deep, can be obtained. Technological improvements such as the use of dual mode transducers (for imaging and therapy) or the performance under MRI guidance allowed monitoring the treatment in real-time.
High resolution angular measurements with single vector sensors and arrays
Authors: Clark Joseph A. , Huang Dehua
Published: May 2008

The direction finding capability of acoustic sensors that directly measure acoustic particle velocity alone or in combination with pressure measurements (vector sensors) is well known. The angular resolution of the measurements can be improved by using arrays of vector sensors. It is also possible to improve angular resolution by additional processing of data from even a single vector sensor. This approach could be especially advantageous for sonar systems designed to operate from small platforms such as autonomous underwater vehicles. In this talk linear and non-linear methods for processing data from one or more vector sensors to achieve high angular resolution will be reviewed. Experimental investigations comparing the methods will be reported and factors found to limit the localization and detection performance of sonar systems employing the methods will be discussed.
Acoustic sensor systems on a flying wing underwater glider and two prop-driven autonomous underwater vehicles
Authors: D'Spain Gerald , Zimmerman Richard , Jenkins Scott A. , Rimington Dennis B. , Luby James C. , Brodsky Peter
Published: May 2008

The Marine Physical Laboratory, Scripps Institution of Oceanography operates several underwater vehicles including an autonomous underwater glider based on a flying wing design and two prop-driven autonomous underwater vehicles (AUV) manufactured by Bluefin Robotics. The objective of this presentation is to describe the acoustic sensor systems on these platforms and provide sample results from the at-sea data. The glider, with a 6.1-m wing span, was developed jointly by the Marine Physical Lab and the Applied Physics Laboratory, University of Washington. It is designed to maximize the horizontal distance traveled between changes in buoyancy (i.e., maximize its "finesse") while quietly listening to sounds in the ocean. A 27-element hydrophone array with 5 kHz per channel bandwidth is located in the sonar dome all along the wing's leading edge. In addition, it has a four-component acoustic vector sensor in its nose. The two prop-driven AUVs have been equipped with hull-mounted hydrophone arrays with 10 kHz bandwidth for passive synthetic aperture studies, an acoustic vector sensor, and active acoustic imaging systems for ocean bottom/subbottom mapping. Results from the data processing illustrate the tight coupling between acoustic sensor systems, signal/array processing methods, and vehicle behavior. [Work supported by the Office of Naval Research.]
Influence of the geometrical parameters in flue instruments on the vorticity modulation near the separation points of the jet
Authors: Blanc François , Lagrée Pierre-Yves , De La Cuadra Patricio , Fabre Benoit
Published: May 2008

In the making of the recorder, great care is given to the shape of the chamfers at the exit of the channel. Makers insist on the need of sharp chamfers, for a good tone quality. Recorders made with rounded chamfers present a noisy sound. On the other hand, in the flute, the channel is made by the lips of the musician, defining a rounder geometry. Previous work show that variations of the geometry of the exit of the channel has little influence on the velocity profile of the jet and on the position of the separation points. Thus, variations of the geometry are expected to affect mainly the interaction between the air jet and the acoustic field. The paper will present measurements together with direct Navier Stokes calculations for different geometrical configurations of a jet emerging in a transverse oscillating velocity field. We investigate the modulation of the vorticity of the jet shear layers by the acoustical field, in the vicinity of the separation points, in an attempt to develop a model that allows to predict the influence of the geometry.
Preliminary screening of flow behavior around airfoils using a microphone phased array
Authors: Remillieux Marcel C. , Burdisso Ricardo A. , Devenport William J.
Published: May 2008

Recently, as a part of research projects for the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories, several full-scale, wind-turbine airfoils were tested at various speeds (high Reynolds numbers) and angles of attack in the Virginia Tech Stability Wind Tunnel. This unique facility is aerodynamically closed and acoustically open, which allows better aerodynamic performance than a free jet facility, while maintaining comparable acoustic performance. Flow measurements consisted of monitoring the surface pressure around the airfoils with a distribution of pressure taps on the airfoil surface. Acoustic measurements were carried out with a microphone phased array. The phased-array data was post-processed to generate acoustic maps of the noise generated by the airfoils exposed to the flow as well as their noise spectra. In addition to the tests, two-dimensional CFD computations of the flow field around the airfoils were carried out using a k-ε turbulent model. The acoustic maps clearly show the noise sources generated by potential turbulent flow around the airfoils. The very good correlation between the acoustic maps and the flow characteristics of the airfoils, both numerical and experimental, allows for phased-array measurements to be used as a tool for preliminary screening of the flow behavior around a given airfoil.
Large-eddy simulation of roughness-generated boundary-layer noise
Authors: Wang Meng , Yang Qin
Published: May 2008

A computational study is carried out to predict rough-wall boundary layer noise and elucidate noise generation mechanisms. As a first step, the sound radiation from a single hemispherical roughness element in a turbulent boundary layer at Reθ=7500 is investigated. The roughness height is 3.6% of the boundary layer thickness, or 95 wall units. The flow field is computed by large-eddy simulation. The velocity statistics show reasonable agreement with the experimental data measured at Virginia Tech. Acoustic calculations are performed based on the Curle-Powell integral solution to the Lighthill equation. The sound radiation is dominated by unsteady drag dipoles and their images in the wall, with the spanwise dipole of similar magnitude or stronger compared to the streamwise dipole. The viscous contribution to the drag dipole is negligible relative to the pressure contribution. Numerical experiments are performed to isolate the roles of vortex shedding and diffraction of convected hydrodynamic pressure by the roughness element; both are shown to be important noise source mechanisms. The effects of roughness height, upstream wake, and multiple roughness elements are discussed as well.
Urban Noise Action Planning - an integrated approach towards noise abatement in the frame of urban development: Tools and recommendations developed within the SILENCE project
Authors: Kloth Melanie
Published: May 2008

Noise action planning following the European Directive on Environmental Noise is for many cities a new, additional task. It will probably be not very successful when considered as mere duty separated from other urban policy areas. Today, noise does not rank high on the local political agenda. Human and financial resources provided for noise abatement tend to be low. Furthermore, looking at concrete noise abatement measures it becomes clear that most effective measures also impact on other policy areas (air quality, mobility, etc.). Therefore it is advisable to link noise action planning closely with other urban plans like development plans, mobility plans, clean air programmes, etc. This requires a strong involvement of the relevant stakeholders as well as knowledge about the potential impact of noise abatement measures on other policy areas. To support local authorities in this complex task the SILENCE project developed a guidebook which comprises recommendations on organisational settings, on the involvement of stakeholders and the public, the action planning process as well as on a range of noise abatement measures. The description of these measures refers not only to their noise abatement potential but takes also into account their - positive or negative - impact on other policy areas.
Optimizing localization of noise monitoring stations for the purpose of inverse engineering applications
Authors: Reiter Malgorzata , Kotus Jozef , Czyzewski Andrzej
Published: May 2008

Long-term environmental monitoring of noise levels can be done using autonomous measurement stations. Because of the high cost of monitoring systems and management of these stations, it is essential to identify how many of measuring localization points are really required. In cases related to complex noise generation schemes, when there are various noise sources, the differences between calculations and measurements can be difficult to estimate. Therefore, it is vital to find some most appropriate locations for measurement stations which would ensure obtaining an adequate number of measurement results to be employed in the reverse engineering. These measurements can be then utilized to update dynamic noise maps. Furthermore, predictive noise models may be developed accordingly to certain local requirements. This could result in a better accuracy of dynamic noise maps. The paper focuses on defining the proper choice of the measurement points localizations. The experiments described include a comparison between real-life measurement results performed with the Multimedia Noise Monitoring System developed at the Multimedia Systems Department of the Gdansk University of Technology and the noise level prediction results. The optimization of the number and location of noise monitoring points with regard to the measurement accuracy is also discussed.
Possibilities of supporting municipal authorities in processes of acoustical environment management
Authors: Ka Mierczak Jan
Published: May 2008

EU directives and state law acts oblige municipal authorities of European towns to create and exploit strategic acoustic maps. The further decisions of these authorities, considering both sustainable local development strategies and results of analysis of environmental effects (such as noise), ought to form suitable living conditions in the towns. The people, responsible for such decisions, ought to dispose suitable knowledge and skills. Author of this paper leaded in recent years the consortium of R&D units involved in the research project, focussed on preparing technology of creating acoustic maps of urban areas. The project resulted in the method of acoustic mapping, based on GIS technology. Apart of “purely acoustical” problems, the forming of competencies of these members of municipal staff, responsible on preparation and then exploitation of acoustic maps, has been mentioned as a problem of essential importance in this research. In result of discussions with potential users of strategic acoustic maps, the need was formulated to give municipal units some effective tools of supporting them by means of offering necessary knowledge and expertises in the field of management of acoustical environment in urban areas. The concept of network-based system focussed on such a target is presented in the paper.
Noise mapping for large urban areas - the city of Vienna
Authors: Talasch Werner
Published: May 2008

The Environmental Noise Directive 2002/49/EG requires noise maps for the main noise sources railway, road and aircraft and as well for agglomerations. For agglomerations there are also industrial sites (restricted to IPPC plants) a relevant noise source. The noise maps for the agglomeration of Vienna includes the City of Vienna and 5 further municipalities. These are Brunn am Gebirge, Maria Entersdorf, Mödling, Perchtoldsdorf, and Wiener Neudorf. The area of the agglomeration is about 460 km2. The most difficult part in the task of creating the noise maps was the 3D model of the agglomeration. Most of the relevant objects were available as 3D objects. Only some objects are only available as 2D objects and caused therefore a lot of work.
A comparison between predicted and measured noise levels at the Rijeka - Zagreb motorway
Authors: Grubesa Sanja , Horvat Marko , Domitrovic Hrvoje
Published: May 2008

The current calculations used for predicting the levels of road traffic noise can and usually do give results that can differ significantly from the results of measurements of noise levels performed in the field. In order to examine these discrepancies, levels of road traffic noise have been measured on two locations on the Rijeka - Zagreb Motorway. After that, the geographical layout of these locations has been prepared and then input into a computer simulation program with the goal of obtaining simulated road traffic noise levels. Following the assumption that these results will be different, the goal is to determine which of the simulation models used today will provide results that are in the best agreement with the results obtained from the actual field measurements, with the emphasis on this particular geographic region, namely, the Republic of Croatia.
Measurement of acoustic and mechanical parameters of poroelastic materials by mean of active control and wave-based methods
Authors: Batifol Cedric , Galland Marie-Annick , Ichchou Mohamed
Published: May 2008

Poroelastic materials are used in sound barriers for sound insulation and absorption. At low frequencies, the medium is modeled using the Biot theory. This homogenised model needs to be feed by at least eight parameters using the Johnson-Allard approach. The presented characterisation method relies on two specific test facilities. First, acoustic parameters are obtained thanks to a modified Kundt tube. The porosity and resistivity are obtained by direct measurements of the surface impedance with hard wall and zero pressure boundary conditions on the rear face of the sample, respectively. This last boundary conditions is achieved thanks to active control procedure. Finally, the remaining acoustic parameters are obtained in a least mean square sense. Mechanical parameters are then measured on a second test bench. A beam made of the poroelastic sample is subjected to mechanical broadband forcing. The transverse displacement is measured along the beam thanks to a laser vibrometre. Dispersion curves are then obtained by calculating the Inhomogeneous Wave Correlation (IWC) ratio. The Young modulus and loss factor of the sample are estimated thanks to an optimisation procedure applied to the finite element model of the test. Results are compared to those obtained using more classical quasi-static methods.
Rubber/air acoustic band gap materials: Elastic and viscoelastic effects
Authors: Merheb Bassam , Deymier Pierre , Jain Manish , Aloshyna-Lesuffleur Marie , Greger Richard , Mohanty Sanat , Berker Ali
Published: May 2008

Two-dimensional elastic and viscoelastic phononic crystals structures are investigated theoretically and experimentally. These are two-dimensional arrays of cylinders of air inclusions in a solid silicone rubber matrix as well as arrays of silicone rubber cylinders in an air matrix. In this study, viscoelasticity is modeled with a compressible general linear viscoelastic fluid model. Numerical calculations of transmission spectra and band structures are conducted by extending the finite difference time domain (FDTD) method to account for linear viscoelastic materials which exhibit time-dependent moduli. These systems demonstrate very wide band gaps in their transmission spectra that extend to frequencies in the audible range of the spectrum. Experimental and calculated transmission spectra for a rubber matrix/air inclusions phononic crystal show that the system behaves as a fluid/fluid composite with respect to the longitudinal polarization of acoustic waves due to the large contrast between the transverse and longitudinal speeds of sound. We also demonstrate that viscoelasticity can attenuate transmission over very wide ranges of frequency leaving only passing bands at very low frequency. These phononic crystals demonstrate the practical design of elastic or viscoelastic solid rubber/air acoustic band gap sound barrier with small dimensions.
Plate waves in phononic crystals slabs
Authors: Chen Jiu-Jiu , Bonello Bernard
Published: May 2008

We have computed the dispersion curves of plate waves propagating in periodic composite structures composed of isotropic tungsten cylinders embedded in a isotropic silicon background. The phononic crystal has a square symmetry and the calculation is based on the plane wave expansion method. The direction of propagation is defined by the angle φ between ΓX in the reduced Brillouin zone and the wave vector k. If φ=0 {0} or φ=90 {0}, SH modes are simple hyperbolas and do not couple to the Lamb wave modes polarized in the sagittal plane. If is different from 0 {0} or 90 {0}, SH modes convert to Lamb wave modes and couple with the flexural and dilatational modes. The symmetric modes splitting in the band structures along this direction and all three components of the particle displacements demonstrate this phenomenon which is different from the pure isotropic plate case where SH waves decouple to Lamb waves whatever the propagating direction.
Design and characterization of stop-band filters using PZT layer on silicon substrate phononic crystals
Authors: Vasseur Jérôme , Hladky-Hennion Anne-Christine , Dubus Bertrand , Djafari-Rouhani Bahram , Morvan Bruno
Published: May 2008

Phononic crystals are periodic structures exhibiting absolute band gaps i.e. frequency bands in which the propagation of elastic waves is forbidden in all directions. Filtering is then a possible application of phononic crystals. Recently, the existence of absolute band gaps has also been theoretically demonstrated for guided elastic waves in a piezoelectric plate on a substrate [J. Vasseur et al, J. Appl. Phys, 101, 114904 (2007)], which is a geometry of interest for possible co-integration on silicon chip. The 2D phononic crystal was constituted by a square arrangement of cylindrical holes in a PZT layer deposited on a silicon substrate. In this communication, the realization of a stop-band filter constituted by a periodically patterned PZT layer, polarized along thickness, on silicon substrate and interdigitated electrodes (IDE) for emission/reception of guided elastic waves, is investigated. The filter characteristics are theoretically evaluated by using finite element simulations: dispersion curves of patterned PZT layer are computed for various pattern geometries to obtain the absolute band gap. Complete structure is then modeled, with appropriate IDE to propagate a guided mode in the piezoelectric layer. Finally, filtering capability of the structure is evaluated. Work supported by STMicroelectronics (Nano2008 program of French ministry of industry).
Review of phononic crystals, nonlinear processes, devices and prospects
Authors: Nikitov Sergey , Gulyaev Yurii , Grigorevsky Valery , Grigorevsky Alexander , Lisenkov Ivan , Popov Roman
Published: May 2008

The review of current state of the art of bulk and surface linear and nonlinear acoustic wave propagation in phononic crystals (PhC) is given. First, theoretical analysis of bulk acoustic waves propagation in 2D phononic crystals composed of elastic medium with periodic systems of air holes with different symmetry is considered. The properties of hypersonic bulk and surface acoustic waves (Love, Lamb) in PhC are considered theoretically and expermentally. We studied bulk waves propagation in microstructured optical fiber preforms made of quartz. The study of simultaneous propagation of acoustic waves and light in structures being both photonic and phononic crystals was done. We study also properties of guided waves (Lamb modes) propagating in layered structures containing the magnetic films with two-dimensional periodic structures. In these structures we discovered a strong coupling between elastic and magnetic properties leading to effective waves transformation between magnetic and elastic systems. Such structures are so called magnonic-phononic crystals. The recommendations of use such unusual BAW and SAW properties in PhC for development of solid state devices are given. This work is supported by RFBR grant 08-02-00785.
Laser-generated surface acoustic waves in copper line arrays on silicon
Authors: Maznev Alexei A.
Published: May 2008

Laser-generated acoustics waves are widely used to control the fabrication on metal interconnect structures in the semiconductor industry. On the other hand, acoustic properties of such structures, typically comprised of periodic arrays of metal lines embedded in a dielectric film on a silicon substrate, pose some interesting wave propagation problems. We will report measurements of surface acoustic waves (SAWs) performed using laser-induced transient grating technique on periodic arrays of micron-wide copper lines. As expected, SAW dispersion curves yield small band gaps at the Brillouin zone boundary. However, much larger band gaps are observed within the 1st Brillouin zone. We believe that these giant band gaps are formed due to avoided crossing of the 1st and 2nd order surface acoustic modes of the film/substrate structure when the 1st mode dispersion curve becomes folded due to periodicity. Another observed phenomenon is a spectacularly sharp increase in the acoustic attenuation occurring when the folded surface mode becomes coupled to a bulk wave.
Nonlinear seismo-acoustic landmine detection
Authors: Donskoy Dimitri
Published: May 2008

The seismo-acoustic methods are among the most promising emerging techniques for the detection of landmines. Numerous field tests have demonstrated that buried landmines manifest themselves at the surface through resonance and nonlinear responses (or signatures) to acoustic/seismic excitation at the frequencies below 1000 Hz. The resonance signatures are primarily due to mine's housing structural resonances. The nonlinear signatures explained by high contact nonlinearity at the mine-soil interface. These phenomena are utilized for landmine detection demonstrating high provability of detection and low false alarms. The paper provides overview of theoretical and experimental investigations conducted by the author and his colleagues at Stevens Institute of Technology. Among major accomplishments are discovery and explanation of mine's resonance behavior; soil/depth effect on buried mine's resonances; discovery and analysis of nonlinear acoustic interactions at the soil-mine interface; development of nonlinear quadratic and intermodulation detection algorithms based on dual-frequency excitation. Work supported by the U.S.Army NVESD, ARO and ONR.
Sequential integration in the perception of tone sequences
Authors: Van Noorden Leon
Published: May 2008

The seminal book of Albert Bregman on Auditory Scene Analysis had not yet appeared at the time of my dissertation research (1970-1975). One of the major difficulties that I had was to come at grips with the concept of a sequence of tones that form a 'gestalt' of tones 'belonging' together. This Sequential Integration, as coined by Bregman, has not received as much attention as the 'Differentiation' aspect. A number of experiments show that this sequential integration process is characterised by a resonance process with a broad peak near 2 Hz. This resonance process can explain several phenomena such as subjective rhyhmisation, the data on tapping along polyrhythms and the histogram of musical tempi. Confronting these findings with the measurements of the Temporal Cohence Boundary may indicate where pitch movement detectors may play a role. Recent publications have linked this resonance with a movement control process.
Temporal fine structure cues in auditory stream segregation of complex tones
Authors: Grimault Nicolas , Gaudrain Etienne
Published: May 2008

The ability to understand speech-in-speech is generally described to be related to the capacity to segregate one auditory stream among others sound sources. The channeling theory suggests that sequential stream segregation is basically sustained by frequency selectivity. However, it has been evidenced that sequences of stimuli that evoked the same excitation pattern can be streamed apart based on temporal cues only. Other results involving hearing impaired listeners with enlarged auditory filters hardly fit in with this theory. More recently, several reports in the literature and new attempts of modelization underline the potential interest of temporal fine structure cues for stream segregation. The current study is dedicated to test further the potential interest of temporal fine structure cues to stream apart sequences of unresolved complex tones with alternating fundamental frequencies. Several conditions of envelope saliency (positive and negative Schroeder phase complex tones) and several conditions of fine structure will be used in a streaming test leading to an objective measure related to segregation.
Auditory streaming and coherence
Authors: Shamma Shihab , Elhilali Mounya
Published: May 2008

Auditory streaming is a phenomenon that manifests itself in the everyday ability of humans and animals to parse complex acoustic information arising from multiple sound sources into meaningful auditory “streams.” For instance, the ability to follow a conversation at a noisy cocktail party or hear the violin in the orchestra both rely on the formation of auditory streams. While seemingly effortless, the neural mechanisms underlying auditory streaming remain a mystery. In this talk, we shall discuss physiological experiments that address the role of coherence in mediating this percept. The experiments contrast the perception and neural responses evoked by the classic two-tone stimuli when presented in alternating or synchronous modes. Briefly, while the percepts in these two conditions are very different, being much more “streamed” in the alternating case, physiological responses to the tones did not differ significantly enough to explain this change in percept. This result casts doubt on the simple spatial segregation hypothesis, and instead argues for a substantial role of coherence of stimuli across different channels in mediating streaming.
A new approach to electric-acoustic stimulation
Authors: Brown Christopher A. , Bacon Sid P.
Published: May 2008

When low-frequency acoustic stimulation is combined with either real or simulated electric stimulation from a cochlear implant (electric-acoustic stimulation, or EAS), speech intelligibility in noise can improve dramatically. This improvement has been shown in simulation to be due in part to the presence of fundamental frequency (F0) and amplitude envelope information in the low-frequency region. The current experiment extends those findings to implant patients. Six patients who had residual low-frequency hearing in either their implanted or unimplanted ear participated. A target talker was combined with multitalker babble and presented to the implant. In the low-frequency region, patients heard either no stimulus, target speech, or a tone that was modulated in frequency to track the dynamic changes in F0, and in amplitude with the amplitude envelope of the low-pass target speech. Results showed that the tone provided, on average, about 58 percentage points of improvement over electric-only stimulation. Both the tone and target speech provided a statistically significant benefit over electric stimulation only (p<0.0001), and were statistically equivalent to each other (p>0.05). These results demonstrate that a tone that conveys F0 and amplitude envelope information can provide significant benefit in EAS.
Investigating the influence of pulse rate and duration on pitch perception in cochlear implants
Authors: Stohl Joshua S. , Throckmorton Chandra S. , Collins Leslie M.
Published: May 2008

Multirate sound processing strategies may potentially provide improved speech recognition and music perception in cochlear implants (Nie et al., 2005; Throckmorton et al., 2006), although it may be necessary to tune these strategies using psychophysical data to provide maximum benefit to the user (Throckmorton et al., 2006). To investigate the need for tuning, cochlear implant users participated in several rate-based psychophysical experiments. Subjects performed single- and two-rate pitch ranking tasks to investigate the influence of pulse rate on the overall pitch structure. The introduction of a second rate resulted in frequent pitch reversals between closely spaced electrodes. In addition to the multi-rate pitch structure, the duration necessary to perceive a rate change must also be considered. Experiments were performed using ABA stimuli, where rate B was higher than rate A. Subjects completed an embedded rate discrimination task in which the duration of B was fixed and its rate varied adaptively for durations ranging from 20-200 ms. The rate of segment B was then fixed, and its duration varied adaptively. Results imply that embedded rate difference limens may be a function of duration, and that the minimum duration required for detecting a change in pulse rate is subject specific.
Use of simultaneous stimulation to represent fine structure in cochlear implant processors
Authors: Litvak Leonid , Saoji Aniket , Spahr Anthony , Kulkarni Abhijit , Marzalek Michael
Published: May 2008

In cochlear implants, simultaneous stimulation of adjacent electrodes, can be used to shape the electric fields generated within the cochlea. For example, simultaneous in-phase stimulation of nearby electrodes can be used to create activation patterns which may have maxima at locations that are intermediate to the locations of the stimulated electrodes. Psychophysically, such “virtual channels” give rise to intermediate pitch sensations. Simultaneous out-of-phase stimulation of two flanking electrodes in addition to the center electrode can be used to presumably produce more focused activation at the cost of larger overall stimulation currents. Forward masking patterns indicate that for sufficiently large compensation currents, such “focused” stimulation can lead to a more spatially contained excitation. In some cases, current focusing also could lead to sensations that are more tonal relative to monopolar. This presentation will review recent results obtained in our laboratories with both “virtual channel” and “focused” configurations. We will also address how both techniques can be used to better represent the within-channel fine structure in a wearable sound processing strategy.
Binaural jitter improves sensitivity to interaural time differences in electric and acoustic hearing
Authors: Laback Bernhard , Majdak Piotr , Goupell Matthew J.
Published: May 2008

Cochlear implant (CI) listeners are often sensitive to fine structure ITD at low pulse rates, but their sensitivity declines at higher pulse rates which are required for speech coding. We hypothesized that this limitation is related to the binaural adaptation phenomenon [Hafter and Dye, J. Acoust. Soc. Am. 73 644-651 (1983)], associated with periodic stimulation. With five CI listeners, we tested the effect of introducing binaurally-synchronized jitter (binaural jitter) in the stimulation timing, assuming that this reduces the periodicity in the neural response and thus avoids binaural adaptation. Pulse rates from 400 to 1515 pulses per second (pps) were tested. In addition, we performed a similar experiment with normal-hearing (NH) listeners using bandpass-filtered acoustic pulse trains and testing the pulse rates 600 and 1200 pps. The CI listeners showed large improvements in ITD sensitivity from binaural jitter at high pulse rates (800 - 1515 pps). The NH listeners also showed large improvements from binaural jitter. The results are consistent with the hypothesis that random temporal variation reactivates the adapted binaural auditory system. Thus, binaurally-jittered stimulation improves the access of bilateral CI listeners to ITD information. Partly supported by the Austrian Science Fund, FWF, project number P18401-B15.
Enhanced coupled mechanical-acoustic field computations on nonmatching grids
Authors: Triebenbacher Simon , Kaltenbacher Manfred , Meiler Martin , Landes Hermann
Published: May 2008

In this work we extend our research on nonmatching finite element grids, as used in the analysis of coupled mechanical-acoustic systems, from standard (bi-)linear grids to higher order Lagrangian grids. In practical applications, such as the simulation of thin membranes, the use of higher order finite elements is often advantageous to prevent locking effects. For the comparison of the radiated sound from a loudspeaker with measurements an acoustic propagation domain is required which is very large in relation to the size of the speaker. To keep the number of unknowns in this domain low the discretization should be chosen as coarse as possible without becoming susceptible to numerical dispersion. Due to the same reason it is also desirable to use a uniform discretization and to be able to adjust the approximation order. To gain more flexibility, we introduce a nonmatching interface between the subdomains and discretize them independently, both in space and approximation order. Our enhanced scheme applies the mortar finite element method to coupled mechanical-acoustic field problems. We demonstrate the applicability of our approach to practical applications. We analyze the system response of an electrodynamic loudspeaker and the sound radiation of an electric transformer.
Structure-borne modeling of a vehicle in the mid-frequency range using Virtual SEA: experimental validation
Authors: Thenail Denis , Baratier Julien , Duval Arnaud , Borello Gérard , Gagliardini Laurent
Published: May 2008

Virtual SEA is a modeling process using FE computations to build an SEA model including equivalent masses, modal densities, and CLF, but excluding DLF since damping modeling in the mid-high frequency range is still an open issue. This technique, previously proposed by some of the authors, is applied to a production vehicle in the range 200-1000 Hz. The actual vehicle is simultaneously measured at a subset of the FE nodes. The automated sub-structuring provided by Virtual SEA (20 subsystems at 630Hz) is used to favorably position 64 sensors on the body. Next, an experimental SEA procedure is performed: a full transfer matrix is measured between more than 1000 excitation (hammer) locations and the sensors. In order to compensate for structural heterogeneity, input mobilities are measured at every point and used to normalize the transfer matrix As all measurement points are associated to FE nodes, computed input mobilities can be compared to measurements. Finally, the SEA model identification is carried out for both experimental and virtual SEA. As far as damping (DLF) can only be known experimentally, comparisons of the numerical and experimental approach only concern the orher SEA parameters (CLFs, modal densities ...) and transfer functions.
High resolution modal analysis
Authors: Ege Kerem , Boutillon Xavier , David Bertrand
Published: May 2008

The Fourier-transform-based traditional modal analysis techniques perform poorly when modal overlap η exceeds 30%, due to the ΔT.Δf limitation. In view of filling the gap between the low- and the high-frequency domains where modal analysis and statistical methods respectively apply, a technique based on the high resolution analysis algorithm ESPRIT (Roy & Kailath, IEEE Transactions on Acoustics Speech and Signal Processing, 37(7), 984-995, 1989) has been developed. A pulselike force is repeatedly applied to the structure and the response is measured in a number of points. In each point, the impulse response of the structure is retrieved by deconvolving the pulselike force and filtering the response with the result. In a second step, the number of modes in the reconstructed impulse response is evaluated by the novel procedure ESTER (Badeau et al., IEEE Transactions on Signal Processing, 54(2), 450-458, 2006) and various preconditioning techniques are applied. The ESPRIT algorithm finally extracts the modal frequencies, damping factors, and complex amplitudes at each point. Two applications are presented: the separation of twin modes of a square plate (η =200%) and the partial modal analysis of a 1620 × 1000 × 5 mm aluminum plate up to a modal overlap η =70%.
Reduction of radiated sound from a continuum using low-damping vibration absorbers
Authors: Yamaguchi Zenzo , Sugimoto Akio , Yano Yoshio , Bolton J. Stuart
Published: May 2008

When reducing the sound radiated from a resonant structure, it is necessary to ensure that the driving frequency does not correspond to any of the system resonance frequencies. In addition, it may be desirable to use dynamic vibration absorbers to reduce the response at the driving frequency. In this paper, a low-damping vibration absorber is studied for solving noise radiation problems from a resonant, light-gauge structure driven by a force whose frequency and amplitude are constant and whose frequency does not match any of the system natural frequencies. When the driving frequency and the structure's natural frequency are different, the structure cannot be represented by as a SDOF system. Therefore, the conventional design method, based on equivalent mass, is inapplicable. In this paper, a design method based on the mobility of the structure is proposed. By means of the proposed method, the sound power radiated from a simply supported beam with an attached absorber is calculated and it leads to the following results: 1) When the absorber is installed at the driving point, it reduces the sound power as predicted; 2) An increase in radiated noise may occur when the absorber is not installed at the driving point.
A fluid level sensor using A0 Lamb wave mode
Authors: Boubenider Fouad
Published: May 2008

The aim of this study was to examine the feasibility of creating a fluid level sensor operating in A0 Lamb wave mode. The experimental sensor is composed of a plate of stainless steel 1.3 meters high, in which, an A0 Lamb wave mode is generated. The choices of the material, the plate thickness and the wave vibration mode are all important. We therefore plotted the phase and group velocity curves, and the transversal and longitudinal displacements versus the product frequency x thickness. These curves enabled us to visualize the best target point for the excitation energy on a suitably guided wave mode at an appropriate frequency; this point is referred to as the operating point. When the chosen wave mode is generated, the echo from the reflection at the guide-water interface is easily detected by the transmitter-receiver transducer and can be worked efficiently.
Effect of degradations' distribution in a corpus test on auditory ratings
Authors: Côté Nicolas , Durin Virginie
Published: May 2008

Speech quality of telecommunications systems is usually evaluated thanks to auditory tests, which must be carried out in accordance with ITU-T Recommendations. In these tests, subjects are asked to assess the quality of speech sample by giving a score on a five-level scale. The averaging of subjects' scores yields the Mean Opinion Score (MOS) which represents the speech quality for a given condition. However, MOS values can be strongly influenced by many factors. In this paper, we focus on a specific bias: the distribution of the impairments in the stimuli set. In effect the rating of a narrow-band stimulus (300-3400 Hz) may have a lower quality score in a mixed-band set (mixed of narrow-band and wideband (50-7000 Hz) conditions) than in a purely narrow band set. This effect is detailed through results of auditory tests recently carried out. Consequently, the validity of MOS value is theoretically limited within a test which prevents MOS comparison between different tests. Finally, two solutions are proposed to avoid this effect: first, an improvement of auditory tests methodology and then, a new approach to assess speech quality, based on the subject's behaviour.
The acoustic and perceptual bases of diachronic /u:/-fronting in Standard Southern British
Authors: Harrington Jonathan , Kleber Felicitas , Reubold Ulrich
Published: May 2008

In a recent experiment concerned with diachronic /u:/-fronting in Standard Southern British, it was shown both that the /u:/ category boundary was perceptually retracted for older compared with younger listeners of this variety, and that they compensated perceptually to a greater extent for the coarticulatory fronting effects of the preceding consonant on /u:/ in words like used. In the present study, these perceptual differences were related to the same speakers' productions of words containing a /u:/ nucleus in a fronting (e.g., 'used') and non-fronting (e.g., 'swoop') contexts. The relative acoustic distance of /u:/ between front and back vowels was measured in a three-dimensional space formed by applying the discrete-cosine-transformation to the entire F2-trajectory shape separately for each speaker. Compatibly with their perceptual responses, older listeners had a more retracted /u:/ on this measure and exhibited a greater coarticulatory influence of the preceding consonant. The mechanism of this sound change is considered both from the point of view of a shift in the perceptual compensation for coarticulation and recent developments in episodic models of speech perception
A new speaker-intrinsic vowel formant frequency normalization algorithm for sociophonetics
Authors: Fabricius Anne , Watt Dominic
Published: May 2008

This paper evaluates the strengths and weaknesses of a speaker-intrinsic vowel formant frequency normalization algorithm initially proposed in Watt and Fabricius (2002) and modeled by Thomas and Kendall (2007) for direct comparison with other normalization algorithms. We evaluate the merits of the new routine as a sociophonetic research tool relative to those of two well-known speaker-intrinsic methods documented in Lobanov (1971) and Nearey (1977) through comparisons of the values of two parameters: degree of overlap of vowel spaces and vowel space area ratios. Measurements of angles and Euclidean distances between pairs of points in the vowel space (a method presented in Fabricius 2007) also provide a comparative parameter revealing how different algorithms model the vowel space. The study uses two existing datasets: 1) a corpus of RP vowels compiled from Hawkins and Midgley (2005) and Moreiras (2006) and 2) previously unpublished data from Aberdeen, northeast Scotland.
Acoustic validation of the analysis of diadochokinesis in normal speech using the motor speech profile program
Authors: Wang Yu-Tsai , Chung Yuh-Mei , Kent Ray D. , Lu Hsiu-Jung
Published: May 2008

The purpose of this study is to evaluate the suitability, reliability, and concurrent validity of the analysis of diadochochinesis (DDK) in normal speech using a computer program, Diadochokinetic Rate Analysis (DRA) in the KayPENTAX Motor Speech Profile. Fifteen healthy participants were recorded at UW-Madison as they repeated various syllables as quickly and steadily as possible. The DDK samples were executed by the DRA protocol to generate immediate quantitative information at different thresholds and were also hand-measured. When the lowest peak intensity during consonant-vowel syllables is lower than the highest peak intensity during intersyllable pauses, the DRA output is incorrect and the DDK sample is defined as nonexecutable. Analyses were based on the percentage of nonexecutable DDK samples and the comparisons of the results between repeated analyses at different thresholds and between automatic and manual measuring methods. Results: (1) One-ninth of the DDK samples was nonexecutable; (2) when the protocol was executable, the reliability at different thresholds and validity between different measuring methods were both satisfactory; and (3) the temporal variation between different measuring methods were larger than the intensity variation. Implications of the findings will be discussed in terms of the application of the DRA to general clinical purposes.
Analysis of short-time speech transmission index algorithms
Authors: Payton Karen , Shrestha Mona
Published: May 2008

Various methods have been shown to compute the Speech Transmission Index (STI) using speech as a probe stimulus (Goldsworthy & Greenberg, J. Acoust. Soc. Am., 116, 3679-3689, 2004). Frequency-domain methods, while accurate at predicting the long-term STI, cannot predict short-term changes due to fluctuating backgrounds. Time-domain methods also work well on long speech segments and have the added potential to be used for short-time analysis. This study investigates the accuracy of two time-domain STI methods: envelope regression (ER) and normalized correlation (NC), as functions of window length, in various acoustically degraded environments with multiple talkers and speaking styles. Short-time STIs are compared with a short-time Theoretical STI, derived from octave-band signal-to-noise ratios and reverberation times. For windows as short as 0.3 s, the ER and NC Methods track the short-time Theoretical STI and both the Theoretical and ER Methods converge to the long-term result for windows greater than 4 s. Short-time STIs are also compared to intelligibility measurements on clear/conversational speech. Correlations between STI and intelligibility scores are high at the sentence and word levels and, consistent with the scores, short-time methods predict a higher average value of STI for clear than for conversational speech.