bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic monitoring of pile driving activities at the proposed NaiKun wind farm site.
Authors: Austin Melanie E. , Racca Roberto G.
Published: October 2010

Underwater sound level measurements were obtained during marine pile driving activities at the proposed NaiKun wind farm site in Hecate Strait, British Columbia, Canada. Three hollow steel piles 0.9 m in diameter were driven into the seafloor to secure in place a truss to support a meteorological instrumentation mast. The activities involved both vibro-hammering and impact hammering. Measurements were collected at 10 m range to fulfill regulatory requirements for real-time monitoring of the near-source sound pressure levels and also at a selection of longer ranges to allow a characterization of the propagation conditions of the environment. A bubble curtain was utilized to mitigate the underwater noise generated by impact hammering after trial measurements over a few hammer strikes showed that unmitigated levels exceeded a regulatory threshold. Results from this study were used to derive source level estimates for a subsequent sound propagation modeling study conducted as part of the environmental assessment process. Results from the real-time monitoring at 10 m from the source (with and without the use of the bubble curtain) and from measurements obtained between 100 m and 3 km range will be presented.
Assessment of the acoustic effects of offshore wind turbines on the marine ecosystem.
Authors: Miller James H. , Potty Gopu R. , Vigness Raposa Kathleen , Casagrande David S. , Miller Lisa A. , Nystuen Jeffrey A. , Scheifele Peter M. , Clark John Greer
Published: October 2010

The University of Rhode Island recently completed an assessment of the potential acoustic and other effects of the wind farms on the ecosystem. A developer has proposed to initially construct eight 3.6-MW wind turbines on lattice jacket structures 5 km south of Block Island and approximately 100 turbines in a second stage 20 km east of Block Island. Construction on the first stage is tentatively planned for summer of 2011, and pile driving will be the main source of noise. The main source of operational noise will likely be vibration from the turbine conducted through the lattice jacket structure into the water. Two passive aquatic listener (PAL) systems were deployed 5 km of Block Island from October 6 to November 11, 2008. Two more PAL systems were deployed on meteorological buoys, one near the first farm and one near the larger farm, for 12 months in 2009/2010. Using data from the PALs, ambient noise budgets and histograms were computed for this pre-construction phase. The largest sources of noise were found to be shipping, wind, rain, and biological sources. An assessment of the effects of the offshore wind farms will be presented for both the construction and operational phases.
What it takes to meet the International Council for the Exploration of the Sea underwater noise limit for research vessels.
Authors: Bahtiarian Michael
Published: October 2010

Prior to 2010, the International Council for the Exploration of the Seas (or ICES) is the only organization to have developed and specified underwater (radiated) noise limit for commercial research vessels. European vessels were among the first to be built to this specification, which was given in a 1995 report. Since 2004, the US has built five ICES capable vessels, four of which were Fishery Research Vessels (FRV) for the National Oceanic and Atmospheric Administration (NOAA). In the US two more ICES capable vessels are in construction, another two are under consideration, and another three vessels are being built to an underwater noise requirement similar to ICES. This paper discusses the types of propulsion, machinery elements, and noise control features that are required in these vessels in order to meet the ICES underwater noise requirement. Design features and results will be presented from two specific, new vessel construction programs. The first is the NOAA FRV-40 program, which resulted in four fishery research vessels built at VT Halter Marine in Pascagoula, MS. The second program was for a smaller single research vessel for the University of Delaware.
A distributed micro sonar network for marine mammal monitoring.
Authors: Rotker Nicholas A. , Stein Peter J. , Edson Patrick , Wood John
Published: October 2010

The design of a distributed micro sonar network (DMSN) is presented. The DMSN is a miniaturized, low-power, and high-frequency version of the swimmer detection sonar network used to detect and track marine mammals at ranges out to 500 m. The intent is to use it for monitoring during potentially harmful military and commercial activities such as high-powered Navy sonar, oil and gas exploration, explosive removal of offshore structures, seismic exploration for research and oil and gas, pile driving to install maritime structures including offshore wind farms, and marine hydrokinetic energy devices such as free turbines. The system will consist of multiple single-beam sonars, each transmitting and receiving a unique signal in a narrow beam. The hardware and software will initially be ported to a Xilinx FPGA, with future versions done within a custom made ASIC. Initial hardware and software research and development will be described, as well as the work done to create computationally efficient signal processing algorithms. This work will potentially lead to the first ever prototype of a sonar-on-a-chip implementation. [Work supported by the NAVAIR SBIR Program and ONR.]
Space-time parabolic equation in horizontal plane for description of non-stationary horizontal refraction in shallow water.
Authors: Katsnelson Boris
Published: October 2010

Propagation of the sound signals in inhomogeneous anisotropic shallow water environment is studied. Because the waveguide dispersion shape of the radiated pulse is being changed, waveguide modes have different group velocities and, generally speaking, propagate along different ray paths in the horizontal plane. It can lead to simultaneous redistribution of the sound pulse intensity in the horizontal plane and compression/decompression in time. For a description of the spatial and temporal variation of the traveling pulse, space-time horizontal rays and space-time parabolic equation in the horizontal plane are derived using a standard approach used in electrodynamics based on integral non-local connection between field and response. Non-stationary parabolic equation (PE) is an extension of the well known approach of vertical modes and PE in the horizontal plane. This equation is analyzed and its solutions are constructed for different models of perturbation: nonlinear internal waves, coastal slope, etc.
Modeling of broadband acoustic energy evolution in dynamic ocean environments using high-performance computing resources.
Authors: Sidorovskaia Natalia
Published: October 2010

In recent years there has been considerable interest in predicting the acoustic energy temporal evolution over large 3-D volumes. Most of the standard Navy models are inherently 2-D and produce the acoustic pressure distribution of a point harmonic source in the vertical source-receiver plane. There are several computational challenges that have to be addressed when using these models for quantitative modeling of the acoustic pressure distribution from natural or man-made sources: broadband and complex spatial structure of a source, dynamic propagation environment, a need for 3-D dynamic acoustic energy reconstruction, and an efficient visualization of a large amount of generated data. An attempt to resolve any of the mentioned issues pushes the computational time on a personal state-of-the-art computer to several days (or weeks) and strongly dictates a need for upgrading these models to the high-performance computing (HPC) environment. The range-dependent acoustic model (RAM) was transferred into the HPC environment and upgraded to model broadband acoustic energy distribution from spatially distributed sources. The MPI domain decomposition approach to run the model on several cluster nodes is discussed. The data demonstrating computational time efficacy for multi-node multi-processor runs versus standard serial implementation are presented. [Research supported by TeraGrid Pathways Fellowship.]
Interaction of acoustic modes with internal-wave oscillations.
Authors: Mignerey Peter C. , Smith Chad M. , Bradley David L.
Published: October 2010

Acoustic modes propagating in shallow oceans interact with internal-wave-induced oscillations in the thermocline to produce fluctuations in the acoustic field that govern spatial and temporal coherence. Such interactions are described by both adiabatic-mode path-integral theory and coupled-mode scattering-matrix theory. In both theories there occurs an integral over the water depth that sums the interaction between the buoyancy, acoustic modes, and internal-wave modes. This paper explores the strength of that interaction for the Transverse Acoustic Variability Experiment, which took place in the northern limit of the East China Sea in 65–80 m of water. A towed CTD chain provided measurements of the density and sound-speed profiles required to compute the necessary acoustic and internal-wave modes. Within this environment, two main conclusions pertain. First, with respect to internal-wave mode contributions, the first mode contributes most significantly with a lesser contribution from the second mode and negligible contributions from higher modes. Second, with respect to acoustic mode contributions, the adiabatic mode contribution is most significant with lesser contributions from adjacent modes, and negligible contributions from widely separated mode pairs. [Work supported by the Office of Naval Research.]
An overview of time-reversal acoustics in biomedical engineering.
Authors: Fink Mathias
Published: October 2010

Time-reversal is a very powerful method for focusing ultrasound through complex and heterogeneous media and shows very promising results in biomedical applications. Here, we review the main applications investigated in medicine in this last decade. From the iterative time-reversal processing to the diagonalization of the time-reversal operator, we will discuss the various approaches for correcting distortions induced by different aberrators (skull, ribs, and abdominal layers). A complete discussion about the various targets available in tissues will show that in many situations time-reversal focusing can be used very efficiently. Several examples in ultrasound therapy and in ultrasound imaging will be presented.
Time-reversal techniques in ultrasound-assisted convection-enhanced drug delivery to the brain: Technology development and in vivo evaluation.
Authors: Lewis George K. , Fillinger Laurent , Lewis George K. , Olbricht William L. , Sarvazyan Armen
Published: October 2010

We describe a drug delivery method that combines time-reversal acoustics (TRA) with convection-enhanced delivery (CED) to improve the delivery of therapeutics to the interstitium of the brain. The ultrasound-assisted CED approach (UCED) circumvents the blood-brain barrier by infusing compounds through a cannula that is inserted into the brain while simultaneously delivering ultrasound to improve the penetration of pharmaceuticals. CED without ultrasound-assistance has been used to treat a variety of neural disorders, including glioblastoma multiforme, a malignancy that presents a very poor prognosis for patients. The mixed clinical success of CED suggests that the technique needs to be improved. We describe a novel TRA system that is used to infuse fluids into the brain parenchyma while simultaneously exposing the tissue to safe levels of 1-MHz, low-intensity, ultrasound energy. The system includes a com-bined infusion needle-hydrophone, a 10-channel ultralow-output impedance amplifier, a broad-band ultrasound resonator, and MATLAB®-based, TRA control and user-interface. TRA allows easy coupling of ultrasound therapy through the skull without complex phase-correction and array design. The smart targeting UCED system has been tested in vivo and results show that it provides 1-mm spatial resolution for UCED and improves tracer distribution in the brain six to eight times over CED alone.
Three dimensional focusing through the ribs using the decomposition of the time reversal operator.
Authors: Cochard Etienne , Prada Claire , Aubry Jean-François , Fink Mathias
Published: October 2010

Thermal ablation induced by HIFU is a promising non invasive technique to treat liver tumors. However, skin burns have been reported due to the high absorption of ultrasonic energy by the ribs. We propose to use the decomposition of the time-reversal operator to build an acoustic focusing field that spares the ribs. This method requires a fully programmable multi-channel electronic device and a 2-D array of 121 elements working at 370 kHz. In the first step, the array response matrix is measured. The dominant singular vectors of this matrix are associated with the ribs (strongest scatterers). The weight vector is then calculated as the projection of a focusing vector onto the subspace orthogonal to these eigenvectors. This procedure can be repeated for any focusing law. It is, therefore, possible to steer around the whole tumor while avoiding the ribs. This procedure is better than successive angulations of a time-reversed signal measured at the center of the tumor which may send energy on the edge of the ribs. The rib sparing and the effect of angulation have been investigated and compared to time reversal focusing.
Waveform interpolation for applications of time-reversal acoustics.
Authors: Raghavan Raghu , Berryman James G.
Published: October 2010

Acoustic waves can force fluids and small objects along the direction of sound propagation (streaming). Potential applications include forcing the flow of fluid and small particles for drug delivery into the brain, or of underground fluids, such as oil, toward a borehole collection point. Well-focused beams are needed for amplitudes to be large enough to be effective. Time-reversal acoustics (TRA) permits focusing of sound in heterogeneous media, but requires a sensor near a point of desired focus. There is a need, addressed in this talk, to send signals off the grid of available sensors so that forces may be delivered in regions between receivers, and no receiver need be at a point where focus is desired. The Acoustic Shepherd introduces interpolation or data matching of TRA-derived Green functions for this purpose. One particular scheme of geometric-mean interpolation is analyzed, and the curve along which the focus moves from one receiver to another as the interpolating weights are varied is shown. General approximation methods from statistical estimation theory are also described. These methods are expected to work better in heterogeneous media (having unknown acoustic properties) than well-known beam forming methods designed for homogeneous media.
Time reversal acoustic approach for non-lethal swimmer deterrent.
Authors: Sutin Alexander , Sinelnikov Yegor
Published: October 2010

Protection against surface and underwater threats from swimmers constitutes one of the most challenging aspects of port security. The envisioned risk mitigation consist of passive acoustic detection and localization and active diver deterrent, which can be done by focusing high intensity acoustic waves. The main goal of this study is to explore the possibility of using the time reversal acoustics (TRA) sound focusing system for non-lethal swimmer neutralization. This breakthrough technology enables the precision targeting of a hostile diver with minimum impact to the marine environments. The acoustic noise radiated by the diver is used to focus the acoustic energy, while the moving diver acts as an active self-disclosing acoustic beacon. In a shallow water environment the radiated noise, direct and multi-path interference, is rich and is exploited through the use of TRA. The effectiveness of the TRA focusing and the diver deterrence zone are modeled taking into consideration the frequency range, harbour depth, and geometry of the transducer array. The real diver noise and hydroacoustic signature parameters collected by Stevens Institute of Technology are used in the theoretical analysis. It is demonstrated that outside the focal region, the TRA system produces acoustic intensities that are not harmful for marine life.
Adaptive transthoracic focusing using dual-mode ultrasound arrays.
Authors: Casper Andrew J. , Ballard John R. , Ebbini Emad S.
Published: October 2010

Dual-mode ultrasound array (DMUA) systems have been recently shown to be capable of refocusing high-intensity focused ultrasound beams in the presence of strongly scattering objects, e.g., the ribs. A refocusing approach based on a modified forward/inverse propagation operator accounting for the ribs was experimentally demonstrated. The propagation operator is obtained from DMUA-based images of the target region, including the ribs. This image-based approach to refocusing implicitly accounts for the heterogeneity by defining a propagation operator to the proximal rib surface using DMUA directivity vectors assuming a homogeneous medium. In this paper, we address the consequences of this simplification on the quality of the refocused beam. We also present an adaptive refocusing approach that identifies the inhomogeneous directivity vectors to the target location(s) in the presence of the ribs. Example experimental results will be presented using a true real time DMUA system where the adaptive refocusing is achieved within milliseconds. Implications on real time adaptive refocusing in the context of scanning multiple target points and motion compensation will also be discussed with illustrative experimental data.
Three types of nonlinearity in physics of radiation force and acoustical streaming.
Authors: Rudenko Oleg , Sarvazyan Armen
Published: October 2010

Thousands of papers on radiation force (RF) and acoustical streaming (AS) have been published since Faraday, Rayleigh, and Langevin. There have been more papers on RF in biomedicine published in the last decade than were written in the entire 20th century. Nevertheless, some nonlinear acoustic phenomena significant for engineering and biomedical applications are still misunderstood. The presentation contains discussions regarding frequently occurring inaccuracies and contradictions. In particular, it features three types of nonlinearities which can appear independently. First, equations for RF, which are nonlinear by themselves, can contain the nonlinear modulus of a medium. Second, the nonlinear distortion of the acoustic field, depending on sound intensity and geometric and physical nonlinearities, can govern the RF and AS. Third, hydrodynamic nonlinearity often appears at the development stage of streaming. The latter nonlinearity may be observed in weak acoustic fields if RF acts for a long period of time on a low-viscosity fluid. Evaluations and formulas are given, indicating conditions for separate observation of each type of nonlinearity. Some contradictions existing in the literature are resolved. Experimental data illustrating developed theory are shown.
Effect of low-frequency sound modulation on the acoustic radiation force in Newtonian fluids.
Authors: Guzina Bojan , Donsov Egor
Published: October 2010

This study investigates generation of the acoustic radiation force (ARF) in Newtonian fluids when the amplitude of high-intensity sound field is modulated using frequencies that are, relative to the frequency of sound, on the order of the Mach number. This configuration, which is frequently deployed by emerging biomedical sensing technologies, turns out to be unresponsive to the usual time-averaging procedure owing to the fact that the mean acoustic fields remain plagued by the rapid oscillation features. The asymptotic treatment is pursued within the framework of plane waves via scaling approach that splits the temporal variable into “fast” and “slow” time, permitting one to track the contribution of (time-harmonic) sound and its modulation separately in the solution. In this setting the second-order solution, written in terms of “fast”-time averages, is shown to (i) be free of rapid oscillations and (ii) permit compact formulation in terms of “modulation-corrected” ARF that accurately captures the effect of sound modulation. The developments are illustrated by the analytical solution for a sinusoidal modulation envelope with quiescent past, which both exposes the limitations of earlier treatments and highlights the possibility of ARF generation in a lossless fluid when a modulated, high-intensity sound field is propagated through it.
Method for measuring the sensitivity of loudspeakers in diffuse field conditions.
Authors: Bascuñan Vial Fancisca , Osses Vecchi Alejandro , Espinoza Catalán Víctor , Ramirez Bunster Nícolas
Published: October 2010

A method for measuring the sensitivity of loudspeakers in diffuse field conditions is proposed. This method uses sweeps as excitation signals capturing information related not only to the loudspeaker but also related to the room (reverberant chamber). To approximate this measurement to a free field condition, digital signal possessing techniques are used to remove the components that are related to the room. The results are compared with measurements done following the method described in the international standard IEC 60268-5 for a free field condition.
Banded acoustic characteristic and optimization of serially connected horns.
Authors: Heo Yong-Ho , Ih Jeong-Guon
Published: October 2010

When two different diverging and converging horns are serially connected, it is known that the radiation efficiency is increased in a certain frequency range. Because the radiation efficiency of a sound source system can be improved by increasing the horn input impedance, it is used as the performance index of a horn. The input impedance of a horn system can be calculated by using the transfer matrix under the linear plane wave assumption, considering the flare constant, throat area, and length of the horn to know the acoustic characteristics. Exhaustive calculations varying the design parameters revealed that the serially connected horns can be used as an acoustic device improving the radiation efficiency at a desired frequency range. Optimization of the design variables of the two serially connected exponential horns was conducted to increase the efficiency of the horn-driver assembly, which is the ratio between the radiated sound power and the input electric power. The optimized result showed that the suggested configuration of the two connected horns is better in efficiency at the target frequency band compared to a single exponential horn by sacrificing the low-frequency range due to the increased cutoff frequency of the horn. [Work supported by BK21.]
Resolution of circuits from a physical point of view.
Authors: Gimenez de Paz Juan C.
Published: October 2010

The resolution of electrical circuits and its acoustic homologous from a physical point of view is presented here. Based on the structural analogy with a mechanical system in equilibrium, it is possible to associate a Lagrangian depending on the generalized forces in a viscous medium with friction coefficients and with a set of holonomic constraint functions. By means of the Hamilton principle applied to this Lagrangian associated with a circuit, an equation of a function of a set of independent variables can be obtained, which turns out to be the condition for the resolution of a typical problem of linear programming. This minimized expression represents, in turn, the power dissipation. From all the possible values that could take a set of speed and pressure, the principle picks out one and only one (the true values) with the condition of producing the least power dissipation. All acoustic devices or systems that could be represented by an electric circuit may be solved by this method with the physical meaning described here.
Piezoelectric fibers for energy harvesting.
Authors: Guillot Francois M. , Beckham Haskell W. , Leisen Johannes
Published: October 2010

Most energy harvesting devices rely on traditional piezoelectric materials integrated in structures subjected to mechanical vibrations. A new kind of commercially available composite sensors consists of several PZT fibers embedded in a passive polymer matrix with interdigitated electrodes deposited on the polymer. The main advantage of these sensors is that they combine the large transduction capabilities of PZT with the mechanical flexibility of polymers. The present study evaluates the performance of single PZT fibers, with electrodes directly deposited onto the ceramic and with individual polymer jackets. This approach should optimize the amount of electrical energy available from the material by placing the electrodes on its surface and by maximizing the active piezoelectric volume. Fibers with tubular and “crimped” cross-sections were electroded, poled, and glued to a vibrating cantilever beam equipped with a strain gauge. The performance of the fibers was compared to that of the composite sensors, and the influence of the polymer jacket on the strain transmission to the fiber was also evaluated. A potential application is to incorporate these fibers into fabrics that would be capable of harvesting mechanical energy from the environment (wind, currents) or from human motion. [Work supported by the National Textile Center.]
First empirical works in acoustics done by freshman students at a public university in Argentina.
Authors: Kogan Pablo , Cardozo Mayra
Published: October 2010

A Bachelor of Science in Sound Engineering of five years was created at the Universidad Nacional de Tres de Febrero in Argentina in the year 2007. The first course of the specialty that students should take is Introduction to Acoustics and Psychoacoustics. It has a four month duration, is located in freshman year, and does not require any previous course of math or physics. The course intention is to give beginners a global point of view of acoustics and its branches, the nature of sound, some elementary concepts of acoustics, and the basic methodological directions to elaborate academic projects on acoustics. As a very early stage training in scientific method and project development, the undergraduates have to choose a topic to perform a project during the semester. At the middle of the course, the pupils ought to consign a project progress report. At the end of the course, they submit the final report and give an oral presentation to their classmates. This work expounds the empirical work in class and summarizes some student projects carried out during the courses taught between years 2007 and 2010.
Ideas for effectively teaching architectural acoustics to students of architecture.
Authors: Wang Lily M.
Published: October 2010

Because the process of designing and constructing buildings often has the architect in the role of project manager, it is crucial that architects be trained in the fundamentals of architectural acoustics. Students of architecture, though, are often not interested in that required course on acoustics (if there is one), as their education tends to push them to be more visually inclined. This paper provides some ideas on how to effectively teach architectural acoustics to students of architecture, based on the author’s own experiences. In particular, (a) engaging the students to experience sound in rooms through a course-long listening journal assignment, (b) pulling in case study examples, and (c) promoting a collaborative environment between architects and consulting engineers have seemed to be successful techniques. A brief review of the Robert Bradford Newman Student Award Fund, whose goal is to promote the study of architectural acoustics among those in the building industry, will also be provided.
Information technologies applied to acoustics learning.
Authors: Franco Martinez Maria Teresa , Vazquez Saldaña Amparo , Negrete Redondo Jose de Jesus
Published: October 2010

The rather new information and communication technologies are computing tools that transmit, process, stores and present information in several different ways. The teaching process based on these techniques can promote diverse experiences due to interaction with pears and collaborative learning. This paper is developing within the acoustics field in the topic Electroacoustics and Transducers, where two groups of the seventh semester (BSc level) participate in the experiment, one as a control group subject to regular teaching, while the other works with the techniques described. At the end, an evaluation of both groups will show whether there is a significant difference.
The new causes for irregularity in students of communications and electronics engineering at the Superior School of Electric and Mechanical Engineering Zacatenco.
Authors: Felipe Duran Fedrico , Martinez Ignacio
Published: October 2010

The superior school of electrical and mechanical engineering is a Mexican higher education school. It has six different degrees: Electrical, Communications and electronic, Mechanical, Aeronautic, Robotics, and Computer Science. All degrees have a strong problem about low grades of the students, and many students are failing in the credits. This paper analyzes old and new causes that produce that irregularity, especially in the Communications and Electronics engineering, where majors can be taken in five areas, Acoustic, Control, Electronic, Computation and Communications.
Visually supported analysis of music.
Authors: Kostek B.
Published: October 2010

Subjective tests are highly regarded means for determining musical sound timbre, sound and music quality, audio-visual correlations, etc. The multimedia development created a new domain of interests, namely, quality of experience, in which subjective evaluation has proven to be one of, if not, the most important tool. It should be pointed out that experience is not only subjective but also context-dependent. In addition to the external factors related to the environment aspects, perception and cognitive state clearly play a critical role in the context. Despite significant advances in objective measuring methods, the only way to evaluate subjective audio/video signal quality is to acquire opinions of subjects, and then to quantify resulted choices. Many multimedia applications stimulated new methods of subjective evaluation. Also, audio-visual perception evaluation requires a new methodological approach, which can be fulfilled while employing gaze-tracking technology. Gaze-tracking-based experiments consist in determining the part of the screen that the user is looking at and in superimposing it against an audio-video content. This method allows for measuring the attention and performance of the subject, thus making the subjective tests more reliable. The proposed methodology based on the gaze-tracking technique applied to audio-visual correlation tests will be shown.
Non contact thin film local thickness measurements through a thick plate using zero group velocity lamb modes.
Authors: Ces Maximin , Prada Claire , Clorennec Dominique , Royer Daniel
Published: October 2010

It has been shown that a homogeneous isotropic plate can support non-propagating Lamb modes having a zero group velocity (ZGV) for nonzero values of their wave number. Optical means such as a pulsed laser source and a heterodyne interferometer can be used for non-contact generation and detection of these elastic waves. With this experimental setup, local and accurate measurements of material parameters such as bulk waves velocities and very small plate thinning detection were obtained from the resonance spectrum of ZGV Lamb modes. A thin layer deposited on the plate induces a significant down shift of the set of ZGV resonance frequencies. Experimentally, thin gold layers down to 100 nm were detected through a 1.5-mm thick Duralumin plate. Optical measurements were performed at the same point as the generation on the non-covered face of the thick plate. The frequency shift, which is typically 1 kHz for the S1-Lamb mode at 1.9 MHz, can be approximated by a formula, which allows us to calculate the layer thickness. Since the material parameters are temperature-dependant, the influence of temperature was also studied.
Shear wave speed measurements in viscoelastic wormlike micellar fluids.
Authors: Gladden J. R. , Skelton C. E. , Mobley J.
Published: October 2010

In viscous Newtonian fluids, support of shear waves are limited to the viscous boundary layer. Non-Newtonian fluids which have shear modulus, however, support shear waves over much longer distances. We report low-frequency (50 Hz) shear speed measurements in wormlike micellar fluids, an aqueous mixture of surfactant molecules and salt, as a function of surfactant concentration. Specifically, we use cetyltrimethylammonium bromide for the surfactant and sodium salicylate as the salt. We exploit the birefringent properties of these fluids to make the acoustic measurements. We find a roughly linear dependence of wave speed on concentration which increases from 0 mm/s for pure water (extrapolated) to about 500 mm/s at 160 mM of surfactant. The linear scaling is supported by the concentration scaling theory of the shear modulus in these fluids. Supporting rheological data will also be presented.
Interferometric nanogold sensor with sensibility-controlled acoustical signal.
Authors: Torres-Torres Carlos , Torres-Martinez Reydezel , Moreno-Valenzuela Javier , Trejo-Valdez Martin
Published: October 2010

Experimental and numerical results for acoustical wave detection performed by a nanostructured interferometric system with optical excitation wavelengths near the surface plasmon of resonance of Au nanoparticles are presented. A colloidal gold sample located at the arm of a Michelson interferometer was used. It is shown that the precipitation of metallic nanoparticles with different sizes in a fluid can be driven by acoustical frequencies in order to induce changes in the properties of the sample. The measurements are based on the identification of the optical transmittance associated with the distribution density that results when an acoustical signal is in propagation through the sample. The modification on the absorptive and refractive optical response of the sample containing Au nanoparticles was investigated. It is demonstrated that a high accurate stabilization of the optical properties of the sample can produce important differences in the sensibility of the interferometric system for detecting other physical perturbations by remote sensing. [Financial support from CONACyT through Grant nos. 80024 and 82708; from IPN through Grant nos. SIP-20100800, SIP20100836, SIP20100553, and SIP 20100564; and also from COFAA is gratefully acknowledged.]
Analysis of rotating ocean wave energy converters.
Authors: McDaniel J. Gregory , Shivers Alexandra M.
Published: October 2010

Approaches are currently being developed for converting ocean wave energy by creating mechanical rotations within buoys. These devices benefit from the absence of mechanical stops that may destroy devices that utilize mechanical translations within buoys. In the present work, an analysis is developed that quantifies the mechanical coupling of ocean waves to rotational motions within a buoy. The analysis accounts for motions that are nonlinear with respect to the rotation angle, thus including devices in which internal bodies may spin completely around. It is assumed that the device impedance is small relative to the wave impedance, so that the device does not alter the motion induced by the incident ocean wave. In this limit, the imposed motion on the exterior of the buoy is assumed known from wave height and period. Conversion of the rotational energy to electrical energy is modeled by representing the power takeoff as an attached frequency-dependent impedance. The analysis is coupled to an optimization process that maximizes energy conversion by varying design parameters such as eccentric mass, eccentricity, power takeoff, and buoy geometry.
Paradigm leveling in Buenos Aires Spanish sibilants.
Authors: Rohena-Madrazo Marcos
Published: October 2010

Buenos Aires Spanish (BAS) lacks a voicing contrast in fricatives; however, there is an apparent voicing mismatch in its fricative inventory: /f,s,x/ vs /ȝ/. Since the mid-twentieth century, /ȝ/ has been undergoing a devoicing change to [∫], sensitive to factors such as age, sex, and social class. This study analyzes the devoicing rates of /ȝ/ and compares them to voiceless fricative /s/ in order to investigate the progress of this devoicing change. The data come from word list and sentence reading tasks. Using onset/offset of high frequency energy as a guide for segmentation, the percentage of voicing during frication was measured for tokens of /ȝ/ and /s/. Preliminary results from 16 native BAS speakers (stratified by age, sex, and class) show that 9/16 speakers actually present no significant difference between the percentage of voicing for /s/ and that of /ȝ/, and of the younger speakers only 1/8 exhibits significantly higher voicing rates for /ȝ/. These results suggest that, for most of the younger generation, /ȝ/ has been devoiced to the level of /s/. The previous sensitivity to social factors associated with /ȝ/ seems to be ceding to the phonetic/phonological pressures of paradigm leveling toward a voiceless fricative inventory: /f,s,∫,x/.
Linguistic effects on speaker discrimination.
Authors: Narayan Chandan R. , Babel Molly
Published: October 2010

We report the results from experiments aimed at measuring linguistic influences on speaker discrimination. In experiment 1, listeners heard two speakers in each trial (10 total speakers balanced within and across gender), each saying a single English word with a 100 ms ISI. Listeners were asked to determine whether the two words were spoken by the same speaker or not in a 2AFC design. In some cases the two words formed a common compound (i.e., year-book) and others a nonsense compound (i.e., year-crow). Listeners’ response and reaction times were measured as a function of semantic cohesion. Experiment 2 examined speaker effects on listeners’ knowledge of compounds. Listeners were asked whether two words, spoken by either the same or different speaker, formed a compound or not. Results are discussed in terms of the facilitative and inhibitory effects of semantic cohesion on speaker discrimination.
Predicting the effect of talker differences on perceived vowel category.
Authors: Vitela Antonia D. , Story Brad H. , Lotto Andrew J.
Published: October 2010

It has been clear for more than 50 years that listeners sometimes shift their categorization of target vowels as a function of the information in preceding carrier phrases. These results have been interpreted as evidence for a talker normalization process that allows listeners to tune their speech perception to the peculiarities of individual talkers. However, it is still not clear what information is being extracted about the talker from the context phrases. In the current set of studies, carrier phrases (“He had a rabbit and a”) spoken by different “talkers” were produced by manipulating the length and oral/pharyngeal cavity ratios of an articulatory synthesizer. [Story, J. Acoust. Soc. Am. 117, 3231–3254 (2005).] These phrases preceded a series of target stimuli varying from “bit” to “bet” produced by the standard vocal tract for the synthesizer. Shifts in the perceived target vowel were obtained for some of these vocal tract manipulations but not others. The presence/absence of effects was most readily predictable from the long-term spectral average of the carrier phrase. These results support the idea that listeners are extracting general acoustic information from the context and not specific information about the talker’s vocal tract. [Work supported by NIH-NIDCD.]
Neural correlates of dialect perception in early infancy.
Authors: Egorova Natalia , Cristià Alejandrina , Vendelin Inga , Filippin Luca , Long Bria , Gervain Judit , Minagawa-Kawai Yasuyo , Dupoux Emmanuel
Published: October 2010

A wealth of behavioral research suggests that infants become increasingly specialized in their native dialect/language in infancy. In contrast, few studies document how this early specialization is reflected in neural activation, most of which have compared familiar and unfamiliar languages, and none focused on different dialects. This study aimed to fill that gap, focusing on cerebral activation in temporal areas, as measured with near infrared spectroscopy. Audiovisual infant-directed speech was recorded from talkers of either Parisian or Quebecois French. These videos were presented to 5-month-old Parisian infants in blocks within which videos from two talkers alternated in one of two ways. In pure blocks, both talkers were either Parisian (pure-familiar) or Quebecois (pure-unfamiliar). In mixed blocks, the two talkers had different dialects. A robust and mostly bilateral activation was found for both mixed and pure blocks. Follow-up comparisons revealed a stronger activation for mixed blocks than for pure ones, and a trend for more activation in response to the unfamiliar dialect than to the familiar one. These findings are congruent with behavioral studies showing early sensitivity to dialects and extend the brain imaging literature on early neural attunement to the language as spoken in the infant’s environment.
Acoustic measurement of Canadian English and Canadian French interlingual homophones.
Authors: Castonguay Paula L. , Andruski Jean E.
Published: October 2010

The purpose of this study was to examine how interlingual homophones of Canadian English (CE) and Canadian French (CF) differ along acoustic dimensions as a prelude to perceptual tests. Two male Canadian monolingual speakers of English and French produced sentences in which interlingual homophones were embedded (e.g., two /thu/ and /tu/ meaning all). Voiced onset times (VOTs), formant frequencies (F1 and F2), and vowel-inherent spectral changes (VISCs) of each respective speaker were examined. First, it is expected that the CE monolingual speaker will have aspirated (long-lag) voiceless stops, while the CF monolingual speaker will have unaspirated (short-lag) voiceless stops regardless of the context. Second, it is expected that CF vowels will have lower F1 values for lax vowels and will be produced more peripherally (with respect to F2 values) than CE vowels (i.e., French front vowels will be more advanced, and French back vowels will be more posterior). Lastly, it is expected that CF vowels will have less vowel-inherent spectral change than CE vowels. Results from this study will provide insight on the phonetic representation of interlingual homophones, enabling the understanding of acoustic-phonetic influences on the processes of speech perception in bilinguals (CE and CF).
Perception boundary between fricative and affricate in Korean speakers.
Authors: Yamakawa Kimiko , Amano Shigeaki
Published: October 2010

Previous study has shown that perception boundary between fricative /s/ and affricate /ts/ in Japanese speakers is represented by a linear function with two variables: a rise time and a sum of steady and decay time [Amano et al. (2009)]. This study investigated characteristics of the boundary in non-native Japanese speakers such as Koreans, because they often have trouble in distinguishing /s/ and /ts/. Thirty-two Korean speakers listened to 2-D stimulus continua coordinated with a rise time and the sum of steady and decay time of [s]/[ts] in 1–4-mora Japanese words and made two-alternative forced choice between /s/ and /ts/. A logistic regression analysis of the identification ratio of these phonemes showed that the perception boundary in Korean speakers was well represented by a linear function with the same variables as in Japanese, but the boundary shifted to a smaller value both in the rise time and in the sum of steady and decay time, which indicates a greater identification ratio of /s/. The results suggest that Korean speakers’ perception of [s]/[ts] are affected by their native language, which does not have /ts/.
The influence of language background on the relative perception of vowels.
Authors: Sjerps Matthias J. , Smiljanic Rajka
Published: October 2010

Individual differences in vowel production result in an extensive overlap of vowel categories in F1 × F2 vowel space, especially in languages with large vowel inventories. When perceiving vowel categories, listeners compensate for this variability by identifying vowels relative to the voice characteristics of individual speakers. The present study examines the effect of language background on the relative perception of vowels, i.e., whether listeners engage in vowel normalization differently in languages with vowel inventories of varied sizes and with different amounts of category overlap due to across-speaker variability. To that end, we compare English and Dutch, both with 10+ vowels and a substantial category overlap, and Spanish, with only 5 vowels and less category overlap. Vowel targets from an /o/–/u/ continuum were embedded in sentences spoken by native speakers of all three languages. F1 of the precursor sentences was modified to be either high or low. Seventy-two listeners participated in the vowel categorization task. Preliminary analyzes reveal that listeners of all three languages compensate for F1 context similarly regardless of vowel inventory size and independent of their proficiency in another language. These results suggest that the normalization processes may be automatic and involve a language general mechanism.
Predicting vowel backness variability in Tommo-So.
Authors: McPherson Laura , Ryan Kevin
Published: October 2010

Tommo-So (Dogon, Mali) has highly restrictive vowel phonotactics in stems. While any of its seven vowels may occur in the first syllable, the set of possible subsequent vowels is small, and noninitial nonlow vowels often exhibit a wide range of gradient variation in backness (while their phonological height remains fixed). Our study examines the second vowel of disyllabic words at all nonlow heights where (1) V1 = V2, (2) V1 is high and V2 is mid, and (3) V1 is mid and V2 is high, as well as the definite enclitic in various consonantal contexts. Preliminary acoustic analysis reveals that backness variation in V2 covers the whole range of front to back and yet is significantly less bimodal than would be expected if it were variation between discrete front and back allophones. Moreover, the majority of the variation cannot be attributed to coarticulation; that is, the same speaker will produce the same stimulus differently at different times. Nonetheless, if the first vowel is identical, variation is much restricted. We predict that grammatical morphemes such as the definite will display greater variation than lexical items.
An adaptive sparse sensing approach to shallow water acoustic channel estimation and tracking.
Authors: Sen Gupta Ananya , Preisig James
Published: October 2010

The shallow water acoustic channel is challenging to estimate and track due to the ill-conditioned nature of the problem, the need to optimize over a complex field, and the time-varying nature of the channel coefficients. We have previously presented a geometric mixed norm approach to estimate and track the channel delays and delay-Doppler spread function coefficients that exploit the often sparse distribution of the channel coefficients. In this work, we present the effectiveness of our approach over a range of field data collected at 15 m depth over ranges of 60, 200, and 1000 m at various wind conditions. We also compare the performance of the estimation and tracking algorithm against other sparse sensing approaches to shallow water acoustic channel estimation, e.g., the L1-regularized least squares algorithm. We show that the choice of the sparsity factor λ, which is an essential design parameter in all sparse sensing methods, plays a critical role in the effectiveness of sparse reconstruction of real field data, and present novel ways to track the sparsity factor over time in a way that is consistent with the time-varying nature of the shallow water acoustic channel.