bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic observation of hydrothermal flows
Authors: Jones Christopher D. , Jackson Darrell R. , Rona Peter A. , Bemis Karen G.
Published: July 2012

Acoustic backscatter has been used to observe hydrothermal flows at several sites on the Juan de Fuca Ridge at frequencies of 200 and 330 kHz. In the case of plume discharges (‘‘smokers’’), backscatter from particulates is used to obtain three-dimensional images and to measure flow via Doppler shift. For diffuse flows, acoustic scintillation of the signal backscattered from the seafloor is detected using ping-to-ping correlation. Mapping of diffuse flows using both fixed and moving platforms will be discussed. The magnitude and time lag dependence of ping-to-ping correlation have been linked to flow parameters using the Rytov scattering approximation. [Work supported by NSF Grant OCE 98-18841.]
Monostatic and bistatic scattering by a single bubble near a pressure release interface: Laboratory measurements and modeling
Authors: Kapodistrias George , Dahl Peter H.
Published: July 2012

Scattering by a single bubble near a flat pressure release interface is investigated theoretically and experimentally. A ray-acoustic interpretation is used to describe the four scattering paths, from source to bubble to receiver. Multiple scattering effects are accounted for using a closed-form solution derived from the multiple scattering series. A bubble with radius a≊425 μm is placed on a fine nylon thread, which is practically transparent to sound, at a distance dB from the interface. The primary variable is dB and it ranges from 1a to 100a. Experiments are performed at a frequency of 120 kHz with the transducers arranged in both bistatic and monostatic configuration. Theory and experiment are in excellent agreement, verifying the dominant effect of the four paths in the response of the bubble, with multiple scattering playing a role for kdB<1, where k is the wave number of the medium. In the long-range limit our simulations agree with those of Ye and Feuillade [J. Acoust. Soc. Am. 102, 798–805 (1997)] including the shifting of the bubble’s resonant frequency. The dependence of scattering on transducer arrangement, range to bubble, grazing angle, and phase relation among the four paths, vis-à−vis monostatic and bistatic scattering, are discussed.
Space-time sound fluctuations due to internal solitons in shallow water
Authors: Katsnelson Boris G. , Pereselkov Serguey A. , Petnikov Valery G. , Sabinin Konstantin D. , Serebryany Andrey N.
Published: July 2012

In this paper results of numerical modeling of sound propagation in shallow-water waveguide with internal waves are presented on the basis of experimental data about internal solitons (IS) registered in the Japan sea [A. N. Serebryany, Sov. Phys. Oceanol. 27, 225–226 (1987)]. These IS constitute some sequences of oscillations with amplitude up to 10 m moving toward coastal line with the velocity about 0.25 m/s. The wavelength of separate oscillations in this group is about 325 m; total length of the packet is about 4 km. Three-dimensional sound-speed distribution is constructed using the mentioned data. On the basis of this model, space-time fluctuations of intensity of the sound propagating in such medium are calculated. The modeling is carried out within the framework of the parabolic equation method in the horizontal plane and the modal approach in the vertical one. These fluctuations can be interpreted as the forming of a sound waveguide in the horizontal plane; space-time scales of fluctuations correlate with space-time scales of IS. Different numerical examples are presented; possible experimental setup is discussed. [Work supported by RFBR, Grant 00-05-64752.]
Real-time observation of inception and growth of HIFU-induced tissue lesions
Authors: Lafon Cyril , Bailey Michael R. , Couret Lisa N. , Kaczkowski Peter J. , Brayman Andrew A. , Crum Lawrence A. , Sapozhnikov Oleg A.
Published: July 2012

To study the biological effects of high-intensity focused ultrasound (HIFU), experiments are usually performed on isolated or perfused tissues. Indeed, the complex phenomena occurring in tissue during HIFU-induced coagulation necrosis is difficult to mimic with synthetic phantoms. A good phantom should first match the acoustical and thermal properties of tissues. Furthermore, heating above a thermal threshold should induce a permanent, localized and observable change corresponding to protein denaturing in tissue. Lastly, the choice of a transparent material makes possible real-time examination of the development of coagulation necroses. We have used bovine eye lenses in this aim. The density, sound speed, attenuation, and thermal threshold for irreversible damage to the bovine lens were measured and found to be similar to those for liver or muscle, common tissues for HIFU experiments, although acoustic attenuation is slightly higher in the lens. Transparency of the lens allowed us to observe HIFU-induced lesion evolution in real time. The shape and size of the lesions obtained in the lens agreed well with results obtained in liver. In conclusion, the transparent bovine eye lens is a useful model for visualization of thermal lesions. [Work supported by ONR.]
Two-dimensional ultrasound phased array for treatment of benign prostatic hyperplasia
Authors: Helser Janelle L. , Sparrow Victor W. , Smith Nadine
Published: July 2012

In the prostate, focused ultrasound offers an attractive means of noninvasive tissue ablation for treatment of Benign Prostatic Hyperplasia (BPH). Intracavitary two-dimensional, ultrasound arrays allow for deep localized heating and are capable of generating sufficient power for tissue ablation. A two-dimensional array design is capable of focusing electronically in three dimensions, by controlling the power and phase, instead of having to physically adjust or reposition the transducer. The goal of this project was to design a 1.5 MHz, two-dimensional, linear, PZT transducer that could steer a focus throughout the region of the prostate. Pressure fields for the array were theoretically determined, using amplitude shading and varying elemental sizes to reduce grating lobe and side lobe levels. The amplitude shading was altered each time the transducer was refocused so that the peak amplitude was located in the element normal to the focus. Based on this 100-element theoretical array, a 1.5 cm×8 cm transducer array was constructed to evaluate the feasibility of delivering thermal therapies from a two-dimensional array.
Platelet activity as a result of exposure to high-intensity focused ultrasound
Authors: Poliachik Sandra L. , Ollos Ryan J. , Mourad Pierre D. , Crum Lawrence A. , Chandler Wayne L.
Published: July 2012

Using platelet-rich plasma, we investigated the capability of 1.1-MHz cw high-intensity focused ultrasound (HIFU) to produce ‘‘acoustic primary hemostasis,’’ including platelet activation, aggregation, and adhesion to a collagen-coated surface. Platelet activity was evaluated for exposure durations of 100–500 s at intensities of 0–2250 W/cm2. In order to avoid heating effects, temperatures in platelet trials were maintained below 42 °C through use of a tank cooling system and control of exposure parameters. Flow cytometry, laser aggregometry, conventional microscopy, environmental scanning electron microscopy, and passive cavitation detection were used to quantify platelet activation, aggregation, adhesion, and associated cavitation. HIFU can activate platelets and cause them to adhere to a collagen-coated surface. Cavitation was monitored during aggregation trials and was quantified to provide a relative measure of the amount of cavitation that occurred in each aggregation trial. Regression analysis shows weak correlation between aggregation and intensity, and a strong correlation between aggregation and cavitation occurrence. [Research supported by DARPA.]
An attempt to explain turbulence occurring when yeast cells suspended in water-rich ethanol mixtures are irradiated in a quasistanding ultrasonic plane wave at 2.2 MHz
Authors: Radel Stefan , McLoughlin Aiden J. , Groeschl Martin , Benes Ewald
Published: July 2012

Ultrasonic resonators are successfully used for the separation of suspended particles or cells, e.g., as cells filters in biotechnology. These systems are based on the radiation forces spatially rearranging the particles in the pressure nodal planes of the quasistanding ultrasonic wave field. When yeast—as this technology is tested to be applied in brewing—is suspended in water this separation/immobilization takes place as predicted. However, suspensions of yeast in water-rich ethanol mixtures show a breakdown of the spatial distribution above certain concentrations of ethanol and the cells are turbulently mixed in the separation system. This has earlier been reported to go along with an impaired viability of yeast in a 12% (v/v) ethanol/water mixture. The scope of this paper is to attempt an explanation based on the acoustic contrast between the cells and the liquid as water-rich ethanol mixtures have unexpected acoustical and physical properties. Data of the spectral behavior of the system at in situ levels of true electrical power input are shown as well as the results of examinations, if (sub) harmonic and/or transient cavitation were taking place. [Work supported in part by the European Commission’s TMR Programme, Contract No. ERBFMRXCT97-0156, EuroUltraSonoSep.]
Potential errors in contrast-agent-mediated estimates of regional myocardial perfusion arising from myocardial anisotropy
Authors: Miller James G. , Sosnovik David E. , Baldwin Steven L. , Holland Mark R.
Published: July 2012

Recently developed imaging modalities based on the nonlinear response of contrast agents are dependent upon the local acoustic pressure. Thus, regional variations of acoustic pressure arising from myocardial anisotropy can result in nonuniform ‘‘apparent perfusion’’ in the absence of a perfusion defect. Measurements of regional variation of myocardial attenuation in the septum and lateral walls of excised sheep hearts are reported. Studies were carried out on hearts obtained immediately after slaughter from 8 healthy adult sheep. These measurements of attenuation were carried out in orientations analogous to those encountered in the apical four-chamber view, which is the preferred view for clinical studies of myocardial perfusion using contrast-agent-enhanced echocardiography. The video signal analysis method introduced by the University of Wisconsin group was used to analyze data obtained with a commercially available (ATL) clinical scanner using a linear array (L 7-4) operating in fundamental mode. Tissue mimicking phantoms were imaged under identical conditions. Normalizing sample data by reference data from the phantoms yields quantitative estimates of slope of attenuation. Results of these experimental measurements document significant transmural variations in attenuation that could lead to apparent perfusion anomalies in contrast-agent-mediated estimates of regional myocardial perfusion. [Work supported by NIHHL40302.]
Simulation of tissue displacement using ultrasonic speckle tracking
Authors: Lawu Tjundewo , Ueda Mitsuhiro
Published: July 2012

The quantitative evaluation of ultrasonic displacement in tissue under externally applied forces is a necessary step in the field of ultrasonic diagnostics. In this study, the speckle tracking method is used to investigate the motion artifact produced by a rotating tissue. An analytic prediction of this motion artifact in relation to system characteristics (i.e., beam width, pulse duration, frequency, and phase of the signal) is presented. The tissue is modeled as a random array of numerous point scatterers, and rf signals are computed based on the convolutions between the transmission pulse and the impulse response of each scanning line. These analytical predictions are then compared to the computer simulation of the model. The results show that the artifact resulting from the speckle tracking method depends on the ultrasonic beam parameters. The method is quite general and can be extended to study the effects of other tissue motion, in particular, the deformation of tissue.
Acoustic reflectometry for estimation of lung gas-phase volume during partial liquid ventilation in sheep
Authors: Raphael David T.
Published: July 2012

Acoustic reflectometry was studied as a possible tool to measure the lung gas-phase volume during partial liquid ventilation (PLVSM). With IRB approval, healthy sheep (weight 10–22 kg) (n=3) were anesthetized, intubated, mechanically ventilated in the supine position, and underwent a low-lying tracheostomy. A base-line functional residual capacity (FRC) via a N2 washout technique was measured. Perflubron (LiquiVent®, Alliance Pharmaceutical Corp., San Diego, CA) was instilled through the tracheostomy tube in successive aliquots, each consisting of 20% of measured FRC, up to 100% FRC. A Hood Labs acoustic reflectometer was used to obtain lung gas volume determinations for the FRC measurement and after perflubron instillations. The acoustic reflectometer was used to generate a cross-sectional area versus axial length curve. The subglottic lung gas-phase volume was calculated by integrating area over length. The reduction in the subglottic lung gas-phase volumes for each animal exhibited a strong linear correlation with the amount of perflubron instilled. Linear least-squares regression models run on the individual sheep data were all significant, with the largest p value being 0.0067. Acoustic reflectometry may be of use in the monitoring of lung gas-phase volume in PLV and respiratory disease.
Doppler ultrasound detection of shear waves remotely induced in tissue phantoms by focused ultrasound
Authors: Barannik Evgen A. , Girnyk Sergii A. , Tovstiak Volodymyr V. , Sarvazyan Armen P.
Published: July 2012

Remote generation of shear waves in tissues by radiation force of focused ultrasound is the basis of shear wave elasticity imaging (SWEI), a new acoustic method of medical diagnostics. Feasibility of SWEI was previously demonstrated in the experiments with optical and NMR detection of ultrasonically induced shear waves [Sarvazyan et al., Ultrasound Med. Biol. 24, 1419 (1998)]. In the present study the SWEI system with ultrasonic pulsed Doppler detection of shear waves was designed and tested using a range of gelatin-based phantoms and muscle tissue. Radiation force was generated by a focusing transducer of 8 cm diameter and 7 cm focal length. The carrier frequency was 1 MHz with intensity 1.85 W/cm2 at the surface of the transducer. The Doppler detection transducer operating at 3.5 MHz was installed in the center of the pumping transducer. The developed procedures of tissue motion detection and Doppler signal-processing algorithms based on the autocorrelation method allowed estimation of the velocity with accuracy better than 0.2 mm/s. The waveforms of the shear wave at various distances from the pumping ultrasonic beam axis were measured and the shear wave velocities were evaluated. The oscillation character of relaxation process for some phantoms and muscle tissue was shown experimentally.
International key comparison of ultrasonic power measurements
Authors: Beissner K.
Published: July 2012

One of the worldwide key comparisons performed at present under the auspices of the International Committee for Weights and Measures (CIPM) covers the time-averaged ultrasonic power emitted by an ultrasonic transducer into water. The ultrasonic power value is particularly important in characterizing the output of diagnostic and therapeutic medical equipment. Nine national metrology institutes participate in the comparison. The time schedule is from July 1999 to November 2001. The aim is to demonstrate the international consistency of calibration and measurement certificates. An ultrasonic standard transducer is circulated and power measurements are to be made at frequencies of 2, 6 and 10 MHz and at five power levels in the milliwatt and watt ranges. The measurement procedures applied and the main details of the technical protocol will be discussed.
International comparisons of hydrophone calibrations
Authors: Preston Roy C. , Robinson Stephen R. , Van Buren Arnie L.
Published: July 2012

In the global markets which are increasingly dominating industrial trade, international comparison of hydrophone calibrations is the primary mechanism of ensuring harmonization of underwater acoustics measurement standards across national borders. This paper describes the results of several recent comparison exercises initiated in Europe and the USA. These include both informal comparisons of hydrophone calibrations of a bilateral nature and formal comparisons involving a number of countries organized under the auspices of regional or international metrology organizations. Completed projects which will be described include a Euromet/European Commission project involving a total of 12 participants from seven European countries and a comparison between the Russian Federation and China. In these cases, results will be given and the important conclusions summarized. Finally, a relatively new comparison project will be described which has been set up under the auspices of the Consultative Committee for Acoustics, Ultrasound and Vibration (CCAUV) of the Bureau International des Poids et Mesures (BIPM) in Paris. This key comparison has now been agreed to for the kilohertz frequency range 1–500 kHz and will involve the circulation of three hydrophones. Countries participating in the comparison include the UK, China, Germany, Russian Federation, and USA, with Canada expected to join soon.
Importance of the free-field calibration of microphones
Authors: Nedzelnitsky Victor
Published: July 2012

Numerous regulatory requirements, standards, and product characterization and quality control procedures important for industry, commerce, health, and safety rely on practical measuring instruments including sound level meters, personal sound exposure meters (noise dosimeters), and standardized measuring microphones. Such instruments are usually large enough that the effects of diffraction must be considered throughout a significant portion of the operating frequency range. These effects cause differences between the free-field, the pressure, and the diffuse-field sensitivities of instruments, particularly at high frequencies. Differences can also result from other phenomena, such as the effects of a microphone’s static (barometric) pressure equalization vent, especially at low frequencies. Different calibration procedures have evolved, so that an appropriate calibration is available for each of the field types: free, pressure, and diffuse. Critically important free-field procedures and some of the most accurate and widely used diffuse-field procedures should be, but are not always, traceable to primary free-field calibrations of microphones by the reciprocity method. Future international key comparisons at the highest level of accuracy should include determinations of the free-field sensitivities of laboratory standard microphones such as IEC type LS2 by the reciprocity method.
Reference sound source calibration at various temperatures and site altitudes
Authors: Campanella Angelo J.
Published: July 2012

Adjustments are made for atmospheric temperature and barometric pressure when calibrating a sound power reference sound source (RSS) and when applying an RSS in the substitution method to evaluate an unknown sound power. Experience with Hemianechoic calibration of a dozen RSS units outdoors at various temperatures near sea level and a special test series on one RSS unit at three higher sites up to 9927 feet and applying a pistonphone reference to verify microphone and sound-level meter stability are described. According to these varied temperature results and the theoretical work of others [Allan Powell, J. Acoust. Soc. Am. 32, 982–990 (1960), Eqs. (41)–(42), after Lighthill], it appears that the mechanical fan-type RSS is a multipole—chiefly quadrupole and octupole—type sound source. It was apparent, according to these varied altitude results, that emitted sound pressure and sound power are both linear functions of barometric pressure. Experimental results will be presented. Practical applications to determine actual sound power, to report normalized sound power, and to predict actual sound pressure and sound power expected at a remote site under nonstandard conditions are described.
Boundary-element simulation used in the design of a sound intensity calibrator
Authors: Gramtorp Johan , Cutanda Vicente , Eriksen Anders , Sandermann Olsen Erling
Published: July 2012

The recent introduction of hand-held intensity measurement equipment has created a growing need for verification of the measurement equipment in the field. The key feature for easy field use is the possibility of calibrating the two-microphone intensity probe without dismounting the spacer. Working models were built, but none of them worked to more than approximately 3 kHz. Compliance with IEC 61043 requires the calibrator to work up to 7.1 kHz. A lot of modifications on these models were tried, but none of them worked. The development project was close to being stopped. A boundary-element model of the sound intensity calibrator was built. It verified the measured result from the working models. Based on the boundary-element model the best type and position of the sound source and the optimum dimensions of the calibrator cavity were found. Measurements on a final model verified the simulation results. The calibrations could now be made without dismounting the spacer.
Frequency response of a nonlinear acoustical resonator of arbitrary shape
Authors: Hamilton Mark F. , Ilinskii Yurii A. , Zabolotskaya Evgenia A.
Published: July 2012

The frequency response of a nonlinear acoustical resonator is investigated analytically and numerically. First, natural frequencies of a resonator whose shape is close to cylindrical are studied analytically by perturbation. An asymptotic formula is derived for the natural frequencies as a function of resonator shape. The solution at first order in the perturbation shows that each natural frequency can be shifted independently via appropriate spatial modulation of the resonator wall. Numerical calculations for resonators of different shapes establish the limits of the asymptotic formula. Second, the nonlinear interactions of modes in a nearly cylindrical resonator are investigated with Hamiltonian formalism as a basis for studying wave interaction in a resonator of arbitrary shape. A nonlinear frequency response function for the fundamental mode is derived by assuming that nonlinear interaction occurs only with the second harmonic. Bent tuning curves are predicted which lean up or down depending on whether the second-harmonic frequency is above or below the corresponding natural frequency, respectively. A fully nonlinear 1-D numerical code is used to verify the analytical result for the frequency response. [Work supported by ONR.]
Fluctuation before onset of oscillations in a thermoacoustic device
Authors: Kwon Young Sang , Symko Orest G. , Durrant Karin
Published: July 2012

The onset of oscillations in a resonant device where a temperature gradient produces a sound is a fundamentally interesting problem as it consists of a transition where random gas motion, when biased, produces an almost pure sound. This was studied in small 1/4-wave resonant tubes containing a fibrous stack across which a temperature gradient was maintained by means of heat exchangers at each end. The temperature gradient biases the random motion of the gas to trigger a standing wave in the resonator. The acoustic spectrum was measured as the temperature gradient approached the onset for oscillations. Factors affecting the transition to oscillation consist of stack gain, quality factor of the resonator, magnitude of the temperature gradient, and acoustic load. The directed diffusion of the gas along the stack leads to a series of sharp pressure pulses whose stochastic behavior triggers resonant oscillations in the tube. Onset temperature differences less than 50 °C have been observed and this could further be reduced by a suitable choice of parameters affecting the onset. This is an example of a thermal ratchet engine biased by a temperature gradient.
A graphical software application for design and simulation in thermoacoustic research (DSTAR)
Authors: Hofler Thomas J. , Purdy Eric , Curtis Scott
Published: July 2012

A graphical application called DSTAR has been written for the 32-bit Windows environment, for the purpose of thermoacoustic heat engine analysis. Written in C++ and MFC, the application uses pull-down menus and tabbed dialog boxes, and has additional graphical features such as automatic plotting of thermoacoustic state variables and geometry output in CAD file format. DSTAR supports a variety of variable units including dimensionless units, which are extremely convenient in the design phase of an engine. Current versions of the software are freely available at http://cooler.physics.nps.navy.mil/hofler/.
Redesign of a small thermoacoustic refrigerator
Authors: Underwood Tamra S. , Morley Bryan S. , Kuritz Benjamin L. , Muehleisen Ralph T.
Published: July 2012

At the Fall 1999 meeting of the Acoustical Society of America, the design and initial performance of a small, electrically powered thermoacoustic refrigerator was presented. The refrigerator has nominal dimensions of 5 in. long and 1 in. diameter with a target of 10 W of cooling over a 25°C temperature span using 2-bar helium as the working gas. Because of limitations in the acoustic transducer, performance was limited. A new design with a more powerful acoustic transducer is presented. The performance of the actual device will be compared to the predicted values. [Work supported by the Office of Naval Research.]
A two-microphone thermoacoustic impedance tube
Authors: Simmons Timothy , Raspet Richard , Hiller Robert
Published: July 2012

An experimental arrangement has been developed to explore the thermoacoustic properties of stack materials. The apparatus may be viewed either as a thermoacoustic engine with two microphones mounted in the tube wall, or as a two-microphone impedance tube that accommodates thermoacoustic elements. A sample stack material is placed between two heat exchangers and specific acoustic impedance measurements are taken as a function of frequency and at low-drive amplitude (to avoid nonlinear effects). The design is such that nearly all physical elements and operational parameters can be varied fairly easily. The ‘‘tube’’ is composed of three (flanged) pipe sections of different length, which independently contain a loudspeaker, stack and heat exchangers, and a termination. The test is performed with and without a temperature gradient imposed across the stack. The tube may be pressurized—allowing for different gases held at various ambient pressures—while the relative positioning of the elements within the tube may be varied. Hence a very wide range of testing conditions may be achieved. [Work sponsored by ONR.]
High-amplitude viscous effects in single pores
Authors: Petculescu Andi , Wilen Larry
Published: July 2012

Recently, we reported on a new technique to measure viscous effects of single pores [A. Petculescu and L. Wilen, J. Acoust. Soc. Am. 107, 2819 (2000)]. The method involves a simple lumped-element analysis of a compliant region in parallel with the pore. The pore impedance is determined by subtracting off the measured compliance. With two lengths of the same pore and a second subtraction, one can determine the impedance of the uniform middle part of the pore as well as the impedance of the pore ends. We have extended our measurements to higher amplitudes to look at nonlinearities in the pore. We will discuss how we can determine that the nonlinear effects are principally due to the pore ends, and how we measure these effects. Specifically, results will be presented for the amplitude dependence of the impedance as well for as the generation of higher harmonics. Different end geometries will be considered (such as rounded versus sharp tube ends) and the implication for jet pumps will be addressed. [Work supported by ONR.]
Natural frequencies of nonaxisymmetric vibration of prolate spheroidal shells
Authors: Hayek Sabih I. , Boisvert Jeffrey E.
Published: July 2012

The equations of motion for nonaxisymmetric vibration of prolate spheroidal shells of constant thickness were derived using Hamilton’s principle. The thin shell theory used in this derivation includes three displacements and two changes of curvature. The effects of membrane, bending, shear deformations, and rotatory inertias are included in this theory. The resulting five partial differential equations are self-adjoint and positive definite. The nonaxisymmetric modal solutions are expanded in a doubly infinite series of comparison functions. These include associated Legendre functions in terms of the prolate spheroidal angular coordinate, and circular functions of the circumferential coordinate. The natural frequencies and the mode shapes were obtained by the Galerkin method for each circumferential mode. Numerical results were obtained for several shell thickness-to-length ratios ranging from 0.005 to 0.1, and for various diameter-to-length ratios, including the limiting case of a spherical shell. [Work supported by Office of Naval Research and the Navy/ASEE Summer Faculty Program.]
Categorical perception and the convergence of social learning
Authors: Liberman Mark Y.
Published: July 2012

About 50 years ago, Alvin Liberman and his colleagues at Haskins Laboratories discovered ‘‘categorical perception’’ of certain phonetic dimensions, where discrimination is hardly better than identification. They proposed this as one piece of converging evidence for a special perceptual mode for speech, part of a species-specific evolutionary adaptation for articulate language. This special sensory-motor module, they argued, makes human speech so uniquely efficient at transmitting discrete symbol sequences in sound. Lively arguments about all aspects of this reasoning continue to this day. This paper broadens the discussion beyond perception in individuals, by suggesting a role for categorical perception in enabling communities of speakers to form and maintain consensus about the pronunciation of tens of thousands of morphemes. Through computer simulations, simple and plausible assumptions will be shown under which the ‘‘pronouncing dictionaries’’ of the members of a speech community will converge rapidly from random starting points. Among these assumptions, a form of categorical perception plays a key role. With it, simulations converge to a consensus from which deviations occur rarely and hardly ever spread. Without it, individual pronunciation beliefs wander chaotically across time in the phonetic space, and at a given time, differences in belief increase rapidly with social distance. The role of partly categorical perception, as in so-called ‘‘magnet effects,’’ will also be addressed.
A biological basis for writing and reading
Authors: Studdert-Kennedy Michael
Published: July 2012

As Alvin Liberman taught us many years ago, speech is a complex acoustic code on the phonological units of its message, but writing is a simple cipher on that message. Yet we learn to speak more readily than we learn to read and write—a fact central to Liberman’s biological view of speed. Must there not, however, also be a biology of writing and reading? Why is writing possible at all? What property enables language, alone among systems of animal communication, to be transduced into an alternative, but no less efficient, perceptuomotor modality? The outline of an answer emerges when we recall that writing systems, like speech itself, represent not meaning, but the intrinsically meaningless units, whether syllables or phonemes, on which the hierarchy of language is raised. Such units lend themselves to transduction not only because they have no meaning, but also because, as vehicles of communicative ‘‘parity’’ between speakers and listeners, they are neither sensory nor motor but cognitive and abstract. The nature and origin of these particulate entities at the base of language was the topic of a paper that Liberman and I were planning at the time of his death. The paper was to have been called ‘‘A Biological Basis for Writing and Reading.’’
The importance of parity; its implications for understanding speech perception
Authors: Fowler Carol A.
Published: July 2012

Early in his career, Alvin Liberman obtained experimental findings that he describes in his book, Speech: A Special Code, as ‘‘an epiphany.’’ The findings revealed that listeners track speakers’ articulations. From these findings and subsequent others, Liberman developed his motor theory of speech perception. In addition, however, he set out to understand why listeners track articulation. His explanation was that humans evolved a phonetic system jointly responsible for producing coarticulated speech and for recovering intended phonetic segments from coarticulated signals. Underlying the claim that production and perception are linked in this way is the idea of parity. In Liberman’s interpretation, parity is the requirement that, for language to serve as a major component of human communication systems, listeners and talkers must agree on what set of perceivable human actions can count as components of a linguistic message. In addition, and more concretely, in their conversational interactions, listeners and talkers must typically achieve a relation of parity between messages sent and received. This paper will focus on how this parity requirement rationalizes the body of findings that listeners track articulatory gestures.
Perceiving speech: A developmental perspective
Authors: Werker Janet F.
Published: July 2012

The question of how we so instantaneously and effortlessly perceive the rapidly changing and highly encoded speech signal was one of the guiding questions in Alvin Liberman’s research career. From the original presentation of the ‘‘motor theory’’ through the rich body of research it generated and its subsequent revisions, he posed for the field a challenge to view speech in a radically different way from what he called the ‘‘dominant’’ view. On my first trip to Haskins Laboratories as a young graduate student, Alvin Liberman listened carefully to and took seriously the (naive) research questions I was attempting to ask about young infants, and challenged me to consider whether my approach was sufficiently rich to capture the essence of speech perception. That challenge continues to guide my work. In this talk I will present research that I (and others) have conducted with infants and young children in an attempt to understand the nature of speech perception in the young infant, and how that changes as a function of experience—both heard and seen—with the native language.
Acoustic coherence imaging through the atmosphere
Authors: Benson Jonathan W.
Published: July 2012

The process of making images of acoustic scenes through the atmosphere has been investigated. Representations of the acoustic power with angle and the power spectrum with angle can be formed. The performance of interferometric imaging methods based on the Van Cittert–Zernike theorem has been evaluated using data collected in a series of field experiments. An array of microphones received the far-field emissions from a pair of large loudspeakers that reproduced broadband random noise signals. Both the loudspeakers and the array are located near the ground. All imaging is done in the horizontal plane. Pairs of microphones in the array are correlated to form measurements of the complex coherence. An image is then formed via an inverse Fourier transform operation. The field data show that making accurate acoustic images outdoors is difficult due to the effects of turbulence. The image distortion, signal-to-noise ratio, and variance associated with the coherence measurements were calculated as a function of the average wind speed. Even at moderate wind speeds (6 m/s) turbulence can cause an order of magnitude increase in the variance of coherence measurements. Guidelines were drawn that define the expected performance based upon the observed wind speed. Methods for image enhancement are discussed.
The use of complex images in acousto-elastic propagation problems
Authors: Fawcett John A.
Published: July 2012

In many propagation and scattering problems it is necessary to compute a half-space (for example, water over a seabed) Green’s function for a variety of source/receiver positions. For example, in the boundary integral equation method (BIEM), the kernel of the integral equation involves the Green’s function, and numerically the Green’s function must be evaluated at a large number of source/receiver positions. The distances involved may range from near-field, where the Green’s function will have a singular behavior, to the far-field. In this paper a method from the electromagnetics literature [e.g., Vitebskiy et al., IEEE Trans. Antennas Propag. 44, 143–151 (1996)] is described which reduces the usual wave number integral representation to a small number of image sources with complex positions. This representation is valid over a large range of source/receiver distances and hence is appropriate for efficiently evaluating the Green’s function for many source/receiver positions. Numerical examples are presented illustrating the accuracy of the method for both fluid and elastic seabeds.
Numerical results for an approximate form of the nonlocal small slope approximation scattering strength
Authors: Broschat Shira L.
Published: July 2012

Voronovich introduced the nonlocal small slope approximation (NLSSA) as a generalization of the small slope approximation to explicitly include nonlocal interactions. He showed that the NLSSA generally accounts for double scattering in the high-frequency limit. Broschat and Thorsos presented numerical results for the lowest-order NLSSA scattering strength for two-dimensional pressure-release surfaces. Their results agreed well with Monte Carlo integral equation results and, in particular, were better than the higher-order SSA results at low forward grazing angles. However, the computational cost was extremely high, and results were unobtainable at low grazing angles. In this paper, we discuss the results obtained by making an ad hoc approximation to the lowest-order NLSSA scattering cross section that reduces the computational complexity of the integration substantially. In addition, we discuss the difficulties of the numerics and how they are handled. Numerical results for the scattering strength are presented for 2-D pressure-release surfaces. For the cases presented, the NLSSA and its approximate form give virtually the same results. Also, results at low grazing angles are obtainable and accurate with the approximate form. [Work supported by ONR.]
Evolution of metrics used in ‘‘real world’’ concert sound level management systems
Authors: Cann Richard G.
Published: July 2012

With the ever increasing popularity and proliferation of outdoor amphitheaters and the advent of more powerful amplification systems serving high-energy performing groups, nearby residents are inevitably threatened by higher sound levels. To address these concerns, acoustical consultants have specified monitoring systems that must use simple metrics for the management and control of music facility sound emissions. These metrics must be pragmatic; the visiting artist and sound engineer, the concert promoter, the concert facility management personnel, and even local regulatory personnel must be able to easily understand and interpret their meaning. Furthermore, the management system must accommodate rapid real-time implementation of necessary management control measures and store accurate, permanent, electronic records for future reference. This paper describes the evolution of the Grozier sound level management systems that use simple, accurate metrics developed for several amphitheater venues with diverse local conditions and requirements.
Acoustics of Asian drums
Authors: Rossing Thomas D.
Published: July 2012

Drums have played an important role in nearly all musical cultures, including those of Asia. The tabla and mrdanga of India are specially tuned to have harmonic partials so that they convey a strong sense of pitch. The very important drums in Balinese and Javanese gamelans, on the other hand, do not have a strong pitch. The large o-daiko of Japan have modes of vibration that are somewhat similar to those in the bass drum. Smaller drums, such as the tsuzumi, have spectra that vary considerably with playing style.
Tuned sets of bells from ancient China
Authors: Bagley Robert W.
Published: July 2012

Tuned sets of bronze bells appeared very early in China, sometime around 1200 B.C., and over the next millennium underwent an extraordinary development. The most spectacular set known so far consists of 65 bells found in 1978 in the tomb of Marquis Yi of Zeng (deceased 433 B.C.), ruler of a small and previously unknown state in central China. The set has a range of five octaves, within which is a three-octave chromatic stretch; the largest bell weighs 200 kg. Despite much study of this and other sets, it remains unclear how tuned sets were designed and cast; it has not been possible to deduce a scaling rule from measurements of bells. Invoking both archaeological evidence and musical considerations, a hypothesis will be presented to suggest how tuned sets might have been invented and elaborated.
Wet-walled thermoacoustics
Authors: Slaton William V. , Raspet Richard
Published: July 2012

An analytic solution of sound propagation in wet-walled tubes with a temperature gradient will be presented. The tube contains an inert gas-vapor mixture with a thin layer of condensed vapor coating the tube wall. The vapor phase condenses and evaporates from this layer during an acoustic cycle. This phased evaporation and condensation modifies traditional energy density and wave number equations. It is found that mass and heat transport act in parallel thereby increasing the acoustic energy density for proper choice of gas mixtures. This increase in energy density due to inert gas-vapor working fluids can be quite large and even dominate the traditional thermal transport contribution. The use of phased evaporation-condensation in gas mixtures provides a path to higher energy density in thermoacoustic systems. The effects on sound propagation, energy density, and efficiency due to the presence of an inert gas-vapor working fluid in tubes with wet walls will be discussed. [Work supported by the Office of Naval Research.]
Hydrodynamics of otoacoustic emissions
Authors: Jaffer Taha , Kunov Hans
Published: July 2012

In this paper, a novel boundary condition for the classical cochlear model will be outlined that allows the realistic simulation of tone-burst transiently evoked otoacoustic emissions (TEOAEs). OAEs are sounds that are emitted from the inner ear and have been related to hearing function. Classical cochlear models suffer from an inability to realistically simulate OAEs because of the simplistic treatment of the hydrodynamics at the interface between the oval window, stapes, and cochlear fluid. In the classical cochlear model, there are two boundary conditions; the first describes the helicotrema, and the second details how fluid is displaced by the oval window in response to sound entering the ear. In this model, OAE production cannot be simulated because once the stimulating sound is stopped, the oval window is immobile and incapable of transmitting acoustical energy back out of the inner ear. In this paper, this boundary condition will be reconsidered in light of the additional fluid displacement caused by the movement of the cochlear partition. The addition of this boundary condition yields realistic simulations of tone-burst OAEs, both in time evolution and frequency content.
The form of the expansive nonlinearity in cochlear implant stimulation
Authors: Chatterjee Monita
Published: July 2012

In electrical stimulation with cochlear implants, loudness grows as an expansive function of stimulus amplitude. The mathematical form of the nonlinearity is difficult to discern, primarily because of the limited current range over which measurements can be made without reaching uncomfortably loud sensations. Both power and exponential functions appear to fit measured loudness estimates reasonably well over the dynamic range. For a given pulse train, increasing the pulse phase duration (D) and/or the separation between active and return electrodes in the cochlear (M) results in increased loudness. Power function fits to the loudness functions show that while the exponent of the power function is insensitive to these stimulus parameters, the multiplicative constant is not. In contrast, the best fitting exponential functions show systematic changes in the exponent with changing M and D. The two kinds of functions also yield different predictions for the level-dependence of modulation sensitivity. When the nonlinearity is a power function (as in normal hearing), modulation sensitivity is predicted to show negligible dependence on level; when the nonlinearity is exponential, a strong level-dependence is predicted. In cochlear implant listeners, modulation sensitivity is strongly level-dependent, tipping the balance in favor of an exponential nonlinearity. [Work supported by NIDCD.]
Up/down asymmetry in FM identification
Authors: Gordon Michael , Poeppel David
Published: July 2012

Temporal limits of the human auditory system with regard to identifying the direction of frequency modulation (FM) were investigated: How brief can frequency change be without compromising FM direction identification? Such abilities may relate to processing formant transitions. In a 2AFC paradigm, subjects binaurally heard linear FM sweeps rising or falling in frequency between 1000 and 1500 Hz. Ten FM rates were used for both FM directions. The FM rate was modulated by varying stimulus duration from 5 to 640 ms. Each FM stimulus was presented 20 times, in pseudorandom order, for a total of 400 trials. Subjects (n=24) identified the direction of frequency change. There was a marked difference between up and downward FMs. For upward FMs, 90% accuracy in direction identification was achieved at a rate as fast as 17 Hz/ms. A considerably slower rate, 3 Hz/ms, was needed for identifying downward FMs with an accuracy of 90%. Humans are better at identifying rapid upward FMs than downward ones. This result is congruous with studies revealing lower thresholds for detecting rapid upward FMs (Collins and Cullen, 1978) and higher magnitude evoked potentials elicited by upward FMs (Maiste and Picton, 1989). [Work supported by Comparative and Evolutionary Biology of Hearing Training Program.]
Causal and unique reconstruction of nonminimum reflection phase for a class of submerged structures
Authors: Clarke Cory L. , McDaniel J. Gregory
Published: July 2012

An approach is presented for uniquely determining the phase of an acoustic reflection from an object whose impedance magnitude approximates the acoustic impedance of the surrounding medium. This approximation defines a semiannular region in the complex impedance plane that lies between the rigid and pressure-release limits. When this region is mapped onto the complex reflection coefficient plane, the approximation allows for a wide range of reflection coefficients. A Taylor series expansion for the square of the reflection coefficient magnitude is used to estimate the phase of the reflecting impedance. The causality condition is invoked to recover the magnitude of the impedance from its phase. Once the magnitude and phase of the impedance is known, the complex-valued reflection coefficient algebraically follows regardless of whether or not the reflection coefficient is minimum phase. The approach is useful in experimental situations that only allow the accurate measurement of reflection magnitude and not phase. As an example, the approach is demonstrated on one-dimensional numerical simulations that simulate uncertainty in target location and ambient noise. [Work supported by ONR.]