bluuebunny/crossref_metadata_2025 huggingface dataset:
Ira at 80: The acronyms of a career in acoustics
Authors: Weisenberger Janet M.
Published: October 2013

In a career that spans some 54 years to date, the name of Ira J. Hirsh has been associated with significant scientific contributions to psychoacoustics, outstanding mentoring of research scientists, and dedicated service to the fields of acoustics, audiology, and psychology. It is a career that can be traced by acronyms that are part of the daily vocabulary of hearing scientists. These include acronyms of location: Early work at the Psychoacoustics Laboratory at Harvard (PAL), a long tenure in research at the Central Institute for the Deaf (CID), service as faculty member, chair, and dean at Washington University (WashU); acronyms of professional societies that have honored him: Acoustical Society of America (ASA), International Commission of Acoustics (ICA), American Psychological Association (APA), American Psychological Society (APS), American Speech-Language-Hearing Association (ASHA), American Association for the Advancement of Science (AAAS); acronyms of his service to the National Academy of Science: National Research Council (NRC), Commission on Behavioral and Social Science and Education (CBASSE); and acronyms of his contributions to psychoacoustics: Masking Level Difference (MLD), Temporal Order Judgments (TOJ). In large part, these acronyms are part of our vocabulary because of Ira’s contributions, and tracing them over the past half-century yields a substantive look at the development of the field of hearing science.
Events, sequences, and patterns: Hirsh’s prescient proposals
Authors: Watson Charles S.
Published: October 2013

Over four decades ago, Ira Hirsh was one of the first to recognize the need for auditory research to expand beyond the study of single tones, noise burst, and clicks. He wrote, ‘‘We propose to examine auditory perception at a more complex level. The discrimination among and identification of single sounds, which we shall refer to as acoustic events, is undoubtedly an important part of the perceptual process, but perhaps more important are the rules by which we distinguish and identify sequences of acoustic events. Auditory psychophysics has been concerned with the acoustic characteristics of the sequence parts, the events; but we need to know more about the ways in which the parts combine to form patterns which, since they are generated in time, we may call sequences’’ [J. Acoust. Soc. Am. 31 (1959)]. This must be one of the more prescient proposals of that era, followed as it was not only by Hirsh’s series of studies of temporal processing, but by a raft of other adventures into the world he forecast, including research on a great variety of auditory patterns and sequences. Theoretical interpretations of that work and of the general problem areas that Hirsh pioneered will be discussed.
An equivalent solid (u) formulation for poroelastic materials
Authors: Pilon Dominic , Panneton Raymond
Published: October 2013

Finite element formulations based on Biot’s poroelasticity equations have been used extensively throughout recent years. The most common are Biot’s displacement (u_,U_) and mixed displacement-pressure (u_,p) formulations. They are used to predict the structural and acoustical behavior of poroelastic mediums within multilayered structures. These models, while accurate, lead to the resolution of large linear systems: they need, respectively, six and four degrees of freedom per node in order to efficiently describe the poroelastic medium’s vibroacoustic behavior in 3-D problems. In this paper, a simplified displacement (u_) formulation is presented. It is also based on Biot’s equations, but requires only three degrees of freedom per node, related to the solid phase displacement field, to describe the behavior of poroelastic mediums in 3-D problems. The development of the governing (u_) equations for the equivalent solid poroelastic formulation is detailed. The limitations of this approach are also discussed. Numerical and experimental validations are presented in order to show the accuracy and effectiveness of the formulation within its prescribed field of application.
On the dynamics of fuzzy structures
Authors: Mencik Jean-Mathieu , Berry Alain
Published: October 2013

In this presentation, one proposes a prediction at low- and mid-frequencies of the dynamics of fuzzy structures. As introduced by Soize, the term ‘‘fuzzy structure’’ designates a master structure, whose geometrical, material characteristics, boundary conditions, and excitations are known, coupled with complex systems, called the structural fuzzy or fuzzy, whose characteristics are imprecisely known. Previous works done on this subject analyze the concept of a master structure coupled with a locally homogeneous fuzzy, composed of a large number of linear oscillators excited by their supports. In the present work, the concept of a homogeneous fuzzy is extended to an elastic continuum medium. One theoretically formulates the action of the elastic fuzzy on the master structure: it is shown that the proposed formulation is different from the solution proposed by Soize, derived from the model of a linear oscillator excited by its support. The proposed theory is successfully applied to the case of a homogeneous structural fuzzy composed of a large number of elastic bars whose lengths and cross sections are randomly chosen.
Determining the sources of sounds: Psychological acoustics
Authors: Yost William A.
Published: October 2013

Perhaps the most important task performed by an organism’s sensory system is determining objects in the world surrounding the organism. This is a challenging task for the auditory system, especially when many objects exist at the same time. The peripheral auditory system provides the neural code for the spectral-temporal structure of the complex sound impinging on the ears. It does not code for the sources of the sound. Neural centers beyond the periphery most analyze this spectral-temporal code in order to form perceptual images that make up the auditory scene. Recent psychoacoustical and perceptual research on sound source determination and segregation will be described. This research is just beginning to suggest ways in which the auditory scene is determined. [Work sponsored by NIDCD.]
HELS based near-field acoustic holography for a highly nonspherical structure
Authors: Moondra Manmohan , Wu Sean
Published: October 2013

The Helmholtz Equation Least Squares (HELS) method [Wu and Yu, J. Acoust. Soc. Am. 104, 2054–2060 (1998); Wu, ibid. 107, 2511–2522 (2000)] are validated experimentally in both exterior and interior regions of a highly nonspherical structure. This is contrary to the common belief that expansion solutions based on spherical coordinates are valid within the region bounded by spheres. Detailed explanations for this phenomenon, known as the Rayleigh hypothesis, are given in a separate paper. Shown here are the experimental validations of the acoustic fields reconstructed by the HELS method for a cabinet with overall dimensions 2.05 m ×1.05 m ×0.75 m. A loudspeaker is placed inside the cabinet. The white noise produced by the speaker is measured by an array of 48 microphones stationed outside. The acoustic pressures in the near- and far-fields are reconstructed and validated with respect to those measured at the same locations. Also reconstructed is the normal component of the time-averaged acoustic intensity, from which the transmission paths are identified. Such transmission paths cannot be revealed based on the acoustic pressure distribution alone because pressure is a scalar quantity. The interior acoustic pressures are reconstructed with the speaker placed outside and microphone array inside the cabinet. [Work supported by NSF.]
Reconstruction of acoustic radiation from a finite object in nonfree space
Authors: Wu Sean , Zhao Xiang
Published: October 2013

The near-field acoustic holography (NAH) techniques developed so far have focused on reconstruction of acoustic radiation from a vibrating structure in either an unbounded exterior region or an enclosed region so that it can be solved as an interior problem. In practice, many vibrating structures are mounted on a solid foundation or in the vicinity of reflecting surfaces. For NAH to become a robust diagnostic tool, the effect of acoustic pressure reflection from nearby surfaces must be considered. In this paper, the Helmholtz equation least-squares (HELS) method [Wu, J. Acoust. Soc. Am. 107, 2511–2522 (2000)] will be modified which expresses the field acoustic pressure as a superposition of both out-going and in-coming spherical waves. The latter will be used to approximate the acoustic pressure reflection from nearby surfaces. To guarantee a convergence of the reconstructed acoustic field, a constrained minimization will be conducted with respect to the expansion functions to determine the optimal numbers of expansion terms for both out-going and in-coming waves. This concept will also be extended to reconstruction of acoustic radiation from an arbitrarily shaped vibrating structure for which the conventional HELS formulation has been shown to have difficulties to yield satisfactory reconstruction. [Work supported by NSF.]
Multi-platform sonar concepts for buried target detection and classification
Authors: Edwards Joseph R. , Liu Te-Chih , Schmidt Henrik
Published: October 2013

Buried target classification is of paramount importance in mine countermeasures (MCM) applications. The Generic Oceanographic Array Technology Sonar (GOATS) project approaches this fundamental problem by exploiting the assets of autonomous underwater vehicles (AUVs). Recent developments in unmanned vehicle technology have opened the door for new sonar design concepts that may be applied to create alternative target detection and classification methods in complex environments. Adaptive vehicle behaviors provide the potential for the sonar system to adjust its geometry for optimal performance. The vehicles can also access very shallow water environments, which allows for more complete multi-aspect views of targets of interest than are possible with remote towed array systems. In this paper, it is demonstrated that the multi-platform system can provide improved detection and classification capability, while at the same time reducing the computational requirements. Data from prior GOATS experiments (1998 and 2000) are used to illustrate the effectiveness of the multi-platform sonar concepts, and real-time simulations are used to show the planned implementation of these techniques on-board the AUVs for GOATS’02.
Offline and online tempo detection and beat tracking
Authors: Laroche Jean
Published: October 2013

Tempo detection and beat tracking consist of measuring the tempo and estimating beat locations in musical signals. Online beat tracking refers to situations where the tempo at a given instant is estimated with access to a limited portion of the future at this time. In offline beat tracking, the whole track is available for processing, which makes the task somewhat easier. Our algorithms use a short-time Fourier analysis of the signal to extract a time-varying measure of the energy variations in several frequency subbands, resulting in an energy flux signal showing large values around note onsets, percussion hits, and other musically relevant events. At regular intervals (every second), the flux signal is correlated with a series of periodic discrete pulses corresponding to various candidate tempos and beat locations. The tempo- and beat-location candidates showing the best fit are retained for the next stage, where a dynamic programming algorithm is used to select the best series of beat locations, based on a measure of tempo continuity, and consistency between tempo and beat. Dynamic programming is used both for offline and online processing with fairly good results.
Efficiency of acoustic power sources from 200 to 20,000 watts
Authors: Spoor Philip S. , Corey John A.
Published: October 2013

The emergence of acoustic ‘‘pulse-tube’’ refrigerators with no moving parts, and with the capacity to provide tens, hundreds, and even thousands of watts of cooling at cryogenic temperatures, is generating considerable commercial interest. To become economically feasible, these cryocoolers require efficient, compact, and inexpensive sources of acoustic power. The authors will discuss a series of five acoustic drivers available from CFIC that range in power from 200 watts to 20,000 watts, using opposing pairs of STARTM linear motors. Efficiency data for units throughout the range will be presented, showing the relative importance of different loss mechanisms for each size. In particular we will focus on I2R losses, which are well understood in the small motors but seem anomalously high in the larger motors.
A fast effective fluid model for the scattering of normally incident sound off of a buried landmine
Authors: Velea Doru , Waxler Roger , Sabatier James M.
Published: October 2013

Landmines buried in the ground can be found acoustically by insonifying the ground and detecting a contrast between the vibratory motion of the ground surface directly above the mine and away from the mine. A model to predict the near-field scattering of low-frequency (∼100 Hz) acoustic waves off of a landmine is presented. The mine is assumed to be a rigid cylinder with a compliant top. The ground (soil) is modeled as an effective fluid. Because of the short range of the scattered field at low frequencies it has been possible to replace a full space model with a waveguide model that is straightforward to implement numerically. The predictions of the model will be discussed. [Work supported by the U. S. Army Communications-Electronics Command Night Vision and Electronic Sensors Directorate and the U.S. Army Research Office.]
Effects of room reverberation on spatial release from masking
Authors: Freyman Richard L. , Zurek Patrick M.
Published: October 2013

When signal and masker sources are separated horizontally in an anechoic space, one of the primary benefits is that the acoustic shadow from the head leads to a substantial improvement in signal-to-noise ratio in the high frequencies at one of the ears, relative to conditions in which signal and noise are presented from a common location. This presentation will examine how the improved signal audibility created by head shadow is affected by room reverberation. Through room-simulation models, the effects of three variables will be examined: degree of horizontal separation, distance between the listener and the signal and masker, and degree of room reverberation. This paper will present an evaluation of how well the effects of these variables can be predicted by generalized room acoustics equations incorporating room volume and surface absorption. The reduction in high-frequency head-shadow effects in reverberant environments, combined with a disruption of cues for low-frequency binaural release from masking, severely reduces the benefits of spatially separating signal and noise. Fortunately, due to the precedence effect, the perceived locations of signal and noise are accurate even in a reverberant space. The intelligibility benefits of perceived differences in signal and masker locations will be discussed. [Work supported by NIDCD.]
Turbulent boundary layer pressure fluctuations at large scales
Authors: Sanders Wendy , Judge Carolyn , Winkel Eric , Ceccio Steven , Dowling David , Perlin Marc
Published: October 2013

The pressure fluctuations underneath a turbulent boundary are an important excitation source for noise and vibration for both aircraft and ships. This presentation describes experimental results from a new study of flat-plate turbulent boundary layer pressure fluctuations in water at large scales and high Reynolds number. The experiments were performed at the U.S. Navy’s William B. Morgan Large Cavitation Channel in Memphis, TN on a polished flat plate 3.05 m wide, 12.8 m long, and 0.18 m thick. Flow velocity, skin friction, surface pressure, and plate acceleration measurements were made at multiple downstream locations at flow speeds ranging from 0.5 m/s to 19 m/s for a Reynolds number (based on downstream distance) range of several million to 200 million. Dynamic surface pressures were recorded with 16 flush mounted pressure transducers forming an L-array with streamwise dimension of 0.264 m and cross-stream dimension of 0.391 m. Measured 99% boundary-layer thicknesses were typically of order 0.10 m. Results for spatial and temporal correlation functions, as well as auto- and cross-spectra are presented and compared with prior lower-Reynolds-number results using either inner or outer variable scaling. [Work sponsored by the Defense Advanced Research Projects Agency and ONR Code 333.]
On learning to recognize spectrally reduced speech: II. Individual differences
Authors: Chiu Peter , Eng Michelle , Strange Bethany , Yampolsky Sasha , Waters Gloria
Published: October 2013

When patients with cochlear implants attempt speech recognition, or when listeners with normal hearing try to recognize spectrally reduced speech, performance may suffer because of additional demands on cognitive resources imposed by sensory degradation. Some previous studies have reported a significant correlation between digit span and recognition of spectrally reduced speech, but others have not [Eisenberg et al., J. Acoust. Soc. Am. 107, 2704–2710 (2000)]. In this study, we administered 3 separate measures of working memory capacity (i.e., digit span, alphabet span, and sentence span) and 1 measure of reading ability (American National Adult Reading Test, ANART) to normal-hearing listeners who participated in our previous studies [Chiu et al., J. Acoust. Soc. Am. 109, 2501 (2001) and Fishbeck and Chiu, J. Acoust. Soc. Am. 109, 2504 (2001)]. Preliminary data show that the listener’s ability to recognize spectrally reduced speech shows the strongest relationship with ANART scores and the weakest relationship with digit span. Implications of the current findings on theories of speech recognition and working memory will be discussed. [Work supported by URC, Univ. of Cincinnati.]
Perception of talker similarity by normal-hearing children and hearing-impaired children with cochlear implants
Authors: Cleary Miranda
Published: October 2013

This project investigated judgments of perceptual similarity, specifically, how similar do two sentences need to be in terms of fundamental and formant frequencies for children to categorize both utterances as spoken by the same talker? Same–different judgments were obtained using an adaptive testing procedure in which the similarity of voice pairs was systematically varied. Participants included five-year-old normal-hearing children and prelingually deafened school-age cochlear implant users with 2+ years of implant experience. Stimuli consisted of natural sentence-length utterances of a fixed syntactic form processed and resynthesized to form a stimulus continuum of differentially similar-sounding voices. Auditory comprehension skills were measured using materials from the same stimulus set. Comprehension was also measured against a competing talker masker. An adaptive testing procedure adjusted the similarity of masker voice to target voice according to each child’s performance. The probability of ‘‘same talker’’ judgments is reported for each group of children as a function of pitch difference size. Preliminary results indicate a commonality in the auditory skills necessary for both talker discrimination and auditory comprehension. The relationship between discrimination of similar-sounding talkers and the ability to perceptually separate voices will also be discussed. [Work supported by NIH-NIDCD.]
Identification of musical instruments by normal-hearing subjects listening through a cochlear-implant simulation
Authors: Reich Rebecca D. , Eddington Donald
Published: October 2013

Signal processing in a cochlear implant (CI) is primarily designed to convey speech and environmental sounds, and can cause distortion of musical timbre. Systematic investigation of musical instrument identification through a CI has not yet revealed how timbre is affected by the implant’s processing. In this experiment, the bandpass filtering, rectification, and low-pass filtering of an implant are simulated in matlab. Synthesized signals representing 12 common instruments, each performing a major scale, are processed by simulations using up to 8 analysis channels. The unprocessed recordings, together with the 8 simulation conditions for 12 instruments, are presented in random order to each of the subjects. The subject’s task is to identify the instrument represented by each item. The subjects also subjectively score each item based on similarity and pleasantness. We anticipate performance using the simulation will be worse than the unprocessed condition because of the limited information delivered by the envelopes of the analysis channels. These results will be analyzed as a confusion matrix and provide a basis for contrasting the information used by subjects listening to the unprocessed and processed materials. Understanding these differences should aid in the development of new processing strategies to better represent music for cochlear implant users.
Comparison of approaches to estimate the speech modulation transfer function
Authors: Payton Karen L. , Chen Shaoyan , Braida Louis D.
Published: October 2013

Using speech as a probe stimulus to compute the Speech Transmission Index (STI) has been of great interest to speech researchers. One technique is based on first computing the speech modulation transfer function (SMTF). Approaches used to obtain the SMTF include those developed by Steeneken and Houtgast [H. Steeneken and T. Houtgast, Proc. 11th ICA, Paris 7, 85–88 (1983)] and Drullman et al. [R. Drullman, J. M. Festen, and R. Plomp, J. Acoust. Soc. Am. 95, 2670–2680 (1994)]. This paper compares these two approaches and a new one to the theoretically obtained modulation transfer function (MTF) for reverberant and noisy environments. The new method computes the magnitude of the cross-power spectrum rather than the real part used by Drullman. As previously reported, Houtgast’s method exhibits artifacts at high modulation frequencies. Drullman’s approach eliminates artifacts in the reverberant environment but does not predict the theoretical MTF for the noisy environment. The new method outperforms the other two approaches in matching the theoretically derived MTF across both environments. This paper also examines the SMTF of amplitude-compressed speech for these three methods. [Work supported by NIDCD.]
Speech perception with tactile support in adverse listening conditions
Authors: Drullman Rob , Bronkhorst Adelbert W.
Published: October 2013

Since long, different methods of vibrotactile stimulation have been used as an aid for speech perception by some people with severe hearing impairment. The fact that experiments have shown (limited) benefits proves that tactile information can indeed give some support. In our research program on multimodal interfaces, we wondered if normal hearing listeners could benefit from tactile information when speech was presented in adverse listening conditions. Therefore, we set up a pilot experiment with a male speaker against a background of one, two, four or eight competing male speakers or speech noise. Sound was presented diotically to the subjects and the speech-reception threshold (SRT) for short sentences was measured. The temporal envelope (0–30 Hz) of the speech signal was computed in real time and led to the tactile transducer (MiniVib), which was fixed to the index finger. First results show a significant drop in SRT of about 3 dB when using tactile stimulation in the condition of one competing speaker. In the other conditions no significant effects were found, but there is a trend of a decrease of the SRT when tactile information is given. We will discuss the results of further experiments.
Passive sonar calibration spheres
Authors: Deveau David M.
Published: October 2013

The need for calibrated sonar targets is addressed with the development and testing of a set of thin-walled spheres filled with a high-density fluid. Using historical research information as a guide, a set of thin-walled metal spheres was developed and filled with a high-density fluid. The combination of the spherical shape and the acoustic focusing effects of the fluid enhanced the acoustic scattering strength of the shape so that it was not only stable with temperature but also significantly greater in amplitude. The simple passive nature of the spheres makes them ideal acoustic targets for long-term unattended deployments. Using a reference level measurement, each sphere was calibrated over a wide frequency range in order to provide the user with a curve of measured scattering strength versus frequency. The resulting curves showed a high degree of correlation between the individual spheres and the modeling that was used to extrapolate the theoretical values.
Scattering by a buried elongated object
Authors: Lim Raymond
Published: October 2013

The feasibility of combining spherical and spheroidal basis sets in formulating a transition matrix for scattering by elongated objects embedded in an attenuating medium such as an ocean sediment is investigated. While a description completely in terms of spheroidal bases would likely yield optimal stability, spheroidal functions are more difficult to compute and well-tested algorithms are scarce for complex arguments. Therefore, a hybrid approach that expands the surface fields of the scatterer in spheroidal bases and all other exterior fields in spherical functions is tried. This approach mitigates the need for spheroidal functions of a complex argument. The merits of the hybrid approach are assessed by comparison against standard transition matrix formulations. [Work supported by ONR.]
Low-frequency propagation and scattering in the ocean
Authors: Sammelmann Gary
Published: October 2013

This discussion describes various methodologies used to model the performance of low-frequency active systems with an emphasis on developing models for low-frequency signal-to-noise estimates and coherent imaging simulations. The global matrix method of Schmidt is adapted to define a numerically stable routine for finding the solutions of the characteristic equation for the normal modes. The effects of attenuation, surface loss, and bottom loss are added through perturbation theory. Techniques for transforming the normal-mode equations into a time-domain representation are presented. Expansions of the normal-mode functions in terms of spherical and spheroidal basis functions at the source and receiver locations are discussed. A prescription for computing reverberation is presented, and a comparison between low-frequency and high-frequency models is presented. [Work supported by Codes 321OE and 32MIW of the ONR.]
Optimal source localization in a partially saturated fluctuating waveguide
Authors: Zanolin Michele , Makris Nicholas C.
Published: October 2013

When the propagation path between an acoustic source and receiving array is infested with natural disturbances, such as internal waves, part of the received field may be randomized by these waveguide fluctuations. When the fluctuations cause modal decoupling sufficient for this randomized portion of the field to obey the Central Limit Theorem, it will follow a circular complex Gaussian random process in time. The total field is then said to be partially saturated. In this case the signal is partially deterministic and partially random so that both the mean and covariance of the field depend on the source position. The asymptotic bias, covariance, and signal-to-noise ratio presented in Naftali and Makris [J. Acoust. Soc. Am. 110, 1917–1930 (2001)] for a Gaussian random field are extended to treat this more general case. Analytic expressions and simulations are performed to determine the minumum signal-to-noise ratio necessary to optimally localize an acoustic source in practical scenarios in typical continental shelf environments as a function of saturation level. The specific scenarios investigated are for the New Jersey Strataform area which serves as a natural laboratory for numerous Office of Naval Research Ocean Acoustic Experiments.
Matched field processing in a highly variable shallow water site
Authors: Siderius Martin , Porter Michael B. , Hursky Paul , Nielsen Peter L. , Sellschopp Jurgen
Published: October 2013

Variability in the ocean environment can have a big impact on acoustic propagation. Acoustic receptions often contain multi-path contributions with fluctuations that vary significantly from the direct path to the higher order multi-path. Matched-field processing (MFP) is a beamforming method that takes advantage of the multi-path to extract information about the location of the sound source. Matched-field processing is generally successful in environments that are well known and can be incorporated into propagation models. However, in some cases the environmental conditions are too extreme for good propagation predictions. To explore the limits of MFP in highly variable environments, an experiment (ASCOT-01) was conducted last June off the New England coast. The acoustic measurements were made over several days between a sound source and a moored vertical line array of receivers. Extensive environmental measurements were made including the use of a vertical CTD chain (conductivity, temperature and depth) that was towed through the propagation path to provide a detailed view of the ocean sound speed profile. Results characterizing the difficulties of MFP at this site will be presented. Standard estimators will be compared to new alternatives intended to be robust against harsh environmental conditions.
Nonspecular sound reflection and phase conjugation
Authors: Lyamshev Leonid M.
Published: October 2013

A strong back reflection is observed at certain angles of incidence of sound waves at a limited plate or shell in a liquid. This reflection is termed nonspecular reflection. It arises whenever the condition for coincidence or spatial resonance in a plate is satisfied, i.e., in other words, when the velocity of the incident wave trace coincides with the propagation velocity of any free wave in a plate or shell. If the surface of a plate or shell performs forced vibrations at the frequency doubled in comparison with the frequency of the incident wave, back reflection is observed at any incidence angle. This phenomenon is termed phase conjugation. It is caused by nonlinear interaction of an incident wave with the vibrations of a plate or shell. Fundamentals of nonspecular reflection and phase conjugation are given, i.e., theoretical concepts and some experimental data. The generality and differences of the phenomena of nonspecular reflection and phase conjugation are discussed as well as their importance for practice. [Work supported by the Russian Foundation for Basic Research.]
Ultrasonic scattering by blood: theories, experimental results and biomedical applications
Authors: Shung K. Kirk
Published: October 2013

In this paper, theoretical and experimental efforts that have been undertaken to better understand the phenomenon of ultrasonic scattering in blood will be reviewed. This subject is of interest in biology and medicine because the echoes generated by blood are used to extract blood velocity by ultrasonic Doppler flow and imaging devices. In the course of these investigations it became clear that ultrasonic scattering from blood is dependent upon such hematological and hemodynamic properties of blood as hematocrit, plasma protein concentration, flow rate and flow cycle duration. Several aspects of these experimental results have been successfully modeled by recent theoretical developments. An unexpected consequence of these efforts is that ultrasound appears to be a viable tool for blood flow visualization and hemodynamic measurements. Two unique hemodynamic phenomena that have never been reported in the hemodynamic literature have been observed: the black hole, a low echogenic zone in the center stream of whole blood flowing in a blood vessel under steady flow and the collapsing ring, an echogenic ring appearing near the periphery of a vessel at the beginning of a flow cycle, converging toward the center, and eventually collapsing during pulsatile flow. Similar observations have been made during clinical scanning of patients.
Development of a high sensitive MEMS hydrophone using PVDF
Authors: Varadan Vijay K. , Zhu Bei , K.A Jose
Published: October 2013

The design and experimental evaluation of a PVDF-based MEMS hydrophone is presented in this paper. The basic structure of the hydrophone was fabricated on a silicon wafer using standard NMOS process technology. A MOSFET with extended gate electrode was designed as the interface circuit to the sensing material, which is a piezoelectric polymer, polyvinylidene difluoride (PVDF). Acoustic impedance possessed by this piezoelectric material provides a reasonable match to water, which makes it very attractive for underwater applications. The electrical signal generated by the PVDF film was directly coupled to the gate of the MOSFET. To minimize the parasitic capacitance underneath the PVDF film and hence improve the device sensitivity, a thick photoresist was first employed as the dielectric layer under the extended gate electrode. For underwater operation, a waterproof Rho-C rubber encapsulated the hydrophone. A silicon nitride layer passivated the active device, which is a good barrier material to most mobile ions and solvents. The device after passivation also shows a lower noise level. The theoretical model developed to predict the sensitivity of the hydrophone shows a reasonable agreement between the theory and the experiment.
On windscreen insertion loss
Authors: Buzduga Mariana , Peppin Richard J.
Published: October 2013

Microphone windscreens are used to attenuate wind noise. They add impedance between the source and microphone, not accounted for when the system is checked by acoustical calibrator or when used in the field. The procedure for the characterization of the attenuation has recently been addressed in ANSI S1.17/2000 part 1. But to date, no windscreens have been tested in accordance with that standard. Partially, the reason is that the precision of the procedure has not been determined. As of January 2002 a round robin is addressing just that issue. By June 2002 the results of the uncertainty determination will be available. In the meantime, we have tested some of the samples used and others in a small chamber approaching free-field conditions. We present the results of the tests of insertion loss (not in accordance with S1.17 because we do not have a reverberation room). We will show that, in some cases, the use of a windscreen can easily change a measurement using type 1 instruments to type 2 or worse. Without knowing information about a particular windscreen, the use of a windscreen in still air can drastically change uncertainty of measurement. In moving air conditions we expect even more severe problems.
Automation of calculation and design of means of protection of buildings from transport noise
Authors: Shubin Igor L. , Sorokina Irina L.
Published: October 2013

There are stated basic principles of design using the created computer program on calculation and projection of means of protection of the build- ings from transport noise. A number of problems have been considered which are connected with the use of the existing methods of evaluation of the conditions of transport noise distribution in the urban area and the effectiveness of protection of buildings and constructions from noise (with the use of the automated calculations and design of noise protection).
A simple analytical model for prediction of aeroacoustic cavity oscillations
Authors: Bliss Donald , Franzoni Linda
Published: October 2013

High-speed flow over cavities in vehicle surfaces often produces intense tonal pressure fluctuations. Although this problem has been of concern for decades, especially for aircraft, the underlying physical mechanisms have not been well understood. A fairly simple analytical model has been developed that improves understanding of the physical mechanisms of pressure fluctuations in shallow rectangular cavities exposed to high-speed flow. The new model describes the important features of the phenomena, and gives good agreement with experimental data. The analysis is constructed by combining waves that can exist in a system having a finite thickness shear layer dividing two acoustic media, one at rest and one in motion. The wave types for this configuration can be interpreted in physical terms. A new aspect of the analysis shows the important effect of shear layer thickness on the convective waves. Fundamentally, only two convective waves and three acoustic waves suffice to represent the phenomenon. The analysis shows the important role of mass addition and removal at the rear of the cavity due to shear layer oscillation. Certain conditions on energetics and shear layer motion at the rear of the cavity must be satisfied simultaneously for oscillation to occur.
Design of model reduction and robust controller for underwater echo cancellation
Authors: Chang Woosuk , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2013

This paper presents the design and development of a simple and robust control system for structural acoustics based on state space control theory. The controller was developed using model Hankel singular value (MHSV)-based model reduction, and analog controllers are fabricated. MHSV is developed for a model coordinate system describing vibrating structures, and analog controllers were designed from transfer functions of controllers, which have great advantage over digital controllers in terms of simplicity and cost. This controller design for structural acoustics is applied for controlling sound transmission and reflection. MHSV shows good model reduction of finite-element-based structure models. The feasibility of this controller for the underwater active reflection cancellation is also studied. 1-3 piezocomposite material is used as a transducer that generates the acoustic signal. Its electroacoustic model is developed using the Mason circuit and the control parameters are directly derived. The controller has been designed accordingly and its performance is evaluated using pulse tube. The simulation and measurement show the possibility of achieving a very good reflection reduction in a desired frequency band.
The development of perceptual attention and articulatory skill in one or two languages
Authors: Fowler Carol , Best Catherine
Published: October 2013

Infants acquire properties of their native language especially during the second half of the first year of life. Models, such as Jusczyk’s WRAPSA, Best’s PAM, Kuhl’s NLM, and Werker’s account describe changes in perceptual or attentional space that may underlie the perceptual changes that infants exhibit. Unknown is the relation of these changes to changes in speechlike vocalizations that occur at the same time. Future research should address whether the perceptual models predict production learning. Other issues concern how the perceptual and articulatory systems develop for infants exposed to more than one language. Do multiple perceptual spaces develop, or does one space accommodate both languages? For infants exposed to just one language, but living in an environment where the ambient and pedagogical language is different (say, infants in a monolingual Spanish home in the U.S.), early language learning fosters learning the native language, but it may impede learning the ambient language. How much or how little does early exposure to the ambient language allow development of perceptual and articulatory systems for the ambient language? A final issue addresses whether the emergence of lexical, morphological and/or syntactic abilities in the second year is related to further changes in speech perception and production. [Work supported by NICHD.]
Estimates of the prevalence of anomalous signal losses in the Yellow Sea derived from acoustic and oceanographic computer model simulations
Authors: Chin-Bing Stanley A. , King David B. , Warn-Varnas Alex C. , Lamb Kevin G. , Hawkins James A. , Teixeira Marvi
Published: October 2013

The results from collocated oceanographic and acoustic simulations in a region of the Yellow Sea near the Shandong peninsula have been presented [Chin-Bing et al., J. Acoust. Soc. Am. 108, 2577 (2000)]. In that work, the tidal flow near the peninsula was used to initialize a 2.5-dimensional ocean model [K. G. Lamb, J. Geophys. Res. 99, 843–864 (1994)] that subsequently generated internal solitary waves (solitons). The validity of these soliton simulations was established by matching satellite imagery taken over the region. Acoustic propagation simulations through this soliton field produced results similar to the anomalous signal loss measured by Zhou, Zhang, and Rogers [J. Acoust. Soc. Am. 90, 2042–2054 (1991)]. Analysis of the acoustic interactions with the solitons also confirmed the hypothesis that the loss mechanism involved acoustic mode coupling. Recently we have attempted to estimate the prevalence of these anomalous signal losses in this region. These estimates were made from simulating acoustic effects over an 80 hour space-time evolution of soliton packets. Examples will be presented that suggest the conditions necessary for anomalous signal loss may be more prevalent than previously thought. [Work supported by ONR/NRL and by a High Performance Computing DoD grant.]
Reduction of tissue injury without compromising stone comminution in shock wave lithotripsy
Authors: Zhou Yufeng , Auge Brian , Preminger Glenn M. , Zhong Pei
Published: October 2013

To ameliorate vascular injury without compromising stone comminution in shock wave lithotripsy, we have recently developed an in situ pulse superposition technique to suppress large intraluminal bubble expansion [Zhong and Zhou, J. Acoust. Soc. Am. 110, 3283–3291 (2001)]. This strategy was implemented using a simple modification of a HM-3 lithotripter reflector. In this work, further optimization of the reflector geometry was carried out based on theoretical analysis and in vitro pressure waveform measurements using a fiber optical hydrophone. Using the upgraded reflector, no rupture of a cellulose hollow fiber (i.d.=0.2 mm) vessel phantom could be observed around the lithotripter beam focus even after 200 shocks at 24 kV. In comparison, less than 50 shocks were needed to cause a rupture of the vessel phantom using the original reflector at 20 kV. At corresponding output settings, stone comminution is comparable between the two reflector configurations, although the size of the fragments produced by the upgraded reflector is slightly larger. In addition, preliminary results from animal studies have demonstrated a significant reduction in tissue injury using the upgraded reflector, which confirms the validity of this approach in vivo. [Work supported by NIH.]
Ultrasound mediated gene transfection
Authors: Williamson Rene G. , Apfel Robert E. , Brandsma Janet L.
Published: October 2013

Gene therapy is a promising modality for the treatment of a variety of human diseases both inherited and acquired, such as cystic fibrosis and cancer. The lack of an effective, safe method for the delivery of foreign genes into the cells, a process known as transfection, limits this effort. Ultrasound mediated gene transfection is an attractive method for gene delivery since it is a noninvasive technique, does not introduce any viral particles into the host and can offer very good temporal and spatial control. Previous investigators have shown that sonication increases transfection efficiency with and without ultrasound contrast agents. The mechanism is believed to be via a cavitation process where collapsing bubble nuclei permeabilize the cell membrane leading to increased DNA transfer. The research is focused on the use of pulsed wave high frequency focused ultrasound to transfect DNA into mammalian cells in vitro and in vivo. A better understanding of the mechanism behind the transfection process is also sought. A summary of some in vitro results to date will be presented, which includes the design of a sonication chamber that allows us to model the in vivo case more accurately.
Statistical modeling of scattering from biological media
Authors: Shankar P. M.
Published: October 2013

The statistics of the backscattered ultrasonic echo from tissue can provide information on its characteristics. Such information is useful in the classification of tissues in biomedicine. For example, some of the tissue properties may point to malignancies in certain lesions in liver, breast, or kidneys. The models employed in describing the backscattered echo are therefore very crucial to the success of these classification methods. These models must take into account the number density of scatterers, cross sections of scatterers, variation in cross sections of the scatterers, and any alignment (periodic, quasiperiodic, and purely random) of the scatterers. Parameters reflecting these features can be extracted from the backscattered echo using these models. They can be directly related to the properties of the tissue such as the presence of an abnormal growth, and further classification of the growth as benign and malignant. They may also be used to form parametric images to assist the clinicians in making a medical diagnosis. A number of models ranging from Rayleigh, Poisson, K-, Weibull, and Nakagami will be discussed along with the relevance of their parameters and utility of the parameters in biomedicine. Specific applications to classification of breast lesions in ultrasonic B-scans will be described. [Work supported by NIH-NCI No. 52823.]
Multiparameter classification of masses in ultrasonic mammography
Authors: Dumane Vishruta , Shankar Mohana , John Reid , Piccoli Catherine , Forsberg Flemming , Goldberg Barry
Published: October 2013

Ultrasonic characterization of breast masses for the detection of cancer can be performed based on various features of the mass. Statistical techniques that utilize the parameter of the Nakagami distribution after spatial diversity and compounding have been utilized in the past to perform the classification. The parameter demonstrated a reasonable capability for characterization of the tissue. However, there is a need to improve the performance to reach clinically acceptable standards. The work described here undertakes a combination of the Nakagami parameter after spatial compounding at the site, the skewness parameter at the site, the signal-to-noise ratio of the envelope at the site of the mass, and the margin index parameter that describes the sharpness of the boundary. The improvement in performance for characterization of the masses will be demonstrated through ROC analyses. [Work supported by NIH-NCI Grant No. CA52823.]
UV spectroscopic studies of SBSL bubbles in lithium halides
Authors: Khong Anthony , Xu Ning , Doschek Elizabeth , Apfel Robert
Published: October 2013

As was reported previously, stably levitated bubbles were observed in LiCl and LiBr solutions under SBSL conditions. Stable bubbles were recorded for LiCl concentrations ranging from 0.47 to 1.4 M. Beyond 1.4 M, no SL was detected. In contrast, stable SBSL can be detected over a larger range of LiBr concentrations, from 0.56 to 2.5 M. At 3.0 M, unstable short-lived transient bubbles were noticed. A striking feature common to both salt solutions is the pronounced decrease in SL light intensity, measured with a PMT with peak detection sensitivity at 400 nm, as the salt concentration increases. Light intensities were close to one order of magnitude less than in pure water under similar conditions. The focus of the current study is geared toward resolving the observed reduction in light intensity with respect to chemical processes occurring in the bubble. UV spectroscopy will be key to procuring vital information relating to these processes based on the absorption patterns and the spectral ranges of peak absorptions. Similar salt solutions in D2O, aimed at revealing differences in the chemical processes in the case of heavy water, will also be investigated. [Work supported by a generous grant from University of Washington.]