bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterizing ocean ambient noise using infrasound network
Authors: Le Pichon Alexis , De Carlo Marine , Ardhuin Fabrice , Arnal Thibault , Cerana Lars
Published: April 2018

The ability of the International Monitoring System (IMS) global infrasound network to detect atmospheric explosions and events of interest strongly depends on station specific ambient noise signatures which include both incoherent wind noise and real coherent infrasonic waves. To characterize the coherent ambient noise, broadband array processing was performed on historical continuous IMS recordings. Ocean wave interactions contribute to the atmospheric coherent ambient noise field, and we apply wave action models to model these microbarom sources. We use two-dimensional energy spectrum ocean wave products to build a global reference database of oceanic noise sources. Then, we compare observed and modeled directional microbarom amplitudes at several stations. The expected benefits of such studies concern the use complementary data to finely characterize the coupling mechanisms at the ocean-atmosphere interface. In return, better knowledge of ambient ocean noise sources opens new perspectives not only by enhancing the characterization of explosive atmospheric events, but also by providing additional integrated constraints on middle atmosphere dynamics and disturbances where data coverage is otherwise sparse.
Monitoring infrasound from a Tornado in Oklahoma
Authors: Elbing Brian R. , Petrin Christopher , Van Den Broeke Matthew S.
Published: April 2018

Tornado-producing storm systems emit infrasound (sound at frequencies below human hearing) up to 2 hours before tornadogenesis. Weak atmospheric attenuation at these frequencies allows them to be detected hundreds of miles away. Hence, passive infrasonic monitoring may be used for long-range study of tornadogenesis as well as characterization of tornado properties if the infrasound can be correlated with flow-field properties. This requires characterization of infrasound during the life of a tornado as well as other background sources. This is being accomplished as part of the Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD-MAP) project, a multi-university collaboration focused on the development and implementation of unmanned aerial systems (UAS) and their integration with sensors for atmospheric measurement. The current work focuses on analysis of a small tornado that occurred on May 11, 2017, about 19 km from an infrasonic monitoring station at Oklahoma State University. Results from this tornado will be reported as well as the available radar data.
The echo that rolled into thunder: Otoacoustic emissions and newborn hearing screening
Authors: Prieve Beth
Published: April 2018

Kemp’s 1978 publication that described “stimulated acoustic emissions” changed the basic understanding of the cochlea and provided a window to assess cochlear mechanics non-invasively in humans. The emissions, referred to early on as “Kemp’s echoes,” were adopted as the measure of choice by the Rhode Island Hearing Assessment Screening Program, a clinical research study that boldly investigated the ability to screen every baby for hearing loss. This presentation will review how a new, slightly suspicious, physiological measure was used as an integral part of improving hearing healthcare in newborns. The use of distortion-product and transiently evoked otoacoustic emissions as screening tools to identify hearing loss in newborns and their use in the differential diagnosis of hearing loss will be discussed. Clinical findings from infants with and without hearing loss will be presented that support current otoacoustic emission models, and new measures tied to cochlear physiology will be suggested that could lead to improved clinical use. This presentation emphasizes that the science of basic measures from the auditory system has fueled the national and international movement of improving hearing healthcare and habilitation in newborns.
David Kemp’s contributions to using otoacoustic emissions for protection of noise-exposed ears
Authors: Marshall Lynne
Published: April 2018

In 1978, David Kemp published a paper that demonstrated a new auditory phenomenon, OAEs. Since then, OAE research expanded broadly, with continued contributions by Kemp. Significantly, Kemp and his colleagues early-on developed commercially-available equipment. Used in the default settings, the equipment was good for hearing screening. But those who wanted to dig deeper could set up solid clinical-research protocols. This allowed translational and clinical research to progress alongside basic research. While OAEs are most often used clinically as pass/fail hearing-screening or site-of-lesion tests, Kemp at the outset inspired other uses, including detection of cochlear changes. He laid out critically important principles that have served as cornerstones for applied OAE research in the area of noise exposure.
Case studies in teaching and research mentorship for undergraduates in structural acoustics and vibration
Authors: Bliss Donald B. , Villa Mauricio , Raudales David , Franzoni Linda P.
Published: April 2018

A hybrid educational model that mixes classroom learning and individual mentoring is presented for junior and senior undergraduates interested in structural acoustics and vibration. In this activity, talented undergraduates take Duke’s first graduate level acoustics course and simultaneously take multiple semesters of independent study for academic credit. The independent studies are co-supervised by faculty members and graduate students. The student research projects are individualized and typically separate from ongoing graduate student research. This structure allows the undergraduate students to feel strong ownership, while giving graduate students teaching and mentoring experience, and providing faculty with a vehicle to explore new ideas. Projects typically have both analytical and experimental components that allow the students to develop their proficiency with visualization and computational tools while developing their physical insight. Several case studies are presented that show impressive results and substantial intellectual growth, including examples of long term commitment to a career in structural acoustics.
Evaluating immersion of spatial audio systems for virtual reality
Authors: Aspöck Lukas , Kohnen Michael , Vorlaender Michael
Published: April 2018

Multiple aspects influence the quality of experience of different VR presentations. One popular aspect which is usually considered for rating the presentation is the concept of immersion. Its complex nature as well as indistinct definitions make it challenging to use it as an objective measure in scientific experiments. Additionally previous studies revealed contradictory definitions of immersion and its separation from the concept of presence. To investigate immersion, a nomological net was developed which connects various items contributing to immersion. These items were assigned to subcategories and should ideally be well defined and measurable. For each item, multiple questions were formulated. Pre-testing on their linguistic quality and unambiguity was conducted to identify suitable questions for each item. These questions were applied in two listening experiments: A between-group design for the evaluation of the chosen questions and a within-subject design for the evaluation of differences between Higher-Order Ambisonics, VBAP, and binaural loudspeaker reproduction.
Homogeneous vs heterogeneous nucleation, a comparison
Authors: Church Charles C.
Published: April 2018

Vapor bubbles of sufficient size to serve as effective acoustic scatterers or cavitation nuclei may form in materials having regions of very low interfacial tension when exposed to an acoustic wave. These regions may be simple “hot spots,” i.e., collections of molecules having higher-than-average kinetic energies which therefore have lower surface tension than is found a room temperature, or the interfaces between dissimilar materials, e.g., the lipid coating on a microdroplet of liquid perfluourocarbon used as an ultrasound contrast agent. In addition, the curvature of such interfaces can act to focus an impinging acoustic beam in such a way as to increase its rarefactional pressure above that of the incoming wave. Another factor not often considered is that any foreign material, whether dissolved liquid or minute solid particulate, can act to disrupt the normal molecular structure of the liquid, thereby providing local regions of reduced interfacial tension. The energetics of the nucleation process shows that the rate of nucleation events is highly sensitive to the instantaneous temperature and moderately sensitive to both the magnitude and the duration of the rarefactional pressure of the acoustic wave. These and additional factors influencing nucleation processes will be discussed.
Spatiotemporal modulation for mid-air haptic feedback from an ultrasonic phased array
Authors: Kappus Brian , Long Ben
Published: April 2018

A tactile sensation can be experienced by focusing airborne ultrasound using a phased array. Nonlinear acoustic pressure alone is difficult to perceive so traditional methods use amplitude modulation in the range of 10–300 Hz to stimulate nerves on the hand most sensitive to those frequencies. We demonstrate that through rapid translation of focus points similar results can be obtained using spatiotemporal modulation. This allows for volumetric sensations to be created using maximum power possible from the array. This is made possible through a solving approach using a pseudo-inverse of the activation matrix followed by a power iteration eigenvalue solution. Advantages versus amplitude modulation and consequences for parametric audio will be discussed.
Catching a rabbit with a tetrahedron: A contextualist approach
Authors: Shafiro Valeriy
Published: April 2018

A defining characteristic of Jim Jenkins’ long and productive research career was his ability to reconcile contradictory experimental evidence within a coherent conceptual framework that leads to novel insights and experimental approaches. Grounded in the deep knowledge of history of psychology, Jim’s involvement and expertise in different aspects of human behavior, including language, speech, memory, attention, visual, and auditory perception, resulted in important theoretical breakthroughs (and countless stimulating discussions). One such work is the tetrahedral model of memory experiments. It considers four large clusters of experimental variables: subjects, materials, scoring tasks, and testing procedures, whose mutual interactions determine experimental outcomes. [J.J. Jenkins “Four points to remember: A tetrahedral model of memory experiments,” in Levels of Processing in Human Memory, ed. LS Cermak, FIM Craik, (1979)]. Initially proposed to account for inconsistent findings of memory experiments, the model's applications have expanded to other areas of perceptual training and education as a guide to maximize learning outcomes. Following Jim’s lead, I will illustrate how the tetrahedral model can (1) improve the understanding of research findings from two ecologically significant sound classes, speech and environmental sounds, in normal hearing and cochlear implant listeners, and (2) guide the design of effective auditory training programs.
Backscattering enhancement due to weakly damped, leaky, guided waves on cylinders and associated images
Authors: Daniel Timothy D. , Smith Sterling M. , Marston Philip L.
Published: April 2018

In this work, distinct but related targets were studied using a circular synthetic aperture sonar system. Backscattering data from a solid brass cylinder were recorded. The response of the target was significantly spread out in time because leaky guided waves were weakly radiation damped. They gave significant backscattering contributions for a range of tilt angles. The associated meridional and helical wave contributions are also obvious in the frequency domain. (For comparison helical contributions are relatively weak for aluminum cylinders.) The second target is a bi-metallic cylinder made of a 1:1 brass cylinder bonded to a 3:1 aluminum cylinder. For a single-material cylinder, only 90 degrees of data are necessary due to symmetry. This target breaks that symmetry and requires a full 180 degrees of rotation. The distinction between the brass and aluminum ends is discernible in both the time and frequency domain. The join between the two metals affects the timing of certain guided waves that no longer travel the whole length of the compound cylinder. Image reconstruction was performed using Fourier based algorithms for both targets. The location of the compound cylinder joint is deducible from the location of features in the image domain. [Research supported by ONR.]
Stimulus specific adaptation in the auditory system of insects: Can a single neuron learn?
Authors: Schul Johannes , Yost Ryan
Published: April 2018

Stimulus-specific adaptation (SSA) is the suppression of a neuron's activity to repetitive stimuli while maintaining responsiveness to infrequent signals. In Neoconocephalus katydids, one auditory interneuron (TN-1) shows strong SSA in oddball paradigms, when standard and oddball pulses differ in carrier frequency. SSA occurred for pulse rates from >140 Hz down to 1 Hz. At fast repetition rates (>100 Hz), responses to the common pulses ceased, while oddballs elicit single spikes. At slower rates (<50 Hz), both standard and oddball pulses elicited spiking, with responses to oddballs being significantly larger, comparable to SSA described in vertebrate hearing systems. At slow rates, SSA also occurred when the shape of standard and oddball pulses differed, while having identical spectral properties. We identified at least two dendritic mechanisms that contribute to SSA at fast pulse rates (>100 Hz). The mechanisms underlying SSA at slow pulse rates are less well understood; likely, dendritic Ca2 + -gated currents contribute to SSA at slow pulse rates. At slow rates, response reduction to repeated pulses resembles habituation as oddball pulses cause dishabituation, i.e., the response to the following standard pulse is larger than that to the preceding one. Whether this habituation is generated within TN-1 or by its synaptic inputs remains an open question.
Tailoring cavitation nuclei for biomedical applications
Authors: Porter Tyrone M.
Published: April 2018

Cavitation, or the creation and oscillation of bubbles, has a pivotal role in a variety of biomedical applications that involve ultrasound. For example, stable oscillating bubbles (stable cavitation) can reversibly permeabilize biological interfaces, including cell membranes and the blood-brain barrier. Bubbles that collapse inertially (inertial cavitation) radiate broadband emissions that can enhance ultrasound-mediated heating and thermal ablation. These cavitation-mediated bioeffects may provide medical benefit provided the location, type, and intensity of cavitation activity can be controlled. Microfluidic devices can be used to produce monodisperse microbubbles coated with viscoelastic shells that promote nonlinear oscillations. Liquid perfluorocarbon nanoemulsions can serve as long-circulating cavitation nuclei capable of extravasating into extravascular tissues. Using these technologies, cavitation nuclei can be tailored to provide a predictable acoustic response in a targeted location, thus providing a desired biological outcome.
Urinary stone erosion and fragmentation under low-intensity quasi-collimated ultrasound using gas-filled microbubbles with stone-targeting lipid shells
Authors: Pishchalnikov Yuri A. , Behnke-Parks William , Mellema Matt , Hopcroft Matt , Luong Alice , Colonius Tim , Maeda Kazuki , Morrison Kyle , Laser Daniel
Published: April 2018

Urinary stone lithotripsy critically depends on the presence of cavitation nuclei at the stone surface. We hypothesized that introduction of stone-targeting microbubbles could increase cavitation activity at a stone surface sufficiently to allow stone erosion and fragmentation at peak negative pressures much lower than in acoustic energy-based urinary stone interventions with induced cavitation nuclei alone. Gas-filled microbubbles were produced with calcium-binding moieties incorporated into an encapsulating lipid shell. Stone surface coverage with these targeting microbubbles was found to approach an optimal (considering microbubble expansion during insonation) range of 5–15% with incubation times of three minutes or less. Using high-speed photomicroscopy, we observe bound microbubbles expanding 10- to 30-fold under insonation with quasi-collimated sources at mechanical indexes below 1.9. For observed stand-off parameters in the range of 0.2–0.6, the modeled collapse-generated shockwaves exceed 100 MPa. In swine model studies with these targeting microbubbles, stone fragmentation into passable fragments occurs with treatment times around 30 minutes, while post-treatment examination of ureters and kidneys shows no evidence of urothelium damage or renal parenchymal hemorrhage. The stone-targeting microbubbles reported on here have formed the basis for a new non-invasive urinary stone treatment which recently entered human clinical trials.
Analytic prediction of histotripsy-induced bubble growth in an elastic medium
Authors: Bader Kenneth B.
Published: April 2018

Histotripsy is a form of therapeutic ultrasound that liquefies tissue mechanically via acoustic cavitation. Bubble growth due to histotripsy excitation has been calculated analytically with high accuracy in a fluid medium. Tissue elasticity is a determining factor in the therapeutic efficacy of histotripsy, and has not been considered in analytic bubble dynamics calculations. In this study, an analytic model to predict histotripsy-induced bubble expansion based on the medium surface tension, viscosity, and inertia was extended to include the effects of medium stiffness. Good agreement was observed between the predictions of the model and numerical computations. The predictions of the model were also consistent with experimental observation of bubble expansion, though are dependent on the elasticity form. Bubble growth was weakly dependent on the medium elasticity for highly nonlinear, shock scattering histotripsy pulses, but was strongly dependent for purely tensile, microtripsy pulses. For both forms of histotripsy, bubble growth was completely suppressed when the elastic modulus exceeded 20 MPa and the peak negative pressures was less than 50 MPa. These results highlight the importance of the histotripsy insonation scheme on bubble growth in an elastic medium, as well the range of tissue elasticities for efficacious bubble-induced liquefaction.
Hot topics in structural acoustics and vibration: Advances in vibroacoustic modeling and novel materials
Authors: Koch Robert M.
Published: April 2018

Two major areas of current research focus in Structural Acoustics and Vibration (SAV) are in (1) the development of advancements in the Physics-Based Modeling (PBM) and simulation of real-world, large-scale vibroacoustic systems and also in (2) the development and incorporation of novel engineered materials to improve structural acoustic response performance from a broad array of perspectives. This paper presents examples from a wide survey of recent SAV computational PBM research, from the inclusion of additional complex, coupled modeled phenomena, to improvements in modeling efficiency, accuracy, and/or full frequency spectrum response prediction, through computational advances in the ability to solve extremely large-scale, previously intractable, structural acoustics models. Related to the second materials-based SAV research concentration, recent advancements and innovations in SAV-relevant materials including acoustic metamaterials, zero- and negative-Poisson’s ratio materials, single crystal ceramics, nanomaterials, etc., are also presented.
Musical emotion recognition in bimodal patients
Authors: D'Onofrio Kristen , Limb Charles , Caldwell Meredith , Gifford René
Published: April 2018

Several cues are used to convey musical emotion, the two primary being musical mode and musical tempo. Specifically, major and minor modes are regarded as having positive and negative valence, respectively, and songs at fast tempi (i.e., quarter note = 92-196, Gosselin et al. (2005); quarter note = 80-255, Peretz et al. (1998)) are associated with more positive valence compared to songs at slow tempi (i.e., quarter note = 40-60, Gosselin et al. (2005); quarter note = 20-100, Peretz et al. (1998)). Caldwell et al. (2015) demonstrated that CI users relied on tempo (fast vs. slow) with little regard for mode (major vs. minor) when interpreting musical emotion, a finding consistent with spectral cues being poorly represented in CI users. The current study is an extension of Caldwell et al. (2015) examining how mode and tempo cues impact musical emotion recognition in bimodal listeners. Our primary hypothesis is that, unlike CI only users, bimodal listeners—with access to F0 and fine structure—will utilize both mode and tempo cues in a manner similar to normal-hearing listeners. Our secondary hypothesis is that low-frequency spectral resolution in the contralateral ear (via tuning curves and spectral modulation detection) will be significantly correlated with degree of bimodal benefit for musical emotion perception.
Fearless steps: Advancing speech and language processing for naturalistic audio streams from Earth to the Moon with Apollo
Authors: Hansen John H. L. , Sangwan Abhijeet , Kaushik Lakshmish , Yu Chengzhu
Published: April 2018

NASA’s Apollo program represents one of the greatest achievements of mankind in the 20th century. CRSS-UTDallas has completed an effort to digitize and establish an Apollo audio corpus. The entire Apollo mission speech data consists of well over ~100,000 hours. The focus of this effort is to contribute to the development of Spoken Language Technology based algorithms to analyze and understand various aspects of conversational speech. Towards achieving this goal, a new 30 track analog audio decoder was designed using NASA Soundscriber. We have digitized 19,000 hours of data from Apollo 11,13,1 missions: named “Fearless Steps”. An automated diarization and transcript generation solution was developed based on deep neural networks (DNN) automatic speech recognition (ASR) along with Apollo mission specific language models. Demonstration of speech technologies including speech activity detection (SAD), speaker identification (SID), and ASR are shown for segments of the corpus. We will release this corpus to the SLT community. The data provide an opportunity for challenging tasks in various SLT areas. We have also defined and proposed 5 tasks as a part of a community based SLT challenge. The five challenges are as follows: (1) automatic speech recognition, (2) speaker identification, (3) speech activity detection, (4) speaker diarization, and (5) keyword spotting and joint topic/sentiment detection. All data, transcripts, and guidelines for employing the fearless steps corpus will be made freely available to the community.
Toward the automatic detection of manually labeled irregular pitch periods
Authors: Murton Olivia , Choi Jeung-Yoon , Mehta Daryush , Shattuck-Hufnagel Stefanie
Published: April 2018

Irregular pitch periods (IPPs) occur in a wide variety of speech contexts and can support automatic speech recognition systems by signaling word boundaries, phrase endings, and certain prosodic contours. IPPs can also provide information about emotional content, dialect, and speaker identity. The ability to automatically detect IPPs is particularly useful because accurately identifying IPPs by hand is time-consuming and requires expertise. In this project, we use an algorithm developed for creaky voice analysis by Kane et al. (2013) incorporating features from Ishi et al. (2008) to automatically identify IPPs in recordings of speech from the American English Map Task database. Short-term power, intra-frame periodicity, inter-pulse similarity, subharmonic energy, and glottal pulse peakiness measures are input into an artificial neural network to generate frame-by-frame creak probabilities. To determine a perceptually relevant threshold probability, the creak probabilities are compared to IPPs hand-labeled by experienced raters. Preliminary results yielded an area under the receiver operating characteristic curve of 0.82. Thresholds above 0.1 produced very high specificity, but even lower thresholds yielded fairly high sensitivity and specificity. These results indicate generally good agreement between hand-labeled IPPs and automatic detection, calling for future work investigating effects of linguistic and prosodic context.
Duration of connected speech needed to accurately estimate the articulatory-acoustic vowel space of a reading passage
Authors: Whitfield Jason A. , Gravelin Anna , Kriegel Zoe , Mehta Daryush
Published: April 2018

Unlike other vowel space metrics, the articulatory-acoustic vowel space (AAVS) is calculated from the generalized variance of continuously sampled formant (F1-F2) traces. Given a sufficiently long speech sample, the AAVS should stabilize, though the duration required for the measure to converge remains unknown. The current investigation aimed to determine the amount of formant data needed for the AAVS to stabilize. Formant traces (20 ms frames, 10 ms intervals) were extracted using a Kalman-based autoregressive approach from readings of the Caterpillar passage produced by 16 speakers using habitual speech. The absolute percent difference (error) between cumulative AAVS estimates and the passage AAVS was calculated by iteratively adding F1-F2 pairs from successive voiced frames. Power functions were fit to the error plots using a least absolute residuals method to determine the frame at which the upper bound of the function fell within 5% of the passage AAVS. Across all speakers, the AAVS converged within 1065 voiced frames (i.e., 10.65 seconds of voiced speech). In terms of absolute speaking duration, all samples converged within 18 seconds (mean = 8.26; SD = 5.04). These data suggest that 15 to 20 seconds of connected speech is sufficient to provide a reasonable estimate of working vowel space using the AAVS.
Google speech recognition of an English paragraph produced by Korean college students in clear or casual speech styles
Authors: Yang Byunggon
Published: April 2018

These days voice models of automatic speech recognition software are sophisticated enough to process the natural speech of people without any previous training. However, not much research has reported on the use of speech recognition tools in the field of pronunciation education. This paper examined Google speech recognition of a short English paragraph produced by Korean college students in clear and casual speech styles in order to diagnose and resolve students’ pronunciation problems. Thirty three Korean college students participated in the recording of the English paragraph. The Google soundwriter was employed to collect data on the word recognition rates of the paragraph. Results showed that the total word recognition rate was 73% with a standard deviation of 9.1%. The word recognition rate of clear speech was around 77.3% while that of the casual speech amounted to 68.7%. The reasons for the low recognition rate of casual speech were attributed to both individual pronunciation errors and the software itself as shown in its fricative recognition. Various distributions of unrecognized words were observed depending on each participant and proficiency groups. From the results, the author concludes that the speech recognition software is useful to diagnose each individual or group’s pronunciation problems.
Evaluating the LENA recording system for investigating speech input in a French-English bilingual context
Authors: Orena Adriel John , Polka Linda , Srouji Julia
Published: April 2018

The Language ENvironment Analysis (LENA) recording system is rapidly gaining acceptance as a useful tool for assessing a child’s speech input. The success of this tool is due to LENA algorithms which provide automated measures of the child’s auditory environment, including the amount of words. The adult word count (AWC) measure has been validated in several monolingual language contexts, including English, French, Dutch, and Mandarin. Here, we evaluate LENA performance in counting words when two languages are present within the child’s input stream. Twenty French-English bilingual families with a 10-month-old infant contributed full-day recordings. Nine 5-minute segments from each family was transcribed, for a total of 900 minutes of transcribed speech. We assessed the accuracy of LENA-generated AWC for French-English bilingual speech by comparing them to human-transcribed word counts. Linear mixed modelling reveals a positive linear relationship between these two measures. Critically, the correlations between these two measures were strong for both French and English, and these correlations were not significantly different from one another. These results confirm that the LENA algorithms are sufficiently accurate in counting words in two languages, and provide support for researchers and clinicians wishing to use the LENA recording system to assess bilingual speech.
Biomedical applications of sparse hemispherical ultrasound arrays
Authors: Jones Ryan M. , O'Reilly Meaghan A. , Deng Lulu , Hynynen Kullervo
Published: April 2018

Sparse arrays have been employed in biomedical ultrasound for diagnostic and therapeutic purposes to reduce the technical complexities associated with dense arrays while maintaining adequate performance characteristics. Sparse arrays are particularly attractive when large apertures are desired, which is often the case for therapy to achieve high acoustic gains and tight focal volumes. Large aperture arrays provide similar benefits on receive during multichannel beamforming of passively detected acoustic emissions, which is a promising approach for guiding cavitation-mediated ultrasound therapies. Our group has designed and fabricated sparse hemispherical phased arrays for ultrasound brain imaging and therapy. Ultrasound field simulations were carried out to optimize the spatial distribution of array elements. We have employed these devices for skull computed tomography-array registration, 3D spatial mapping of microbubble activity in vivo through ex-vivo human skullcaps via noninvasive aberration correction methods, and have harnessed this spatiotemporal cavitation information to calibrate exposure levels for safe, volumetric ultrasound-induced blood-brain barrier opening. In conjunction with techniques borrowed from optical microscopy, we have demonstrated trans-skull 3D microbubble imaging beyond the diffraction limit, which may have application in ultrasound-based cerebral angiography. This talk will review our progress to date in the development and biomedical application of sparse hemispherical ultrasound arrays.
Azimuth-elevation direction finding, using three uni-axial velocity sensors as an arbitrarily sparse linear array
Authors: Song Yang , Wong Kainam T. , Khan Salman , Khan Mohammad Asaduzzaman
Published: April 2018

A tri-axial velocity sensor measures the acoustic particle-velocity vector, by all three of its Cartesian components. This particle-velocity vector equals the spatial gradient of the acoustic pressure field. Song & Wong [1] has advanced an algorithm to estimate an incident source's azimuth-elevation (θ, Φ) direction-of-arrival using three uni-axial velocity sensors that are orthogonally oriented among themselves and placed arbitrarily in three-dimensional space. This work will focus on a particular array geometry whereby the three uni-axial velocity sensors are placed on a straight line in three-dimensional space but the inter-element spacings may be entirely arbitrary. This work will show how to estimate a far-field emitter's azimuth-elevation direction-of-arrival, despite the three elements’ spatial separation, and despite the separation's arbitrary length and possible sparseness. Furthermore, the Cramer-Rao Bounds (CRB) will be presented analytically for the case of the linear array being aligned along the x-axis. This work differs from [2], which requires an additional pressure-sensor. [1] Y. Song & K. T. Wong, “Acoustic direction finding using a spatially spread tri-axial velocity sensor,” IEEE Trans. Aerosp. Electron. Syst. 51(2), 834–842 (2015). [2] Y. Song & K. T. Wong, “Azimuth-elevation direction finding, using one four-component acoustic vector-sensor spread spatially along a straight line,” Proc. of Meetings on Acoustics—Meeting of the ASA, Pittsburgh, U.S.A., May 18–22, 2015.
Scattering of low-frequency sound by shallow underwater targets
Authors: Baynes Alexander B. , Godin Oleg A.
Published: April 2018

Rayleigh scattering of sound by a target can be described as a wave radiated by virtual point sources inside the target. When a target is located close to the ocean surface or another reflecting boundary, reflections of the incident and single-scattered waves from the boundary lead to multiple scattering from the target, with the target being insonified by nearby virtual sources. At low frequencies and for shallow targets, the distance from a virtual source to the target is not necessarily large compared to acoustic wavelength or the target’s dimensions. This paper takes advantage of the virtual source concept and recently derived explicit analytic representations of 2-D and 3-D acoustic Green’s functions in unbounded fluids with inclusions of a circular cross-section, to develop a simple and numerically efficient model of multiple scattering. Scattering from soft, hard, fluid, and solid objects is considered. The model is used to study the acoustic field in the vicinity of shallow targets, calculate normal-mode compositions of the multiple-scattered field, examine conditions of applicability of the single-scattering approximation, and investigate implications of multiple scattering for target detection and classification.
Amplified music and variable acoustics—Controlled low frequencies and envelopment at high
Authors: Adelman-Larsen Niels W.
Published: April 2018

Subjective ratings from 25 professional musicians and sound engineers were obtained to assess two Danish rock venues of similar size and similar low frequency reverberation times, but different high frequency reverberation characteristics. The musicians rated one hall outstanding and significantly better than the other, substantiating a hypothesis that pop venues can have a longer reverberation time at mid to high frequencies at least in the empty condition with no seats installed. Possible causes for this is an enhancement of the musicians’ ease of expressing dynamics as well as of their ability to sense the audience for whom they are playing. It has formerly been shown, that what characterizes the best halls for amplified music is a relatively short reverberation time at low frequencies. However, in this study, a fairly long reverberation time in the 63 Hz octave band is found to be acceptable, especially in the hall with the longer mid-high frequency reverberation time, pointing towards a tolerance for longer reverberation in this band in general. Further, this hints at the possibility that mid-high frequency reverberation can mask, at least 63 Hz band challenges. The 125 Hz octave band RT, which thereby remains the single most important to control for amplified music, is app. 1 sec in the two venues that hold some 700 standing audiences
Formulation of a Burgers’ equation for shock waves in a turbulent atmosphere
Authors: Lonzaga Joel B.
Published: April 2018

The theoretical formulation of a Burgers’ equation accounting for the attenuation and dispersion of shock waves due to scattering in a turbulent medium is presented. The physical effect treated here is in addition to the effects of geometric spreading, large-scale inhomogeneity, nonlinearity, viscous and thermal dissipation, and molecular vibrational relaxation. Although all Burgers’ equations are inherently a one-way approximation, here the scattering effects are incorporated into the Burgers’ equation through a correction to the small-amplitude sound speed. Such a correction is obtained from the full wave equation using a perturbative technique, and physically arises from multiple scattering of the signal due to small-scale inhomogeneities. The sound speed correction is complex, and is dependent on the frequency and the variance and length scale of the fluctuations. The real part of the correction gives rise to the dispersion of the signal while the imaginary part leads to signal attenuation. The latter is manifested by the increase in the rise time of the shock waves. The physical effect presented here is integrated into an existing sonic boom propagation code with minimal additional computational time. Numerical results will be compared with experimental data.
Exploring heterogeneity and disorder In tunable elastic metamaterials
Authors: Celli Paolo , Yousefzadeh Behrooz , Daraio Chiara , Gonella Stefano
Published: April 2018

The dominant paradigm in the design of elastic metamaterials revolves around periodic arrays of identical resonating elements, which are known to allow subwavelength locally-resonant bandgaps. In this work, we deliberately explore the wave manipulation capabilities of metamaterial configurations that are characterized by significant heterogeneity and disorder. Heterogeneity is here intended as the coexistence of multiple types of resonators tuned to resonate at distinct frequencies. Disorder refers to the arrangement of the resonators, which is randomized in space. The metamaterials of choice are thin elastic sheets endowed with heterogeneous populations of tunable telescopic pillars whose resonant characteristics can be agilely tuned through simple manual operations. The configurability of our experimental platform allows to seamlessly fabricate and compare a multitude of specimens, thus allowing to extract some empirical yet general rules. We first document how heterogeneity can lead to broadband mechanical filtering. More specifically, we illustrate how randomized spatial arrangements consistently outperform their functionally graded counterparts in terms of maximum achievable bandgap width. Our investigation shows that the design space of mechanical metamaterials can be stretched beyond the limits imposed by order and homogeneity, thus highlighting the engineering significance of the emerging concepts of organized disorder and design modularity.
Effects of training on the perception of talker information in degraded speech
Authors: Tamati Terrin N.
Published: April 2018

A fundamental property of human speech perception is its robustness in a wide range of listening conditions. Listeners are able to successfully recognize and understand speech under a wide range of adverse and challenging conditions, such as in noise, reverberation, or multi-talker babble, and with noise vocoding. Noise vocoding, a manipulation that reduces spectral resolution, has been shown to result in less accurate speech comprehension and also poorer perception of indexical information (e.g., talkers’ voices). However, speech comprehension quickly improves with exposure, as listeners learn to better extract information from the systematically degraded speech. The extent to which the learning of noise-vocoded speech transfers to other talkers or tasks is still largely unknown. The current study investigated whether training, consisting of transcribing sentences or identifying talkers’ voices from sentences, leads to improvements in the perception of talker information. Preliminary results suggest that both training tasks resulted in improved perception of talker information, as participants learned general information about the degradation. Larger improvements were observed after talker identification training, which focused attention on talker differences. Differences between training tasks, and implications for cochlear implant users, will be discussed. [Funding: VENI Grant (275.89.035) from the Netherlands Organization for Scientific Research (NWO).]
Effects of speech competitors on encoding features of novel word-object pairs
Authors: Simeon Katherine M. , Grieco-Calub Tina M.
Published: April 2018

Fast-mapping is the ability to map novel word-object pairs with very few exposures (Carey & Bartlett, 1978), and is thought to underlie language acquisition. However, language learning often happens in natural environments that contain competing sounds. Previous studies examining whether competing sounds affect fast-mapping yielded inconsistent results, likely due to methodological differences. The present study adds to this body of work by testing the effect of competing sounds on the depth of encoding novel word-object pairs during a fast-mapping task. Three-to-four-year-old children performed a fast-mapping task in quiet and in the presence of a two-talker speech competitor presented at a + 2 dB signal-to-noise ratio. In each condition, children were trained on three novel word-object pairs, whereby the object was verbally labeled and associated with related attributes while moving across a computer screen (e.g., “This modi can bounce”). Children were then tested on their recognition of each word-object pair. Children associated words to objects equally well in quiet and speech competitor conditions, but recalled fewer object attributes when speech competitors were present. Results suggest that speech competitors disrupt encoding of the semantic features of word-object pairs. This presentation will highlight how different methodologies demonstrate varying effects of competing sounds on fast-mapping.
Massively parallel structural acoustics in Sierra-SD
Authors: Bunting Gregory , Miller Scott T. , Walsh Timothy F.
Published: April 2018

Sierra-SD is a massively parallel finite element application for structural dynamics and acoustics. Problems on the order of 2 billion degrees of freedom and running on as up to one hundred thousand distributed memory cores have been solved. Sierra-SD offers a wide range of modern acoustic capabilities. Unbounded problems can be solved with either an absorbing boundary condition, infinite elements, or perfectly matched layers. Problems can be solved in the time domain, frequency domain, or as a linear or quadratic eigenvalue problem. Structural acoustics problems can be solved with monolithic strong coupling, or a Multiple Program Multiple Data (MPMD) coupling with the linear and nonlinear structural Sierra applications. One way handoff is available from other applications in the Sandia National Laboratories’ Sierra Mechanics suite, enabling loading through the Lighthill tensor from incompressible fluid codes to calculate far field noise. Real world applications include ship shock loading and vibration of reentry bodies. [Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.]
Scattered field formulation applied to 3D models for buried targets
Authors: Gunderson Aaron M. , Bonomo Anthony L. , Isakson Marcia J.
Published: April 2018

Calculation of the acoustic scattering from buried targets in a seafloor environment is a task ideally suited for finite element software. A complication arises though when the target’s environment is modeled as two infinite half spaces of water and sediment, each surrounded by perfectly matched layers (PML’s) to satisfy the Sommerfeld radiation condition. Each half space requires a surrounding PML tailored to its material properties, resulting in abrupt discontinuities in PML structure at the corners where the sand-water interface meets the edges of the physical domain. Acoustic energy incident on these corners results in nonphysical reflections directed back into the physical domain. It has previously been shown in a 2D axisymmetric geometry [Zampolli et al., JASA 122, 2007] that using a scattered field formulation, where the incident, reflected, and transmitted fields are applied as background fields, bypasses the discontinuity and eliminates these spurious reflections. Here, the theory is extended to full 3D geometries, allowing the scattering from 3D buried objects to be evaluated and tested against experimental and analytical benchmark results. Once complete, the 3D model template is easily modified to consider any target at any level of burial. [Work supported by Applied Research Laboratories IR&D and ONR, Ocean Acoustics.]
In vivo ultrasound thermal ablation controlled using echo decorrelation imaging
Authors: Abbass Mohamed A. , Mahalingam Neeraja , Krothapalli Krishna S. , Ahmad Syed A. , Mast T. Douglas
Published: April 2018

The utility of echo decorrelation imaging feedback for real-time control of in vivo ultrasound thermal ablation was assessed in rabbit liver with VX2 tumor. High-intensity focused ultrasound (HIFU) and unfocused (bulk) ablation was performed using 5 MHz linear image-ablate arrays. Treatments comprised up to nine lower-power sonications, followed by up to nine higher-power sonications, ceasing when the average cumulative echo decorrelation within a control region of interest exceeded a predefined threshold (−2.3, log10-scaled echo decorrelation per millisecond, corresponding to 90% specificity for tumor ablation prediction in previous in vivo experiments [Fosnight et al., Ultrasound Med. Biol. 43:176-186, 2017]). This threshold was exceeded in all cases for both HIFU (N = 13) and bulk (N = 8) ablation. Controlled HIFU trials achieved significantly smaller average lesion width compared to previous uncontrolled trials. Both controlled HIFU and bulk ablation trials required significantly less treatment time than uncontrolled trials. Prediction of local liver and VX2 tumor ablation using echo decorrelation was tested using receiver operator characteristic curve analysis, showing prediction capability comparing favorably with uncontrolled trials. These results indicate that control using echo decorrelation imaging may reduce treatment duration and increase treatment reliability for in vivo thermal ablation.
Patient-specific large-volume hyperthermia in the liver for ultrasound-enhanced drug delivery from thermosensitive carriers
Authors: Chu Brian , Cleveland Robin , Coussios Constantin
Published: April 2018

Ultrasound-mediated mild hyperthermia in the range of 39C to 42C is a promising technique for noninvasive targeted release of thermally sensitive carriers in cancer therapy. The need to sustain a temperature rise of a few degrees evenly throughout a large volume currently limits this therapy to regions with a large accessible acoustic window. Furthermore, the need to continuously scan clinically available highly focused therapeutic ultrasound transducers typically used for ablation limits the volume that can be maintained at this temperature for tens of minutes, and greatly extends treatment time per unit volume. In addition, bone structures, such as the ribs, significantly restrict accessible target locations in areas such as the liver and play a significant role in preventing this therapy from entering into clinical practice. In order to overcome these limitations, we present a combined 3D full wave finite element modelling and experimental approach to design a sectored lens that can be placed on focused transducers to enable direct mild heating of a larger volume in the liver while accounting for patient-specific aberration in the prefocal path. [Work supported by the RCUK Digital Economy Programme, grant number EP/G036861/1 (Oxford Centre for Doctoral Training in Healthcare Innovation).]