bluuebunny/crossref_metadata_2025 huggingface dataset:
The pollution effect and novel methods to reduce its influence in the mid-frequency range
Authors: Rouse Jerry W. , Walsh Timothy F.
Published: November 2019

The classical Galerkin formulation is nearly ubiquitous in production-scale finite element codes. The formulation uses effectively the same space of polynomials for both the solution (trial) and weighting (test) functions. Further, the standard h refinement method of decreasing element size to achieve convergence is equally universal, typically involving only linear and second order polynomial elements. For geometries that are several wavelengths in size the above methodology is sufficient for accurate predictions. However, extending beyond several wavelengths, ever-present interpolation and pollution errors degrade the predictions at a linear and nonlinear rate, respectively. As the number of wavelengths in the geometry increases, the nonlinear (pollution) term eventually dominates the approximation error. Prediction accuracy can be maintained by correspondingly increasing the number of elements per wavelength but at a cost of increasing computational need. This talk shall present an overview of interpolation and pollution errors and their effects, as well as a number of cutting-edge methodologies developed to overcome their influence in the mid-frequency range.
On using geometry-based high-order finite element approximations for mid-frequency response of fluid-loaded elastic structures
Authors: Dey Saikat
Published: November 2019

Accurate solution of the exterior scattering and radiation problems in the mid-frequency regime remains of high interest and a computationally challenging task. For wave-dependent problems with large dispersion errors, high-order approximations provide several advantages, including increased accuracy and error convergence rate compared to low-order methods. The effective use of high-order finite element type approximations require special attention to geometry. In particular, one must use high-order (curved) meshes in order to preserve the accuracy and convergence advantages. We present recent developments in the use of geometry-based high-order approximations for computing scattering response of fluid-loaded elastic structures submerged in an acoustic medium. We present examples with validation against experimental data to demonstrate the effectiveness of these techniques as well as highlight future technical challenges to push to the higher ends of the mid-frequency regime.
Scaled boundary finite element method for mid-frequency interior acoustics
Authors: Natarajan Sundararajan , Padmanabhan Chandramouli
Published: November 2019

In this talk, a semi-analytical framework, based on the scaled boundary finite element method (SBFEM), is proposed, to study interior acoustic problems in the mid-frequency range. The SBFEM shares the advantages of both the finite element method (FEM) and the boundary element method (BEM). Like the FEM, it does not require the fundamental solution (Green's function) and similar to the BEM only the boundary is discretized, thus reducing the spatial dimensionality by one. The solution within the domain is represented analytically, while on the boundary, it is represented by finite elements. Different choices of boundary representations, such as Lagrange and NURBS description will be discussed. The proposed framework is validated using closed-form solutions and direct comparisons are made with conventional FEM based on Lagrangian description; this will be demonstrated using two two-dimensional cavities available from the literature. The improved accuracy and reduced computational time can be attributed to the semi-analytical formulation combined with the boundary discretization.
San Diego accents: A preliminary investigation into the vowel spaces of young males and females
Authors: Gold Erica , Earnshaw Kate
Published: November 2019

This study investigates the vowel spaces of eight native San Diego speakers (four males and four females) that are: born and raised in San Diego County, only lived outside San Diego for a maximum of four years, English dominant speakers, Caucasian, and aged between 23 and 32 (mean = 28.6 years old). All participants were recorded using handheld Zoom H2n audio recorders. Participants read a word list of 74 monosyllabic words, 80 sentences (mean = 6.5 words per sentence), and participated in a short 20-minute sociolinguistic interview about themselves and the San Diego area. For the purposes of this study, F1–F3 were measured in Praat for all vowels in the read speech of the eight participants using dynamic formant measurements at 10% intervals across each vowel. Results are normalised across all speakers, and then analyzed in Excel and R. Although this is a preliminary study, this investigation provides some of the first acoustic-phonetic results looking at the San Diego accent in young males and females.
Acoustic and aerodynamic variation in voiced plosives
Authors: Herd Wendy
Published: November 2019

This study investigates variation in the production of word-initial /b, d, ɡ/ by native speakers of English in Mississippi. Forty speakers were recorded reading a short passage and a series of words in isolation. As previously found in this geographic region, phonetic realizations of /b, d, ɡ/ included both short positive and long negative VOTs, with speakers who identified as African American producing plosives with negative VOTs more often than those who identified as Caucasian American; however, negative VOTs were observed among both groups of speakers. Amplitude trajectories and spectral characteristics during the voice bar of the plosives with negative VOTs suggest that phonetic realizations of /b, d, ɡ/ included both prevoiced and prenasalized plosives. As with frequency of negative VOTs, prenasalization was observed among both groups but was higher among African American participants than Caucasian American participants. Nasal airflow data collected from a subset of the participants confirmed that plosives with nasal-like spectral characteristics were produced with greater nasal airflow than those lacking those characteristics. Converging acoustic and aerodynamic evidence indicate that /b, d, ɡ/ variants in Mississippi include unaspirated plosives, prevoiced plosives, and prenasalized plosives. These results also provide evidence of socio-ethnic variation in the production of /b, d, ɡ/.
Voice quality of coarticulated Mandarin tones
Authors: Huang Yaqian , Chai Yuan
Published: November 2019

Tonal coarticulation often induces changes in F0 (Xu, 1997; Brunelle, 2009) as well as voice quality (DiCanio, 2012). In Mandarin, voice quality covaries with F0, such that when the F0 is higher or lower than the mid-range pitch, the voice quality often becomes creakier (Kuang, 2017). However, fewer studies have examined how coarticulation can affect a tone’s voice quality. Using audio and electroglottography (EGG), this study investigates how F0 and voice quality of Mandarin tones are affected by coarticulation. The stimuli consisted of trisyllabic Mandarin compounds, where each of the four Mandarin tones is flanked by varying tones, for a full range of contextual variation. We expect that the F0 of a high tone (e.g., Tone 1) would become lower when flanked by a low tone (e.g., Tone 3), whereas the F0 of a low tone would become higher when adjacent to a high tone. Moreover, the voice quality of Tone 3 that is raised in F0 should become more modal, if voice quality depends on F0. Discussion of results will emphasize how F0 and voice quality of Mandarin tones can vary according to tonal context and how articulation (as measured by EGG) informs patterns of acoustic realization.
Contextual and speaker variation of glottalic stops in Q'eqchi'
Authors: Liang Kevin , Kuang Jianjing
Published: November 2019

Because of the complex coordination of laryngeal and supralaryngeal articulations, the realization of glottalic stops is highly variable across both languages and speakers. Therefore, it is important to discern the range of variation of glottalic stops. In Q’eqchi’, like other Mayan language, the production of bilabial glottalic stops varies between implosive and ejective. The present study explores whether the phonetic realization of glottalic stops in Q’eqchi’ systematically varies based on phonetic context. We also investigate whether different speakers have preferences for certain realizations of glottalic stops. Examining acoustic measures, we found that (1) both types of glottalic stops (implosive and ejective) are variably produced by speakers, and they are acoustically distinct, (2) ejective-like stops are more likely to occur in word-initial position, and that, (3) individual speakers have preferences towards either producing more implosive-like stops or more ejective-like stops. This study supports the hypothesis that variation of glottalic stops is conditioned by phonetic context, and that differing speakers have different preferences for the realization of these stops.
Within- and between-speaker acoustic variability: Spontaneous versus read speech
Authors: Lee Yoonjeong , Kreiman Jody E.
Published: November 2019

Using principal component analysis (PCA), our previous study [JASA 145(pt. 2), 1930, (2019)] of read sentences found surprisingly similar acoustic voice spaces for groups of female and male talkers and for the individuals within groups. Formant frequencies and the balance between higher harmonic amplitudes and inharmonic energy in the voice accounted for the most acoustic variance within and across talkers, but many further details varied idiosyncratically for individual talkers. In this study, we replicated this finding using a set of recorded phone conversations from 99/100 original speakers (49 F), hypothesizing that the same measures would characterize both individual and population acoustic spaces, despite greater acoustic variability for spontaneous utterances. F0, formant frequencies, spectral noise, source spectral shape, and their variability were measured every 5 ms from vowels and approximants. Individual and group PCAs revealed that the acoustic voice spaces derived from spontaneous speech are highly similar to those spaces previously identified based on read speech. One significant difference between the two speaking styles was that unlike read speech, variability in F0 emerged as one of the variables that accounted for significant acoustic variability in spontaneous speech. Implications for voice learning, recognition, and discrimination will be discussed. [Work supported by NIH/NSF.]
The vowel nasalization found in Murcia, Spain: A case study of this phenomenon
Authors: Lopez Vera Alexandra
Published: November 2019

Of all the linguistic features that characterize the southern dialect spoken in Spain, the vowel nasalization found in Murcia is the most distinctive one. Vowel nasalization in Spanish mostly affects vowels between two nasals and in utterance-initial position following nasals. The nasalized vowels found in this region, however, are not in either of those contexts. As an example, the word especial [epeθjal] > [epeθjã] presents a nasalized final vowel in an unexpected context. There are authors believing that the nasalization becomes an acoustic marker of a word limit. The goal of this study is to determine the contexts where nasalization occurs based on the analysis of recordings made by speakers of this dialect. A number of factors were targeted as potential predictors of nasalization, including internal factors such as words with stressed first or final syllable and composed by random consonant phonemes which obey the Sonority Principle: vowel (or diphthong) + /l/, /r/, /d/, /s/ and /ʃ/, and external factors such as gender, age, social class and level of education. Results indicate that women nasalize less than men, age does not have an impact, and the lower the social class or the education is, the higher index of nasalization is found.
An intonational model of Shanghai Wu: A pitch-accent analysis
Authors: Roberts Brice D.
Published: November 2019

This paper presents an intonational model of Shanghai Wu in the Autosegmental-Metrical framework. Shanghai’s peculiar phrasal tonal system, which spreads lexical tones over sandhi domains, is well-discussed in the literature; however, there is no account of the language's contrastive intonational elements and their phonetic realization. Grounded in phonetic data collected from 14 Shanghainese speakers born between 1945 and 1963, the paper analyzes the language as a pitch-accent system rather than a tonal one, with three distinctive accents: L* + H, H* + L, and L*. These pitch accents pair with one of two accentual phrase-like boundary tones, La and LHa with specific tonotactic requirements. Additionally, I will describe the prosodic hierarchy, as determined by the intonation, as having two levels above the accentual phrase, the intonational phrase (marked via initial pitch range expansion and one of three boundary tones: L%, %, and H%) as well as the major phrase. Together with a labelling system, this analysis allows for easy annotation of Shanghainese tonal events, similar to the ToBI-type models for languages such as Japanese and Serbo-Croatian.
The interaction between lexical prominence and pre-boundary lengthening in Japanese
Authors: Tsai Karen , Katsika Argyro
Published: November 2019

Pre-boundary lengthening, also known as phrase-final lengthening, is a well-established phenomenon. In stress languages, pre-boundary lengthening has been shown to interact with lexical prominence (i.e., stress), affecting the boundary-adjacent constriction gestures in stress-final words, but being attracted towards the stressed syllable when stress is non-final. However, the interaction between pre-boundary lengthening and lexical prominence in a language with lexical pitch accent, like Japanese, is not well understood. The current study uses kinematic data collected with Electromagnetic Articulography (EMA) to investigate this interaction in Japanese. We examine pre-boundary lengthening in trisyllabic phrase-final words as a factor of pitch accent position (initial-accented, medial-accented, final-accented, and no accent). Preliminary results based on duration measurements of the consonant constriction gestures comprising the phrase-final words show that in words with no pitch accent, pre-boundary lengthening has a progressive effect extending two syllables away from the right edge of the phrase, being strongest in the word-final syllable. If pitch accent is present, pre-boundary lengthening is affected by the former’s position. The lengthening effect is limited to the final syllable in initial- and medial-accented words, and disappears in final-accented words. Typological dimensions of the interaction between prominence and boundaries are discussed. [Work supported by NSF.]
Sibilant production and perception in the North American West
Authors: Vaughn Charlotte , McAuliffe Michael , Babel Molly E.
Published: November 2019

This paper explores variability in English /s/-/ʃ/ production and perception across the North American West. Although this dialect region has long been considered monolithic, recent work has begun to explore the phonetic diversity within the region. However, much of this work has investigated vocalic variation, and sibilants have remained relatively underexamined. Given reports of /s/-retraction as a change-in-progress in varieties of English around the world (particularly in /str/ clusters), sibilants are of particular interest. In this study, monolingual participants from Oregon, California, and British Columbia provided single word productions and performed a /s/-/ʃ/ perception task. Preliminary results indicate the prevalence of /str/ retraction in the region, with most retraction in speakers from California, followed by Oregon, followed by British Columbia. Region-internal differences in perception of /s/-/ʃ/ were minimal, though a speaker’s /str/ retraction ratio contributed to predicting perception for speakers with smaller distances between /s/ and /ʃ/, consistent with prior work finding more perceptual similarity for speakers for whom two sounds are in an allophonic relationship. Taken together, these results contribute to the description of speech in the western region of North America, as well as add data to ongoing questions about variation in production, perception, and their relationship.
Multi-dimensional scaling (MDS), Euclidean distance matrices (EDMs), matrix completion and outlier identification in array calibration and beamforming
Authors: Hursky Paul
Published: November 2019

The matrix of inter-element distances, a Euclidean Distance Matrix (EDM), is symmetric with zero diagonal. It thus has N(N-1)/2 distinct values, which we know are a function of 3N-6 xyz coordinates. Indeed, the EDM for the elements of a 3-D array has rank 3. As a result, it is possible to reconstruct missing elements of the EDM, using a process called matrix completion. Array calibration (aka array element localization or AEL) is determining the relative 3-D coordinates of all array elements, so that they can be incorporated into various beamforming processes. The eigenvectors of a complete and noise-free EDM immediately yield the array element xyz coordinates, using a method called Multi-Dimensional Scaling (MDS). If an EDM has missing measurements and/or is noisy, its matrix completion can recover a complete and more accurate EDM that then yields better relative xyz coordinates. Alternatively, testing a noisy EDM for its know properties can be used to identify outlier measurements (among the inter-element distances), before AEL is performed. We will present the mathematics underlying EDMs, MDS, and matrix completion, and demonstrate AEL results for incomplete and noisy EDMs, using these concepts.
Experimental validation of a distributed sensor network concept
Authors: Mignerey Peter C. , Finette Steven I. , Edelmann Geoffrey F. , Emokpae Lloyd , Schindall Jeffrey
Published: November 2019

Autonomous distributed systems comprising many sensors provide a new paradigm for passive detection of acoustic sources in the ocean. Such systems can be designed to achieve global consensus concerning source detection through distributed computation without the presence of a fusion center. In this presentation, individual sensors make information-theoretic assessments of whether a target is present or absent, and communicate that information within a network to enable a global detection consensus. To obtain the consensus, each sensor obtains neighboring information that populates a state vector, which is reduced by an inner-product with a dynamical-system iteration vector to obtain a scalar estimate of the global information. The process iterates until the network reaches a consensus on the detection information, after which the process starts anew on a subsequent block of acoustic data. An experiment was conducted on the New Jersey Shelf in early May 2019 to evaluate the above ideas. This talk will cover an overview of information-theoretic detection, the convergence of a linear state system on a network graph, robustness with respect to node failure, and the behavior of a dynamical detection system deployed in the ocean. [Work supported by the U.S. Office of Naval Research.]
Estimation of clock errors in underwater acoustic instruments
Authors: Udovydchenkov Ilya A. , Blair Ballard J. , Stephen Ralph A. , Egnor Dianne E.
Published: November 2019

All underwater acoustic sensors require accurate on-board clocks for subsequent data analysis and interpretation. Unfortunately, most clock oscillators change their frequency over time, which occurs due to environmental changes, aging, and other factors. Typically, clock errors are accounted for by referencing the instrument clock to a known accurate clock (such as GPS) before and after the deployment and applying a correction during data post-processing. This method, however, does not accurately estimate clock errors during a specific experimental event. A method to estimate clock performance during the specific event of interest has been developed. It is shown that advanced signal processing techniques can be used to accurately reconstruct the motion of the acoustic source, which, in turn, can improve the accuracy of the acoustic receivers deployed on the seafloor in the deep ocean. A small subset of data collected on the last day of the Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June–July 2013 is analyzed for the demonstration of these techniques. [Work supported by the MITRE Corporation’s R&D Program.]
Experimental evaluation of passive underwater acoustic markers
Authors: Satish Aprameya , Trivett David , Sabra Karim G.
Published: November 2019

Autonomous Underwater Vehicle (AUV) navigation requires accurate positioning information underwater which is most commonly achieved using active acoustic transponders. Such transponders typically require maintenance, power and are not covert. As an alternative, the concept of using passive underwater acoustic markers with layered media for underwater navigation has been previously explored theoretically and experimentally using flat interfaces [Satish et al., JASA-EL 145(1), EL84–EL89]. In order to design passive acoustic markers with a more isotropic scattered response, acoustic markers with curved symmetry were investigated experimentally using scaled ultrasonic testing of 3-D printed concentric hemispheres. Subsequently, larger acoustic markers using acrylic hemispherical shells are constructed and insonified by conventional high-frequency SONAR, and their acoustic signatures are measured and compared to theoretical responses. Tag design considerations and preliminary results for the scattered response from different acoustic markers are compared for uniqueness of acoustic signature.
Effects of rough surface on frequency responses in non-anechoic tank
Authors: Xie Dingding , Li Qi , Tang Rui , Shang Dajing
Published: November 2019

The tank used for acoustical measurements should have sufficiently smooth frequency response curves. However, limited by number of modes, excitation and reception of sound field, the curves in non-anechoic tank fluctuate greatly, which causes unsatisfactory results. In this study, a method that reduces the fluctuation by rough surface is suggested. Numerical simulation by finite element computation is presented for sound field with rough surface. Simulation results reveal that there are more modes when the surface fluctuates randomly. Experiment results in non-anechoic tank with randomly fluctuant surface and in the static one are given. It is shown that smoother frequency response curves can be obtained with stronger modal behavior. The compared results between measurement and simulation show good agreements, which validates the effects of rough surface on frequency responses. This study provides a useful method for measuring the characteristics of narrowband signals in non-anechoic tank, and the applicability of the method is provided.
Spiral wave front sonar for active target localization on an unmanned underwater vehicle
Authors: Dzikowicz Benjamin , Kost Jason L. , Heddings Jacob T. , Brown David A.
Published: November 2019

Spiral wave front sonar is a non-imaging, active sonar technique for remote target localization. It operates by transmitting in rapid succession a leading reference signal, a spiral signal whose phase varies by 2π over the transducer's azimuthal plane, and then a trailing second reference signal. Individual echos can be analyzed for range by time-of-flight, radial velocity by measuring the Doppler effect between the leading and trailing reference signals, and bearing by computing the phase difference between reference and spiral signals across a range of frequencies on a single receive channel. In addition, the spectral response of the target is available for classification algorithms. A prototype compact spiral sonar system (spiral transducer array, hydrophone receiver, amplifiers, and data acquisition) was developed and built for use on a Unmanned Underwater Vehicle (UUV). This talk will focus on analysis of results from initial experiments with this system conducted at NRL's Chesapeake Bay Detachment. Target bearing, range, and radial velocities are computed for a number of targets detected within the field. In addition, several targets were tracked over multiple sonar pings. [Work funded by the Naval Research Laboratory.]
Multi-unit analysis of noise level exceedances over time in hospitals
Authors: Ahrens Stephanie A. , Ryherd Erica E.
Published: November 2019

The purpose of this project is to expand the knowledge base of health care soundscapes by analyzing noise level exceedances in a relatively large sample of hospitals and units, in order to more clearly define the range of sound levels typically experienced in modern healthcare noise environments. Occurrence rate is a newer measure of how often peak and maximum sound levels occur over a measurement period. Other metrics analyzed in this project include the occurrence rate of minimum sound levels and the difference between maximum and minimum sound levels. These and more traditional sound level metrics are evaluated along with standard percentile noise levels over time. The data analyzed in this project are from the Healthcare Acoustics Research Team (HART) library of hospital research and includes 4 hospitals, 18 units, and several measurement locations in each unit. The large sample size provides a greater degree of certainty in the development of standard levels of noise exceeded over time in hospitals.
Distraction factors on doctors and nurses in open-plan examination room
Authors: Nadiroh Ainun , Arifianto Dhany , Purnami Nyilo
Published: November 2019

In Indonesia, there exist open-plan examination rooms in government-owned general hospitals serving thousands of patients each day. In this study, we developed a questionnaire with 70 questions to assess the effect of background noise level to 45 doctors-nurses working at pediatric, obstetrics and gynecology, and audiology clinics, respectively at Dr. Soetomo General Academical Hospital. The subjects have been working for more than five years. The background noise includes conversations, baby cries, announcements whose level is about 60 dBA daily. We used a simple statistical technique to determine the most to the least distracting sounds perceptually. The results are, then, crossed the spectrum of the background noises to find out the characteristic of the most intrusive noise. The results showed that the Pediatric clinic has the highest level and dominantly with high pitch baby cries in the waiting lounge. The distraction to either the medical doctor or the nurse may have lost of focus during an examination, determining a diagnosis based on the symptoms, attentively listening to the patient. Furthermore, the intrusive noise characteristic that distracted the staffs were perceptually different. In the on-going research, we investigate a suitable masker to reduce the intrusiveness of the background noises.
Recognition of marine sound events using an echo state reservoir and a K-nearest neighbor classifier
Authors: Graupe Cristian E. , Van Uffelen Lora J.
Published: November 2019

A sound event detection and classification algorithm was developed to sift through passive acoustic data, and to extract and classify signals of interest. Segments of data containing interesting sound events were identified from raw audio files using framing techniques and standard deviation-based event detection, and statistical acoustic features from the temporal and spectral domains were extracted for each segment. An adapted cyclical reservoir model was employed to accumulate time varying information over the duration of each sound event, evolving raw features to an echo state space representation with a fading temporal memory. A K-Nearest Neighbor classifier was trained on the echo states extracted from a library of recordings corresponding to broad classes of common ambient marine sound types and self-produced noise from autonomous underwater vehicles. A simple majority voting scheme was then utilized to obtain a single representative class label for each sound event. Validation of the classifier using available underwater acoustic libraries and passive acoustic datasets collected using Seagliders equipped with acoustic sensors indicates small improvements in both the per-frame and per-label performance for a model trained on states over one trained on raw features.
Modelling the coastal, ambient, marine noise field in space, time and frequency
Authors: Robinson Calder , Barclay David R. , Vagle Svein
Published: November 2019

The objective of this work is to model the natural ambient noise level in coastal regions based on local environmental forcing and propagation conditions. 546 continuous hours of noise were recorded between April 15 and May 7, 2018 in Sooke Inlet, British Columbia, a coastal, shallow-water region with complex bathymetry and diverse surface traffic. Optimal 1-hour lagged correlation between raw wind speed and hourly minimum sound pressure level (dB re 1 μPa/Hz) is computed as a function of frequency. Low frequencies (10–500 Hz) are characterized by poor correlation due to flow noise and near continuous shipping and small vessel traffic. Mid-frequencies (0.5–10 kHz) show increasing correlation with the shift from ship to wind dominated forcing. High frequencies (10 kHz +) show good correlation with wind. The empirically derived relationship between noise and wind speed is used to validate a predictive ambient noise model, driven by local weather and oceanographic conditions, an acoustic transmission loss model, and a wind to wave energy model. The noise model’s sensitivity to temporal and spatial resolution of environmental and forcing data, and knowledge of bathymetry and bottom type will be quantified with the objective of model portability to other coastal regions.
Scattering statistics of a negatively buoyant thermal plume
Authors: Forge Timothy B. , Olson Derek R.
Published: November 2019

High frequency acoustic scattering from inhomogeneous ocean environments is often assumed to be entirely coherent or incoherent. We hypothesize that the mean background stratification (which can also be interpreted as long-wavelength components of the inhomogeneity spectrum) cannot be ignored when estimating the total scattered power, leading to the sum of a coherent and incoherent component in the received pressure. In this work, we report laboratory measurements of scattering from a negatively buoyant thermal plume at 70, 120, and 200 kHz. Simple estimation of the coherent component was not possible because the sonar system rectified the signal. An alternative method to estimate the coherent component was to fit the pdf of the scattered field to a Rice distribution. It was found that at all frequencies, the pdf of the field scattered by plume boundary was lighter than Rayleigh and well fit by the Rice distribution. The coherent-to-incoherent power ratio of the field was highest for the lowest frequency. Scattering from the plume center was well fit by a Rayleigh distribution, indicating that the effect of background stratification is minimal away from the plume boundaries. Accompanying temperature and Doppler velocity measurements of the plume were used to support the acoustic measurements.
A time-domain model of high-frequency backscatter from sea ice with applications to upward looking sonar data analysis
Authors: Ivakin Anatoliy
Published: November 2019

Upward looking sonar (ULS) systems are commonly used in ice-covered environments to evaluate sea-ice draft and related characteristics (such as the ice thickness distribution). The involved backscatter data inversion algorithms are mostly based on estimating the two-way propagation time and using some simplifying assumptions which may result in significant limitations, uncertainties, and errors. This work is aimed to develop an improved remote sensing technique of sea-ice characterization based on a more detailed, physics-based analysis of the backscatter intensity time series, the echo shape. The underlying model accounts for two major mechanisms of high-frequency acoustic backscatter, the ice-water interface roughness and volume heterogeneity of the ice layer, provides an estimate of their relative contributions, and includes the echo parameterization in terms of ULS system characteristics (such as the frequency, transmitted pulse’ duration and shape, and the directivity pattern). Using this model, computer simulations were performed for the ULS received signal time series to provide a sensitivity analysis for various physical properties of the ice. Optimal parameters of the system to enhance the ice-properties’ inversion are suggested which, in particular, may result in a possibility to remotely discriminate between first-year and multi-year ice types. [Work supported by ONR.]
Catheter-mounted dual-frequency ultrasound transducers for intravascular contrast-enhanced superharmonic imaging
Authors: Kim Jinwook , Kasoji Sandeep , Markley Eric , jiang xiaoning , Dayton Paul
Published: November 2019

Vulnerable atherosclerotic plaques are a source of morbidity and mortality and are hypothesized to be correlated with abnormal development of microvasculature in arterial walls. Thus, there is an interest in assessing microvascularity for the plaque diagnosis. However, conventional catheter-delivered, high-frequency (>20 MHz) intravascular ultrasound imaging is unable to resolve vasa vasorum microvessels. We present here the development of a custom dual-frequency transducer-tipped catheter for contrast-enhanced superharmonic imaging of plaque-associated microvasculature. We exploit our previous design of the miniaturized dual-element, stacked-type needle transducer. A 4/22 MHz dual-frequency transducer with a lateral dimension of 800 μm is assembled with a 70 cm-long drive shaft inside a 4 Fr-catheter. We designed a 4 MHz-transmitter element to generate moderate amplitude (>1 MPa peak-negative-pressure) pulses for bubble excitation. A confocally aligned 22 MHz-receiver element is designed to detect contrast generated superharmonics (>10 MHz) with substantial tissue rejection. We tested the catheter in a tissue-mimicking phantom simulating an arterial lumen with surrounding microvasculature. The in vitro imaging data were acquired through a rotational pull-back (2 mm) imaging procedure with microbubble infusion. The resulting superharmonic images display a clearly defined microvessel with an approximated contrast-to-tissue ratio of 12 dB and an axial resolution of 300 μm.
Modifying whole blood oxygen levels via acoustic droplet vaporization nucleated with an intravascular ultrasound system
Authors: Jahanpanah Newsha , Benton Rachel P. , Bo Bin , Clark Abigail R. , Mercado-Shekhar Karla P. , Haworth Kevin J.
Published: November 2019

Tunable oxygen scavenging via acoustic droplet vaporization (ADV) has been demonstrated in buffers. Whole blood presents a unique challenge due to the potent oxygen carrying capacity of hemoglobin. The objective of this study was to determine whether whole blood hemoglobin oxygen saturation (SO2) and oxygen partial pressure (PO2) could be modified via ADV. Perfluoropentane droplets were manufactured using high-speed shaking and microfluidic protocols. Droplets and Definity® were diluted in anticoagulated bovine whole blood at concentrations up to 2.5 × 10-3 ml/ml and 1.5 × 10-4 ml/ml, respectively. The whole blood (SO2 = 96% and PO2 = 105 mmHg) was pumped through an in vitro flow phantom at 37 °C and exposed to ultrasound (2.35 MHz, 1.5 MPa peak negative pressure, 40 or 120-cycles, 2 ms pulse repetition period) using an EkoSonic® catheter driven with a function generator and amplifier. SO2 and PO2 were measured using inline optical sensors. The occurrence of ADV was concurrent with decreases in SO2 and PO2. Increasing droplet concentrations and ultrasound pulse durations resulted in larger decreases in SO2 and PO2 with reductions to venous gas values (SO2 = 84% and PO2 = 34 mmHg). These results demonstrate a change in whole blood oxygen content can occur by ADV using an intravascular ultrasound catheter.
Modeling nonlinear fractional diffusion-wave equations with Burgers-type evolution equations
Authors: Simon Blake E. , Hamilton Mark F.
Published: November 2019

Fractional partial differential equations (FPDEs) with a time derivative of fractional order are used to describe wave motion in complex viscoelastic media with non-traditional equations of motion. Kappler et al. [Phys. Rev. Fluids 2, 114804 (2017)] derived a fractional diffusion-wave equation for a nonlinear Lucassen wave propagating along an elastic layer coupled to a viscous substrate. The fractional time derivative of order 3/2 in the linear form of this equation lies midway between order 1 for a diffusion process described by a parabolic equation, and order 2 for the traditional hyperbolic wave equation. The inclusion of nonlinear elasticity tends to inhibit purely progressive wave motion that is associated with classical nonlinear plane waves in fluids and solids, and which is described accurately by parabolic-like, Burgers-type evolution equations. In this work, a general FPDE is analyzed in a parameter space consisting of varying nonlinearity and time fractional orders. The focus is on conditions under which the FPDE can be modeled accurately with a Burgers-type evolution equation for progressive wave motion. The method of lines in combination with a general Runge-Kutta method for forward integration is used for numerical analysis. [B.E.S. is supported by the ARL:UT McKinney Fellowship in Acoustics.]
Application of a multi-sector parabolic equation approach to compute acoustic scattering by non-canonically shaped impenetrable objects
Authors: Ramamurti Adith , Calvo David C.
Published: November 2019

While parabolic equation (PE) methods have seen great use in ocean acoustic waveguide propagation, it is not as widely known that a multi-sector PE method, originally proposed by Levy and Zaporozhets [J. Acoust. Soc. Am. 103, 735–741 (1998)], can be applied to compute the scattered field about an object. Previous work was only able to benchmark the method with canonical geometries. In this talk, we demonstrate favorable agreement between free-field PE-based and finite-element based computations, the latter being taken as a benchmark, in two and three dimensions for non-canonically shaped impenetrable objects. Run-time scaling comparisons are also presented, which demonstrate the great advantage of the PE method in the high-frequency limit when a target is several or more wavelengths long. We also show how wide-angle PE and multiple-scattering corrections can be incorporated to treat concave scatterers. [Work sponsored by the Office of Naval Research.]
Far-field acoustical measurements during GEM-63 static firings
Authors: Bassett Michael S. , Irarrazabal Francisco J. , Rasband Reese D. , Novakovich Daniel J. , Gee Kent L. , Jithame Raiarii , Johnson Jon P.
Published: November 2019

This paper expands on prior measurements and analyses of noise data from static rocket firings in northern Utah [e.g., see B. O. Reichman et al., Proc. Mtgs. Acoust. 25, 045006 (2017)]. Far-field acoustical measurements were made on two separate occasions for the GEM-63 motor, a 1660 kN-thrust solid-fuel booster. Measurements were taken at angles between 40 and 120 deg (relative to the plume direction) and distances of 985–1832 diameters from the nozzle, using both 6.35 mm and 12.7 mm diameter microphones and at sampling rates of at least 50 kHz. This paper discusses the measurement setups, as well as other appreciable features relevant for data analysis, such as the local meteorology and surrounding terrain. Statistical, spectral, and correlation analyses are used to understand the frequency and temporal characteristics of the noise as a function of angle, as well as consistency between the two motor tests. [Work supported in part by NSF and NASA.]
Spectral analysis of directivity and source location of turbulent jet noise
Authors: Schmidt Oliver T. , Nekkanti Akhil
Published: November 2019

We use spectral proper orthogonal decomposition (SPOD) of two high-fidelity numerical simulation databases of turbulent jets at M = 0.9 and M = 1.5 to investigate the directivity of jet noise. By spatially windowing the SPOD, we investigate the dependence of the far-field pressure PSD as a function of radiation angle on frequency, and study the source location of different modal contributions. The low-rank behavior of the far-field sound is addressed by reconstructing the total PSD using the leading SPOD modes. To understand the energetically most efficient mechanisms of energy transfer from hydrodynamic fluctuations in the near-field to the acoustic far-field, we further solve a generalized SPOD eigenvalue problem that was originally devised for the empirical computation of resolvent modes from data. Here, we specialize this method to optimal input-output relations between different components of the state vector.
Furthering resolvent-based jet noise models
Authors: Pickering Ethan M. , Colonius Tim
Published: November 2019

Resolvent analysis continues to provide promising results for modeling the hydrodynamic near-field and acoustic far-field in turbulent jets, particularly when compared to modes deduced through spectral proper orthogonal decomposition (SPOD) of high-fidelity large eddy simulations (LES). Although previous studies have shown that the acoustic field for supersonic jets is of low-rank and primarily described by the Kelvin-Helmholtz instability, the agreement between the acoustically optimal resolvent mode (Kelvin-Helmholtz) and optimal SPOD mode is still lacking. The discrepancy is due to the spatial coloring of turbulent mechanisms in supersonic jets and presents a challenge for reconstructing the acoustic field, as well as the full field flow statistics. To account for coloring, additional (i.e., suboptimal) resolvent modes, associated with the Orr mechanism, must be included and their correlation to other modes determined. Here, we estimate the coloring between resolvent modes by projecting onto an ensemble of LES realizations and reconstructing the realizations in the resolvent basis. The associated projection coefficients provide an ensemble of observations which inherently possess the statistical information necessary to reconstruct the flow and to which we propose a reduced-order stochastic model. We find that the inclusion of a few resolvent suboptimal modes (i.e., Orr-type) allows for modeling of the acoustic field to within 2 dB and increases the region of acoustic agreement when compared to a single mechanism model.
Laboratory simulations of conversation scenarios: questionnaire results from patient and partner
Authors: Nelson Peggy B. , Anderson Elizabeth , Beechey Timothy
Published: November 2019

Hearing-related questionnaires can reveal much about the daily experience of hearing aid users. Nonetheless, results may not fully reflect the lived experience for several reasons, including: users’ limited awareness of all communication challenges, limitations of memory, and the subjective nature of reporting. Multiple factors can influence results obtained from questionnaires (Nelson et al. ASA Louisville). Consideration of the perspectives of both hearing aid wearers and communication partners may better reflect the challenges of two-way everyday communication. We have developed simulations of challenging conversational scenarios so that clients and their partners can make judgments of sensory aid performance in realistic, but controlled conditions. Listeners with hearing loss and their partners use a client-oriented scale (adapted from the COSI, Dillon, 1997) to report challenging listening conditions such as small group conversations, phone conversations, health reports, and media. Representative scenarios are simulated in the laboratory where clients and partners make ratings of intelligibility, quality, and preference. Results are compared to outcome measures such as the Speech, Spatial and Qualities of Hearing Scale (SSQ, Gatehouse and Noble, 2004) and Social Participation Restrictions Questionnaire (SPaRQ, Heffernan et al., 2018). Results will help refine methods for evaluating the performance of emerging technologies for hearing loss.
Sound-source localization when listeners and sound sources rotate: The Auditory Filehne illusion
Authors: Yost William , Pastore M. Torben
Published: November 2019

Wallach [J. Exp. Psychol. (1940)] pointed out that localizing a sound source in the three-dimensional world depends on an integration of information about auditory-spatial and head-position cues. Yost et al. (JASA, 2015 and 2019) suggested that a simple sum of the two cues might account for world-centric sound-source localization. Freeman et al. [J. Exp. Psychol.: Hum. Percept. Perform.(2017)] showed that there is an auditory analog to the visual Filehne illusion (FI). For the auditory FI, a stationary sound source is sometimes perceived as rotating in the opposite direction of head rotation. The perception of a stationary sound source appears to occur when the sound-source also rotates at a rate that is approximately 15% of the head rotation rate. Thus, the integration of auditory-spatial and head-position cues may not be a simple sum. We investigated conditions like the auditory FI for a variety of stimulus and rotation conditions to gain additional insights into how auditory-spatial and head-position cues are integrated for world-centric sound-source localization. [Research supported by grants from NIH (NIDCD), R01DC015214 to WAY; F32DC016808 to MTP; and Facebook Reality Labs to WAY&MTP.]
“Phantom Words” are heard more frequently as coming from the right side of space
Authors: Deutsch Diana , Dooley Kevin , Henthorn Trevor
Published: November 2019

To experience the “Phantom Words” illusion (Deutsch, 2003) the listener sits in front of two loudspeakers, with one to the left and the other to the right. A sequence is repeatedly presented consisting of two monosyllabic words, or one word composed of two syllables. The sequences coming from both loudspeakers are identical; however, they are offset in time so that when the first sound (word or syllable) is coming from the speaker on the right the second sound is coming from the speaker on the left; and vice versa. Listeners generally perceive different illusory words and phrases, and those appearing as from the right are often different from those appearing as from the left. Here, 20 righthanders and 20 non-righthanders (left-handers and mixed handers) listened to seven such sequences. For each handedness group, ten subjects were seated facing the loudspeakers and ten were seated facing the opposite direction. There was a highly significant tendency for righthanders to hear illusory words and phrases as coming from their right, regardless of their orientation relative to the loudspeakers. Non-righthanders also showed this tendency, but it was less pronounced. Implications for cerebral dominance are here discussed, and illusory sequences are presented as sound examples.