bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental drivers of the low-frequency ambient noise on the Chukchi Shelf
Authors: Bonnel Julien , Kinda Bazile , Zitterbart Daniel P.
Published: November 2021

This study presents an analysis of the low frequency (250–350 Hz) ambient noise (after individual transient signals are removed) recorded on the Chukchi shelf during the CANAPE experiment from October 2016 to July 2017. Ambient noise drivers are evaluated by correlating noise levels with external oceanographic data including local wind speed, local ice coverage, and distant ice drift magnitude. Also, the experimental area is known to be home of the Beaufort duct, a warm layer intrusion which creates an acoustic channel that favors long range propagation and impacts the ambient noise. The study shows that, as usual in polar areas, the ambient noise is quieter and wind force influence is reduced when the sea is ice-covered. More interestingly, the study demonstrates that the ambient noise drastically reduce (up to 10 dB/Hz) when the Beaufort duct disappears. It also shows that a large part of the noise variability is driven by distant cryogenic events. [Work supported by the Independent Research & Development Program at WHOI and by the Office of Naval Research.]
Estimation of gassy sediment parameters in shallow water using shipping noise signals in frequency domain near cut-off
Authors: Yarina Marina , Lunkov Andrey , Katsnelson Boris
Published: November 2021

Modal structure of shipping noise in a shallow water waveguide is studied experimentally and theoretically. Experiments were carried out in the Sea of Galilee (Lake Kinneret, Israel) having maximal depth of 40.5 m and remarkable concentration of methane bubbles in the upper sedimentary layer. Receiving system consisted of 27-m vertical line arrays (VLAs) with ten hydrophones at each. They spanned a lower part of the waveguide with interval ∼3 m. The VLAs were fixed in the centre of the lake with the distance ∼40 m between them. R/V “Hermona” was moving along a straight line connecting VLAs at the range of up to 1 km from the arrays. Modal filtration technique on two synchronized VLAs with a phase correction was proposed to extract complex eigenvalues of each mode, including modal attenuation, which strongly increase in the proximity of cut-off frequency for all normal modes. Based on frequency dependences of attenuation coefficients of lower modes, sound speed in gas-saturated bottom layer was estimated. For application of this technique, there is no need to know exact coordinate and speed of noise source, which seems to us to be an advantage of the method. [Work was supported by RFBR, Grant No. 20-05-00119.]
Fisher information and Cramér-Rao bound analysis with stable gradients for ocean acoustic models
Authors: Mortenson Michael C. , Neilsen Tracianne B. , Transtrum Mark K. , Knobles David P.
Published: November 2021

The Fisher Information Matrix (FIM) and the Cramér-Rao Bound (CRB) are powerful tools for quantifying uncertainty in multi-parameter models. However, it is difficult to estimate the derivatives needed to calculate the FIM and CRB in ocean acoustic models. In this work, a methodology for estimating derivatives using physics-guided parameter preconditioning and Richardson extrapolation is presented. The method is validated on a case study of transmission loss from a range-independent normal mode model in ocean environments with a single sediment layer over a basalt basement. Five examples of sediment types ranging from mud to gravel are considered across frequencies from 50–400 Hz. Results demonstrate the utility of FIM and CRB analysis in quantifying both model sensitivities and parameter uncertainties, and in revealing parameter coupling in the model. This methodology is a general tool that can inform model selection and experimental design for inverse problem applications. [Work supported by ONR Contract No. N00014-19-C-2001.]
Comparison of measured and modeled speed of sound in the challenger deep
Authors: Loranger Scott , Barclay David R.
Published: November 2021

Echo sounding and acoustic propagation in the hadal zone (depths below 6 km) rely on models of sound speed that suffer from uncertainty due to a paucity of measurements at those depths. In order to assess models of sound speed in deep water, and to provide additional measurements, the Deep Acoustic Lander, a passive acoustic profiler, was deployed into the Mariana Trench from the RV Pressure Drop in April 2021. The Deep Acoustic Lander houses an array of hydrophones along with an AML Scientific CTD and AML MinosX sound speed meter. Pressure, temperature and salinity data measured by the CTD were used to inform some of the most commonly used sound speed models. The modeled sound speed was then compared with direct measurements of the speed of sound in the hadal zone to depths beyond 10 000 m. The goodness of fit between each model and the direct measurements was then compared to assess the performance of each model in deep water.
Predicting the acoustic energy radiated by melting glacier ice
Authors: Johnson Hayden A. , Deane Grant B. , Stokes M. Dale , Glowacki Oskar , Moskalik Mateusz , Chitre Mandar , Vishnu Hari
Published: November 2021

Ice sheets are expected to be major contributors to sea level rise in the coming decades and centuries. Ocean-forced melting at marine terminating glaciers has the potential to be an important driver of mass loss from these ice sheets, but is difficult to measure directly using conventional techniques, and thus remains poorly understood. The air pressure in bubbles trapped in glacier ice is typically greater than the hydrostatic pressure near the surface of the water. This pressure difference causes the bubbles to expand rapidly and radiate sound when they are released as the ice melts. This sound presents a promising signal which could be used to make passive acoustic measurements of submarine melting at glacier termini, if it can be characterized sufficiently. Prior work has demonstrated that there is considerable variability in the acoustic energy radiated by the release of individual bubbles. Here we show that the total acoustic energy radiated by small blocks of glacier ice as they melt is correlated with the total potential energy stored by the compressed air bubbles in the ice. We find that the conversion efficiency is highest for the most energetic blocks of ice, and present some modelling efforts to explain this trend.
Diminishing comminution of urinary stones with subsequent laser pulses
Authors: Pishchalnikov Yuri A. , Behnke-Parks William M. , Stoller Marshall L.
Published: November 2021

Ureteroscopic lithotripsy with Holmium:YAG lasers is a common treatment for urinary stones but the physical mechanisms of stone comminution are still under investigation. The dominant mechanisms were reported to be associated with the direct action of light on the stone surface causing the photothermal decomposition of stones and explosive vaporization of interstitial water. The objective of this study was to better understand stone fragmentation by the direct action of light and other potential mechanisms (cavitation) using ultra-high-speed video microscopy. Stone fragmentation was quantitatively assessed using an Open-source library of Computer Vision algorithms (OpenCV) with programs written in Python. Stone fragments were identified by detecting difference between the images and tracked with identification numbers considering cross-section areas and velocities of the fragments. Images of stone comminution were collected using a Shimadzu HPV-X2 camera at 200 000–500 000 fps with dry stones in air and those hydrated in water. Stone fragmentation by the direct action of light was observed to diminish with subsequent laser pulses. The diminishing fragmentation, however, was offset by the action of cavitation bubbles that continued to erode and fragment stone surface, augmenting stone breakage with subsequent laser pulses. [Work supported by the NIDDK of the NIH under Award R43DK129104.]
Dual mode piezoelectric lithotripter for efficient breakup of urinary stones
Authors: Hall Timothy L. , Roberts William W.
Published: November 2021

The coalescence and dispersion of cavitation bubbles through Bjerknes forces created by supplemental low amplitude acoustic fields has been shown to greatly improve the efficiency of shockwave lithotripsy for breaking urinary stones. Unfortunately, the large size of extracorporeal lithotripters typically leaves little acoustic window for additional transducers to create these fields. In this study, we explored the feasibility of using a piezoelectric lithotripter transducer in a dual mode generating both shockwaves for stone comminution and low amplitude tone bursts for bubble coalescence and dispersion. A piezoelectric lithotripter head and driver unit (piezolith 3000) was provided by the manufacturer (Richard Wolf GmbH). A custom class-D driver circuit was constructed from very high voltage blocking IGBTs and wired in parallel with the manufacturer’s excitation circuit for shockwave generation. Acoustic output was measured with a fiber optic probe hydrophone at the focus in a tank of degassed water. The driver produced acceptable 200 kHz tone bursts of 5–100 cycles up to at least 1 MPa amplitude. Lithotripter power settings 1–3 could be safely used with the combined driver and were sufficient to break model begostones in vitro. Future studies will compare efficiency of stone comminution using the dual mode system.
Single-framework simulations of acoustic-wave–bubble cloud–stone interactions
Authors: Spratt Jean-Sebastien A. , Rodriguez Mauro , Bryngelson Spencer H. , Cao Shunxiang , Colonius Tim
Published: November 2021

Understanding the interaction of acoustic waves and stones is of principal importance to the development and optimization of shock wave and ultrasound-based therapies, such as shock wave and burst wave lithotripsy (SWL and BWL). Simulating these interactions is useful in furthering our understanding, but the development of simulation tools is complex. These tools often use separate numerical frameworks for compressible fluids and solids. Introducing cavitating bubble clouds which can occur during these therapies further complicates the problem, introducing a broad range of relevant spatio-temporal scales. To tackle these challenges, we have developed a single-framework code capable of simulating all relevant physics. Cavitating bubble clouds are introduced via a sub-grid model, and a hypoelastic model simulates solid materials, all in the same Eulerian framework. These are implemented in our open-source Multi-component Flow Code (MFC) [Bryngelson et al., Comp. Phys. Commun. (2020)]. We demonstrate the solver's capabilities for 3D SWL and BWL simulations, where we can obtain the stress state in the stone for various configurations. GPU-accelerated simulations also elucidate the computational advantages of the single-framework approach. [This research was supported by the National Institutes of Health (NIH Grant No. 2P01-DK043881) and the Office of Naval Research (ONR Grant No. N0014-18-1-2625).]
The importance of acoustic cavitation in the evolving technologies of therapeutic ultrasound
Authors: Crum Lawrence A.
Published: November 2021

Cavitation has played an active and important role in the development of therapeutic ultrasound. From its vital role in the effectiveness of lithotripsy to its essential role in the application of histotripsy, the awareness of cavitation must be considered in practically every clinical implementation of High Intensity Focused Ultrasound. This lecture will present several examples of how cavitation has been an essential ingredient of many current and promising therapeutic ultrasound methodologies and technologies.
Cavitation and microbubble modeling
Authors: Church Charles C.
Published: November 2021

Bubbles in tissue may either help or hinder biomedical ultrasound. Exogenously introduced ultrasound contrast agents may comprise suspensions of micrometer-sized gas bubbles of sulfur hexafluoride, perfluorocarbon, or other low-solubility gas that are stabilized against dissolution by shells of lipids, proteins or synthetic, or alternatively, quasi-stable micro-droplets of certain liquids that nucleate gas bubbles in response to an impinging acoustic beam. However, tiny vapor bubbles may form spontaneously in tissues and act as potentially damaging cavitation nuclei under the influence of an acoustic wave. Microbubbles respond to the acoustic field by contracting and expanding to a much greater extent than does the surrounding tissue. This ‘acoustic cavitation’ may be violent, producing highly reactive chemical species, emission of ultraviolet and soft x-ray photons, and radiated shock waves, or less powerful, inducing, e.g., continuous heat production, radiation forces on neighboring particles, and microstreaming. Much early work assumed cavitation bubbles were surrounded by simple liquids, but biological tissues are viscoelastic, which can significantly affect bubble responses and thus must be considered. Mathematical models for these and related processes will be presented and compared, and details of their various physical mechanisms and the effects they may produce in biological tissue will be discussed.
Comparison of dry or wetted sand column vibrating over a clamped elastic plate: A nonlinear sand-plate-oscillator
Authors: Santos Emily V. , Korman Murray S.
Published: November 2021

The sand plate oscillator apparatus uses two aluminum circular flanges sandwiching and clamping a thin circular elastic acrylic plate (density 1.21 g/cc). Dry sifted or wetted masonry sand is supported at the bottom by the clamped acrylic plate (4.5 in.) and stiff cylindrical sidewalls. Sifted masonry sand has a density of 1.55 g/cc. An accelerometer centered on the plate measures vibration response using a swept tone spectrum analyzer between 50 and 850 Hz. The plate was driven from below by a small loudspeaker. Three experiments were performed. (1) Nonlinear tuning curve response required driving the loudspeaker and incrementing the signal amplitude between sweeps. A fixed column of 354 g of dry masonry sand was used, with comparisons when 0, 11, 22, and 33 g of water were carefully sprayed on. (2) At constant drive amplitude, tuning curve response with 354 g of dry sifted sand was compared with results when 2 g of water were sprayed every 104 s. (3) Fixed drive amplitude tuning curves for incremental dry sand loading with 47 g for each layer were compared to incremental layers of 47g dry sand sprayed with 12 g water. The wetted sand had increased stiffness.
Acoustoelastic wave propagation in initially stressed solids using a pure stress formulation
Authors: Kube Christopher M. , Norris Andrew N.
Published: November 2021

Wave propagation in homogeneous elastic solids is governed by Cauchy's first law of motion, which relates the acceleration of material points to the divergence of stress. For Hookean solids, the stress is typically written in terms of displacements to form an equation of motion with displacement as the dependent variable, i.e., Navier's equation of elastodynamics. Previously, the authors considered wave propagation in anisotropic elastic solids by formulating the equation of motion using only stress as the dependent variable. Eigenvalue solutions provided the (stress) wave phase velocity in terms of elastic compliance constants. In this presentation, the stress formalism is extended and applied to the nonlinear problem of stress wave propagation in an initially stressed material (also known as acoustoelasticity). The stress formulation is viewed as a more natural fit over historical derivations, which were based on wave displacements superimposed on an initially strained material state. The stress formulation of elastodynamics is firstly reviewed. Then, the extension to stress wave propagation in an initially stressed material is given. The phase velocity of the stress wave is related to the initial stress through second- and third-order compliance constants (instead of elastic stiffnesses in traditional acoustoelasticity).
Influence of residual stress on the free vibrations of an elastic solid; application to resonant ultrasound spectroscopy (RUS)
Authors: Kube Christopher M. , Gillespie Jared
Published: November 2021

Resonant ultrasound spectroscopy (RUS) is a standard technique for experimentally measuring the elastic constants of anisotropic elastic materials. Traditionally, the influence of internal or residual stresses on the measurement of elastic constants is not taken into consideration. However, it is well-known that residual stress can impart a small variation in the phase velocity of ultrasonic bulk waves, which is known as the acoustoelastic effect. Thus, it is plausible that residual stress will influence the resonances of samples measured during RUS. In this presentation, the elastodynamic theory for describing free vibrations is reformulated by using a stress-dependent constitutive relationship. The model culminates in an eigenvalue problem with a stiffness matrix being dependent on the spatially varying residual stress field within the domain of the sample. The model is evaluated by considering a realistic residual stress distribution. Results show the degree at which frequencies of resonance depend on the residual stress. While accounting for residual stress is expected to improve the estimates of elastic constants, there is also potential to use RUS as a tool to assess and characterize the residual stress present in samples.
Improved understanding of natural weathering on the seismic-to-acoustic coupling ratio over buried containers
Authors: Sabatier James , Hubbard Brandon
Published: November 2021

The long term effects of natural weathering on the acoustic-to-seismic coupling ratio over buried containers is being investigated at a test site near the campus of the University of Mississippi. The weathering experiment has been carried out over five years. Two containers were buried at a 30 cm depth in 2014 and the coupling ratio monitored during 2014 and 2017. During this time period the soil matrix was not disturbed. Four different containers, buried at 15 cm in 2021, are exposed to the natural weather and the coupling ratio is being monitored. The soil water potential or pressure is measured continuously over the measurement periods. This talk will present the long-term effects of natural weathering on the ratio of normal velocity component of a surface geophone normalized by a surface microphone in response to normally incident airborne sound. As the soil matrix dries it becomes more consolidated increasing the soil acoustic stiffness, the S/A ratio becomes less sensitive to the hydraulic capillary pore pressure. During the rainy season, the soil consolidation relaxes resulting in an increased coupling ratio. The phenomenon is cyclical with the local annual soil wetting and drying cycles.
Far-field acoustic subwavelength imaging with blind structured illumination
Authors: Lin Jinuan , Ma Chu
Published: November 2021

The blind structured illumination microscopy (blind-SIM) is an optical method to surpass the diffraction limit, a fundamental limitation to all wave-based imaging techniques. By illuminating the object with multiple structured illumination patterns, the spatial frequency mixing between the object and the illuminations converts evanescent waves to propagating waves that can be detected by sensors in the far field. In this work, we develop blind-SIM in the acoustic domain. The blind acoustic structured illuminations (ASI) are generated by randomly located scatterers with subwavelength spatial distributions. The image of the object can be reconstructed with a subwavelength resolution from multiple far-field measurements (each produced by an ASI pattern) utilizing a compressed sensing algorithm. We demonstrate subwavelength acoustic imaging resolution in both kilohertz airborne and megahertz underwater acoustic imaging systems. The developed blind-SIM method has great potential in medical imaging, non-destructive testing, and underwater acoustic imaging for improving the imaging resolution of objects far away from the sensors.
Unbounded full-aperture acoustic wave experimentation using multidimensional deconvolution
Authors: Li Xun , Becker Theodor , Ravasi Matteo , Robertsson Johan , van Manen Dirk-Jan
Published: November 2021

Physical experiments are set up to study acoustic wave propagation in a laboratory. However, wave propagation experiments carried out in a size-limited volume often suffer from unwanted reflections at the boundaries of the experimental domain. We propose a method of multidimensional deconvolution (MDD) to process recorded data such that the undesired imprint of the laboratory boundary is completely removed from the data. The MDD results consist of Green's functions between any pair of points on a mathematically closed receiver surface, sampling the scattering wavefield related to an object of interest with a full aperture. We apply the MDD algorithm to process data recorded in a 2D acoustic waveguide in which a rigid steel block is placed inside of a circular recording array. The scattering imprint of the waveguide boundary is removed from the data, and the scattering Green’s functions only related to this steel block are obtained. The MDD methodology used for the physical experiment is also validated using synthetic simulations; this further corroborates the effectiveness of MDD in obtaining the desired Green's functions associated with arbitrary scatterers in unbounded domains.
Subcortical measures of individual tolerance to background noise and sensitivity to speech distortions induced by noise-reduction processing
Authors: Kim Subong , Bharadwaj Hari
Published: November 2021

Listeners with sensorineural hearing loss have significant difficulty understanding speech in noisy environments. Thus, current digital hearing aids employ noise-reduction (NR) algorithms to suppress background noise. Unfortunately, the NR algorithms distort some speech cues. Though considerable variability exists in hearing-aid users’ reactions to these conflicting effects, little is known about the neural underpinnings contributing to the variance in perceptual outcomes with the addition of noise and the use of NR processing. Recently, we documented that neuroimaging-based measures of cortical responses can predict individual speech-in-noise perception benefits (or lack thereof) from NR processing. Here, we describe novel objective subcortical measures for quantifying individual noise tolerance and individual sensitivity to speech-cue distortions. Preliminary results show that the effect of adding noise and introducing NR processing on brainstem responses varies considerably across individuals. Because the brainstem responses are relatively unaffected by cognitive processes like selective attention, these preliminary results suggest an independent “bottom-up” contribution to individual variations in NR benefits. We will also discuss how the neurophysiological measures of subcortical encoding of speech sounds relate to individual profiles of peripheral (cochlear) pathophysiology and to individual perceptual outcomes.
Development of temporal cues perception in noise and reverberation
Authors: Peng Ellen , Easwar Viji
Published: November 2021

When compared to adults, children’s speech perception is particularly vulnerable to reverberation from indoor environments such as classrooms. Temporal acoustic cues, such as amplitude modulation (AM) and voice onset time (VOT), provide important information for perceiving speech in noise, and are susceptible to temporal smearing from reverberation. How children develop the ability to perceive distorted temporal cues is not well understood. Here, we compared school-age children between 9–14 years old with adults on their perception of temporal cues in quiet, in speech-shaped noise (SSN), in moderate reverberation, and in combined SSN with reverberation. In experiment 1, we measured children’s just-noticeable-difference threshold of detecting AM depth at the rate of the fundamental frequency (F0; ∼100 Hz). In experiment 2, we measured children’s categorical boundary of VOT using a voiced-voiceless /b/-/p/ consonant contrast. Preliminary findings suggest that the elevation of AM thresholds at F0 is more strongly affected by noise rather than reverberation. On the contrary, the salience of VOT is harder to maintain in reverberation than in noise, resulting in a more biased percept toward voiced consonant. Further, our preliminary analysis suggests that adverse acoustics lead to more severe performance deterioration in children than adults for both temporal cues of interest.
Perceptual weighting of acoustic cues for word stress in normal hearing listeners and cochlear implant users
Authors: Fleming Justin T. , Winn Matthew B.
Published: November 2021

Accurate perception of word stress is key to segmenting and understanding speech. We examined perception of four acoustic cues to word stress in English—vowel quality (VQ), pitch, syllable duration, and intensity—and how perception of these cues is affected by specific kinds of signal degradation. Cochlear implants (CIs) severely degrade VQ and pitch, which could demand different relative reliance on these cues. We tested NH listeners in unprocessed, vocoded, and simulated bimodal (unprocessed low frequencies, vocoded high frequencies) conditions as well as CI users. Stimuli included stress-contrastive word pairs (DESert versus dessERT, SUBject versus subJECT) with orthogonal manipulations of each cue. For both NH and CI listeners, there were strikingly different patterns of cue weighting between these word pairs, highlighting how stress cue weighting is flexible across words rather than being absolute. Vocoding the stimuli led to a downweighting of VQ and pitch cues and a compensatory upweighting of duration and intensity; perception of pitch and VQ were largely restored in the bimodal conditions with 250 and 800 Hz bands preserved, respectively. CI users relied on duration more than the NH controls in any condition, while also showing a surprising ability to use VQ and pitch cues.
Individual perceptual profiles derived from automated psychophysical measures
Authors: Cherri Dana , Eddins David A. , Ozmeral Erol J.
Published: November 2021

Older adults with normal pure-tone thresholds or with age-related hearing loss face difficulties understanding speech in noisy environments. Despite this common challenge, the potential root deficits are likely heterogeneous across listeners and vary in the extent of severity beyond pure tone sensitivity. To better serve patients with listening challenges, it is believed that more precision in diagnostics and treatment are currently needed, and to that end, the purpose of the present study was to achieve more robust auditory perceptual profiles from a diverse population. Specifically, the present study tested three groups of listeners (young, normal hearing; older, normal hearing, and older, hearing-impaired; n = 20 per group) on a large battery of psychophysical measures using the Portable Automated Rapid Testing (PART) platform, which includes automated, unsupervised measures of: spectral resolution, temporal resolution, informational masking, binaural processing, working memory, and visual-spatial processing. Data show significant differences between the younger and older listeners, and broad variations in perceptual measures among the older listeners with normal hearing and hearing loss. These multi-dimensional variations were reduced using confirmatory factor analysis to reveal unique perceptual profiles that one day may inform targeted intervention options. [Work supported by NIHR21DC017832 and NIHR01DC01505.]
Lateralization biases for narrowband stimuli in listeners with typical and symmetrical hearing thresholds
Authors: Goupell Matthew J. , Best Virginia , Colburn H. S.
Published: November 2021

In listeners with normal audiometric thresholds, it is assumed that stimuli presented over headphones with zero interaural differences are perceived to be centered in the head. In this study, intracranial lateralization was measured by having ten young adults with normal and interaurally symmetric thresholds (within 5 dB) point to perceived sound locations along a visual reference scale. The stimuli were either tones or 50-Hz-bandwidth narrowband noises, at frequencies of 300, 400, 500, 600, and 700 Hz. A range of interaural time differences (ITDs) was applied while the interaural level difference was always zero. To diminish any transducer-based effects, the headphones were reset and reversed between each of ten blocks of trials. Lateralization curves for five of the ten listeners showed a substantial bias to one ear at a subset or all frequencies tested; the worst individual case demonstrated a perceived 60% lateralization bias (from the midline to the left ear) for a zero ITD. This result challenges a long-standing assumption held in binaural hearing and, while similar results have been observed previously, the basis of the phenomenon remains largely unexplored.
Development of an auditory fitness-for-duty standard that predicts performance in military hearing tasks from auditory thresholds and performance on the 80-word modified rhyme test
Authors: Brungart Douglas S. , Sheffield Benjamin , Makashay Matthew J. , Galloza Hector
Published: November 2021

Military operations often require Service Members (SMs) to make life-and-death decisions based on information they can only obtain auditorily. However, the wide variety of critical sounds, essential spoken messages, and masking environments encountered while performing military missions makes it difficult to use clinical tests to predict the operational performance of hearing-impaired SMs. In this study, ≈2400 SMs performed listening tasks derived from binaural recordings made during realistic battlefield exercises at the US Army Joint Readiness Training Center. The listening tasks included standardized speech recognition tasks based on the Oldenburg Matrix Test and Modified Rhyme Test (MRT), as well as scenario-based multiple-choice tasks where questions were asked about unmodified verbal exchanges that occurred between SMs engaged in the battlefield simulation. The scores SMs achieved on these operational tasks were then compared to their hearing thresholds and to their scores on the MRT80. The results show that an auditory fitness-for-duty standard that requires individuals with thresholds that exceed the values defined in the new US Army H3 Profile to obtain a minimum score on the MRT80 is generally able to identify individuals who are most at risk of performing abnormally poorly on militarily relevant listening tasks. [The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of the Army, Department of Defense, or U.S. Government.]
Individual band-importance functions for children with normal hearing and children with hearing loss
Authors: McCreery Ryan , Bosen Adam K. , Spratford Meredith , Walker Elizabeth
Published: November 2021

Band-importance functions represent the contributions of frequency regions to speech recognition. Average band-importance functions for adults with normal hearing are used to estimate speech intelligibility and in hearing-aid signal processing. Children and listeners with hearing loss show considerable individual variability in band-importance, but the factors that contribute to differences in band-importance are not well-understood. Two experiments were conducted to examine auditory and developmental factors that predicted individual band-importance for children with normal hearing and children with hearing loss. In the first experiment, the effects of receptive vocabulary and selective attention on band-importance for 5–12 year-old children with normal hearing was measured for words and nonwords. Our hypothesis was that children with larger vocabularies and better selective attention skills would have larger importance weights for mid-frequencies, a pattern consistent with adult band-importance functions than children with poorer skills in these domains. In the second experiment, the effects of audibility on band-importance functions for a group of children with mild-to-moderate sensorineural hearing loss was measured for words. Our hypothesis was that band-importance would be higher for bands where children had better audibility through their hearing aids. The results confirmed these hypotheses. Implications for future research are discussed.
Predicting the effect of hearing-protection devices on horizontal-plane sound localization
Authors: Spencer Nathaniel J. , Ennis Zachariah N. , Jackson Natalie , Simpson Brian D. , Thompson Eric R.
Published: November 2021

Hearing-protection devices (HPD) are critical to hearing health in hazardous noise environments, but can be detrimental to job effectiveness and safety when degrading a wearer’s sound localization accuracy. Understanding specifically how localization is disrupted by HPDs is critical for mitigating the deleterious effects of HPDs on situation awareness. This study attempts to better quantify the effects of the degradations by predicting horizontal sound localization. A 360 deg horizontal array with 10 deg between-speaker spacing is used to collect head-related transfer functions (HRTFs) and to measure localization [ANSI/ASA S3.71] for the different conditions (open-ear, passive plugs, and both passive and active muffs). Our model attempts to select the response location that was most likely to have elicited the observed stimulus for the trial, by comparing narrow-band statistics between prior knowledge (“templates”) and trial observations. Bone conduction related noise is added, and the degree to which the priors are “device-related” (i.e., based on HRTFs captured for the device) or “open ear” related is varied. Results are discussed in terms of two potential mechanisms: (1) the wrong location is chosen due to a prior/template mismatch in percent device-related and (2) multiple response locations are viable because cue variability is reduced between locations compared to within.
Application of methods to determine time-dependent damping of flanged, bolted plates
Authors: Jerome Trevor W.
Published: November 2021

The dynamic and steady-state response of flanged, bolted plates when excited with a hammer and acoustic methods exhibit nonlinear effects. Established Hilbert methods are used to estimate time-dependent and amplitude-dependent damping due to the joint, and the findings are presented here. Nonlinear damping of this system is sensitive to boundary conditions, and each of the first few modes behave nonlinearly in unique ways. Insight gained from knowledge about relationships between amplitude and damping may help to better understand friction joint dynamics.
Broadband vibration attenuation via nonlocal acoustic black hole metastructures
Authors: Nair Siddharth , Jokar Mehdi , Semperlotti Fabio
Published: November 2021

In recent years, the application of Acoustic Black Holes (ABH) to passive vibration attenuation, vibroacoustic control, and vibration-based energy harvesting of thin walled structures has seen a rapidly growing interest. It is well known that the dynamic operating range of an ABH is limited by the existence of a cut-on frequency below which the ABH is not effective. The specific value of this frequency bound is connected to the ABH characteristic dimension, typically its diameter. In order to expand the dynamic operating range and lower the cut-on frequency, ABH features require larger diameters. However, design and manufacturing constraints impose stringent limitations that are often incompatible with required ABH dimensions. This work introduces the concept of nonlocal ABH metastructures and explores the feasibility of using intentionally introduced nonlocality to extend the dynamic operating range of periodic ABH lattices towards the lower frequencies. The role of nonlocality is investigated via a dedicated semi-analytical model, and the dynamic performances of different nonlocal designs are studied numerically. Results show a remarkable ability of the nonlocal design to expand the operating range of the ABH metastructure and to achieve vibration attenuation behavior at frequencies significantly below the cut-on frequency of the individual ABH.
Experimental evaluation of carbon/epoxy laminates with concentrated carbon nanotube interlayers for high damping
Authors: Brown Avery , Bakis Charles E. , Smith Edward
Published: November 2021

Carbon nanotubes (CNTs) embedded in carbon/epoxy (c/ep) composites offer a lightweight, stiff solution with high damping for structural components. To manufacture CNT/c/ep hybrid composites with high concentrations of CNTs, a CNT yarn interlayer concept is used. Through a mechanism known as stick-slip, the interface between CNTs and c/ep laminates dissipate energy during dynamic cycling. It is predicted that altering the interfacial bond strength can enhance dynamic properties: loss factor, loss modulus, and storage modulus. In this research, the effect of surface treatments on CNT yarns prior to inserting the CNTs into the laminate was explored to determine if the dynamic properties of the composite were enhanced. It was determined that 2,3-dibromo-1,4-butanediol (23D14B), Triton X-100 (TX) and a solution of sulfuric and nitric (S/N Acid) were the best treatments of 12 tested based on the increased dynamic properties. For a composite with 5 vol% CNT yarn interlayers, 23D14B, TX, and S/N Acid increased Loss Factor by 230%, 130%, and 160%, respectively. Elevated temperature, moisture-saturated/elevated temperature, and cyclic loading frequency were investigated on 5vol. % CNT interlayers to determine their effects on dynamic properties of the CNT hybrid composites.
Flutter prediction on combined EPS and carbon sandwich structure for light aircraft wing
Authors: Arifianto Dhany
Published: November 2021

Flutter prediction is an important step before conducting a flight test. In this study, we performed flutter prediction of a half-wing structure without control surfaces. The half-wing structure is made to resemble the scaled-down wing of a Boeing 737 NG at a scale of 1:39.34. The airfoil profile used is the wing profile of the Boeing 737 NG obtained from airfoiltools. The structure is constructed using a combination of carbon sandwich andEPS. The advantages of choosing this material are its low-cost and easymanufacture. We used the p-k method in the FEMAP software for flutter prediction. From the prediction results, the calculated flutter speed is ∼14.5 m/s. The flutter mode shape is a combination of lateral bending and twist. Dimensional analysis was also carried out to predict the maximum speed on the scaled model and predicted at 27.88 m/s. Based on calculated flutter speed, the maximum operating speed of a constructed structure should be far less than the flutter speed. Thus, the structure's maximum speed is below the predicted value. Based on carried out flutter prediction, the wing structure, constructed using a combination of carbon sandwich and EPS, can fly safely at a maximum cruise speed of 10 m/s.
The non-native canonical accent—And how to use it
Authors: Tjalve Michael
Published: November 2021

One of the key benefits of modern globalization is cross-pollination of cultures. This global community encourages diversity of thinking and communication across language boundaries. However, learning to speak a foreign language is predictably challenging and non-native speakers offer a quasi-infinite source of pronunciation variation. This variation presents a challenge to AI-based technologies where we make assumptions about user behavior and expected runtime input to the models. Inconsistent usage therefore is difficult to model successfully. A study of pronunciation patterns from a set of non-native speakers uncovered some of the underlying dynamics of different levels of non-nativeness. Anchored in key differences in phoneme inventory and phonotactic distance between L1 and L2, the notion of a non-native canonical accent is introduced. This accent captures a significant portion of the speakers in the data and allows us to describe the variation with the precision needed to model it. If we can more consistently anticipate the characteristics of the variation, we're better positioned to handle it. This means that by explicitly focusing on the pronunciation patterns that are likely to be challenging to non-native speakers, we can adapt the technology to build more robust speech recognizers and more personalized foreign language learning experiences.
Speech and hearing for the next billion users
Authors: Slaney Malcolm , Lyon Richard F.
Published: November 2021

Speech recognition has not withered in the years since John Pierce's 1969 editorial. Far from it, speech recognition is everywhere, and now works very reliably, even when speaking to a speech assistant in another room with music playing in the background. If the current speech technology is widely available to billions of users, then the next frontier is to provide the same technology to the next billion users (NBUs). In addition, all of us have limited capabilities to speak and understand the acoustic world around us, whether it rises to the level to be labeled a real disability, or arises due to fatigue or being distracted. The next frontier for speech and hearing is to accommodate all of our needs, disabled or not as they arise in the real world, for not just the first billion users, but the next billion, and the next billion after that. The available technologies include real-time speech recognition (and translation) for the hard of hearing, real-time speech enhancement, and auditory attention decoding from EEG signals.
Bayesian inference for boundary admittance estimation using a multipole model for room-acoustic simulation
Authors: Chen Ziqi , Horoshenkov Kirill V. , Xiang Ning
Published: November 2021

Acoustic surface admittance/impedance at room boundaries is essential for wave-based room-acoustic simulations. In this work, two levels of Bayesian inference are applied to estimate the surface admittance based on a multipole admittance model. This work estimates the order of the multipole admittance model through the high level of inference, Bayesian model selection. The first (low) level of inference, Bayesian parameter estimation, is applied to estimate the parameter values of the surface admittance model once model order is selected. This work approximates the frequency-dependent admittance from experimentally measured a set of acoustic surface admittance data. Analysis results demonstrate that multipole model-based Bayesian inference is well suited in estimating the frequency-dependent boundary condition within wave-based simulation framework. Numerical simulations verify the estimation results of Bayesian inference.
Employing deep learning method to predict global head-related transfer functions from scanned head geometry
Authors: Wang Yuxiang , Zhang You , Duan Zhiyao , Bocko Mark
Published: November 2021

We propose an HRTF personalization method in which a Convolutional Neural Network (CNN) is employed to learn subjects' HRTFs from the scanned geometry of their heads. The trained model can then be employed to predict the global HRTF set (for all directions) from the subject's head scan data alone. In our trial, the HUTUBS HRTF database was used as the training set. A truncated spherical harmonic expansion of head scan data was used to preserve the boundary shape features that are important in the acoustic scattering process. Each HRTF for a given subject also was represented by a truncated spherical harmonic expansion. The SHT coefficients of the scanned head geometry and the HRTFs serve as training data for a CNN that subsequently can be used to predict HRTFs from geometric scan data. A leave-one-out validation with log-spectral distortion (LSD) metric was used for evaluation. The results show a decent LSD level at both spatial & temporal dimensions compared to the ground truth, and have lower LSD than the finite element acoustic simulation of HRTFs that the database provides. In continuing work, we are validating the prediction results in listener tests.
Enabling multi-input, multi-output measurements with a fluidic transducer
Authors: Bühling Benjamin , Maack Stefan , Strangfeld Christoph
Published: November 2021

Ultrasonic testing is a widely used method for detecting damage and material characteristics in fields ranging from medicine to aerospace applications. The use of air-coupled ultrasound (ACU) enables an increase in testing speed, since no coupling medium needs to be applied to the transducer-specimen interface at each measurement point. The time needed for testing can be further decreased by using multiple-input, multiple output (MIMO) measurement systems. These systems require the ultrasonic signals to be uncorrelated so the that the individual pulses can be discriminated. Recently, the fluidic transducer was introduced, which generates acoustic pulses in the low ultrasonic frequency range. Experimentally, it is shown that each pulse contains a unique phase signature, that can be extracted by removing the signal envelope information. This technique is used to uniquely discriminate between simultaneously triggered pulses from two fluidic transducers and measure their individual times of flight.
Audio feature optimization approach towards speaker authentication in banking biometric system
Authors: Zaporowski Szymon , Czyzewski Andrzej , Kostek Bozena
Published: November 2021

Experiments were carried out using algorithms such as Principal Component Analysis, Feature Importance, and Recursive Parameter Elimination dentifying most meaningful Mel-Frequency Cepstral Coefficients representing speech excerpts prepared for their classification are presented and discussed. The parameterization was made using Mel Frequency Cepstral Coefficients, Delta MFCC and Delta MFCC. In the next stage, feature vectors were passed to the input of individual algorithms utilized to reduce the size of the vector by previously mentioned algorithms. The vectors prepared in this way have been used for classifying vocalic segments employing Artificial Neural Network (ANN) and Support Vector Machine (SVM). The classification results using both classifiers and methods applied for reducing the number of parameters were presented. The results of the reduction are also shown explicitly, by indicating parameters proven to be significant and those rejected by particular algorithms. Factors influencing the obtained results were considered, such as difficulties associated with obtaining the data set, and ts labeling. The broader context of banking biometrics research carried-out and the results obtained in this domain were also discussed. [Project No. POIR.01.01.01-0092/19 entitled: “BIOPUAP—A biometric cloud authentication system” is currently financed by the Polish National Centre for Research and Development (NCBR) from the European Regional Development Fund.]
Optimizing ultrasound frequency in burst wave lithotripsy
Authors: Sapozhnikov Oleg A. , Bailey Michael R.
Published: November 2021

Unlike shock wave lithotripsy, burst wave lithotripsy (BWL) uses tone bursts, consisting of many periods of sine wave. The fragmentation threshold of a stone depends on the burst frequency or, for a given frequency, on the stone size. In this work, an analytical theoretical approach to modeling mechanical stresses in a spherical stone has been developed. The theory is based on the method previously used to study the acoustic radiation force acting on an elastic stone [Sapozhnikov and Bailey, J. Acoust. Soc. Am. (2013)]. It has been shown that at low frequencies, when the wavelength is much greater than the diameter of the stone, the maximum principal stress is approximately equal to the pressure amplitude of the incident wave. With increasing frequency, when the diameter of the stone begins to exceed about half the wavelength in a surrounding liquid (the exact condition depends on the material of the stone), the maximum stress increases and can reach five times the pressure amplitude or even more. This observation suggests adjusting the BWL frequency depending on the stone diameter in order to comminute it into passable fragments. [Work supported by NIH, Nos. P01-DK043881 and RBBR 20-02-00139.]