bluuebunny/crossref_metadata_2025 huggingface dataset:
Speckle-free estimation of tissue elasticity with single track location shear wave elasticity imaging
Authors: Hollender Peter J.
Published: April 2018

Shear Wave Elasticity Imaging (SWEI) is commonly used to characterize tissue elasticity, but conventional, multiple-track-location SWEI (MTL-SWEI) techniques are resolution-limited by speckle. MTL-SWEI techniques use plane wave ultrasound to monitor an induced shear wave as it propagates across a set of tracking beams within a region of interest. The scattering process creates a random, yet stationary, spatial sensitivity pattern for each beamformed location, called speckle bias, which causes errors in MTL-SWEI shear wave speed estimates that cannot be improved through averaging. Single Track Location SWEI (STL-SWEI) overcomes speckle bias by using a single track beam, subsequently exciting and tracking different push locations, and comparing the timing of the recorded shear wave signals from different push locations to estimate shear wave speed. Two and three-dimensional STL-SWEI imaging techniques are presented and compared to MTL-SWEI and Acoustic Radiation Force Impulse (ARFI) imaging in phantoms and in vivo experiments. Tradeoffs and techniques for sequencing, beamforming, shear wave speed estimation, and image formation are discussed. For applications where tissue heating and motion are not limiting factors, STL-SWEI provides superior imaging in terms of lateral resolution and contrast-to-noise ratio compared to MTL-SWEI and ARFI. [This work was supported by NIHR37HL096023 and NIHR01EB01248.]
Identifying nonalcoholic fatty liver disease from quantitative ultrasound measures
Authors: O'Brien W. D. , Han Aiguo , Sy Ethan Z. , Loomba Rohit , Sirlin Claude B. , Erdman John W. , Andre Michael P.
Published: April 2018

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the United States, affects 30% of adult Americans, may progress to nonalcoholic steatohepatitis (NASH) and end-stage liver disease, and is a risk factor for diabetes and cardiovascular disease. The diagnosis, grading, and staging of NAFLD currently is based on liver biopsy with histologic analysis. Noninvasive image-based methods to evaluate the liver in adults with NAFLD are urgently needed. The objective is to identify the relationships between quantitative ultrasound (QUS) outcomes [backscatter coefficient, BSC, and attenuation coefficient, AC] and tissue properties to validate the diagnosis and/or grading of NAFLD. 83 participants with known or suspected NAFLD (thus few uncompromised liver samples expected) received contemporary QUS and MRI (proton density fat fraction) PDFF to estimate liver fat fraction. Of this group, 74 participants also received liver biopsy. Participant recruitment is continuing. Currently, observations show good correlations of both BSC and AC with PDFF, where PDFF ranged from 3% to 42%. Of the 74 biopsy participants, all stages of fibrosis have been pathologically identified [F0,25; F1,22; F2,13; F3,10; F4,4] suggesting both QUS identification opportunities and confounder challenges. [Support: NIH R01DK106419 and NIH R37EB002641.]
A nonlinear grid-search inversion for cortical bone thickness and ultrasonic velocities
Authors: Tran Tho N. , Sacchi Mauricio D. , Nguyen Vu-Hieu , Ta Dean , Le Lawrence H.
Published: April 2018

Cortical thickness and elasticity are important determinants of bone strength. This study proposes a nonlinear grid-search inversion to estimate the thickness and ultrasonic velocities of long cortical bones from axially-transmitted data. The inversion scheme has been developed in the frequency-phase velocity domain to recover bone properties. The method uses ultrasonic guided waves to retrieve cortical thickness, compressional, and shear-wave velocities of the cortex. The inversion strategy requires to systematically examine a set of trial dispersion curves within a pre-defined model space to match the data which minimizes the objective function in a least-squares sense. The theoretical dispersion curves required by the inversion are computed for bilayered bone models using a semi-analytical finite-element method. Its application demonstrates the feasibility of the proposed approach on synthetic data for a 5 mm-thick bone plate, and in-vitro dataset from a bovine femur plate with 2 mm-thick soft-tissue mimic on top. Our results indicate that one can recover the cortical thickness and wave speeds with less than 5% error. The accuracy can be improved by refining the grid; however, the computational cost of the method will increase. In the future, we aim at applying the method to clinical data.
Survey of simulations techniques used in balanced armature transducers
Authors: King Charles
Published: April 2018

Balanced armature transducers, also known as receivers, are commonly used in hearing aids, hearables, and in-ear monitors. These are difficult to simulate. They are very small devices, designed to fit inside the ear canal, and measurement of basic quantities is physically difficult. Additionally, multiple magnetic non-linearities are balanced to create a high-efficiency / high-output device. Spice simulations are well suited to understand the linear frequency response of the device. Finite element simulations are well suited to study steady state magnetic and geometric non-linearities. Time domain algebraic differential equation techniques can bridge these two simulation regimes. With this tool the amplitude response, frequency response, and distortion caused by the non-linearity’s can be studied. The talk will examine strengths, weaknesses, and when it is appropriate to use each of these individual techniques.
Hearing health across a lifespan: Hearing screening from cradle to grave
Authors: Eichwald John
Published: April 2018

The 2016 National Academies of Sciences, Engineering, and Medicine report “Hearing Health Care for Adults: Priorities for Improving Access and Affordability” included a call to action for government agencies to strengthen efforts to collect, analyze, and disseminate population-based data on hearing loss in adults. In partial response, the Centers for Disease Control and Prevention (CDC) analyzed the most recent available data collected both by questionnaire and audiometric tests of participants aged 20–69 years in the 2011–2012 National Health and Nutrition Examination Survey to determine the presence of audiometric notches indicative of noise-induced hearing loss. Prevalence of both unilateral and bilateral audiometric notches and their association with self-reported exposure to loud noise were calculated. Nearly one in four adults had audiometric notches, suggesting a high prevalence of noise-induced hearing loss. The prevalence of notches was higher among males. Almost one in four U.S. adults who reported excellent or good hearing had audiometric notches. Among participants who reported exposure to loud noise at work, almost one third had a notch. Noise-induced hearing loss is a significant, often unrecognized public health problem in the United States.
Individual differences in suprathreshold hearing and relationship to cochlear synaptopathy
Authors: Bharadwaj Hari M.
Published: April 2018

Threshold audiometry, although the foundation of current clinical hearing evaluations, provides limited information about suprathreshold hearing. Over the last few years, we have documented that even among listeners with normal thresholds and no hearing complaints, large individual differences exist in the ability to perceive subtle temporal features of clearly audible sounds, and to selectively process target speech in the presence of competing sounds. Furthermore, we find that these suprathreshold perceptual differences correlate with suprathreshold physiological measures from the brainstem and auditory nerve suggesting that perceptually-relevant differences may be present early along the auditory pathway. As a candidate mechanism explaining these observations, animal studies of acoustic overexposure and aging have robustly demonstrated that the afferent synapses and nerve terminals innervating the cochlea are especially vulnerable to damage. Interestingly, even a significant loss of cochlear synapses (“synaptopathy”) does not lead to changes in audiometric thresholds. However, synaptopathy, if present in humans may contribute to differences in suprathreshold hearing especially in noisy environments. This presentation will summarize human evidence that is indirectly in support of the notion, and describe our ongoing efforts to test this hypothesis further and translate markers for synaptopathy from small laboratory animals to humans.
Psychophysiological responses during cognitively demanding work in subjectively annoying background noise
Authors: Oliver Jordan N. , Sung Weonchan , Davies Patricia , Francis Alexander L.
Published: April 2018

People who work in noisy environments are at greater risk for stress-related diseases, including hypertension and stroke, even when noise levels are too low to damage hearing. Such noise may be harmful, especially to noise-sensitive individuals, because the psychological annoyance that it causes induces physiological stress responses that are damaging to health over the long term. This study was designed to investigate the link between subjective noise annoyance and physiological measures of arousal and displeasure due to the presence of background noise. Cardiovascular, electrodermal, respiratory, and facial muscular activity were recorded from 32 listeners during the completion of a demanding working memory task under different listening conditions. Participants completed four levels of memory task demand in silence and in two different continuous noises similar to that produced by HVAC equipment. Both noises were comparable in terms of loudness and presentation level (54–60 dBA) but differed in perceived annoyance (based on ratings from a panel of listeners in a previous study) and in acoustic properties associated with noise annoyance (roughness, tonality, and sharpness). Behavioral measures of memory task performance, noise sensitivity, personality traits, and subjective effort will be presented and related to physiological measures, and implications for future research will be discussed.
Progresses with the International Data Centre Infrasound System
Authors: Mialle Pierrick , Arora Nimar
Published: April 2018

The International Data Centre (IDC) advances its methods and continuously improves its automatic system for infrasound technology. The IDC focuses on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. An objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the reviewed event bulletins (REB). Progresses related to several ongoing projects at the IDC will be review:—improving the detection accuracy at the station processing stage by introducing the infrasound signal detection and interactive review software DTK-(G)PMCC (Progressive Multi-Channel Correlation) and by evaluating the performances of detection software;—development of the new generation of automatic waveform network processing software NET-VISA to pursue a lower ratio of false alarms over GA (Global Association) and a path for revisiting the historical Infrasound Reference Event Database (IRED). The IDC identified a number of areas for future improvement of its infrasound system that will be addressed here.
What does infrasound signal duration tell us about signal propagation distance and waveguide structure?
Authors: Green David , Nippress Alexandra
Published: April 2018

A global network of microbarograph arrays is currently being constructed to support verification of the Comprehensive Nuclear-Test-Ban Treaty. The identification of explosively generated infrasound signals that have propagated thousands of kilometers to the arrays, and the subsequent association of signals across the sparse network, remains a challenge. One signal parameter that has not been extensively studied, but may assist in source identification procedures, is the signal duration. The durations of 42 high signal-to-noise ratio signals from 35 near-surface explosions, recorded at distances of between 25 and 6300 km, exhibit a weak relationship with source-to-receiver range; longer propagation paths result in longer signal durations. The variation in signal duration at a given source-to-receiver range depends upon the atmospheric waveguide structure. At propagation distances greater than 2000 km, long duration signals are generated within weak waveguides characterized by a small excess in stratospheric effective sound speed compared to that at the ground surface. These waveguides permit signal propagation with high celerity (up to 335 m/s). Shorter duration signals at these distances occur in stronger waveguides that exhibit greater along-path variability; these signals do not exhibit celerities greater than 315 m/s. The utility of signal duration within the context of explosion monitoring is explored.
The application of acoustic particle velocity sensors to airborne infrasonic signals
Authors: Alberts W. C. Kirkpatrick
Published: April 2018

Infrasound arrays, because of the wavelengths involved and the necessity for minimal spatial aliasing, can be quite large, e.g. an array layout often used for beamforming for frequencies up to 10 Hz is a centered, 17-m radius equilateral triangle. Available real estate is often limited such that optimally sized arrays are not possible. An acoustic particle velocity sensor, in principle, can perform the same job as a large infrasound array, but in a much smaller package (less than the size of a single infrasound sensor) since it provides, in post processing, a direct measurement of the wavefront normal. However, localized meteorological perturbations to the wavefront normal could cause significant bearing estimate errors when using a particle velocity sensor. Recently, as part of the characterization of a mobile infrasound source and during the collection of sounds from space station resupply rockets, acoustic particle velocity sensors were positioned next to infrasound sensors in order to test the concept of using these sensors for accurate pointing at infrasound frequencies. Results from these experiments will be discussed.
The effects of sound coder carrier rate and modulation bandwidth on voice pitch perception in cochlear implant users
Authors: Kovacic Damir , James Chris
Published: April 2018

We employed the dual filter-bank “STEP” coder to separately control the spectral and temporal modulation resolution of analysis channels. Previously we compared vowel pitch ranking and gender classification with eight subjects using enhanced modulation at F0—including across-channel synchronised modulation to the ACE coder. There was no significant improvement using modulation enhanced coding versus ACE across subjects. In a follow-up experiment we looked at the effect of stimulation rate on voice pitch perception. Since there are large inter-subject differences in overall temporal pitch acuity we hypothesised that some subjects’ performance may be more greatly influenced by carrier rate than others, or that some subjects may find sound quality satisfactory with lower carrier rates than those in their clinical processors. We used a version of STEP with a very short temporal envelope analysis window of 2 ms which allows a very low latency real-time processing implementation and large maximum modulation bandwidth. Subjects were tested using carrier rates of 1000, 500 and 250 pps/ch with modulation bandwidths controlled via low-pass filtering. Pilot data indicated that the new low-latency coder provides very good sound quality compared to ACE using 1000 pps/ch or 500 pps/ch. Also the modulation bandwidth could be tuned at different carrier rates to optimize voice pitch perception based on temporal cues. This opens the potential for lower stimulation rates to be used in CI coding while maintaining optimal temporal resolution.
Effect of site of spike generation on temporal coding in the electrically stimulated auditory nerve
Authors: Joshi Suyash N.
Published: April 2018

At least two sites of spike generation are observed in the electrically stimulated auditory nerve, namely, the peripheral axon and the central axon. The peripheral axon responds to the cathodic charge and the central axon to the anodic charge with an approximate spike-latency difference of 200 μs. The peripheral axon also shows longer refractory periods than the central axon. In this study, a phenomenological model of the electrically stimulated auditory nerve described in Joshi et al. [JARO 18(2), pp. 323–342] was used to understand the effect of spike generation sites on the temporal coding. Modulation detection thresholds for different carrier pulse rates were predicted from simulated responses of the auditory nerve, and refractoriness of both the axons was varied to test its effect on temporal coding. The results show that an increase in pulse rate increased the number of spikes generated at the central axon, hence decreasing the modulation detection thresholds. Refractoriness also played a crucial role in encoding the stimulus envelope such that extended refractory periods resulted in enhanced envelope coding. Increase in refractoriness at the central axon improved the envelope encoding. Implications of these findings for developing new stimulation strategies will be discussed.
Towards increasing timing sensitivity in electric hearing
Authors: Laback Bernhard , Srinivasan Sridhar , Lindenbeck Martin , Ferber Maike , Majdak Piotr
Published: April 2018

Sensitivity of bilateral cochlear-implant (CI) listeners to interaural time differences (ITDs) in electric pulse trains is degraded compared to normal-hearing (NH) listeners presented with ITDs in pure tones. This degradation manifests both as an elevated ITD threshold and upper perceptual limit of stimulation rates. Similar limitations were observed for temporal pitch, despite the difficulty to disentangle temporal and place pitch cues in NH listeners. We tested the hypothesis that ITD and monaural rate-pitch sensitivity of CI listeners at high rates of electric stimulation can be improved by introducing extra pulses with short inter-pulse intervals (SIPIs) at low rates in amplitude modulated high-rate pulse trains. Results show that SIPIs significantly improved ITD and monaural rate-pitch sensitivity at low modulation depths. These similar improvements suggest a possible overlapping benefit of SIPIs for CI listeners in everyday environments requiring high rates for encoding speech. Considering the documented effects of neural deprivation, its potential reversal by training, and the potential for NH-like timing sensitivity as observed in exceptional CI listeners, we began to investigate the effects of vision-induced ITD training in CI listeners. Preliminary results will be discussed in the light of the timing sensitivity limitations in electric hearing.
Supervised and unsupervised machine learning approaches to classifying chimpanzee vocalizations
Authors: Desai Nisarg P. , Lehman Clarence , Munson Benjamin , Wilson Michael
Published: April 2018

Quantitative tools for classifying vocal repertoires have been constantly evolving with developments in machine learning and speech recognition research as well as increasing computing power. There are two main methodological considerations in classifying vocalizations: (i) choosing the classification technique and (ii) choosing the features for classification. Current state-of-the-art classification techniques are artificial neural networks (ANNs), support vector machines (SVMs), and ensemble methods like random forests (RFs). Current state-of-the-art features from speech recognition research include mel frequency cepstral coefficients (MFCCs). Bioacoustics researchers have applied these tools to problems including individual-, species-, and call-type identification, and vocal repertoire classification. However, researchers studying non-human primate vocalizations have only recently started adopting these approaches and none have applied them to study chimpanzee vocalizations. Here, we analyze vocalizations recorded in Gombe National Park, Tanzania. First, we use supervised classification techniques (ANNs, SVMs, and RFs) that involve training the models based on predefined call-types to evaluate the classification accuracy. Second, we use unsupervised techniques (that do not require prior knowledge of call-types), namely, K-means clustering, and self-organizing neural networks to identify discrete call types. We discuss the results from both supervised and unsupervised techniques and their strengths over traditional methods.
Successfully persuading architects’ form to follow acoustical function
Authors: Conant David A.
Published: April 2018

Architect Louis Sullivan’s mantra, Form follows function, is no better embedded in any subdiscipline of architecture than that of building acoustics, and this is especially true in the realm of performing arts. This paper describes several examples of performing arts spaces in which MCH involved architects, often rather directly, into acoustical design. These studies were characterized, not by computer-centric tools, but rather were often most effectively and intuitively realized through simple light models that informed optimal room shaping real-time, hand-on exercises with our clients. Some solutions, especially appreciated by architects, successfully invoked indigenous or traditional forms that lent themselves beautifully to excellent speech intelligibility, musical clarity, and envelopment. This paper will discuss projects with acoustically-effective forms drawn from Native American kivas and Taoism, to Moorish tessellated patterns, to geographic forms such as southwest canyons and quarries, and more—including even “hanging chads.”
Insect sound production and transmission in plant materials of different compositions and structures
Authors: Mankin Richard
Published: April 2018

Insects use plants for food and shelter, and many species also have taken advantage of plant acoustical and structural characteristics to communicate for mating and social interaction over extended distances without expending significant energy. Humans have taken advantage of plant acoustical and structural characteristics to detect hidden insect infestations passively by monitoring their feeding and movement activities. This presentation reviews the characteristics of sound transmission as well as the characteristics of insect movement and feeding sounds in plant structures and products. Although insect sounds can be masked by loud background noise, different species produce sounds with particular spectral and temporal patterns that help distinguish them from background signals and from each other. Several practical applications of insect bioacoustics are discussed, including disruption of insect mating, targeting of tree pests, and monitoring of the time course of different pest management treatments.
Acoustics of seagrass photosynthesis
Authors: Hermand Jean-Pierre , Johnson Jay R. , Debeir Olivier , Wilson Preston S.
Published: April 2018

The paper reviews experiments in the Mediterranean that have investigated the use of low frequency sound transmission measurements (0.2–20 kHz) to study metabolism of seagrasses in situ in a noninvasive way and to better evaluate primary production at the scale of a meadow, for Posidonia oceanica and Cymodocea nodosa species. As sound interacts with the canopy and rhizosphere, the cumulative effect of multiple scattering from the aerenchymatic tissues of leaf blade, rhizome, and root changes the character of the environment impulse response. Diel variations of received energy and statistical features are due to oxygen movement which modifies the plant scattering function. During periods of high net photosynthesis, pressurization of the lacunal gas modifies the tissue mechanical properties. High internal oxygen partial pressures cause the release of oxygen into the diffusive boundary layer which can result in bubble formation on the tissue surface when local oxygen concentration exceeds solubility. In situ experimental results will be discussed in the light of laboratory acoustic and microscopic investigations of the tissues. [Work supported by ONR, ONR Global.]
Estimation of sound speed and attenuation in muddy sediments using spatial coherence measurements of sound propagation
Authors: Wan Lin , Badiey Mohsen
Published: April 2018

In the spring of 2017, a multi-national and multi-institute shallow water propagation experiment was conducted in the New England Mud Patch in order to study the acoustic properties in muddy sediments. Different types of acoustic signals (i.e., 31-g explosive charges, combustive sound source, multi-tone, and linear frequency modulation signals) deployed at various ranges, depths and azimuths were measured by one L-shaped array, one horizontal line array, and several vertical line arrays within the 30 km × 10 km experimental area. In this paper, these measured signals are first utilized to obtain the correlation coefficients for vertical coherence (VC) and longitudinal horizontal coherence (LHC), which are sensitive to the seabed geo-acoustic parameters. These spatial coherence measurements are then applied in the VC and LHC based geo-acoustic inversion algorithms [Wan et. al. JASA, 2016] to infer sound speed and attenuation in muddy sediments. Finally, the results from VC and LHC based geo-acoustic inversion approaches are compared with those obtained by using normal mode characteristics (e.g., modal dispersive curve with Airy phase structure, modal attenuation coefficient, and mode shapes). [Work supported by ONR.]
Ship azimuth prediction using supervised machine learning
Authors: Reeves Emma , Gerstoft Peter
Published: April 2018

Machine learning methods are applied to noise from the R/V Endeavor across several days during the SCEx17 experiment to predict the ship's azimuth. Sample Covariance Matrices (SCMs) are formed from received pressures on two vertical line arrays (VLA1, VLA2) and one horizontal line array (SWAMI). Previously, support vector machine (SVM), feed-forward neural network (FNN), and random forests (RF) machine learning methods have accurately estimated the range of a source towed in a linear geometry in shallow water (Niu et al., JASA 142, 1176–1188 (2017); Niu et al., JASA 142, EL455–460 (2017)) where the training and test tracks were close together in time. In this study, we investigate the robustness of SVM and FNN for circular track prediction when the training and test tracks are taken from different days with different sound speed profiles.
Estimating low-frequency sediment sound speed dispersion from the horizontal coherence of the head wave excited by a light helicopter
Authors: Bevans Dieter A. , Buckingham Michael J.
Published: April 2018

A series of shallow-water acoustic experiments has been conducted off the coast of southern California using a Robinson R44 helicopter as a low-frequency (≈ 13–3500 Hz) sound source. The aim of the experiments was to recover the sound speed of a fine to very-fine sand sediment from the horizontal coherence of the head wave excited in the water column by the helicopter. Two hydrophones, separated horizontally by approximately 15 m and situated 0.5 m above the seabed, received the head-wave signals, allowing the coherence function to be formed over the bandwidth of the airborne source. The sediment sound speed was recovered by matching the zero crossings of the measured coherence function to those predicted from a recently developed theory of head-wave generation in shallow water. Using this technique, the dispersion in the sediment sound speed can be estimated over a frequency range extending between 27 Hz, the lowest zero crossing of the coherence function, and 3.5 kHz, the bandwidth of the source. In the middle of the frequency band, the sound speed of the sediment was estimated to be 1682 ± 16 m/s, consistent with the known sediment type. [Research supported by ONR, SMART(DOD), NAVAIR, and SIO.]
Direct measurement of nuclear diameter with high-frequency ultrasound (10–100 MHz) for breast cancer detection
Authors: Doyle Timothy E. , Carlson Jessica E. , Cowan Nicole , Wagner Garrett
Published: April 2018

Two high-frequency (10–100 MHz) ultrasound studies were conducted at the Huntsman Cancer Institute (Salt Lake City, Utah) on breast cancer margin and lymph node specimens from 90 patients, and produced sensitivities and specificities as high as 87.5% and 82.9%. The method used through-transmission measurements and a new parameter that correlated not only to malignant versus benign tissue, but also to various breast cancer types and other pathologies. This parameter, peak density, measures the number of peaks in the ultrasonic spectrum. The data indicated that peak density increased successively for atypical pathologies, ductal carcinomas, and lobular carcinomas as compared to normal tissue. Additional correlations were found between the distribution of peaks in the spectra and the above pathologies. This study’s objective was to test the hypothesis that peak density measures the nuclear diameter of the cells in the tested tissue. A computer model of Mie scattering from a single, nucleated cell was used to calculate ultrasonic spectral peaks in the 10-100 MHz band as a function of nuclear diameter. Experiments were also conducted with agarose tissue phantoms containing polyethylene microspheres having diameters of 10-102 μm. The model and phantom results confirmed the hypothesis that peak density directly correlates to nuclear diameter.
Vibro-acoustic method for detection of osteopenia and osteoporosis
Authors: Ghavami Siavash , Bayat Mahdi , Gregory Adriana , Webb Jeremy , Denis Max , Fatemi Mostafa , Alizad Azra
Published: April 2018

Early detection of osteopenia and osteoporosis is critical in identifying at-risk groups and manage necessary therapy. In this paper, a new noninvasive and quantitative vibro-acoustic method is proposed for detection of osteoporosis and osteopenia. In this method, we excite the bone by an ultrasound radiation force (URF) pulse. The URF pulse induces a vibration in the bone, resulting an acoustic wave that is received by a hydrophone placed on the skin. This prospective study included n = 23 volunteers. The number of volunteers with osteopenia and osteoporosis were 7, 6, respectively, and the number of volunteers with normal bone was 10. URF excitations were applied at four equi-distance points on the bone. The resulting acoustic signals were used for wave velocity estimation based on cross-correlation technique. In general, the hydrophone signal may be modeled as a superposition of different modes of bone vibration. Based on this model, we used variational mode decomposition (VMD) as an efficient technique to decompose the received signal into an ensemble of band-limited intrinsic mode functions. Statistical analysis demonstrates that osteopenia and osteoporosis bones can be differentiated from normal bone with p< 0.001 using Wilcoxon rank-sum test on estimated velocity of the modes with maximum power.
Power law attenuation of shear waves in fractal media
Authors: Holm Sverre , Sinkus Ralph
Published: April 2018

There are two mechanisms for attenuation of mechanical waves: absorption and multiple scattering. We explore the second mechanism for shear waves in the context of MR elastography. The theory for attenuation was first given in the seismic field (O’Doherty & Anstey, Geophys. Prosp. 1971). Later phase was included, and the mean field concept was applied (Banik et al., Geophys. 1985). Then, a more rigorous theory which also deals with random fractals was developed (Sølna, SIAM J ApplMath, 2003; Garnier & Sølna, Multiscale Model Simul, 2009). We have developed this theory further by allowing fractality over a limited length scale and also shown that it gives results that are indistinguishable from those of power law absorption models like the fractional Kelvin-Voigt model (Holm & Sinkus, JASA, 2010). This makes it a challenge to understand whether attenuation in a real medium is due to one or the other mechanism or both. Measurement of dispersion has been done for polystyrene microspheres embedded in agarose which is nearly lossless up to 1000 Hz. The phase velocity has a power law variation with exponent up to d = 0.24 (Lambert et al., PRL 2015). According to the theory this is consistent with a fractional dimension which is d less than the Euclidean dimension.
Quantifying nonlinear elasticity modulus of tissue-like solids using acoustic radiation force
Authors: Panahandeh-Shahraki Danial , Guzina Bojan B. , Kumar Viksit , Urban Matthew W. , Kinnick Randall R. , Ghavami Siavash , Alizad Azra , Fatemi Mostafa
Published: April 2018

As shown in a recent study, estimation of the magnitude of the acoustic radiation force (ARF) in isotropic tissue-like solids is the key to measuring a third-order nonlinear modulus of elasticity (C)—responsible for coupling the shear and volumetric constitutive responses of a material. Due to experimental limitations, a direct measurement of the ARF in tissue is however difficult. To overcome this problem, we deploy 3D elastodynamic finite element (EFE) simulations of the ARF experiment in tissue-mimicking phantoms to estimate (i) the “background” shear modulus from the phase of the induced shear waves; (ii) the ARF magnitude from the shear wave amplitude, and (iii) the modulus C from the knowledge of the ARF. In this way, by interpreting the ARF-generated shear waves through the prism of 3D-EFE simulations, we facilitate local estimation of the nonlinear C modulus with spatial resolution equaling the size of the focal region. We call this method the C-Elastography (CE). In this study, the CE technique is applied to gelatin phantoms containing an agar-based inclusion. The profiles of the C-modulus in phantoms tested demonstrate good correlation with the phantom geometry, showing marked (and sharp) C-contrast at push points acting on the inclusion. [Acknowledgment: NIH-Grant EB23113.]
A deep neural network method for analyzing lung density using lung ultrasound surface wave elastography
Authors: Zhou Boran , Zhang Xiaoming
Published: April 2018

Lung density is directly associated with lung pathology. Computed Tomography (CT) evaluates lung pathology using the Hounsfield unit (HU) but not directly the lung density. We recently developed a lung ultrasound surface wave elastography (LUSWE) technique for measuring the surface wave speed of superficial lung tissue. The objective of this study is to analyze lung density of superficial lung tissue using deep neural network (DNN) and wave speed measurements obtained from LUSWE. The synthetic training dataset (7,88,000 in total) in terms of wave speeds of superficial lung tissue at different excitation frequencies from LUSWE, viscoelasticity and density of lung tissue was used to train the DNN. DNN is composed of 3 hidden layers of 1024 neurons and trained for 10 epochs with a batch size of 4096 and a learning rate of 0.001 with Adam optimizer. Test dataset in terms of wave speeds at different excitation frequencies (100, 150, and 200 Hz) as well as elasticity was used to predict the lung density and evaluate its accuracy. The obtained results showed that predictions matched well with test dataset (validation accuracy is 0.997). This method may be useful to analyze lung density based on the LUSWE measurements.
Artificial design of open-back headphone based on ventilation structure optimization method
Authors: Tsai Yu-Ting , Huang Jin H.
Published: April 2018

The computer-aided analysis of open-back headphone based on finite/bound element method, lumped parameter model, and transduction equations have been investigated for decades. In a serious attempt to reach the optimal design of headphone, various aspects of conceptualization, design, modeling, and simulation are investigated for improvement of headphone in this work. The standardized construction process of the three-dimensional image of the human ear to establish the open-back architecture for the headphone is given. For improving the sound pressure level response of the headphone, the parameter design method is proposed through the optimized dimension modification of special open-cavity structure. All results of studies of the simulated responses are compared with experimental data and have verified the veracity of the simulations. The present work has concluded the feasibility of adjusting the model and parameters for customizing the resulting response for headphone's varied applications.
Miniature implantable low noise piezoelectric diaphragm sound sensor
Authors: Zhao Chuming , Hake Alison , Sung Wang-Kyung , Grosh Karl
Published: April 2018

Piezoelectric diaphragm sound sensors must be miniaturized and environmentally toughened for use in biomedical applications. We study two disparate applications of the sensor, first as the front end of a completely implantable cochlear implant and the second as an intracardiac pressure sensor. The sensor, which is fabricated using micro-electrical-mechanical-system (MEMS) techniques, consists of a circular diaphragm with at least one aluminum nitride (AlN) based piezoelectric layer backed by an air-filled cavity. The sensors are designed to have a lower input referred noise (IRN) compared to other miniaturized piezoelectric diaphragm hydrophones with similar diaphragm size via structural design and electrode area optimization. Sensors are fabricated with varying diaphragm diameters from 300 to 450 μm to test the effect of residual stresses due to the manufacturing process on the frequency bandwidth and IRN. The sensor works in air and underwater with the same sensitivity, but the frequency bandwidth is reduced underwater compared to that is in air because of the water mass loading. A finite element analysis model using COMSOL is built to study the in air and underwater sensing process and the IRN.
Experimental assessment of miniature accelerometers designed for sensing middle ear motion
Authors: Hake Alison , Zhao Chuming , Sung Wang-Kyung , Grosh Karl
Published: April 2018

Sensing human middle ear motion requires miniature, low-noise sensors to detect low-amplitude vibration of the ossicle bones to replace the external microphone in a cochlear implant system. Specifically, a 35 μg/√Hz sensor resolution is needed measure motion at 500 Hz (Young et al., 2012). Motivated by sensing middle ear motion without irreversible alteration to the ossicular chain, a small, piezoelectric accelerometer is considered. Our detailed low-frequency analytical model is used to identify promising micromachined, piezoelectric bimorph cantilever accelerometer designs. We fabricated a first generation of accelerometers using a conservative microfabrication approach, taken to enhance the yield of devices rather than to minimize the input referred noise (IRN). The mathematical model was validated by voltage actuation testing of these accelerometers. The device sensitivity to acceleration is tested, and the resulting IRN is desired to assess the viability of the sensor for the middle ear motion application. The first generation experimental results are compared to the mathematical model to determine the accuracy of the model and the efficacy of the fabrication methodology. This knowledge will influence future sensor designs optimized for minimal IRN.
A new approach for an FE-model optimization of a MEMS piezoelectric accelerometer for implantable hearing devices
Authors: Neves Masson Zargos , Gesing Andre L. , de Lorenzo Matheus , Paul Stephan , Cordioli Julio A.
Published: April 2018

Totally implantable hearing devices have been proposed as a solution to mitigate the constraints related to the presence of external elements in traditional hearing devices. This work reports on a novel approach for the development of a MEMS piezoelectric accelerometer as an implantable sensor for hearing devices. Traditionally these sensors are designed for maximum sensitivity; however, the primary bottleneck for this type of transducer is the internal noise level. Two differential evolution optimization routines were developed. The first used sensitivity maximization whereas the second seeks minimization of the equivalent input noise (EIN). Both methods were applied to different designs of Lead Zirconate Titanate (PZT) MEMS piezoelectric accelerometer in the frequency range of 250 Hz to 8 kHz with layer thickness varying from 0.1 μm to 1 μm. In the latter approach, the sensor's acceleration noise was estimated analytically, considering capacitance and charge response acquired through finite element modeling (FEM) previously validated. Acceleration noise was converted to EIN, in sound pressure level (SPL), through an FE-model of the middle ear considering the sensor coupled at the umbo. Preliminary results indicate that using EIN as optimization goal, opposed to sensitivity, leads to a higher performance over a broader bandwidth.
Modeling and mapping aircraft noise in National Parks
Authors: Rapoza Amanda , Lignell Brent , Fristrup Kurt M. , Hastings Aaron L.
Published: April 2018

Commercial air tours are a common source of noise within many national parks, affecting natural and cultural resources as well as visitor experience. To facilitate interactive modeling and mapping of air tour noise exposure, the Volpe National Transportation Systems Center and National Park Service (NPS), in cooperation with the Federal Aviation Administration (FAA), have created an Aviation Noise Analysis and Mapping Tool. This tool contains a library of park noise maps generated by modeling single aircraft operations on routes flown by that aircraft. The creation of this library is computationally intensive and requires considerable expertise to properly configure and run the models. With this tool and library, a broad range of users can interactively explore composite noise exposure generated by air tour traffic scenarios. Composite noise exposure is calculated by summing, across all aircraft and route combinations, the product of the number of flights on each route and the noise generated by each aircraft on that route. The use of FAA noise models ensures consistency with other U.S. environmental analyses, use of state-of-the-art algorithms, and access to updated aircraft noise databases. The traffic aggregation component can be modified to incorporate specialized interpretations of noise exposure for NPS applications.
A basic research on expression of loudness and orientation of sound source in soundscape by onomatopoeia on pictures
Authors: Akita Takeshi , Koga Takaaki , Sano Naoko , Matsuo Ayako
Published: April 2018

When soundscape is described with words under common acoustic environment, it is usual that the name of the sound source that indicates their category or species is noted. Generally, such kind of description cannot express loudness and orientation of sound source. However, the information of loudness and orientation of the sound source is important, so it is necessary to note them easily at a time. In the present research, it is investigated whether description of soundscape using onomatopoeia on pictures to express loudness and orientation of sound sources is effective or not. Two psychological experiments are carried out to reveal the availability of this description method. Results show that onomatopoeia can present the type of source, and that it can simultaneously express variety of loudness of sound source and noise. It is suggested that the size and number of onomatopoeia described on pictures of the place where noise exists represents loudness of sound and noise, and that the variety of size of onomatopoeia can show the difference of sound pressure level of 20 dB.
Noise dependent coherence-super Gaussian based dual microphone speech enhancement for hearing aid application using smartphone
Authors: Shankar Nikhil , Shreedhar Bhat Gautam , Karadagur Ananda Reddy Chandan , Panahi Issa M.
Published: April 2018

In this work, the coherence between speech and noise signals is used to obtain a Speech Enhancement (SE) gain function, in combination with a Super-Gaussian Joint Maximum a Posteriori (SGJMAP) single microphone SE gain function. The proposed SE method is implemented on a smartphone that works as an assistive device to hearing aids in real-time. Although coherence SE gain function suppresses the background noise well, it distorts the speech. In contrary, SE using SGJMAP improves speech quality with the introduction of musical noise, which we contain by using a post filter. The weighted union of these two gain functions strikes a balance between noise suppression and speech distortion. A “weighting” parameter is introduced in the derived gain function that can be controlled by the smartphone user based on different background noises and their comfort level of hearing, which proves the practical usability of the developed SE method implemented on the smartphone. Objective and subjective measures of the proposed method show significant improvements in both quality and intelligibility compared to the state of the art SE techniques considered in this work for several noisy conditions at the signal to noise ratio levels of -5 dB, 0 dB, and 5 dB.
Estimation of explosive yield using regional distance infrasound
Authors: Blom Philip , Dannemann Fransiska K. , Marcillo Omar
Published: April 2018

Infrasound signals from large above-ground explosions are known to propagate to significant distances while remaining at observable levels due to a combination of the large source energy for such events and decreased absorption for acoustic energy at lower frequencies. Previously, propagation-based, stochastic path geometry and travel time models have been used to improve estimates of location and time for infrasonic sources with promising results. A similar approach has been applied to develop stochastic transmission loss models for infrasonic signals. The resulting models have been utilized in a Bayesian framework to compute a near-source estimate of the acoustic signal, which can then be used to compute a probability distribution for possible explosive yields of the source. Details of the propagation models and yield estimation framework will be presented along with results for application to a number of explosive events.
Improvements to infrasonic detection capabilities through application of a generalized least squares beamformer
Authors: Dannemann Fransiska K. , Blom Philip , Marcillo Omar
Published: April 2018

A common challenge in seismoacoustic research and analysis is detection of low signal-to-noise ratio (SNR) signals in a variable and often coherent background. Previously, the application of an adaptive F-detector to infrasonic data has successfully reduced false detection rates attributed to coherent noise across array elements; however, the detector is applied post-processing after analysis using a standard (Bartlett) beamformer, which raises the detection threshold and can lead to missed detections. Application of a generalized least squares (GLS) beamformer can enhance processing of transient infrasonic signals, particularly in the presence of correlated noise, by adaptively accounting for the background noise characteristics. The GLS beamformer enhancement leads to improved capabilities for accurately detecting low amplitude infrasonic events of interest that would not normally produce a sufficiently high F-statistic to be declared a detection. A statistical analysis of GLS beamformer performance in a variety of noise environment will be presented, along with the statistical significance of enhanced detection capabilities compared to traditional beamforming approaches.