bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian geoacoustic inversion for sediment profiles consisting of a general gradient over a layered substrate
Authors: Dosso Stan E. , Belcourt Josée , Dettmer Jan , Holland Charles W.
Published: April 2018

This paper considers Bayesian geoacoustic inversion and uncertainty estimation for seabed profiles consisting of a smooth gradient of general form overlying a potentially-layered substrate. The profile gradient is parameterized as a linear combination of Bernstein-polynomial basis functions, with the polynomial order determined objectively by applying the deviance information criterion. In this way the form of the gradient is determined by the data, rather than by a subjective prior choice. The substrate below the gradient consists of uniform layers defined by an unknown number of (zero or more) interfaces, sampled probabilistically with trans-dimensional inversion. (Zero interfaces corresponds to a half-space with uniform parameter values equivalent to those at the base of the gradient.) The inversion approach is well suited to seabed environments consisting of an upper layer of soft, fine-grained sediments in which geoacoustic properties vary as a smooth function of depth overlying a harder, layered substrate, such as at the ONR Seabed Characterization Experiment at the New England mud patch. [Research funded by the Office of Naval Research, Ocean Acoustics Program.]
Attenuation in fine-grained sediments for New England Mudpatch in 25–5000 Hz band
Authors: Knobles David P. , Wilson Preston S. , Hodgkiss William S.
Published: April 2018

A subject of considerable importance in littoral ocean environments is the frequency dependence of sediment attenuation for various classes of sediments. The well-known frequency exponent value of 1.8 for sandy sediments was the subject of numerous research studies. For mud-like or mixed sediments, for which there is a scarcity of experimental data, values for the frequency exponent are not well established. Previously, the sound speed structure of a surface mud layer in the New England Seabed Characterization experimental area was estimated with inversion and Bayesian methods. The inversions utilized MK-64 SUS explosive sources in a 25-275 Hz band placed on concentric circles of 2, 4, and 6.5 km radii in the latitude-longitude plane. The area was previously surveyed with CHIRP sonar allowing for multiple sediment layer horizons to be constrained for layer thicknesses by measured two-way travel times. In this analysis, a larger bandwidth (25-5000 Hz) of the SUS, the Combustive Sound Source (CSS), and tonals from towed sources at multiple frequencies allow for the development of posterior probability distributions that contain the statistics of the frequency dependence of sediment attenuation up to about 5 kHz. [Work supported by ONR]
Acoustics of biologically active marine sediments
Authors: Lee Kevin M. , Ballard Megan S. , Venegas Gabriel R. , Wilson Preston S.
Published: April 2018

Biological organisms are prevalent on and near the seabed; however, most predictive theoretical models do not explicitly address the acoustic behavior of biologically active marine sediments. Sediment-acoustics models, such as those based on Biot theory or grain-shearing theory, allow for parameterization of various physical properties including bulk density, porosity, shear strength, or pore fluid viscosity, all of which can be modified by the presence of biological organisms or bioturbation. Other models can include the effects gas bubble distributions, which can also be associated with the presence of benthic biology, on compressional and shear wave propagation. In this paper, we examine sediment-acoustics models in comparison with data from various field experiments focused on infauna- and seagrass-bearing sediments. The model parameters are partially constrained by physical data from core samples collected at the field experiment sites. Empirical relations between the core data parameters and acoustic data will also be examined. [Work supported by ONR and ARL:UT IR&D.]
Implications from a clay/silt suspension model of mud for data from the Seabed Characterization Experiment
Authors: Brown Elisabeth M. , Pierce Allan D. , Lin Ying-Tsong , Chaytor Jason D. , Siegmann William L.
Published: April 2018

Mud-like marine sediments may be modeled as a suspension of flocculated clay particles in water, in which silt particles are embedded in the clay flocs. Recent calculations based on this model [Pierce et al., New Orleans ASA] produced new predictions for the frequency-dependent phase speed and attenuation of compressional waves. For phase speed, very good comparisons between model predictions and archival data were found. Comparisons will be presented using geoacoustic data from sediment cores extracted from the New England Mud Patch. For attenuation, predictions using Gaussian distributions of silt particle radius were calculated. An approach will be described for producing a frequency-dependent effective particle radius to account for size-distribution effects using single-particle attenuation expressions. The influence of non-Gaussian size distributions on the effective radius and on the frequency intervals of near-linear attenuation behavior will be shown. An environmental model for a WHOI AUV track deployed in the ONR Seabed Characterization Experiment was constructed, and initial comparisons were made between transmission loss calculations and acoustic data. Benchmarking will be performed with additional forward calculations, along with estimates of geoacoustic properties. Particular interest is in sediment attenuation and its frequency dependence. [Work supported by ONR.]
Three-dimensional shallow water sound propagation and applications toward acoustical oceanography
Authors: Lin Ying-Tsong
Published: April 2018

Underwater sound propagation in areas of the continental shelf, shelf break, and continental slope can encounter strong horizontal reflection, refraction, diffraction, focusing, and/or defocusing due to a variety of environmental factors, including bathymetric variability, water column fluctuations (internal waves and shelf-break fronts), and boundary roughness. Theoretical, numerical, and experimental approaches have been taken to investigate the underlying physics of these three-dimensional (3-D) sound propagation effects and their temporal and spatial variability induced jointly by marine geological features and dynamic oceanographic processes. Some recent work on theoretical analysis, numerical modeling and field work experiments to study 3-D sound propagation in nonlinear internal wave ducts, over the continental slope and in submarine canyons will be reviewed in this talk. The ultimate goal of investing these 3-D sound propagation effects is to improve long-distance acoustical oceanographic technology in complex ocean environments. An example using a 3-D back-propagation method for acoustic inverse problems will be presented, along with discussion on feature applications. [Work supported by the Office of Naval Research.]
Spectral-based quantitative ultrasound imaging: A model free approach
Authors: Oelze Michael L. , Nguyen Trong , Do Minh
Published: April 2018

Quantitative ultrasound (QUS) imaging can improve the diagnostic capabilities of ultrasound. Spectral-based QUS approaches utilize backscattered ultrasound signals to extract additional information about tissue state. These technique have traditionally relied on scattering models to differentiate tissue state. However, the use of machine learning approaches may obviate the need for models. A model-based and model-free (principle component analysis (PCA)) approach to spectral-based QUS were compared for their ability to differentiate fatty from non-fatty liver in a rabbit model. PCA was observed to provide better differentiation of fatty from non-fatty liver, i.e., PCA predicted fatty liver 86% of the time versus 36% for model-based. In addition, three calibration approaches for spectral-based QUS were compared: the traditional reference phantom, reference free, and an in situ calibration target. To test the calibration procedures, a phantom was scanned with and without a lossy layer placed on top and integrated backscatter coefficients (IBSCs) were calculated from the scattered data. Utilizing an in situ calibration target provided the ability to account for transmission losses and attenuation. The root mean square error between IBSCs estimated from the phantom with and without the lossy layer were 8.28 for the reference phantom versus 1.24 for the in situ calibration approach.
Lung ultrasound surface wave elastography for assessing interstitial lung disease
Authors: Zhang Xiaoming , Zhou Boran , Clay Ryan , Zhou Jinling , Osborn Thomas , Bartholmai Brian , Greenleaf James F. , Kalra Sanjay
Published: April 2018

A lung ultrasound surface wave elastography (LUSWE) technique is developed for assessing interstitial lung disease (ILD). In LUSWE, a 0.1 second harmonic vibration is generated on the chest wall of a subject using a handheld vibrator. An ultrasound probe is aligned with the vibration indenter in the same intercostal region to measure the generated surface wave speed of the lung. A human subject is examined in a sitting position. The lung is tested at the total lung volume. The upper anterior lungs are tested through the second intercostal space in the mid-clavicular line. The lower lateral lungs are tested in the mid-axillary line and the lower posterior lungs are tested in the mid-scapular line. In a prospective clinical study, we measure both lungs through the six intercostal regions for patients and healthy controls. The surface wave speed is measured at 100 Hz, 150 Hz, and 200 Hz. Significant differences of wave speed between patients and controls were found in all lung regions at all frequencies. We also found positive correlation between LUSWE and CT analyses. LUSWE is a safe and noninvasive technique for generating and measuring surface wave propagation on the lung. LUSWE may be useful for assessing ILD.
A revisit to the lumped element model of capacitive MEMS microphones
Authors: Du Yu , Kuntzman Michael , Chen Yenhao
Published: April 2018

Lumped element model (LEM) in the format of equivalent circuits are commonly used to describe dynamic characteristics of electromechanical transducers such as capacitive MEMS microphones. The derivation of such a LEM relies on classical electroacoustic and electromechanical principals and assumes physical elements with simple geometries and boundary conditions. However, practical designs rarely meet these assumptions, which leads to difficulties to extract model parameters with pure theoretical methods and limits the model usage to guide real designs. This study presents an improved LEM for MEMS microphones in which a hybrid theoretical-experimental method is used to extract model parameters. In particular, the mechanical compliance of the moving diaphragm and the transduction coefficient from the mechanical domain to the electrical domain are directly measured using laser Doppler vibrometer, which accounts for the influences of complex boundary conditions and geometrical shapes of actual designs. Furthermore, the diaphragm softening effect due to capacitive loading in the interface circuits is also included. Results predicted by the improved LEM are compared to measurements. It is shown that the newly proposed model can accurately capture the microphone response in the audio region. With care, its use may be extended to the ultrasonic range up to 40–50 kHz.
Miniature microphones: Non-standard fabrication approaches and associated modeling issues
Authors: Rufer Libor
Published: April 2018

Micro-electro-mechanical systems (MEMS) allowed miniature microphones that during the last few decades have left research laboratories to enter a massive industrial development. Their characteristics meet the most demanding specifications of various portable devices. This talk will show some non-standard approaches to the fabrication technology and associated modeling issues using two cases of specific designs in support. The first case is a piezoresistive microphone devoted to high-intensity and high-frequency acoustic fields. To damp the resonance, an atypical diaphragm structure was employed. Such a solution, allowing relatively large airgap required by large diaphragm displacements, will be presented and analyzed. The second case concerns a design of a microphone fabricated with a standard complementary metal oxide semiconductor (CMOS) technology. This technology, in contrast with dedicated technologies typically used by the microphone industry, is readily available to small companies and academic institutions. One of the drawbacks of the CMOS-MEMS approach is a relatively high degree of design constraints represented by materials and layers dimensions involved in the CMOS process. Moreover, the device layout must take into account specific requirements of the fabrication technique. This talk will present some of these constraints and their impact on the microphone performance that will be supported by simulation results.
Hearing health for adults
Authors: Murphy William J.
Published: April 2018

Recent analyses of the National Health and Nutrition Examination Survey estimate that 14% of adults between ages 20 and 69 have hearing loss defined as average hearing thresholds worse than 25 dB HL across four frequencies 0.5, 1, 2, and 4 kHz. Noise exposure is a primary cause of preventable hearing loss in the United States; an estimated 22 million American workers are exposed to hazardous noise every year. Given its associated implications on communication, education, employment opportunities, job performance, injury-risk, depression, and anxiety—hearing loss places a significant burden on society. Preventive initiatives, workplace hearing conservation programs, and habilitation/rehabilitation efforts need to be tailored to specific populations, stages of life, and hearing risk factors. Innovative hearing health programs must be developed, evaluated, and implemented. This presentation will discuss innovations in hearing loss prevention and promote hearing health for adults in the occupational and non-occupational settings.
Development and implementation of a military auditory fitness-for-duty test battery
Authors: Tufts Jennifer B. , Audette William , Wilbur Jed , Clavier Odile
Published: April 2018

Hearing loss is prevalent throughout the active duty military forces. However, there are no validated standards for assessing a service member’s functional hearing ability and how it relates to his or her ability to accomplish the mission. In many cases, hearing-critical tasks take place in non-optimal environments with background noise or competing speech from multiple sources. Presently, hearing abilities are primarily assessed via pure-tone audiometry, without regard for the hearing-critical needs and noise environment of the individual. The development of a test battery to evaluate functional hearing ability is a highly sought-after goal. With support from the Department of Defense, Creare LLC and the University of Connecticut are developing the MILSINT, a new sound-recognition-in-noise test geared specifically for active duty personnel. The MILSINT is one component of an auditory fitness-for-duty test battery that at present also includes the Military HINT, a version of the Hearing In Noise Test (HINT) that uses military-specific phrases. The MILSINT and Military HINT are administered using a tablet interface and wireless sound-attenuating headset developed by Creare, LLC., making these tests highly portable and versatile. This presentation will describe the development of the test battery, its physical implementation, and performance data gathered to date.
Progress in assessing and limiting occupational noise exposures in the United States
Authors: Neitzel Richard , Roberts Benjamin , Sayler Stephanie , Cheng Wenting , Mukherjee Bhramar
Published: April 2018

Occupational noise exposures in the United States (US) have resulted in a substantial occupational health burden on US workers. Despite the presence of regulations mandating exposure assessment and hearing loss prevention measures for highly-exposed workers, the prevalence of noise-induced hearing loss continues to be high. However, several recent efforts may result in progress in reducing exposures to, and health impacts from, occupational noise. First, the American Conference of Governmental Industrial Hygienists has recently proposed revisions to the organization’s Threshold Limit Value (TLV) for Audible Sound, formerly referred to as noise. The proposed revised TLV includes updated documentation as well as notes related to non-auditory health effects of noise (including cardiovascular disease and injuries), which have not previously been considered in an occupational noise exposure limit. Second, a measurement-based national Job Exposure Matrix for Occupational Noise in the US and Canada has been developed at the University of Michigan and is now publicly available (noisejem.sph.umich.edu). This resource represents a useful tool for better understanding exposures to noise by job and industry. These two efforts, along with others, represent important progress in enhancing occupational health by protecting workers from the adverse health effects of noise.
Have the NIOSH age correction tables gone stale?
Authors: Flamme Gregory , Deiters Kristy , Murphy William J. , Themann Christa , Stephenson Mark R.
Published: April 2018

Occupational Hearing Conservation programs permit subtracting cross-sectional trends in hearing sensitivity from the changes observed with an exposed worker. Regulatory agencies in the U.S. define the expected cross-sectional trend using the NIOSH age correction tables, which summarized mean differences in comparatively small groups of men and women 50 years ago. At all ages, hearing sensitivity is better now than it was 50 years ago, and important demographic characteristics (e.g., race/ethnicity) that predict cross-sectional trends were not included in the NIOSH tables. Quantile regression results from the National Health and Nutrition Examination Survey (NHANES) were used to derive revised age correction tables that can be applied to men or women across a wider range of ages and race/ethnicity categories. These age correction tables and comparisons with the prior NIOSH tables will be presented.
Phase-locking in acoustic hearing: Upper limits, enhancement, and transformations
Authors: Joris Philip X.
Published: April 2018

Phase-locking is a remarkable neural property of various mechanoreceptor-based sensory systems, and the neural coding of cochlear vibrations is the primary model system to study this phenomenon. Transduction and synaptic transmission by cochlear inner hair cells enables but also limits temporal coding in the auditory nerve. I will review phase-locking to sound fine-structure in the auditory nerve of various species, including humans, assessed with different types of sound stimuli and using different metrics. The upper-frequency limit of phase-locking in cell populations in the central nervous system is lower than that in the auditory nerve, and at the same time, the nature of the temporal code is transformed in these neurons: phase-locking is enhanced in that it is more consistent and has decreased jitter, and it has profound effects on the average discharge rate of various populations of neurons, both monaurally and binaurally. Similar phenomena (changing upper limits, enhancement, and rate effects) are observed in the temporal coding of envelopes and click trains. While it is increasingly clear that many cell groups in the auditory brainstem have specialized mechanisms towards temporal coding, the relationship of the resulting response properties to perception remains unclear.
Restoring binaural and spatial hearing in cochlear implant users
Authors: Litovsky Ruth , Kan Alan , Thakkar Tanvi , Anderson Sean R. , Peng Z. Ellen , Leclère Thibaud
Published: April 2018

Adults and children who receive bilateral cochlear implants (BiCIs) have the potential to benefit from the integration of inputs arriving at the brain from both ears. Several factors play a key role in determining if patients will demonstrate binaural sensitivity. We are exploring these factors using two experimental approaches. In the first approach, BiCI users receive pulsatile stimulation to specific pairs of electrodes using research processors that synchronize stimulation with fidelity. We vary stimulus parameters such as temporal fine structure and envelope cues, places of stimulation along the cochleae, and number of electrodes to find parameters that maximize sensitivity to interaural differences for each patient. We also investigate the role of the electrode-neuron interface which is affected by numerous factors including neural health. In a second stimulation approach, we use clinical speech processor to deliver binaural stimulation designed specifically for that patient based on their clinical MAP. In these studies, we are using both standard psychophysics and eye gaze paradigms to understand the underlying processing involved in binaural and spatial hearing. This combined approach is enabling us to design multi-channel multi-rate stimulation strategies aimed at restoring binaural sensitivity and preserving speech understanding.
Temporal constraints on neural and psychophysical sensitivity to interaural level difference cues to sound source location
Authors: Brown Andrew D. , Tollin Daniel J.
Published: April 2018

Interaural differences in the timing (ITD) and level (ILD) of impinging sounds carry critical information about source location. However, in everyday listening environments, sounds are often decorrelated between the ears by reverberation and background noise, degrading the fidelity of both ITD and ILD cues. Similar distortions to ITD and ILD are also experienced by hearing-impaired humans who use hearing aids or cochlear implants, as these devices also degrade temporal and intensive features of the signal at each ear. Here, we demonstrate that behavioral ILD sensitivity (in humans) and neural ILD sensitivity (in single neurons of the chinchilla auditory midbrain) remain robust under stimulus conditions that render ITD cues undetectable. Neural and behavioral data were compared to the outputs of a model of ILD processing with a single free parameter, the duration of excitatory-inhibitory interaction. Behavioral, neural, and modeling data collectively suggest that ILD sensitivity depends on binaural integration of excitation and inhibition within a ≳3-ms temporal window, significantly longer than observed in lower brainstem neurons. This relatively slow integration potentiates a unique role for the ILD system in spatial hearing that may be of particular importance when informative ITD cues are unavailable. [Work supported by F32-DC013927 [ADB] and R01-DC011555 [DJT].]
Tracking chimpanzee pant-hoot changes across time and space
Authors: Wilson Michael , O'Bryan Lisa R. , Plummer Andrew R. , Beckman Mary E. , Munson Benjamin
Published: April 2018

Humans differ strikingly from other primates in the capacity for vocal learning. How and why such vocal flexibility evolved remains puzzling. Evidence of geographic variation in the pant-hoot calls of chimpanzees (Pan troglodytes) suggests that chimpanzees have some capacity for vocal learning, which is intriguing given the close phylogenetic relationship between humans and chimpanzees. Many questions remain, however, about the various factors that might contribute to variation in acoustic structure of pant-hoot calls, including body size, health, genetic relatedness, and within-individual variation. We are currently examining these factors in a study of longitudinal recordings from individuals in two neighboring chimpanzee communities in Gombe National Park, Tanzania. As in studies of sound change in human social groups, we need to understand the articulatory mechanisms that produce the vocalizations, to interpret acoustic variation against the backdrop of factors including body size, sex, and age. The same considerations in studies aimed at understanding the ontogeny of human vocalizations have prompted the development of age-specific articulatory synthesis models. We are adapting such models to design analysis-by-synthesis methods for our cross-population longitudinal study, and have organized this session to explore analogous methods for studying other vocalization types in chimpanzees and other non-human primate species.
Physical growth drives vocal sequence development in marmoset infants
Authors: Zhang Yisi , Ghazanfar Asif
Published: April 2018

The vocal sequences of marmosets exhibit many drastic changes during infancy. One of the most pronounced of these is the gradual convergence from a variety of call types in the undirected context to long distance contact calls (aka phee calls). We conjecture that such change is attributed to the interplay between the neural fluctuation and the biomechanics of the developing vocal periphery. To explore such possibility, we first quantitatively characterize vocal sequences and correlate them with animal momentary arousal levels. Based on this, we show that the diversity of respiratory and laryngeal patterns, as well as the commonly produced sequence transitions, can be generated via simple coupled oscillators with a low-dimensional input. In addition, the model predicts that as the respiratory apparatus grows, not only does the oscillatory period increase, but also the proportions of call types become biased towards phee calls. We further empirically test this hypothesis by placing the marmoset infants in a helium-oxygen (heliox) environment where the much lighter air reduces vocal effort, simulating smaller lungs. Consistent with the model prediction, the heliox manipulation reduces phee call duration and increases the proportion of other call types.
Chimpanzee food-associated calls display low referential potential in a wild population
Authors: O'Bryan Lisa R. , Munson Benjamin , Wilson Michael
Published: April 2018

Studies of non-human primate vocal communication commonly focus on “functionally referential signals,” which are thought to function like human words, informing receivers about stimuli in the external environment. Captive studies of the food-associated “rough-grunt” of chimpanzees (Pan troglodytes) report that their acoustic structure varies according to food quality and even type, suggesting the existence of functionally referential communication in humans' evolutionary cousins. Nevertheless, studies of wild chimpanzees have produced mixed evidence that rough-grunts function referentially in natural contexts. The current study builds upon these findings by conducting an acoustic analysis of rough-grunts produced by wild chimpanzees at Gombe National Park, Tanzania, examining acoustic variation in call duration and peak frequency both within and between feeding bouts. We found that peak frequency, but not duration, displayed a bimodal distribution, supporting the view that rough-grunts include at least two acoustic sub-types. Nevertheless, calling bouts produced within each feeding bout reliably encompassed this full range of acoustic variation and calls did not display consistent temporal patterns of variation throughout feeding bouts. Our findings are thus inconsistent with the idea that rough-grunts label food properties. Rather, we argue that rough-grunts broadcast information about the signaler’s foraging or social intentions.
Michael Owren's contributions to methods and models of vocal production for human and non-human primates
Authors: Rendall Drew
Published: April 2018

This part of the special session comprises a review of some of the highlights of Michael Owren's many contributions to adapting methods and models of vocal production across primate species, punctuated by comments and discussion by the invited speakers, in preparation for the larger panel discussion at the end of the session.
Time reversed elastic nonlinearity diagnostic applied to stress corrosion cracking in stainless steel
Authors: Young Sarah M. , Anderson Brian E. , Hogg Stephen M.
Published: April 2018

The Time Reversed Elastic Nonlinearity Diagnostic (TREND) is an inspection technique that enables one to locate damage in a structure using time reversal processing. TREND has been used to detect various types of damage in metals and rocks, but little has been done specific to stress corrosion cracking (SCC) other than the work of Anderson et al. J. Acoust. Soc. Am. 141, EL76–EL81 (2017). SCC in stainless steel, especially around welds, is produced as a result of elevated temperature and saline conditions, and so has different properties from fatigue cracking or delaminations, both of which have been studied with TREND. In current research, welded steel samples exposed to a magnesium chloride bath were created. A number of samples were exposed for successively longer durations in order to study the corrosion damage level versus exposure time. Using TREND, samples were scanned then evaluated for indicators of local cracking at each scan point. Specific changes in spectral characteristics that are indicators of cracking were found to correlate to a longer exposure time and therefore the extent of SCC damage at that location.
Using time reversal focusing for active control of magnetic resonance imaging noise
Authors: Furlong Trent , Anderson Brian E.
Published: April 2018

The noise produced by a Magnetic Resonance Imaging (MRI) scan can cause discomfort to patients. Active Noise Control (ANC) systems have been developed to help reduce the amount of noise a patient experiences. However, due to the small enclosure of the MRI machine, ANC equipment can be cumbersome to use, and is limited to non-ferrous material. Time Reversal Acoustics (TRA) is a technique that can focus sound to a selected position in space that may be far from actual sound sources. We are exploring using TRA to deliver an ANC signal by broadcasting “anti-noise” signals that are focused to the patient’s ears through TRA to cancel the MRI noise. This presentation will explore the applicability of using TRA to deliver different types of ANC signals to determine limitations in this process and show some proof of concept results.
Acoustical balance between the stage and the pit in the Teatro Colón of Buenos Aires
Authors: Basso Gustavo J.
Published: April 2018

The acoustical balance between the singers and the orchestra in the well-known Teatro Colón of Buenos Aires, as an opera theater, is evaluated from several perspectives. The almost ideal balance seems to be a result of a particular combination of architectural features: among others, the shape of the horseshoe, the height and depth of the boxes at the upper levels, and the design of the proscenium and pit. In this sense, the reflections on the stage floor become significant for the higher levels. Some of the architectural causes of this acoustical behaviour have been found out from the results of opinion polls on the perceived sound by the audience, physical measurements, and the outcomes of a digital model. This paper analyses the balance between the singers, placed in various locations on the stage, and the orchestra in the pit. As it will be seen, the architectural characteristics of the theater allows the musicians to maintain the balance in almost ideal values and to preserve the spectral equilibrium and bass response through the entire hall.
Development and implementation of a construction noise and vibration management plan for occupied healthcare facilities
Authors: Jarta Gina , Dick Elliott
Published: April 2018

Acoustics and noise management play an integral role in providing an optimum care environment for patients and staff of healthcare facilities. Indoor noise and vibration affect patient comfort and healing, clear communication, operation of sensitive imaging equipment, and overall occupant satisfaction. Construction and demolition activities often occur in occupied hospitals requiring ongoing noise and vibration sensitive operations to remain active. This case study presents the development and implementation of a construction noise and vibration management plan for a neonatal intensive care unit (NICU) expansion project. The expansion included the addition of 23 NICU beds an existing roof level, directly adjacent to an existing NICU unit, Post-Anesthesia Care Unit, operating rooms, and In Vitro Fertilization clinic which remained in operation during demolition and construction. The acoustical design process from establishment of baseline conditions, prediction of project-related noise and vibration, design of mitigation strategies, and development of the management plan will be presented. Monitoring data collected over the 15 month demolition and construction period will be reviewed along with project implementations strategies and lessons learned.
Acoustic emissions by marine algae during photosynthesis
Authors: Freeman Simon E. , Freeman Lauren , Giorli Giacomo , Haas Andreas F.
Published: April 2018

Coastal underwater soundscapes typically contain signals from soniferous, biological processes. Identifying the sources that contribute to oftentimes acoustically complex soundscapes would facilitate a noninvasive, remote, and volumetrically integrative method to survey underwater ecological state, as has been demonstrated on land. To date the lack of knowledge on these sources has posed a challenge for extracting meaningful ecological information from underwater biological soundscape recordings. We have observed that photosynthesis by macroalgae is an acoustically active process, driven by oxygen bubbles separating from the algal surface and ringing at the Minnaert frequency. The resultant soundscapes correlate with benthic macroalgal cover across ecological gradients on shallow Hawaiian reefs during periods of daylight. Bubble size, production rate, and sound exposure level follow the concentration of dissolved oxygen, which in turn rises and falls with the availability of photosynthetically active radiation. Increased macroalgal cover results from climate related stress, overfishing and/or pollution through nutrient runoff and serves as an indicator of degradation in many underwater ecosystems. Our observation lays the foundation for signal processing methods that quickly and passively evaluate relative algal abundance in littoral waters. These findings can also be applied towards more accurate monitoring of primary production in industrial processes.
Quantifying the effect of random roughness on synthetic aperture sonar image statistics
Authors: Lyons Anthony P. , Olson Derek R. , Hansen Roy E.
Published: April 2018

A perturbation-theory-based model has been developed to predict the effect of random seafloor roughness on synthetic aperture sonar (SAS) image statistics. The continuous variation in scattering strength produced by a random slope field is treated as an intensity scaling on image speckle produced by the SAS imaging process. Changes in image statistics caused by roughness are quantified in terms of the scintillation index (SI). Factors influencing the SI include slope variance, geo-acoustic properties of the seafloor, the probability density function describing the speckle and the signal-to-noise ratio. Example model-data comparisons will be shown for SAS images taken off the coast of Tellaro, Italy, by the NATO Undersea Research Centre, La Spezia, Italy (now the NATO Centre for Maritime Research and Experimentation) using the 300 kHz MUSCLE SAS system, and for data collected with the Norwegian Defence Research Establishment’s 100 kHz HISAS system off the coast of northwest coast of Elba Island, Italy, in 2013. Parameter estimates obtained from high-resolution SAS data collected in these experiments will be used to illustrate the efficacy of the model and its possible use for estimating roughness parameters, such as root-mean-square slope. [Work performed under ONR Grant Nos. N00014-10-1-0051, N00014-10-1-0047, and N00014-10-1-0151, and NOAA Grant No. NA15NOS4000200.]
Pressure and particle velocity measurements from a broad band source at ranges 1–10 km
Authors: Dahl Peter H. , Dall'Osto David R.
Published: April 2018

The IVAR system (Intensity Vector Autonomous Recorder) is a bottom deployed system developed for first-use in the Sediment Characterization Experiment (SCE17), conducted on the New England Mud Patch [40°28’ N, 70°35’ W] in spring 2017. IVAR continuously and coherently records four channels of acoustic data, three from a tri-axial accelerometer embedded in a neutrally buoyant sphere (diameter 10 cm) and one from an omnidirectional hydrophone positioned 10 cm above the centroid of the sphere positioned 1.2 m above the seafloor. The connection of these measurements to understanding seabed properties as part of SCE17 has been discussed previously. Here, emphasis is placed on documenting pressure and particle velocity signals as these quantities evolve with range from a broad band explosive source (Mk64 SUS charge). We explore the phase relation between pressure and components of particle velocity through study of active (in phase) and reactive (out of phase) intensity, as well as corresponding non-dimensional indices of the acoustic vector field, and discuss how these are influenced by propagation conditions. The work has relevance to both the ongoing geoacoustic studies from SCE17 as well as to studies on the sensitivity of fish to acoustic particle velocity generated by explosions.
Reconstructing one-dimensional positions of spherical scatterers from overlapping echoes
Authors: Han Aiguo
Published: April 2018

A new method for identifying the one-dimensional positions of spherical scatterers from overlapping echoes is described. This problem is of interest because various tissues (e.g., solid tumors) can be modeled as an ensemble of discrete scatterers (e.g., tumor cells). Existing quantitative ultrasound methods are successful in estimating the scatterer size by fitting an acoustic scattering model to the backscatter coefficient estimated from the radio-frequency data. However, the scatterer positions cannot be recovered from severely overlapped echoes using such quantitative ultrasound methods alone. In the method proposed herein, the forward scattering problem is formulated based on a sparse discrete scatterer assumption. The forward problem takes into account the effects of attenuation, scattering function, transducer diffraction and system response function, all of which can be estimated or corrected using quantitative ultrasound techniques. The scatterer positions are then recovered by solving the inverse problem using compressive sensing techniques. The detection limit (distances between scatterers and number of scatterers) is investigated through numerical simulations as a function of various real-world factors such as the signal-to-noise ratio. Super resolution capability is demonstrated. Physical phantom experiments performed using single-element transducers will be presented to evaluate the method. [Support: NIH R01DK106419 and NIH R37EB002641.]
A continuous power law wave equation for biomedical ultrasound
Authors: Kelly James F. , Meerschaert Mark M. , McGough Robert
Published: April 2018

The attenuation coefficient in most biological media is a power law with respect to frequency. Measurements indicate that the power law exponent y is near or exactly one for many classes of tissue. In J. Acous. Soc. Am. [124 2861–2872 (2008)], a power law wave equation (PLWE) was proposed to model this power law dependence using Riemann-Liouville fractional derivatives. The PLWE, like most other fractional calculus models for attenuation in the time-domain, is invalid for y =1 due to a discontinuity in the phase velocity. To address this problem, a continuous power law wave equation (CPLWE) is proposed that is valid for all power law exponents between zero and two. The CPLWE utilizes the recently developed Zolotarev fractional derivative of order y, which is a nonlocal operator even for y = 1. The 3D Green's function for the CPLWE that is valid for homogeneous media is derived using stable probability density functions in the Zolotarev M-parameterization. Solutions to the CPLWE that are valid for inhomogeneous media are then expressed as solutions to the wave equation subordinated to an inverse stable density. These subordinated Green's function solutions transition smoothly between y<1 and y>1 power laws, which facilitates estimation of attenuation parameters in biological media with y close to one.
Subharmonic generation by shear waves in a 1D resonator formed with a relaxing material
Authors: Cormack John M. , Hamilton Mark F.
Published: April 2018

The low shear moduli of soft elastic media such as rubber and tissue facilitate the excitation of shear waves that exhibit significant finite-amplitude effects. Measurements performed by Andreev et al. [Acoust. Phys. 57, 779 (2011)] of the amplitude-dependent response of a 1D shear-wave resonator formed with a rubber-like material revealed reasonable agreement with numerical simulations based on a monorelaxing material model. At the previous ASA meeting the present authors developed an augmented Duffing equation as a model for plane shear waves in a resonator formed with a monorelaxing material that is shaken at one end and free at the other [J. Acoust. Soc. Am. 142, 2723 (2017)]. The focus of the previous work was on the response at drive frequencies near the lowest resonance. Here the augmented Duffing model is used to investigate subharmonic generation associated with a drive frequency of approximately three times that of the lowest mode. Conditions on the amplitude and frequency of excitation for which subharmonic generation can occur are obtained from the augmented Duffing equation. Results obtained from the augmented Duffing equation are compared with direct numerical solutions of a nonlinear wave equation. [Work supported by the ARL:UT McKinney Fellowship in Acoustics.]
Parametric phantom study of shear wave velocity image reconstruction
Authors: Urban Matthew W. , Racedo Jorge
Published: April 2018

Shear wave elastography is being increasingly used for multiple applications including investigation of diffuse disease in the liver or kidney and malignancies or neoplasms in the breast and thyroid. It is important to provide robust and accurate reconstructions of shear wave velocity (SWV) for imaging purposes to provide reliable data for diagnosis. One such approach was a two-dimensional method for estimating SWV (Song, et al., Ultrasound Med. Biol. 40, pp. 1343–1355, 2014). This method uses a weighted average using a large window and smaller patches to perform time-domain cross-correlations for the calculation of the SWV. We also implemented a spatial sigmoid weighting to combine reconstruction results from independent reconstructions after directional filtering. We used a Verasonics system equipped with a linear array transducer to conduct a parametric study in phantoms to investigate the effects of the window and patch on image reconstruction metrics. Measurements were made in homogeneous phantoms and in a phantom with cylindrical inclusions of different diameters. Larger windows and patches typically yielded low variability but did not always produce the highest contrast. This investigation is the basis for an adaptive method for reconstructing SWV in soft tissues and choosing optimal parameters for the SWV reconstruction.
Conflicting sounds in natural recreation areas—An historical Minnesota perspective
Authors: Braslau David
Published: April 2018

Minnesota has long seen battles between conflicting activities in natural recreation areas. Snowmobiles were first introduced in the 1960 by two Minnesota firms. By the 1970s physical and noise impacts had increased and a state committee to address trail uses and conflicts was established. In the same time period, a large scale environmental impact study on effects of copper-nickel mining on the BWCAW and national forest was initiated. A noise model was developed by Moorhead State staff that compared mining noise with natural noise levels. This issue rested until 2007 when exploration drilling started 24/7 in the Superior Nation Forest and near the BWCAW. Extensive monitoring and modeling efforts were undertaken by the companies and the Forest Service and limits established on acceptable noise levels. The snowmobile noise problem has not gone away with periodic controversy and assessment. To the south, the Saint Croix National Scenic Riverway (NPS) and the Minnesota Valley National Wildlife Refuge (USFWS) have both addressed potential noise intrusion from adjacent sand and gravel mining activities. Of course, the BWCAW was the center of long term disputes over noise, with motors now limited to only a few lakes and low altitude aircraft flights prohibited.
Acoustic waveform inversion and uncertainty analysis for explosion yield estimation
Authors: Kim Keehoon , Rodgers Arthur
Published: April 2018

Waveform inversion techniques are widely used to extract source information from acoustic signals. The methods exploit full-waveform information and provide further constraints on source inversion than other parameter-based inversions. Infrasound waveform inversion was recently applied to chemical explosions and showed promising results for the determination of explosion yield. The method can improve the accuracy of the estimated yield by using full 3-D numerical Green's functions and incorporating the propagation path effects into the inversion. However, the inversion results are often given without any uncertainty estimation, which is critical for a post-detonation forensic analysis. In this study, we evaluate the yield estimation errors associated with the uncertainty in the atmospheric representation. An ensemble of atmospheric realizations is obtained by adding random turbulence to an atmospheric model and the uncertainty of inversion solution depending on atmospheric variation is quantified. In addition, different atmospheric models derived from local weather data or numerical weather prediction models are validated for yield estimation by using a series of chemical explosion data.
Realistic terrain boundary conditions for the three-dimensional finite-difference parabolic equation method applied to infrasonic propagation
Authors: Khodr Codor , Azarpeyvand Mahdi , Green David
Published: April 2018

Infrasound propagation in the atmosphere can be significantly influenced by environmental parameters such as meteorology and topography. An accurate modelling of these parameters and their effects can improve signal processing of infrasound arrivals and development of more accurate prediction tools. Over the last few decades, much attention has been given to the integration of complex atmospheric features, namely, absorption, turbulence, density, and refraction, into the numerical methods, while topographic effects have usually been neglected. In this respect, the Parabolic Equation (PE) method has been continuously improved to deal with complex configurations encountered in various applications, such as atmospheric waveguides, ocean acoustics and electromagnetics. We have further extended the Beilis-Tappert (BTPE) generalized coordinate transform to three-dimensional propagation in order to account for out-of-plane scattering by irregular three-dimensional topography, in the presence of air density variation with altitude. The resulting PE method is then implemented into a numerical solver and used to model wave propagation over a set of generic and realistic terrain and atmospheric conditions. A comparison against two-dimensional PE simulations allows us to isolate three-dimensional effects enabled by the out-of-plane propagation and to better understand the underlying physics of atmospheric wave propagation with complex terrain and atmospheric conditions.