bluuebunny/crossref_metadata_2025 huggingface dataset:
Decoherence effects in 3D fluctuating environments: Numerical and experiment study
Authors: Real Gaultier , Cristol Xavier , Habault Dominique , Fattaccioli Dominique
Published: June 2017

This paper is devoted to the study of the effects of ocean fluctuations on acoustic propagation. The development of an ultrasonic testbench allowing to reproduce, under laboratory conditions, the influence of 3D fluctuations on received acoustic data is presented. The experimental protocol consists in transmitting, in a water tank, a high-frequency wavetrain throughout an acoustic slab presenting a plane input face and a randomly rough output face. The various regimes of saturation and unsaturation classically used in the literature are explored by tuning the statistics of the so-called RAFAL (RAndom Faced Acoustic Lens). Comparisons to a “corresponding” oceanic medium are obtained via a scaling procedure. In parallel, numerical tools were developed to provide meaningful comparison with the acquired data. Both based on a split-step Fourier algorithm, a 3D PE simulation of the tank experiment and a 3D PE simulation of real scale acoustic propagation programs are presented. Features of acoustic fields perturbed by internal waves are found. The relevance of our procedure is evaluated through calculations of the coherence function (in particular, measurement of the radius of coherence) and statistical distributions of the received complex pressure and intensity. Comparisons between our scaled measurements, numerical computations and analytical results are analyzed.
Experimental modal decomposition of acoustic field in cavitation tunnel with square duct test section
Authors: Boucheron Romuald , Amailland Sylvain , Thomas Jean-Hugh , Pézerat Charles , Fréchou Didier , Briançon-Marjollet Laurence
Published: June 2017

The operational requirements for naval and research vessels have seen an increasing demand for quieter ships either to comply the ship operational requirements or to minimize the influence of shipping noise on marine life. To estimate the future radiated noise of a ship, scale measurements are realized in cavitation tunnel. DGA Hydrodynamics operates its cavitation tunnel with low background noise which allows such measurements. Understanding acoustic propagation in cavitation tunnel remains a challenge. The success of an accurate acoustic measurement depends both on a realistic propagation model and also on an efficient control of acoustic sensor characteristics. This short communication presents the results of experiments performed in GTH (Large Cavitation Tunnel) at DGA Hydrodynamics. An acoustic source radiates pure sine wave at the entrance of the test section and generates an acoustic field measured with flush mounted hydrophones. A modal decomposition is then performed to fit measurements. Complex amplitudes of all propagative modes could be estimated both for upstream and downstream propagation. Results show that for a given frequency range, modal decomposition could be an accurate model for acoustic propagation. Furthermore, different configurations of the test section and source locations have been investigated and show acoustic properties of the tunnel.
Vertical underwater acoustic tomography in an experimental basin
Authors: Li Guangming , Ingram David , Kaneko Arata , Chen Minmo , Gohda Noriaki , Polydorides Nick
Published: June 2017

Ocean acoustic tomography is well developed for monitoring environmental parameter changing for mesoscale ocean distribution. Small scale underwater acoustic tomography could be used for flow profile mapping in experimental tank. Vertical acoustical tomography analyse is a key aspect for 3D mapping of flow current profile. This article investigates vertical underwater acoustic tomography in a circular multidirectional wave/current basin. Two modified coastal acoustic tomography (CAT) systems were deployed in the 25 m diameter circular basin. High frequency (50 kHz) M-sequence signal was transmitted reciprocally for time of flight. The 2 m depth water column was divided into 5 layers for layered analysis. Multipath arrivals reflected by surface and bottom were distinguished by ray tracing. The 0.8 m/s straight flow was generated along the sound propagation path. Vertical layered current velocity was analyzed by solving inverse problem. The study suggest that vertical acoustic tomography could be used in the lab test tank for flow current velocity measurement.
Variability of the sound field interference pattern due to horizontal refraction in shallow water
Authors: Katsnelson Boris
Published: June 2017

Variability of the ocean waveguide’s parameters in horizontal plane (bathymetry, sound speed profile, etc.) can lead to some set of effects in the sound propagation, which are specified as horizontal refraction, or in more general form, as 3D effects. These effects are being studied both in shallow and deep water, some of them were registered in experiments, or were analyzed using different theoretical models. In given paper main attention is drawn to the theory and experimental manifestation of spatial and temporal variations of interference pattern formed by narrow-band signals. Theoretical analysis is carried out using approach “Vertical Modes and Horizontal Rays” and “Vertical Modes and PE in horizontal plane.” It is shown, that dependence of the sound field distribution in horizontal plane (both in a ray or PE approaches) on frequency and mode number, combined with possible multipath propagation, may lead to rather specific observable effects: variations of the amplitude and phase fronts, evolution of signal’s spectrum and shape, appearance of whispering gallery modes in vicinity of curvilinear coastal line. Results of modeling and experiments (mainly Shallow Water 2006) are presented. Data processing techniques to register 3D effects are discussed. [Work was supported by ISF.]
Characteristics of bottom-diffracted surface-reflected arrivals in ocean acoustics
Authors: Stephen Ralph A. , Bolmer S. T. , Worcester Peter F. , Dzieciuch Matthew A.
Published: June 2017

Bottom-diffracted surface-reflected (BDSR) arrivals are a ubiquitous feature in long-range ocean acoustic propagation. BDSRs are distinct from bottom-reflected surface-reflected (BRSR) arrivals because the angle of emergence is not equal to the angle of incidence. They are not predicted by existing forward models based on available bathymetric and bottom properties data. Research cruises in the Philippine Sea and North Pacific, in 2011 and 2013, respectively, were carried out to understand BDSRs in more detail for transmissions out to 50 km range. Transmissions from a controlled source at about 60m depth were received on ocean bottom seismometers and a deep vertical line array of hydrophones. In the North Pacific experiment alone over 40 distinct bottom diffractor locations were identified. Based on these data sets BDSRs can be characterized in terms of: (a) in-plane or out-of-plane diffractors, (b) diffractor location relative to bathymetric features, c) grazing angle of the incident field, d) transmission frequency (from 75 to 310 Hz), (e) receiver type (vertical or horizontal seismometer, hydrophone, etc.), (f) receiver location, and (g) signal strength relative to direct and BRSR paths. [Work supported by ONR.]
Multi-modal and short-range transmission loss in ice-covered, near-shore Arctic waters
Authors: Penhale Miles B. , Barnard Andrew R.
Published: June 2017

Prior to the 1970s, extensive research has been done regarding the sound propagation in thick (kilometers) ice sheets in Arctic and Antarctic environments. Due to changing climate conditions in these environments, new experimentation is warranted to determine sound propagation characteristics in, through, and under thin-ice sheets (meters). In April 2016, several experiments were conducted approximately 1 mile off the coast of Barrow, Alaska on shore-fast, first year ice, approximately 1.5 m thick. To determine the propagation characteristics of various sound sources, Frequency Response Functions (FRFs) were measured between a source location and several receiver locations at various distances from 50 m to 1 km. The primary sources used for this experiment were, an underwater speaker with various tonal outputs, an instrumented impact-hammer on the ice, and a propane cannon that produced an acoustic blast wave in air. In addition, several anthropogenic sources, namely, a snowmobile, generator, and ice auger, were characterized. The transmission characteristics of the multipath propagation (air, ice, and water) are investigated and reported.
Sound propagation in deep water with an uneven bathymetry
Authors: Hu Zhiguo , Li Zhenglin , Zhang Renhe , Ren Yun
Published: June 2017

Water depth has significant effects on sound propagation in underwater. A deep-water propagation experiment along two different tracks with the flat and uneven bottoms was conducted in the South China Sea in 2014. Some different propagation phenomena and horizontal-longitudinal correlations oscillation patterns were observed. Due to the reflection-blockage effects by a sea hill with height less than 1/10 water depth, transmission losses increase up to about 8 dB in the reflection area of the sea hill than that of flat bottom. Moreover, there is an inverted-triangle shadow zone with a maximal depth of 1500 m below the sea surface. The horizontal-longitudinal correlations in the reflection area of the sea hill do not show an obvious cyclical oscillation any longer as that in flat bottom environment. The differences of the transmission losses and the horizontal-longitudinal correlations oscillation patterns are explained by using the ray theory. [Work supported by the National Natural Science Foundation of China under Grant Nos. 11434012, 41561144006, and 11404366.]
Acoustic propagation from the transitional area to deep water
Authors: Qin Jixing , Zhang Renhe , Li Zhenglin
Published: June 2017

Sound propagation over the continental shelf and slope is complicated and is also an important problem. Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at other depths, we study sound propagation from the transitional area to deep water. Numerical simulations with different source depths are first performed, from which we reach the following conclusions. When the source is located near the sea surface, sound wave will be strongly attenuated by bottom losses in a range-independent environment, whereas it can propagate to a very long range because of the continental slope. When the source is mounted on the slope bottom in shallow water, acoustic energy will be trapped near the sound channel axis, and it converges more evidently than the case where the source is located near the surface. Then, simulations with different source ranges are performed. By comparing the relative energy level in the vertical direction between the numerical results and the experimental data, the range of the unknown air-gun source is approximated. The phenomenon can be confirmed by the experiment with a deterministic source located in the transitional area. [Work supported by the National Natural Science Foundation of China under Grant Nos. 11434012 and 41561144006.]
Professor Bertram Y, Kinzey, Jr., mentor, scholar, practitioner, artist, and colleague
Authors: Siebein Gary W.
Published: June 2017

Professor Bertram Y. Kinzey, Jr., had significant impacts on the shape of architectural acoustics today through his teaching, professional practice, research, and service. He influenced several generations of students at Virginia Tech and the University of Florida where he developed innovative, laboratory-based courses to teach architects about acoustics and other environmental technology subjects. At Florida, he initiated graduate coursework to allow students to specialize in Environmental Technology and later architectural acoustics as part of the professional Master of Architecture curriculum, with a thesis in acoustics in addition. His teaching was based on ideas expressed in his landmark textbook, Environmental Technologies in Architecture that was published as a primer in the art and science of sustainable design in 1963, over 50 years ahead of its time. His students entered the profession with ideas of sustainability, integrating serious, graduate level research into their design work, grounded by the experiences that Bert brought to the classroom from his practice where he consulted on most of the major buildings built in Florida from the 1960s until his retirement many years later. The acoustical richness of the buildings that he worked on sounds clearly in all of the cities and towns where he worked!
An appreciation of the educational achievements of Bert Kinzey
Authors: Clautice Edward G.
Published: June 2017

The aim of this paper is to describe the achievements of Bertram Kinzey in the field of acoustics within architectural education. Bert Kinzey’s ability to bridge engineering and architecture is of particular note to the personal experience of the author. With Bert’s personal efforts that the University of Florida was able to begin accepting students into the program who did not have a traditional undergraduate degree in architecture. As the first student to matriculate into the Graduate School of Architecture at the University of Florida from this category the author owes a great deal of his personal career to Bert Kinzey. Bert lead the Environmental Technologies option at the School, which brought the art of music, the art of architecture and the engineering of applied technology into a combination which has enriched the profession(*). The study of concert hall architecture and acoustics has benefited greatly from Bert’s leadership where acoustical modeling and auralization can stand beside traditional visual techniques in the field of architectural modeling.
Enhancement of bass frequency absorption in fabric-based absorbers
Authors: Schira Jonas
Published: June 2017

Variable Acoustics has become an important topic in the acoustic design of multi-purpose venues but also in classical concert halls and opera houses. Varying the reverberation time in the middle and high frequencies can easily be achieved by using fabric-based absorbers like curtains or roll banners. When using fabric-based absorbers, the proportionally low absorption capability in the bass frequencies below 400 Hz can be challenging when planning a multi-purpose facility. A full range variable system would provide a great tool to consultants and architects. Double layer roll banner systems with a highly absorbing fabric are mostly installed freely hanging in front of the wall. Research shows a significant enhancement of the bass frequency absorption if the fabric is installed in an enclosed housing. This paper will examine the fundamental problem of low bass absorption capability but will also show the measurement data and technical solution for the described problem.
Noise insulation of a curtain wall for natural ventilation
Authors: Migneron Jean-Philippe , Potvin Andre , Migneron Jean-Gabriel
Published: June 2017

The growing interest in natural or hybrid ventilation systems brings a challenge for good integration of openings in building façades. In a noisy environment, there is a major limitation for the use of direct openings in common building envelopes. As a part of a research project dedicated to this problem, it is possible to evaluate the impact of a curtain wall that could be added to get a double skin façade. Experimental measurements made in laboratory conditions lead to the estimation of usual noise reduction and sound transmission class. The airflow at constant differential pressure was assessed as a function of the aperture and compared to sound insulation. Analyzing those parameters together give useful information for the design of passive ventilation with a significant airflow when acoustic performance is an important issue. This paper aims to detail performances of common curtain wall assemblies.
Design and optimization of the sound diffusers using radial basis functions-based shapes and genetic algorithms
Authors: Patraquim Ricardo , Godinho Luis , Amado Mendes Paulo
Published: June 2017

Sound diffusers are a common technical solution used in the last four decades for conditioning performance rooms with greater acoustic requirements. A significant number of the acoustic diffusers commercially available are based on the phase grating diffusers or Schroeder-type diffusers. However, in some particular cases, the visual appearance of the acoustic conditioning of the room with QRDs is considered by architects to be unaesthetic or visually unattractive in modern spaces, and thus, other geometrical forms of the diffusive surfaces or elements need to be customized and explored. The optimization of the diffusers’ design has been a topic of intense research in the last years. In this paper, the authors propose an alternative technique to define new shapes of sound diffusion configurations, based on the use of radial basis functions (RBF). In addition, to allow the definition of optimal surface shapes for a given frequency band, a genetic algorithm is used. The diffusion coefficient is computed within the optimization procedure using the Kirchoff integral equation. A set of application results are presented and discussed and experimental evaluation of the diffusers is performed in a simplified semi-anechoic room (to evaluate diffusivity) according to ISO 17497-2 in order to compare the numerical results.
Determining “reasonable” levels of sound insulation in domestic properties for use in building regulations
Authors: Mackenzie Richard G. , Robertson Nicola , Smith Sean
Published: June 2017

The Scottish Building Regulations, similar to other countries regulations, provide standards for the protection of occupants health. Minimum sound insulation standards are provided to control noise passing through walls and floors from neighboring properties. In Scotland, the minimum standard should provide adequate protection for a “reasonable” person from “normal” living activities. This paper presents the findings of a research study undertaken by Edinburgh Napier University, to assess the level of sound insulation that test subjects would deem to be “reasonable” for a range of noise sources passing through a variety of construction types. The study undertaken within the Universities auralization suite assessed the responses involving over 100 participants subjected to common domestic noise sources passing through separating structures. The participants were given the ability to adjust the source noise level for each source type to determine the level of noise from their neighbor they would consider “reasonable” to tolerate. The participants determinations were correlated to the equivalent sound insulation for each source and construction assessed. The paper will present the setup in the test suite, and the results of the study will be presented in a range of acoustic parameters, DnT,w, STC, R’w and be assessed against a range of countries current standards.
Acoustic behavior of facades: Acoustic isolation versus air permeability
Authors: Ferreira Diogo M.
Published: June 2017

Today, the acoustic comfort of dwellings is revealed as a very important factor in the context of overall comfort of its inhabitants. For this comfort, it contributes very importantly the sound insulation that the facades of buildings can provide. Since the facades comprise of an opaque portion and a translucent portion, the latter will be more relevant to the sound insulation that the facade element provides, which is influenced by the window itself, as by the openings and air permeability associated with. In order to evaluate the influence of the possible differences of acoustic insulation on a residential façade over time, an experimental study was developed in LNEC. The experimental work was based on a set of acoustic and air permeability tests considering several opening areas, between 0,5 cm² and 250 cm², in a given test window. The results obtained allow to evaluate in which direction the sound insulation versus air permeability can parameterize the performance of the facades of buildings, and what is its relationship to the well-being of residents. For the 0.5 and 1 cm² areas of aperture, no acoustic or air permeability differences were found in relation to the reference values, assuming that this scenario does not cause any significant variation in a housing façade. For the last two areas studied (200 and 250 cm²), in acoustic and air permeability terms, it is concluded that, for these areas, the scenario is similar to that of an open window due to the high loss of sound insulation and the low air permeability.
Elaborate network of avian intracranial air-filled cavities and its potential role in hearing
Authors: Jensen Kenneth K. , Christensen-Dalsgaard Jakob , Larsen Ole N.
Published: June 2017

Many avian species possess an intracranial air-filled passage, directly connecting the medial surfaces of the tympanic membranes, called the interaural canal. It is known to greatly improve directional hearing by passive acoustics in small animals where the external interaural delay is too minute to allow temporal neural coding. For long, the avian interaural canal was assumed to be a simple cylindrical cavity. Contrary to this, we discovered through CT scans and other techniques that many birds (e.g., zebra finches and pigeons) do in fact have a rather elaborate system of interconnected air-filled cavities throughout the entire skull. The cavities communicate directly or indirectly with the tympanic membranes. How does this network affect the directional hearing in birds? On one hand, it may simply be an adaptation to flight and play little or no role in hearing. On the other hand, theoretical considerations suggest that the directional response may be optimized through frequency dependent “tuning” of attenuation and phase shift through the interaural canal. In this talk, we will first present the anatomy, then present some preliminary directional responses from zebra finch ears, and finally discuss future directions and considerations for what may be the functional interaural canal in birds.
Saliency of temporal fine structure in zebra finch vocalizations
Authors: Prior Nora H. , Smith Edward , Ball Gregory F. , Dooling Robert
Published: June 2017

Previous work has shown that birds. in general, and zebra finches. in particular, have remarkable sensitivity to temporal fine structure (TFS). While spectral, envelope, and TFS cues are present in vocalizations, TFS has been largely ignored since sonographic, and not time waveform, analyses have been the mainstay in bioacoustics. However, birds’ impressive sensitivity to TFS raises the question of whether behaviorally relevant information is carried within the TFS. Indeed, zebra finches have at least 10 call types that both males and females use in sophisticated ways to coordinate activities. Furthermore, zebra finch vocalizations are typically composed of harmonic stacks, rich in TFS. Here, we isolated and described patterns in the TFS between and within individuals for different call types and constructed test stimuli from these patterns of TFS for psychoacoustic experiments. Demonstrating TFS sensitivity within natural stimuli would argue for the increasing salience of TFS for real-life communication in birds. [Work supported by a NIDCD T32 DC000046-16 to NHP.]
Perspectives of ongoing acoustic developments for measuring sediment dynamics
Authors: Thorne Peter D. , Hurther David
Published: June 2017

Sediment entrainment, transport, and deposition over bedforms can be highly dynamic with strong spatially temporal variability. To probe the multi-scaled processes of sediment transport, there has been continuing developments of instrumentation to obtain high resolution measurements of near-bed sediment dynamics. Such observations are used for both the development and assessment of process based sediment transport modeling. Here, results are reported from studies on developing high resolution acoustic instruments, deployed to make co-located observations of bedforms, the near-bed and suspended concentration fields, and the horizontal and vertical components of intra-wave and turbulent flows. To evaluate the instruments, a series of bottom boundary layer measurements were collected over sandy sediments under differing conditions. The acoustic instruments under examination consisted of a Bedform and Suspended Sediment Imager, BASSI, a three dimensional acoustic ripple profiler, 3D-ARP, and high resolution Acoustic Concentration and Velocity Profilers, HR-ACVP. The results obtained from the instruments are used to illustrate ongoing developments in acoustics and its expanding capability for studying the dynamics of near-bed sediment transport processes.
Measuring sediments: Backscatter optics, laser diffraction, acoustics, and combined optics and acoustics
Authors: Agrawal Yogesh C.
Published: June 2017

Over the last 3-plus decades, point measurements of sediment concentrations in water have mostly been made using optical backscatter. Physics tells us that this signal correlates with particle area concentration so that while measuring volume concentrations, suspended load (sand) can be swamped by wash load (fines) and remain unseen. Over 2 decades ago, we introduced laser diffraction to the marine-aquatic environment, delivering concentration, size distribution (and settling velocity spectrum when equipped with a setline tube), with the characteristic of uniform sensitivity to a 200:1 range of grain sizes, excluding flocs which have variable fractal dimensions. Most recently, we introduced a high-frequency 8 MHz acoustic backscatter point-measurement system with the attraction of enhanced sensitivity to suspended load, i.e., opposite of backscatter optics, a higher limit to sediment concentrations, and greater tolerance to fouling. Very recently, a small conceptual jump was made to combine backscatter optics and 8MHz backscatter acoustics into a sensor with nearly uniform sensitivity to sizes over a 1—500 micron size range. I will review each briefly and illustrate how well these methods work in nature. Finally, I will offer thoughts on the information content of multi-frequency acoustics.
Acoustic scattering from flocculating suspensions
Authors: Bass Sarah , King Erin V. , Manning Andrew J. , Thorne Peter D.
Published: June 2017

Acoustic backscatter from sediment suspensions in the marine environment has been limited in application by the lack of understanding of how sound scatters from flocculating particles. To support theoretical development of sound scattering, combined measurements of high frequency acoustic backscatter and particle population characteristics are presented over a range of flocculating suspensions, from natural in-situ muddy suspensions to laboratory controlled pure clay flocs. Field measurements of cohesive suspended sediments were made in the meso-tidal Tamar Estuary, Devon, UK over several tidal cycles during spring tides. Controlled laboratory experiments were conducted using oscillating grid turbulence to suspend kaolin, oxidized, and natural marine sediments sieved below 63 microns. In both field and laboratory cases distributions of floc size and settling velocity were acquired using video techniques (from which effective density was derived) and acoustic backscatter measured over frequencies of 1-4 MHz. Particle measurements were complimented by pumped suspension samples later analyzed for mass and organic content. Measured scattering properties from the various sediments are compared against each other and with predictions from a hybrid elastic-fluid sphere model. Initial results suggest a good agreement with the model for both in-situ field suspensions and oxidized natural sediments from the laboratory.
Sediment transport studies—A brief retrospective look
Authors: Lynch James , Traykovski Peter , Newhall Arthur
Published: June 2017

In this paper, we present a short retrospective look at the evolution of acoustical, optical, and related measurements of sediment transport, bottom stress, and bottom bedforms over the past quarter century, using our programs at the Woods Hole Oceanographic Institution as a “representative sample.” Results from the High Energy Benthic Boundary Layer Experiment, the Sediment Transport on Shelves and Slopes experiment, and the Strata Formation on Shelves and Slopes experiment will be shown. Emphasis will be given to both technological and scientific advances. [Work supported by ONR.]
Stone formation
Authors: Williams James C. , Lingeman James E.
Published: June 2017

How stones are retained within the kidney while small in size is still not fully understood. In this talk, we will show two examples of how stones are retained during early growth: One is growth on Randall’s (interstitial) plaque, and the other is growth on mineral that has formed as a luminal plug in a terminal collecting duct. These two mechanisms of stone retention during early growth have distinctive morphologic features that can be seen by methods that show the microscopic structure of the stones. Stones growing on Randall’s plaque display a mineralized region (composed of apatite) that is typically not large in size (less than 0.5 mm across) but which usually shows luminal spaces, which are signs of its origin in the connective tissue of the papilla. Stones growing on ductal plugs also show attachment to a piece of apatite, but the apatite regions are typically larger (often >1 mm long and >0.5 mm wide), and they are solid, without spaces running through them. Still other stone formers exhibit neither of these known mechanisms of stone retention, and we propose urinary stasis as a third possible way that stones are retained within the kidney. We propose that knowing the mechanisms of stone retention during early stone formation should allow for better treatment of stone diseases.
New insights into the mechanisms and process of stone fragmentation in shock wave lithotripsy
Authors: Zhong Pei
Published: June 2017

Stone fragmentation in shock wave lithotripsy (SWL) is the consequence of dynamic fatigue produced by stress waves and cavitation. Stress waves [longitudinal (or P), transverse (or S), and surface acoustic waves (SAW)] and associated tensile and shear stresses are the primary driving forces to create fracture, initially from pre-existing (or intrinsic) flaws inside the stone. In contrast, cavitation produces pitting on the stone surface, and consequently, introducing new (or extrinsic) flaws to weaken the stone structure during SWL. Stress waves and cavitation act synergistically to produce effective and successful stone comminution in SWL, with cavitation serving as catalysts to enhance the efficiency of stress waves-driven stone fracture. In this talk, contemporary understanding about the mechanisms and process of stone fragmentation in SWL will be summarized, using a heuristic model which incorporates two important lithotripter field parameters (i.e., pressure and dose) that can critically influence the treatment outcome. The effects of stone size, geometry, composition on the transient stress field produced inside the stone, and the potential role of SAW in crack initiation and propagation will be discussed to provide physical insights into improvements in lithotripsy device design and treatment strategy.
Interaction between lithotripsy-induced surface acoustic waves and pre-existing cracks
Authors: Zhang Ying , Yang Chen , Liao Defei , Zhong Pei
Published: June 2017

The interaction between pre-existing cracks and surface acoustic waves (SAW) in lithotripsy is investigated. Surface acoustic waves are generated at a water-glass interface by an incident shock wave produced by the spark discharge of a nano pulse lithotripsy (NPL) device or an electromagnetic shock wave lithotripsy (SWL) source. Evidence of SAW, including leaky Rayleigh wave and Scholte wave, will be presented based on photoelastic imaging and numerical stimulations using COMSOL. A clear correlation between SAW and the location of the maximum tensile stress produced on the glass boundary has been identified, which can lead to ring-like fractures on a flat glass surface exposed to NPL-generated spherically divergent shock waves. To simulate cavitation-induced surface pitting in SWL, pre-existing crack will be introduced on the glass surface by microindentation using a Vickers or Knoop indenter. The interaction of SAW with the pre-existing cracks will be examined to characterize crack extension and branching as a function of their location and orientation to the incident shock wave.
Improving environmental and stone factors toward a more realistic in vitro lithotripsy model
Authors: Ahn Justin , Kreider Wayne , Hunter Christopher , Zwaschka Theresa , Bailey Michael , Sorensen Mathew , Harper Jonathan , Maxwell Adam D.
Published: June 2017

To improve in vitro lithotripsy models, we investigated the effects of multiple experimental variables on stone fragmentation. We performed timed burst wave lithotripsy (BWL) and shock wave lithotripsy (SWL) exposures in a water tank with the following variable parameters: water gas content (60, 30, and 15% O2), temperature (20 and 37°C), stone holder degree of enclosure (open wire basket, polyvinyl chloride (PVC) open-ended gel, and similar material anatomically accurate artificial kidney), and stone type (Begostone at 2 mixture ratios, calcite, calcium oxalate monohydrate (COM), and uric acid). At least 3 stones were treated for each condition, with fragmentation defined as percent stone mass <2 mm. Begostone (2:1 powder:water ratio) treated with BWL at 20°C vs. 37°C showed 75±13% vs. 62±6% breakage, respectively. Using the same stone type, gas concentrations of 60, 30, and 15% O2 showed breakage of 23±4%, 55±8%, and 82±16%, respectively. More enclosed kidney phantoms showed decreasing lithotripsy efficacy of 94±11%, 64±21%, and 13±2% breakage in basket, PVC, and anatomic phantoms, respectively. 2:1 Begostone most closely mimicked COM stone breakage. SWL exposures produced similar trends. This work indicates the importance of controlling multiple variables during in vitro lithotripsy experiments. [Work supported by NIH P01 DK043881 and K01 DK104854.]
Multiphase fluid-solid coupled analysis of shock-bubble-stone interaction in shock wave lithotripsy
Authors: Wang Kevin G. , Cao Shunxiang
Published: June 2017

A novel multiphase CFD-CSD coupled computational framework is applied to investigate the interaction of a kidney stone immersed in liquid with a lithotripsy shock wave (LSW) and a gas bubble near the stone. The main objective is to elucidate the effects of a bubble in the shock path to the elastic and fracture behaviors of the stone. The computational framework couples a finite volume two-phase computational fluid dynamics (CFD) solver with a finite element (FE) computational solid dynamics (CSD) solver. The stone surface is represented as a dynamic embedded boundary in the CFD solver. The evolution of the bubble surface is captured by solving the level set equation. The interface conditions are enforced through the construction and solution of local fluid-solid and two-fluid Riemann problems. The results of shock-bubble-stone simulations suggest that the dynamic response of a bubble to LSW varies dramatically depending on its initial size. Bubbles with an initial radius smaller than a threshold collapse within 1 μs after the passage of LSW; whereas larger bubbles do not. Moreover, this study suggests that a non-collapsing bubble imposes a negative effect on stone fracture while a collapsing bubble may promote fracture on the proximal surface of the stone.
A comparative study of full-wave inversion and local time-of-flight approaches in elastography
Authors: Aquino Wilkins , Bayat Mahdi , Babaniyi Olalekan A. , Fatemi Mostafa
Published: June 2017

Most of the current techniques for elastography rely on a pointwise measurement of the induced shear waves. A common assumption in these methods is plane wave propagation in an unbounded domain and local homogeneity of the medium. Because of these simplifying assumptions, complex wave patterns, boundary conditions, and interfaces can present significant challenges to these methods. On the other hand, general nonlinear optimization approaches with PDE constraints relax the underlying assumptions of planar waves and unbounded domains and, hence, can handle very general conditions. However, this generality usually leads to a higher computationally expense as compared to time-of-flight methods. Therefore, the added computational expense and higher complexity of these optimization approaches needs to be justified in the context of elastography. In this work, we present a recent study that compares shear modulus reconstructions obtained with a PDE-constrained optimization approach with a conventional shear wave elastography method using synthetic data. We show that our optimization approach produced significantly more consistent and accurate results than a conventional SWE method. Moreover, we show that material distributions that lead to strong wave diffraction present serious challenges to time-of-flight local approaches, while they can be handled naturally with optimization-based approaches. [Acknowledgment: This research was supported by NIH Grant R01CA174723.]
A machine learning alternative to model-based elastography
Authors: Hoerig Cameron , Ghaboussi Jamshid , Insana Michael F.
Published: June 2017

Model-based elastography methods suffer severe limitations in imaging the complex mechanical behavior of real biological tissues. We adapted the Autoprogressive Method (AutoP) to address these limitations by approaching the inverse problem with machine learning tools. AutoP combines finite element analysis (FEA) and artificial neural networks (ANNs) with force and displacement measurements to develop soft-computational models of mechanical behavior. Unlike model-based elastography methods, only measurement data inform the material properties learned by the ANNs. Because this machine learning approach foregoes the initial model assumption, AutoP can be applied to anisotropic, time-varying, and nonlinear media common in biomedical imaging applications. We first implemented AutoP to characterize linear-elastic gelatin phantoms and ex vivo rabbit kidneys to demonstrate the potential for medical imaging. Those models required an estimate of the interior geometry via segmentation of the B-mode images. In our current work, the capabilities of AutoP are extended by developing a novel ANN architecture. Incorporating spatial information as part of the input to a pair of ANNs working in tandem allows the models to learn the spatially varying mechanical behavior, thus precluding the segmentation requirement. We will demonstrate this new approach to elasticity imaging by presenting elastograms generated by trained ANN material models.
Breast ultrasound elastography using inverse finite element elasticity reconstruction
Authors: Samani Abbas , Mousavi Seyed R. , Rivaz Hassan , Sadeghi-Naini Ali , Czarnota Gregory
Published: June 2017

Breast cancer is the most common cancer in women worldwide. Its early detection is paramount for its successful treatment outcome. Among imaging techniques developed for breast cancer diagnosis, elastography has shown good promise. In this presentation, a breast ultrasound elastography method will be described, and its application in breast cancer patients will be demonstrated. The method follows the quasi-static elastography approach where the breast is stimulated using regular ultrasound transducer. RF data are utilized within a dynamic programming minimization algorithm for tissue motion tracking, leading to 2D (axial + lateral) strain field. This field is processed within a novel inverse finite-element reconstruction framework to reconstruct the breast Young's modulus distribution. The framework uses Hooke's law to obtain the Young's modulus distribution. It is iterative where the stress distribution is updated using finite element method at the end of each reconstruction iteration. To ensure convergence, the Young's modulus was averaged within 5x5 finite element windows. A phantom study mimicking breast cancer was performed to validate the developed system which demonstrated high (93%) accuracy of Young's modulus reconstruction. The method was then applied to breast cancer patients where elastography images reconstructed using the proposed method showed its effectiveness in clinical setting. The only hardware required in the system is an ultrasound scanner. As such, it is a promising candidate for clinical cancer diagnosis.
When good mics go bad
Authors: Ring Martin D.
Published: June 2017

Billions of MEMs microphones are fabricated each year and the vast majority of them are used for voice pickup in Consumer Electronics (CE) devices where anomalous behavior or failure can cause little more than annoyance. Some millions of these microphones are destined for more sophisticated and/or critical applications where malfunction can lead to unpleasant and possibly dangerous situations for both man and machine. This talk will discuss some of the environmental stimuli that our lives provide and our observations of MEMS microphone thermal variation, pressure overload characteristics, and lack of mechanical robustness to dust, gases, and fluids. In some cases, capacitive and piezoelectric sensors will be compared.
Thermal boundary layer limitations on the performance of micromachined microphones
Authors: Kuntzman Michael , LoPresti Janice , Du Yu , Conklin Wade , Schafer Dave , Lee Sung , Loeppert Peter
Published: June 2017

The extent to which thermal boundary layer effects limit the performance of micromachined microphones is examined. A lumped element network model for a micromachined microphone is presented which includes a ladder network in parallel with the adiabatic back volume compliance to account for the transition of the enclosure from adiabatic to isothermal conditions when the thermal boundary layer becomes large compared to the enclosure dimensions. The thermal correction to the cavity impedance contains a resistive component which contributes thermal-acoustic noise to the system. The model results are compared to measurements taken from commercially available microphone units with various back volume sizes, and the simulated relative noise power contribution of each acoustic noise source is calculated. The impedance of the back volume, including the thermal correction factor, is compared to the adiabatic compliance and the impedance derived from thermoacoustic finite element analysis. It is shown that the noise due to the thermal component of the back volume impedance becomes significant in microphones with small back volumes and effectively sets an upper bound on the signal-to-noise ratio of a microphone of given package dimensions.
Characterization of the vibration response of miniature microphones by subtraction
Authors: Walsh Jonathan D. , Su Quang T. , Warren Daniel M.
Published: June 2017

Presented is a test methodology for characterizing the vibration sensitivity of miniature microphones for hearing aids. A common method for obtaining the vibration sensitivity of a system is to use an electrodynamic shaker to deliver a calibrated vibration input and measure the corresponding output. When the system under test is a microphone, it is difficult to obtain the vibration response since the measured output will also be due to coherent sound created by the vibration delivery system. The method models the microphone as a system with two inputs, vibration and sound, with one electronic output. Using frequency-domain signal processing, this method extracts the vibration response from a shaker-driven signal by subtracting a synthesized acoustic response signal. When compared to vibration measurements under vacuum, the vibration responses from the two methods generally agree. The vibration response estimates produced using this algorithm are more accurate than vacuum chamber data due to the loading and stiffening effects caused by the presence of air, as would occur under standard operating conditions. This test method allows the rapid acquisition of microphone vibration responses by eliminating the need for a vacuum chamber, or carefully designed acoustic baffling.
University at Buffalo, SUNY: Variety of graduate programs in acoustics
Authors: Kobrina Anastasiya
Published: June 2017

University at Buffalo, SUNY has an outstanding reputation, due to its commitment to research and knowledgeable faculty. UB is known for its diversity in auditory research spanning from the psychophysics of hearing in humans and animals to the neurophysiological mechanisms of hearing. This unique variety leads to collaborations spanning departments and laboratories. The Cognitive Psychology doctoral program is aimed at training students for research-oriented careers. Graduate students are exposed to a variety of laboratories and courses in order to develop collaborations and build research skills. In addition, the Psychology Department holds regular colloquia on various general topics in psychology, and the Cognitive Psychology and Behavioral Neuroscience areas both hold weekly “brownbag” seminars, often related to topics in auditory processing and communication. Biological Sciences Department, the Communication Disorders Department, as well as the Center for Hearing and Deafness, make UB a perfect oasis of auditory research. Thus, the University at Buffalo is an ideal fit for training in hearing research and for facilitating collaborations.
The Physical Acoustics Research Program at the University of Louisiana at Lafayette
Authors: Petculescu Andi
Published: June 2017

The Department of Physics at UL Lafayette has a strong history of acoustics research. Recently, the program has expanded considerably as a result of renewed interest in acoustics-related research. Tied into the current rethinking of the Department's multiple physics tracks, the Physical Acoustics Research Program offers ample opportunities for students—both undergraduate and graduate—to be involved in wide-spectrum research in acoustics. This program, unique in Louisiana, involves acoustic sensing of alien environments, atmospheric and underwater acoustics, ultrasonics in the solid state, ultrasonic materials characterization and structural health monitoring, seismology and geodynamics. In parallel to research projects, the faculty offer a variety of acoustics-related courses on topics such as Matlab- and Python-based computational acoustics, solid state acoustics, experimental techniques in acoustics, room acoustics, as well as machine learning techniques for wave propagation.
Graduate training opportunities in the hearing sciences at the University of Louisville
Authors: Zahorik Pavel , Preminger Jill E. , Stilp Christian
Published: June 2017

The University of Louisville currently offers two branches of training opportunities for students interested in pursuing graduate training in the hearing sciences: A Ph.D. degree in experimental psychology with concentration in hearing science, and a clinical doctorate in audiology (Au.D.). The Ph.D. degree program offers mentored research training in areas such as psychoacoustics, speech perception, spatial hearing, multisensory perception, and language development. The program guarantees students four years of funding (tuition plus stipend). The Au.D. program is a 4-year program designed to provide students with the academic and clinical background necessary to enter audiologic practice. Both programs are affiliated with the Heuser Hearing Institute, which, along with the University of Louisville, provides laboratory facilities and clinical populations for both research and training. An accelerated Au.D./Ph.D. training program that integrates key components of both programs for training of students interested in clinically based research is under development. Additional information is available at http://louisville.edu/medicine/degrees/audiology and http://louisville.edu/psychology/graduate/experimental.