bluuebunny/crossref_metadata_2025 huggingface dataset:
The Low Reduced Frequency Limit of Vibrating Airfoils—Part II: Numerical Experiments
Authors: Vega Almudena , Corral Roque
Published: October 2015

This paper studies the unsteady aerodynamics of vibrating airfoils in the low reduced frequency regime with special emphasis on its impact on the scaling of the work-per-cycle curves by means of numerical experiments. Simulations using a frequency domain linearized Navier–Stokes solver have been carried out on rows of a low-pressure turbine (LPT) airfoil section, the NACA0012 and NACA65 profiles, and a flat-plate cascade operating at different flow conditions. Both the traveling wave (TW) and the influence coefficient (IC) formulations of the problem are used in combination to investigate the nature of the unsteady pressure perturbations. All the theoretical conclusions derived in Part I of the paper have been confirmed, and it is shown that the behavior of the unsteady pressure modulus and phase, as well as the work-per-cycle curves, are fairly independent of the geometry of the airfoil, the operating conditions, and the mode-shape in first-order approximation in the reduced frequency. The second major conclusion is that the airfoil loading and the symmetry of the cascade play an essential role in this trend. Simulations performed at reduced frequency ranges beyond the low reduced frequency limit reveal that, in this regimen, the ICs modulus varies linearly with the reduced frequency, while the phase is always π/2, and then, the classical sinusoidal antisymmetric shape of work-per-cycle curves in the low reduced frequency limit turns into a cosinusoidal symmetric shape. It is then concluded that the classical cosinusoidal shape of compressor airfoils is not neither a geometric nor a flow effect, but a direct consequence of the fact that the natural frequencies of the lowest modes of compressors are higher than that of high aspect ratio cantilever LPT rotor blades. Numerical simulations have also confirmed that the actual mode-shape of the airfoil motion does not alter the conclusions derived in Part I of the paper.
Ultrahigh vacuum deposition of higher manganese silicide Mn4Si7 thin films
Authors: Dulal Rajendra P. , Dahal Bishnu R. , Pegg Ian L. , Philip John
Published: October 2015

The authors have successfully grown one of the higher manganese silicides, Mn4Si7 thin films on silicon (100) substrates using an ultrahigh vacuum deposition with a base pressure of 1 × 10−9 Torr. The thickness of the film was varied from 65 to 100 nm. These films exhibit a tetragonal crystal structure and display paramagnetic behavior as predicted for the stoichiometric Mn4Si7 system. They have a resistivity of 3.32 × 10−5 Ω m at room temperature and show a semimetallic nature.
Low-temperature atomic layer deposition of copper(II) oxide thin films
Authors: Iivonen Tomi , Hämäläinen Jani , Marchand Benoît , Mizohata Kenichiro , Mattinen Miika , Popov Georgi , Kim Jiyeon , Fischer Roland A. , Leskelä Markku
Published: October 2015

Copper(II) oxide thin films were grown by atomic layer deposition (ALD) using bis-(dimethylamino-2-propoxide)copper [Cu(dmap)2] and ozone in a temperature window of 80–140 °C. A thorough characterization of the films was performed using x-ray diffraction, x-ray reflectivity, UV-Vis spectrophotometry, atomic force microscopy, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis techniques. The process was found to produce polycrystalline copper(II) oxide films with a growth rate of 0.2–0.3 Å per cycle. Impurity content in the films was relatively small for a low temperature ALD process.
Antifungal coatings by caspofungin immobilization onto biomaterials surfaces via a plasma polymer interlayer
Authors: Griesser Stefani S. , Jasieniak Marek , Coad Bryan R. , Griesser Hans J.
Published: October 2015

Not only bacteria but also fungal pathogens, particularly Candida species, can lead to biofilm infections on biomedical devices. By covalent grafting of the antifungal drug caspofungin, which targets the fungal cell wall, onto solid biomaterials, a surface layer can be created that might be able to provide long-term protection against fungal biofilm formation. Plasma polymerization of propionaldehyde (propanal) was used to deposit a thin (∼20 nm) interfacial bonding layer bearing aldehyde surface groups that can react with amine groups of caspofungin to form covalent interfacial bonds for immobilization. Surface analyses by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed the intended grafting and uniformity of the coatings, and durability upon extended washing. Testing for fungal cell attachment and ensuing biofilm formation showed that caspofungin retained activity when covalently bound onto surfaces, disrupting colonizing Candida cells. Mammalian cytotoxicity studies using human primary fibroblasts indicated that the caspofungin-grafted surfaces were selective in eliminating fungal cells while allowing attachment and spreading of mammalian cells. These in vitro data suggest promise for use as antifungal coatings, for example, on catheters, and the use of a plasma polymer interlayer enables facile transfer of the coating method onto a wide variety of biomaterials and biomedical devices.
Evaluation of the OSC‐TV iterative reconstruction algorithm for cone‐beam optical CT
Authors: Matenine Dmitri , Mascolo‐Fortin Julia , Goussard Yves , Després Philippe
Published: October 2015

Purpose:

The present work evaluates an iterative reconstruction approach, namely, the ordered subsets convex (OSC) algorithm with regularization via total variation (TV) minimization in the field of cone‐beam optical computed tomography (optical CT). One of the uses of optical CT is gel‐based 3D dosimetry for radiation therapy, where it is employed to map dose distributions in radiosensitive gels. Model‐based iterative reconstruction may improve optical CT image quality and contribute to a wider use of optical CT in clinical gel dosimetry.

Methods:

This algorithm was evaluated using experimental data acquired by a cone‐beam optical CT system, as well as complementary numerical simulations. A fast GPU implementation of OSC‐TV was used to achieve reconstruction times comparable to those of conventional filtered backprojection. Images obtained via OSC‐TV were compared with the corresponding filtered backprojections. Spatial resolution and uniformity phantoms were scanned and respective reconstructions were subject to evaluation of the modulation transfer function, image uniformity, and accuracy. The artifacts due to refraction and total signal loss from opaque objects were also studied.

Results:

The cone‐beam optical CT data reconstructions showed that OSC‐TV outperforms filtered backprojection in terms of image quality, thanks to a model‐based simulation of the photon attenuation process. It was shown to significantly improve the image spatial resolution and reduce image noise. The accuracy of the estimation of linear attenuation coefficients remained similar to that obtained via filtered backprojection. Certain image artifacts due to opaque objects were reduced. Nevertheless, the common artifact due to the gel container walls could not be eliminated.

Conclusions:

The use of iterative reconstruction improves cone‐beam optical CT image quality in many ways. The comparisons between OSC‐TV and filtered backprojection presented in this paper demonstrate that OSC‐TV can potentially improve the rendering of spatial features and reduce cone‐beam optical CT artifacts.
On the use of evanescent plane waves for low-frequency energy transmission across material interfaces
Authors: Woods Daniel C. , Bolton J. Stuart , Rhoads Jeffrey F.
Published: October 2015

The transmission of airborne sound into high-impedance media is of interest in several applications. For example, sonic booms in the atmosphere may impact marine life when incident on the ocean surface, or affect the integrity of existing structures when incident on the ground. Transmission across high impedance-difference interfaces is generally limited by reflection and refraction at the surface, and by the critical angle criterion. However, spatially decaying incident waves, i.e., inhomogeneous or evanescent plane waves, may transmit energy above the critical angle, unlike homogeneous plane waves. The introduction of a decaying component to the incident trace wavenumber creates a nonzero propagating component of the transmitted normal wavenumber, so energy can be transmitted across the interface. A model of evanescent plane waves and their transmission across fluid-fluid and fluid-solid interfaces is developed here. Results are presented for both air-water and air-solid interfaces. The effects of the incident wave parameters (including the frequency, decay rate, and incidence angle) and the interfacial properties are investigated. Conditions for which there is no reflection at the air-solid interface, due to impedance matching between the incident and transmitted waves, are also considered and are found to yield substantial transmission increases over homogeneous incident waves.
The effects of noise on key workplace skills
Authors: Molesworth Brett R. C. , Burgess Marion , Zhou Annie
Published: October 2015

This study explored the effect on memory and psychomotor performance of wideband noise (simulated in-cabin aircraft noise) at 75 dBA, which is similar to that experienced during the cruise phase of a commercial flight. The results from the tests were compared to the effects of a widely known and common metric on the same skills, namely, blood alcohol concentration (BAC). All 32 participants, half non-native English speakers, completed three different tests (recognition memory, working memory, and reaction time) presented in counterbalanced order, either in the presence of noise, with or without noise attenuation headphones, and without noise but with a BAC of 0.05 or 0.10. Simulated aircraft noise was found to affect recognition memory but not working memory or reaction time. These effects were more pronounced for non-native speakers and reflected performance similar to that for BAC of 0.05 or 0.10.
The relationship between aircraft noise exposure and day-use visitor survey responses in backcountry areas of national parks
Authors: Rapoza Amanda , Sudderth Erika , Lewis Kristin
Published: October 2015

To evaluate the relationship between aircraft noise exposure and the quality of national park visitor experience, more than 4600 visitor surveys were collected at seven backcountry sites in four U.S. national parks simultaneously with calibrated sound level measurements. Multilevel logistic regression was used to estimate parameters describing the relationship among visitor responses, aircraft noise dose metrics, and mediator variables. For the regression models, survey responses were converted to three dichotomous variables, representing visitors who did or did not experience slightly or more, moderately or more, or very or more annoyance or interference with natural quiet from aircraft noise. Models with the most predictive power included noise dose metrics of sound exposure level, percent time aircraft were audible, and percentage energy due to helicopters and fixed-wing propeller aircraft. These models also included mediator variables: visitor ratings of the “importance of calmness, peace and tranquility,” visitor group composition (adults or both adults and children), first visit to the site, previously taken an air tour, and participation in bird-watching or interpretive talks. The results complement and extend previous research conducted in frontcountry areas and will inform evaluations of air tour noise effects on visitors to national parks and remote wilderness sites.
The precedence effect with increased lag level
Authors: Pastore M. Torben , Braasch Jonas
Published: October 2015

When a pair of sounds arrive from different directions with a sufficiently short delay between them, listeners hear a perceptually fused image with a perceived location that is dominated by the first arriving sound. This is called the precedence effect. To test the limits of this phenomenon, 200-ms noise stimuli were presented over headphones to model a temporally overlapping direct sound (lead) with a single reflection (lag) at inter-stimulus intervals (ISIs) of 0–5 ms. Lag intensity exceeded that of the lead by 0–10 dB. Results for 16 listeners show that lateralization shifted from the position of the lead towards the lag as lag level increased. Response variability also increased with lag level. An oscillatory pattern emerged across ISIs as lag level increased, to a degree that varied greatly between listeners. Analysis of modeled binaural cues suggests that these oscillatory patterns are correlated with ILDs produced by the physical interference of lead and lag during the ongoing portion of the stimulus, especially in the 764-Hz frequency band. Different listeners apparently weighted cues from the onset versus ongoing portions of the stimulus differently, as evidenced by the varying degree of influence the ongoing ILD cues had on listeners' perceived lateralization.
Fast computation of seabed spherical-wave reflection coefficients in geoacoustic inversion
Authors: Quijano Jorge E. , Dosso Stan E. , Dettmer Jan , Holland Charles W.
Published: October 2015

This paper develops a fast numerical approach to computing spherical-wave reflection coefficients (SWRCs) for layered seabeds, which provides substantial savings in computation time when used as the forward model for geoacoustic inversion of broadband seabed reflectivity data. The approach exploits the Sommerfeld-integral representation of SWRCs as the Hankel transform of a function proportional to the plane-wave reflection coefficient (PWRC), and applies Levin integration to the rapidly oscillating integrand cast as the product of a (pre-computed) media-independent matrix and a vector involving PWRCs at a sparse sampling of integration angles. Compared to conventional Simpson's rule integration for computation of the SWRC, the Levin integration yields speed-up factors of an order of magnitude or more. Further, it results in reduced memory requirements for storage of pre-computed quantities, a desirable property when a graphics processing unit (GPU) is used for parallel computation of SWRCs. The paper applies trans-dimensional Bayesian inversion to investigate the impact of forward modeling in terms of PWRCs and SWRCs on the estimation of geoacoustic parameters and uncertainties. Model comparisons are quantified in simulated- and measured-data inversions by comparing the estimated geoacoustic parameters to the true parameters or core measurements, respectively, and by calculating the deviance information criterion for model selection.
Sexual communication in ultrasonic frogs Odorrana tormota involves acoustic and various visual signals
Authors: Feng Albert S. , Zhang Fang , Chen Pan , Zhao Juan , Chen Zhuqing
Published: October 2015

Female concave eared torrent frogs are known to produce courtship calls to attract males; yet, like other anurans, they also display positive phonotaxis toward male’s calls. Thus, it is unclear how amplexus is formed and which sex makes the mating decision. We investigated how males and females interact and communicate during the reproductive season and found that females emitted vocalizations during the gravid state only. In playback experiments in the wild, female's courtship calls elicited numerous males to respond. Males’ vocal responses were range dependent and accompanied by staccato calls and phonotaxis toward (but short of reaching) the loudspeaker. In short range encounters, gravid females are highly selective, and males must wait for female’s invitational signal(s) for amplexus. Only a select male showing prominent dominant male’s postures received invitational signal(s), comprising a variety of visual signals (head bob, belly inflation, toe tapping, and eye blink) and an “admission” acoustic signal. Upon receiving one or more of these signals, the male immediately hopped on the female’s back to form amplexus. Our studies revealed that intersexual communication in concave eared torrent frogs is complex, involving both acoustic and visual signaling.
Re-visiting Al Feng’s contributions toward understanding the peripheral basis of acoustic communication in frogs
Authors: Shofner William
Published: October 2015

Al has made substantial contributions toward understanding the peripheral auditory mechanisms underlying acoustic communication in frogs. Al was the first to demonstrate that the basilar papilla is innervated by high-frequency auditory nerve fibers, while the amphibian papilla gives rise to low- and mid-frequency fibers. As his graduate student, we subsequently showed that the tuning of these end organs changes during post-metamorphic development. Al developed a dorsal surgical approach to the auditory nerve, which allowed the coupling between the ears to be studied. He demonstrated that both the monaural directivity patterns and the coupling between ears are frequency dependent. In a follow-up study, we manipulated the coupling between ears and concluded that the frog’s ear functions as a combination pressure/pressure gradient receiver. In this talk, I will re-visit the frequency-dependent crosstalk between the ears first described by Al in 1980. The crosstalk function is analyzed using an acoustic model of a tube with a side branch. This analysis shows the mouth cavity as the side branch is insufficient and yields a lowpass crosstalk function. Including the nares in parallel with the mouth cavity as a side branch yields a bandpass function for sound transmission that accounts for Al’s empirical crosstalk data.
Airgun array sound measurements in the northeastern Chukchi Sea
Authors: Hannay David E. , Warner Graham
Published: October 2015

Underwater acoustic measurements were made during eight 2D/3D seismic surveys with large airgun arrays and nine shallow hazards surveys using small arrays (2–4 airguns) in the shallow (30–50 m) waters of the northeastern Chukchi Sea between 2006 and 2013. The acoustic measurements were made with calibrated seabed-deployed recorders to assess potential noise exposures to marine fauna. Data were acquired from directly under the airgun arrays to over 150 km distance. The seismic pulses contain signals above ambient noise between approximately 5 Hz and 15 kHz. Modal structure develops by about 1 km distance from the sources at frequencies between approximately 30 Hz and 600 Hz, but it is strongest from 100 Hz to 300 Hz. This ocean environment therefore acts as a frequency band-pass filter, selectively passing the intermediate sound frequencies to long distances. The modes are strongly dispersed, with low frequency components arriving up to 2 s later than the higher frequency sounds of the same mode. This causes received signals to have a down-swept spectral shape. We present sound level measurement results from all of the surveys and we discuss the frequency-dependent acoustic transmission loss in context with the modal propagation characteristics of this ocean environment.
Eight years of passive acoustic monitoring in the Alaskan Beaufort Sea: Lessons learned
Authors: Blackwell Susanna B. , Nations Christopher S. , Thode Aaron M. , Kim Katherine H.
Published: October 2015

Every year during open-water season in 2007–2014, up to 40 passive acoustic recorders with directional capability (DASARs) were deployed in the Beaufort Sea, as part of Shell’s Marine Mammal Monitoring and Mitigation Program. The overarching goal of these deployments was to collect information on the effects of industrial operations, such as seismic exploration and drilling activities, on the behavior of bowhead whales during their fall migration. Recorders were placed on the continental shelf at depths of <55 m, offshore of the North Slope of Alaska, between Barter Island and Harrison Bay. Over the eight-year period, more than 3.1 million bowhead calls were localized. Concurrently, various types of industrial sounds were detected and quantified, such as airgun pulses or the tones produced by machinery. Analyses were then performed by matching—for each recorder—the number of calls localized with the amount of industrial sound detected. These analyses have shown that changes in calling behavior happen at low received levels of anthropogenic sound and lead to complex changes in calling behavior, that are governed by received sound levels, but also other factors, such as distance to the industrial activity or type of industrial sound. [Work sponsored by Shell Exploration and Production Company.]
Using blind signal processing algorithms to remove wind noise from environmental noise assessments: A wind turbine amplitude modulation case study
Authors: Kendrick Paul , von Hünerbein Sabine , Cox Trevor J.
Published: October 2015

Microphone wind noise can corrupt outdoor measurements and recordings. It is a particular problem for wind turbine measurements because these cannot be carried out when the wind speed is low. Wind shields can be used, but often the sound level from the turbine is low and even the most efficient shields may not provide sufficient attenuation of the microphone wind noise. This study starts by quantifying the effect that microphone wind noise has on the accuracy of two commonly used Amplitude Modulation (AM) metrics. A wind noise simulator and synthesized wind turbine sounds based on real measurements are used. The simulations show that even relatively low wind speeds of 3 m/s can cause large errors in the AM metrics. Microphone wind noise is intermittent, and consequently, one solution is to analyze only uncorrupted parts of the recordings. This paper tests whether a single-ended wind noise detection algorithm can automatically find uncorrupted sections of the recording, and so recover the true AM metrics. Tests showed that doing this can reduce the error to ±2 dBA and ±0.5 dBA for the time and modulation-frequency domain AM metrics, respectively.
Integrating acoustics for sustainability
Authors: Eligator Ronald
Published: October 2015

Sustainability is frequently correlated with energy efficiency and environmentally sensitive design. Issues such as energy use, daylight harvesting, waste management, materials manufacturing, and recyclability are all considered. More difficult to quantify but of great importance in determining whether a project is truly sustainable is the degree to which a building or space appropriately serves the function for which it was designed. Thoughtful integration of acoustic design into building projects is required to ensure the finished product will meet the design goals of the client and users, including acoustic performance requirements. Without early integrated design efforts, the need for immediate renovation or other changes to a newly completed project due to acoustic deficiencies becomes much more likely. This presentation will provide case histories of projects made successful, and therefore sustainable, through an integrated design approach. Issues related to these successful outcomes will be discussed, including budget pressures, education of the client and design team regarding the effect design decisions have on the functionality and usability of spaces, and the importance of relationship building in encouraging design team members to take on design ideas which might challenge past approaches or assumptions.
Sound localization in the frog after Albert Feng: Filling in the blanks
Authors: Narins Peter M.
Published: October 2015

In his Ph.D. thesis, Albert described his elegant behavioral study demonstrating that two ears are necessary for frogs to localize sound. Next, he elucidated a series of mechanisms in the frog CNS that is responsible for encoding sound source direction. Inspired by this work, we examined some of the peripheral mechanisms involved in sound processing in the frog. For example, frogs and toads are capable of producing calls at potentially damaging levels that exceed 110 dB SPL at 50 cm. In most frog species, the tympanic membranes (TMs) communicate directly via the large, permanently open Eustachian tubes, resulting in an inherently directional asymmetrical pressure-gradient receiver. One active mechanism for auditory sensitivity reduction involves the pressure increase during vocalization that distends the TM, reducing its airborne sound sensitivity. Another states that if sounds generated by the vocal folds arrive at both surfaces of the TM with nearly equal amplitudes and phases, the net motion of the eardrum would be greatly attenuated. Both mechanisms can explain the results of our direct TM measurements. Moreover, we have measured this eardrum motion under acoustic clamp conditions and shown that blocking the internal interaural connection results in nearly azimuth-independent eardrum velocity, consistent with Albert’s results.
fMRI and electrophysiology of cortical layer-dependent processes in primary sensory cortex
Authors: Goense Jozien
Published: October 2015

To understand cortical function, it is important to better understand the cortical functional units, i.e., its columns and layers. High-resolution fMRI can offer tremendous advantages for the study of cortical circuits in vivo, evidenced by the increasing interest in high-resolution fMRI. However, many questions remain about the size of the cortical features that can be resolved, and how neural activity gives rise to the blood oxygenation dependent (BOLD) signal measured with fMRI. We use high-resolution fMRI combined with electrophysiology to study laminar processing, with the aim of gaining insight into the layer-dependent neural processing and the mechanisms of neurovascular coupling in the primary visual cortex (V1) and temporal lobe of awake and anesthetized macaques. We investigated whether laminar differences in the BOLD, cerebral blood flow (CBF), and volume (CBV) responses can be detected for excitatory and inhibitory stimuli, and found that the mechanisms for positive and negative BOLD responses differ, but also that neurovascular coupling differs in the cortical layers. Furthermore, neuromodulators such as dopamine can alter neurovascular coupling. Our results suggest that neurovascular coupling depends on multiple factors, and that the combination of high-resolution fMRI with electrophysiology can be used to resolve neurovascular coupling in functional microcircuits.
Laboratory measurements of high-frequency broadband acoustic backscatter from sea ice, oil under sea ice, and oil encapsulated in sea ice
Authors: Bassett Christopher , Lavery Andone C.
Published: October 2015

To investigate the potential for detection of crude oil under sea ice using active acoustics techniques, measurements of high-frequency broadband backscattering (75–590 kHz) from crude oil of different thicknesses (0.7–8 cm) under, and frozen within, laboratory sea ice have been performed at the Cold Regions Research and Environmental Laboratory (Hannover, NH). Backscattering measurements were performed at normal and 20 degrees from normal incidence. The data have been analyzed in both the temporal domain and in the frequency domain, allowing scattered spectra from the oil and ice to be measured. The results show structure consistent with scattering from multiple interfaces following the injection of oil under the ice and during the subsequent encapsulation the oil layer. The acoustic estimates of oil thickness are in general agreement with ancillary measurements. The sound speed of the crude oil was separately measured over a range of relevant temperatures, both to inform a scattering model and to accurately infer the oil thickness. Predictions based on a simple scattering model for the frequency-dependent reflection coefficient of oil under ice agree well with the normal incidence measurements prior to oil encapsulation. At angles off normal incidence, volume inhomogeneities appear to dominate the scattering.
Bowhead whale localization using asynchronous hydrophones in the Chukchi Sea
Authors: Warner Graham A. , Dosso Stan E. , Hannay David E. , Dettmer Jan
Published: October 2015

This paper estimates bowhead whale locations and uncertainties from Bayesian inversion of modally dispersed calls recorded on asynchronous recorders in the Chukchi Sea, Alaska. Bowhead calls were recorded on a cluster of seven asynchronous ocean-bottom hydrophones that were separated by 0.5–7.5 km. A warping time-frequency analysis is used to extract relative mode arrival times as a function of frequency for nine frequency-modulated whale calls that dispersed in the shallow water environment. Each call was recorded on multiple hydrophones and the mode arrival times are inverted for: the whale location in the horizontal plane, source instantaneous frequency (IF), water sound-speed profile, subbottom layering and geoacoustic parameters, relative recorder clock drifts, and residual error standard deviation, all with estimated uncertainties. A simulation study shows that accurate prior environmental knowledge is not required for accurate localization. Joint inversion of multiple recorded calls is shown to substantially reduce localization, source IF, and relative clock drift uncertainties. Whale location uncertainties are estimated between 30 and 160 m and clock drift uncertainty is estimated between 3 and 26 ms. The clock synchronization provided by the inversion is sufficient for localizing other types of marine mammal calls using simpler time-difference-of-arrival methods.
Modeling thermal fracturing of sea ice, a historical view
Authors: Stein Peter J.
Published: October 2015

Thermal fracturing of sea ice is an important mechanism not only for ambient noise generation, but also for climate change studies. It is possible that thermal fracturing is a fundamental mechanism behind the weakening of first and multiyear ice. During the late 1980s and early 1990s, a significant effort was conducted to model and measure the thermal fracturing of sea ice by the author and Dr. James K. Lewis. Here, we take a look back at that effort in the broader context of Arctic Ocean ambient noise and climate change.
High-frequency ultrasound for rapid detection of skin cancer and other pathologies: Studies on porcine tissue
Authors: Finch Benjamin F. , Pacheco James P. , Doyle Timothy E.
Published: October 2015

The Breast Cancer Research Laboratory at Utah Valley University has been developing high-frequency (HF) ultrasound (20–80 MHz) to differentiate between malignant and benign tissues. Results from our breast cancer clinical trials thus far are promising, with high sensitivities and specificities. The objective of this study was to determine whether HF ultrasound can provide pathology sensitive measurements for diagnosing skin cancer and distinguishing between tissue structures. Formalin-preserved porcine tissues were first used to test the feasibility of the approach. The results show that both spectral peak density and wave velocity were sensitive to structure, and that normal skin tissue was significantly discernible from other tissues. An 80-patient clinical study is currently being conducted at the Huntsman Cancer Institute with the collection of ultrasonic measurements from at least 320 skin biopsies. Multiple pulse-echo and through-transmission measurements are acquired from each biopsy specimen. The ultrasound data are correlated to conventional pathology to determine sensitivity and specificity. If successful, HF ultrasound may provide an earlier diagnosis of skin cancer and a rapid, intraoperative method for differentiating between melanoma and benign pathologies. By improving on current methods, HF ultrasound may provide dermatologists with faster and more accurate results, and thus better patient treatment and outcomes.
Investigation of on skin surface response due to acoustic radiation from stenosed blood vessels
Authors: Salman Huseyin Enes , Yazicioglu Yigit
Published: October 2015

Arterial stenosis is a form of cardiovascular disease which leads to highest rate of fatalities worldwide. When stenosis is present in arteries feeding the heart, it leads to heart attack and often sudden death. If occlusion is present in arteries feeding brain, it causes stroke and rapid loss of brain functions. Arterial disease is usually not confined to critical organs such as the heart and the brain but observed throughout the peripheral cardiovascular system. Acoustic radiation due to stenosis propagates through soft tissues and reaches to skin surface. Therefore, these signals detected on skin surface may provide valuable information for diagnostic purposes. In this study, effects of acoustic radiation on skin surface due to a stenosis are investigated. Human upper arm is modeled using commercial finite element software ADINA. Realistic geometries and soft tissue mechanical properties are employed. Acoustic pressure distribution due to constriction is modeled using related studies in literature and applied on inner surface of blood vessel. Harmonic analysis is performed for upper arm and pressure distribution on skin surface is obtained. It is observed that increasing level of stenosis leads to an increase in pressure amplitudes on skin surface where the region which is closest to the constricted artery has the highest pressure amplitudes.
Implementation of an augmented reality interface to reproduce and compare soundscapes
Authors: Robinson Philip W.
Published: October 2015

Soundscape design is a growing concern in architectural practice; yet, conveying soundscape properties is a challenge. Quantitative measures like decibel levels offer little utility; birdsong and squealing brakes may be at the same frequency and level, yet one is obviously preferable. Furthermore, visual qualities of the scene have a substantial effect on perception of the acoustic environment. To improve communication between acoustic designers, architects, and clients, an augmented reality interface has been designed to allow comparisons of soundscapes and their relationships to the built environment. The interface consists of a physical scale model, printed data, and a tablet application. The augmented reality application uses a machine vision algorithm to recognize the model and allow on-screen interaction. On the tablet, measurement points are displayed on a live image of the model at their respective locations, and the user may select a point by touch, which will begin sound playback and display an immersive image of the scene. The participant can then look around a spherical image of the scene using the tablet as a movable window, and thereby listen to the environment with appropriate accompanying visual cues. The interface has been a useful tool to communicate urban sound issues.
Acoustic tracking of small aircraft within an airport
Authors: Sedunov Alexander , Sutin Alexander , Sedunov Nikolay , Salloum Hady , Yakubovskiy Alexander , Masters David
Published: October 2015

The Acoustic Aircraft Detection (AAD) system developed by Stevens Institute of Technology for the detection of small aircraft in remote border areas was tested for tracking small aircraft in the airport. The goal of the test was to demonstrate a proof-of-concept capability for the acoustic sensor when applied to tracking aircraft during take off, landing, or taxing in a small airport. Two AAD nodes with five microphones were used to find the direction of arrival of sound produced by an aircraft using time-difference of arrival to pairs of sensors and to localize those by triangulation in real time. Additionally, a portable acoustic recorder system (PARS) with three microphones arranged in a ground plane was deployed to provide more data for post-processing analysis. The nodes separation varied between 150 and 250 m in different experiments. During the two-day experiment, aircraft activity of regular airport traffic was observed. At least 14 different aircraft were recorded during various movement on airport runways as well as takeoff and landing. The tested AAD was developed for another mission and was far from an optimal acoustic system for small airport applications. Suggestions for this system will be presented. [This work was sponsored by DHS S&T.]
Semi-analytical methods for the simulation of the ultrasonic non destructive testing of complex materials
Authors: Chatillon Sylvain , Dorval Vincent , Leymarie Nicolas
Published: October 2015

During the last decade, the role of the NDT simulation has been continuously increasing and diversifying in all the industrial sectors concerned by complex inspection methods. The UT simulation tools gathered in the CIVA software developed at CEA LIST include beam and defect echoes computations. The propagation of elastic waves is computed using an asymptotic paraxial ray approximation. In the case of some heterogeneous materials, such as polycrystalline structures and welds, it requires the definition of equivalent propagation properties for which several methods have been developed. In the case of fine-grained polycrystals, the propagation is first computed for a homogeneous effective medium. Attenuation filters are applied afterwards and structural noise is modeled as the echoes of a random distribution of scatterers. Their parameters can be set empirically or calculated based on microstructural properties. Polycrystals with coarser grains are modeled using Voronoi diagrams. The propagation in the complex structure of an austenitic weld can be modeled by describing it as piecewise homogeneous, though the impedance contrast between neighboring homogeneous domains may cause inaccurate results. As a part of the MOSAICS (ANR) project, the ray tracing method was extended to smoothly inhomogeneous anisotropic media and applied to more realistic descriptions of welds.
Characterization and design of sound absorber materials
Authors: Turo Diego , Glean Aldo A. , Vignola Joseph F. , Ryan Teresa , Judge John A.
Published: October 2015

Sound absorbing materials are widely used to mitigate noise in indoor environments. Foams and fiberglass are commonly used for passive noise control in the automotive, aerospace industries and for architectural design. The physics of sound absorption in porous materials is not typically included in introductory acoustics courses. However, characterization and design of sound absorbing materials and modeling of their properties can be valuable for students interested in applied acoustics. In this laboratory-oriented course at the Catholic University of America, we cover design of multilayered sound absorbers and experimental procedures for testing such materials. These include an introduction to data acquisition using LabVIEW and post-processing (with Matlab) of recorded sound as well as microphone calibration, and measurement of sound pressure level, and the frequency response function of a speaker. The second part of the course focuses on room acoustics, acoustic properties of materials, impedance tube measurements, modeling of sound propagation in porous media, and design of sound absorbers. We validate the Zwikker and Kosten model using a sample with straight cylindrical pores and apply the Delany-Bazley model to predict acoustic behavior of fibrous materials. Finally, multilayered materials are designed using the impedance translation theorem and tested with impedance tube measurements.
Effects of following onsets on voice onset time in English
Authors: Mielke Jeff , Nielsen Kuniko
Published: October 2015

Voice Onset Time (VOT) in English voiceless stops has been shown to be sensitive to place of articulation (Fischer-Jorgensen 1954), to contextual factors such as the height, tenseness, and duration of the following vowel and the voicing of coda consonants (Klatt 1975, Port & Rotunno 1979), to prosodic factors like stress and pitch (Lisker & Abramson 1967), and also to F0 (McCrea & Morris 2005) and speaking rate (Kessinger & Blumstein 1997, Allen 2003). We report two additional factors involving following consonants. We analyzed 120 /p/- and /k/-initial words produced by 148 Canadian English speakers (n = 17742). VOTs of the initial stops were measured semi-automatically and all other segment durations were measured using forced alignment. The results of a mixed-effects regression support earlier findings that VOT is longer in /k/, directly related to following vowel duration, inversely related to speech rate, longer before tense vowels, and shorter before voiceless codas. Additionally, we find that VOT is shorter when the next syllable starts with a phonetically voiceless plosive (i.e., excluding flapped /t/), and that the most relevant measure of vowel duration includes the duration of postvocalic liquids, even those that are typically analyzed as onsets.
Suitability of speaker normalization procedures for classifying vowels produced by speakers with dysarthria
Authors: Lansford Kaitlin L. , Utianski Rene L.
Published: October 2015

Speaker normalization, a process whereby the perceptual system of a listener recalibrates to accommodate individual speakers, is proposed to account for the ease with which we understand speech produced by multiple speakers with different sized and shaped vocal tracts. A variety of vowel-, formant-, and speaker-intrinsic or extrinsic transforms have been proposed to model speaker normalization of vowels produced by multiple speakers (e.g., Mel, Bark, and Lobanov methods). Suitability of such normalization procedures has been examined extensively in non-disordered speaker populations. Unknown at this point, however, is the appropriateness of normalization procedures for transforming spectrally distorted vowels produced by speakers with dysarthria. Thus, we examined the suitability of two transforms, Bark and Lobanov, for normalizing vowels produced by a heterogeneous cohort of 45 speakers with dysarthria. Non-normalized (Hertz) and Bark transformed vowel tokens were classified via discriminant function analysis (DFA) with 55% and 56% accuracy, respectively. Classification accuracy of vowel tokens normalized using Lobanov’s method was 65%. The results of the DFAs were compared to perceptual data, which revealed listeners identified vowel tokens with 71% accuracy. These results suggest vowel-extrinsic and formant- and speaker-intrinsic normalization methods (e.g., Lobanov) are better suited to model speaker normalization of dysarthric vowels.
Arrays of subcritical width rectangular speech bands with interpolated noise maintain intelligibility at high intensities
Authors: Lenz Peter , Bashford James A.
Published: October 2015

Speech intelligibility declines at high intensities for both normally hearing and hearing-impaired listeners. However, this rollover can be minimized by reducing speech in high frequency regions to an array of noncontiguous bands having vertical filter slopes (i.e., rectangular bands) and widths substantially narrower than a critical band. Normally hearing listeners were presented with “Predictability Low” sentences consisting of a 500-Hz lowpass pedestal band and an array of ten 4% bands spaced at approximately 1/3-octave (alternate ERBn) intervals from 1000 Hz to 8417 Hz. The pedestal band was fixed at 70 dB and the subcritical-band array varied from 55 to 100 dB in peak level. Intelligibility did not vary significantly for levels from 65 to 95 dB, ranging from 86 to 89%. Array intelligibility did significantly decrease to 82% when speech level was increased to 100 dB. However, intelligibility was restored to 88% when lower level rectangular noise bands (−30 dB relative spectrum level) were interpolated between speech bands. It is suggested that subcritical width filtering reduces rollover by limiting firing rate saturation to a subset of fibers within critical bands, and that interpolated noise further reduces saturation via lateral inhibition. Hearing aid applications will be discussed. [Research supported by NIH.]
Using automatic speech recognition to identify dementia in early stages
Authors: Sadeghian Roozbeh , Schaffer David J. , Zahorian Stephen A.
Published: October 2015

Early non-invasive diagnosis of Alzheimer’s disease (AD) and other forms of dementia is a challenging task. Early detection of the symptoms of the disorder could help families and medical professionals prepare for the difficulties ahead, as well as possibly provide a recruitment tool for clinical trials. One possible approach to a non-invasive diagnosis is based on analysis of speech patterns. Subjects are asked to describe a picture and their description (typically 1 to 3 minute speech sample) is recorded. For this study, a database of 70 people were recorded, 24 with a clinical diagnosis of probable or possible Alzheimer’s disease. When these data were combined with 140 other recorded samples, a classifier built with manually transcribed versions of the speech was found to be quite accurate for determining whether or not a speech sample was obtained from an Alzheimer’s patient. A classifier built using automatically determined prosodic features (pitch and energy contours) was also reasonably accurate, with several subsets of pitch and energy features especially effective for classification, as assessed by cross validation. The manually transcribed text has now been replaced by automatically transcribed text using automatic speech recognition (ASR) technology. The main objective of this paper is to report on the relative effectiveness of several ASR approaches, including public domain ones, for this task.
Database of musical instruments directivity pattern
Authors: Shabtai Noam , Behler Gottfried , Vorländer Michael
Published: October 2015

The directivity pattern of an acoustic source describes the manner in which the sound radiates from it in the spatial domain. It may be used in virtual reality applications to improve the sense of realism perceived by the user. This work presents a directivity pattern database of 41 historical and modern orchestral instruments. The generation of this database includes the recording session in an anechoic chamber using a surrounding spherical microphone array, followed by a preliminary stage of isolating steady parts from the raw signals. Then, calibration is applied by normalizing the signals with the electrical channel gains and with the microphone gains. The fundamental frequency and overtones are then detected and the energy at each harmonic is saved for each played tone. Source centralization is applied in order to align the acoustic center of the sound source to the physical center of the microphone array. Last, a directivity pattern is generated in the spherical harmonics domain for each third-octave band by averaging the directivity pattern at all the overtones with a frequency belongs to that band.
Non-impulsive signal deconvolution for computation of violin sound radiation patterns and applications in sound synthesis
Authors: Perez Carrillo Alfonso , Bonada Jordi , Valimaki Vesa , Bucci Andres , Patynen Jukka
Published: October 2015

This work presents a method to compute violin body impulse responses (BIR) based on deconvolution of non-impulsive signals. This newly conceived approach is based on a frame-weighted deconvolution of excitation and response signals. The excitation, consisting of bowed glissandi, is measured with piezoelectric transducers built into the violin bridge and the response is measured as sound pressure with microphones. Based on this method, several research works have been carried out in the areas of acoustics and sound synthesis. First, by placing multiple microphones at different angles around the violin, we were able to compute a dense grid of 3D sound radiation patterns without restrictions in the frequency range. Second, the computed BIRs can be convolved with a source signal (captured with the same bridge-transducer and using the same violin), obtaining a highly realistic violin sound very similar to that of a microphone recording. The multiple impulse responses at different directions make has been used to enhance sound synthesis with spatialization effects. Finally, a bowing machine was built to perform repeatable glissandi and therefore be able to compute BIRs across different violins. The bowing machine has been used to compute cross-BIRs that map the pickup signal of electric violins to the radiated acoustic sound of acoustic violins, which allows to imitate the sound of any measured acoustic violin with an electric counterpart.