bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrete Averaging Relations for Micro to Macro Transition
Authors: Liu Chenchen , Reina Celia
Published: May 2016

The well-known Hill's averaging theorems for stresses and strains as well as the so-called Hill–Mandel condition are essential ingredients for the coupling and the consistency between the micro- and macroscales in multiscale finite-element procedures (FE2). We show in this paper that these averaging relations hold exactly under standard finite-element (FE) discretizations, even if the stress field is discontinuous across elements and the standard proofs based on the divergence theorem are no longer suitable. The discrete averaging results are derived for the three classical types of boundary conditions (BC) (affine displacement, periodic, and uniform traction BC) using the properties of the shape functions and the weak form of the microscopic equilibrium equations without further kinematic constraints. The analytical proofs are further verified numerically through a simple FE simulation of an irregular representative volume element (RVE) undergoing large deformations. Furthermore, the proofs are extended to include the effects of body forces and inertia, and the results are consistent with those in the smooth continuum setting. This work provides a solid foundation to apply Hill's averaging relations in multiscale FE methods without introducing an additional error in the scale transition due to the discretization.
Extreme Wave Condition at Doggerbank
Authors: Engebretsen Espen , Haver Sverre K. , Myrhaug Dag
Published: May 2016

In design of offshore wind turbines, extreme wave conditions are of interest. Usually, the design wave condition is taken as the sea state corresponding to an annual exceedance probability of 2 × 10−2, i.e., a return period of 50 years. A possible location for a future wind farm, consisting of bottom fixed wind turbines, is the Doggerbank area. The water depth in this area varies from about 60 m in the north to about 20 m in the south. The hindcast database NORA10 provides sea state characteristics from 1957 to present over a domain covering Doggerbank. Regarding the deeper areas just north of Doggerbank, this hindcast model is found to be of good quality. Larger uncertainties are associated with the hindcast results as we approach shallower water further south. The purpose of the present study is to compare sea state evolution over Doggerbank as reflected by NORA10 with the results of the commonly used shallow water hindcast model SWAN. The adequacy of the default parameters of SWAN for reflecting changes in wave conditions over a sloping bottom is investigated by comparison with model test results. Extreme wave conditions for two locations 102.5 km apart in a north–south direction are established using NORA10. This is done using both, an all sea states approach and a peak over threshold (POT) approach. Assuming the extremes for the northern position to represent good estimates, the wave evolution southward is analyzed using SWAN. The extreme condition obtained from NORA10 in the northern position is used as input to SWAN and the results from the two hindcast models are compared in the southern position. SWAN seems to suggest a somewhat faster decay over Doggerbank compared to NORA10.
In vitro screening procedure for characterization of thrombogenic properties of plasma treated surfaces
Authors: Modic Martina , Mozetič Miran
Published: May 2016

Estimation of thrombogenic surface properties is an important aspect of hemocompatibility studies. To improve our understanding of interaction between blood and biomaterial surfaces, there is a need to employ standardized methods that are both effective and efficient. This contribution details a systematic approach for the in vitro analysis of plasma modified polymer surfaces and human blood platelet interaction, following the recently introduced ISO 10933-4 guidelines. A holistic multistep process is presented that considers all aspects of testing procedure, including blood collection, platelet function testing, and incubation parameters, right through to a comparison and evaluation of the different methods and analysis available. In terms of detection and analysis, confocal light microscopy is shown to offer many advantages over the widely used scanning electron microscopy technique; this includes simpler, less-invasive sample preparation, and less time-consuming analysis procedure. On the other hand, as an alternative to microscopy techniques, toxicology sulforhodamine B based assay (TOX assay) was also evaluated. It has been shown that the assay could be used for rapid estimation of relative concentration of blood platelets on the surface of plasma treated materials, especially when samples do not allow the implementation of microscopy techniques.
Technical Note: Impact of cell repopulation and radionuclide uptake phase on cell survival
Authors: Šefl Martin , Kyriakou Ioanna , Emfietzoglou Dimitris
Published: May 2016

Purpose:

To study theoretically the impact on cell survival of the radionuclide uptake rate inside tumor cells for a single administration of a radiopharmaceutical.

Methods:

The instantaneous‐uptake model of O'Donoghue [“The impact of tumor cell proliferation in radioimmunotherapy,” Cancer 73, 974–980 (1994)] for a proliferating cell population irradiated by an exponentially decreasing dose‐rate is here extended to allow for the monoexponential uptake of the radiopharmaceutical by the targeted cells. The time derivative of the survival curve is studied in detail deducing an expression for the minimum of the surviving fraction and the biologically effective dose (BED).

Results:

Surviving fractions are calculated over a parameter range that is clinically relevant and broad enough to establish general trends. Specifically, results are presented for the therapy radionuclides Y‐90, I‐131, and P‐32, assuming uptake half‐times 1–24 h, extrapolated initial dose‐rates 0.5–1 Gy h−1, and a biological clearance half‐life of seven days. Representative radiobiological parameters for radiosensitive and rapidly proliferating tumor cells are used, with cell doubling time equal to 2 days and α‐coefficient equal to 0.3 and 0.5 Gy−1. It is shown that neglecting the uptake phase of the radiopharmaceutical (i.e., assuming instantaneous‐uptake) results in a sizeable over‐estimation of cell‐kill (i.e., under‐estimation of cell survival) even for uptake half‐times of only a few hours. The differences between the exponential‐uptake model and the instantaneous‐uptake model become larger for high peak dose‐rates, slow uptakes, and (slightly) for long‐lived radionuclides. Moreover, the sensitivity of the survival curve on the uptake model was found to be higher for the tumor cells with the larger α‐coefficient.

Conclusions:

The exponential‐uptake rate of the radiopharmaceutical inside targeted cells appears to have a considerable effect on the survival of a proliferating cell population and might need to be considered in radiobiological models of tumor cell‐kill in radionuclide therapy.
Masked threshold for noise bands masked by narrower bands of noise: Effects of masker bandwidth and center frequency
Authors: Taghipour Armin , Moore Brian C. J. , Edler Bernd
Published: May 2016

This paper examines how masked thresholds depend on the masker bandwidth and center frequency when the masker has a smaller bandwidth than the signal. The signal bandwidth was equal to the equivalent rectangular bandwidth of the auditory filter and the masker bandwidth was 0.1, 0.35, or 0.6 times the signal bandwidth. The masker and signal were centered at the same frequency of 257, 697, 1538, 3142, or 6930 Hz. Masked thresholds were estimated using a two-interval two-alternative forced-choice paradigm and a three-down one-up adaptive staircase method. Masked thresholds increased with increasing masker bandwidth and were lowest for medium center frequencies.
Understanding acoustic methods for cement bond logging
Authors: Wang Hua , Tao Guo , Shang Xuefeng
Published: May 2016

Well cementation is important for oil/gas production, underground gas storage, and CO2 storage, since it isolates the reservoir layers from aquifers to increase well integrity and reduce environmental footprint. This paper analyzes wave modes of different sonic/ultrasonic methods for cement bonding evaluation. A Two dimensional finite difference method is then used to simulate the wavefield for the ultrasonic methods in the cased-hole models. Waveforms of pulse–echo method from different interfaces in a good bonded well are analyzed. Wavefield of the pitch–catch method for free casing, partial or full bonded models with ultra-low density cement are studied. Based on the studies, the modes in different methods are considered as follows: the zero-order symmetric Leaky–Lamb mode (S0) for sonic method, the first-order symmetric Leaky–Lamb mode (S1) for the pulse–echo method, and the zero-order anti-symmetric Leaky–Lamb mode (A0) for the pitch–catch method. For the sonic method, a directional transmitter in both the azimuth and axial directions can generate energy with a large incidence angle and azimuth resolution, which can effectively generate S0 and break out the azimuth limitation of the conventional sonic method. Although combination of pulse–echo and pitch–catch methods can determine the bonding condition of the third interface for the ultra-low density cement case, the pitch–catch cannot tell the fluid annulus thickness behind casing for the partial bonded cased-hole.
Asymptotic limits of some models for sound propagation in porous media and the assignment of the pore characteristic lengths
Authors: Horoshenkov Kirill V. , Groby Jean-Philippe , Dazel Olivier
Published: May 2016

Modeling of sound propagation in porous media requires the knowledge of several intrinsic material parameters, some of which are difficult or impossible to measure directly, particularly in the case of a porous medium which is composed of pores with a wide range of scales and random interconnections. Four particular parameters which are rarely measured non-acoustically, but used extensively in a number of acoustical models, are the viscous and thermal characteristic lengths, thermal permeability, and Pride parameter. The main purpose of this work is to show how these parameters relate to the pore size distribution which is a routine characteristic measured non-acoustically. This is achieved through the analysis of the asymptotic behavior of four analytical models which have been developed previously to predict the dynamic density and/or compressibility of the equivalent fluid in a porous medium. In this work the models proposed by Johnson, Koplik, and Dashn [J. Fluid Mech. 176, 379–402 (1987)], Champoux and Allard [J. Appl. Phys. 70(4), 1975–1979 (1991)], Pride, Morgan, and Gangi [Phys. Rev. B 47, 4964–4978 (1993)], and Horoshenkov, Attenborough, and Chandler-Wilde [J. Acoust. Soc. Am. 104, 1198–1209 (1998)] are compared. The findings are then used to compare the behavior of the complex dynamic density and compressibility of the fluid in a material pore with uniform and variable cross-sections.
Comparison of occupied and unoccupied noise levels in K-12 classrooms
Authors: Brill Laura C. , Wang Lily M.
Published: May 2016

Current research at the University of Nebraska—Lincoln aims to establish how indoor environmental conditions in K-12 school buildings impact student scholastic achievement. A large-scale in-situ survey is being undertaken to gather data on (1) indoor environmental conditions under different seasons or outdoor conditions (fall, winter, and spring), and (2) student’s standardized test outcomes and demographics, as classroom aggregates with no individually identifiable information. In this paper, acoustic data gathered to date from 110 classrooms are mined to determine how occupied and unoccupied noise levels correlate. The ANSI Classroom Acoustics Standard S12.60 (2010) specifies guidelines for unoccupied background noise levels, but students learn in occupied spaces. Logged acoustic data over multiple school days are analyzed to determine if designing for unoccupied noise levels is appropriate to achieve desired occupied acoustic conditions. [Work supported by the United States Environmental Protection Agency Grant Number R835633.]
Cantonese speech intelligibility tests in two Hong Kong primary school classrooms
Authors: Tang Shiu-Keung , Lau Siu-Kit
Published: May 2016

Speech transmission is a very important issue especially in early childhood education during which the children learn languages and pronunciations. There are evidences that the acoustical performance of a classroom can have significant impact on the learning progress and effectiveness of the children. The effect is not only observed in language subjects, but also in the numeracy related subjects. In this study, on-site speech intelligibility tests are conducted using newly developed phonetically balanced (in Cantonese) Chinese character lists suitable for the Year 5 Hong Kong primary school children (10–11 years old) in two classrooms. A trained speaker is recruited to speak out the characters. The classroom acoustical properties are also measured, but in the absence of the pupils because of statutory regulation. The sound of each Cantonese character in general consists of an initial consonant, a vowel, a final consonant, and a tone. A preliminary observation is that there is higher probability for the pupils to give wrong answers when the sound of a character lasts for relatively long duration, especially when there are abrupt temporal changes in the time-frequency spectra. Correct answers are usually given when the corresponding time-frequency spectral energy is more concentrated within a short duration.
A case of classroom acoustic treatment in Tsinghua University
Authors: Yan Xiang , Li Hui
Published: May 2016

Room 114 is an 100 audience classroom located in the Architecture Department Hall of Tsinghua University with unsatisfactory acoustic effects. This paper briefly introduces the whole process of acoustic design for this classroom which included document survey, acoustic test, acoustic simulation analysis, scale model test, auralization simulation, etc. After weighing both the acoustic and visual effects of three designs, the executives determined the final one to put into effect. This case suggests that technology has been able to well solve the problem of the sound quality of the classroom in universities, but how to persuade managers adopt these technologies, maybe more difficult in classroom acoustics which need further studies.
A global index of acoustic assessment in elemental school classrooms
Authors: Peng Jianxin
Published: May 2016

This paper describes the results of a study aimed at developing a method for optimizing the acoustic quality of a classroom. A global index of acoustic assessment in elemental school classrooms was developed for this purpose. It is especially important in classrooms, where suitable conditions should be provided to convey speech communication for teachers and students. The paper presents a method for assessing the acoustic quality of classrooms based on a single number global index and taking into account a number of factors affecting the outcome of the assessment, such as speech intelligibility, noise level, reverberation time, speech sound pressure level, and the age of students. A method is proposed based on an analysis of factors determining whether a room meets applicable acoustic requirements.
Ten tips for communicating with Congress—and why it is worth doing
Authors: Carr Rachel
Published: May 2016

As this year’s AIP-ASA Congressional Science Fellow, I have a up-close view of how scientists’ voices are received on Capitol Hill. I am often surprised, both by what catches the attention of legislators and their staffs and by how impactful a brief meeting can be. With research funding decisions and acoustics-related public policy at stake, there can be major benefits to engaging with Congress and planning these interactions strategically. I will share some suggestions for doing that, based on my observations and advice from House and Senate staffers. While the general guidelines of science communication apply, I will focus on the timelines and tendencies of this unique institution and areas where acoustical scientists may be most connected.
Beyond decibels: Inspiring informed noise management in U.S. National Parks
Authors: Fristrup Kurt M.
Published: May 2016

Noise was not a significant threat to parks when the Organic Act was signed. As recently as five decades ago, road and aircraft traffic were less than a third of their present levels. In response to emerging noise issues, the NPS created an overflights program in 2000, which has evolved into the Natural Sounds and Night Skies Division. Noise is not inevitable. It is crucial to raise awareness of this growing threat without evoking a sense of defeat or resignation. Successful presentations start by arousing a need for action and hinting at the prospects for successful fulfilment. Compelling visualizations are the foundation of effective science presentations. Maps of noise exposure on continental and national park scales have been especially effective. For other scientific graphics, consider starting with an illustration of the simplest message, and sequentially adding elements to support the primary message. Often the most important decision is what to leave out of a figure. It is crucial to connect any measurement or metric to something that your audience cares about and make these units relateable. If you must use decibels, be sure to connect these to sensible effects.
Turn on the lights!
Authors: O'Donoghue Amy
Published: May 2016

Over the decades that I’ve been a reporter and editor in the news business, I've never met a technical expert who was not just a bit pleased and more than a little passionate about the work they do once you coax it out of them. A crime scene technician relishes every little detail in the forensic evidence they collect. Meteorologists enthuse over El Nino or become giddy at the latest iteration of the Madden-Julian oscillation. Nuclear scientists are fascinated by radioactive daughter products. Despite this passion, most scientists don't make a splash about what they're up to. They go about work every day, picking apart technical details in obscurity, even acting mildly surprised if an outsider shows an interest. What cuts across many “subject matter” disciplines is curious modesty and often the mistaken notion by experts that their work is boring or of little public interest. My advice? Speak up. We're anxiously listening, and while you may have to repeat yourself a couple of times for us to “get it,” we want to understand. We have the ability to shine a light on what you do, and explain why it is important, so help us help spread your important messages.
Examples of both expected and unexpected interactions and outcomes when conveying science and technology to traditional print and modern media journalists
Authors: Wilson Preston S.
Published: May 2016

It has been my experience with both traditional print journalists, and with modern media journalists, that unexpected interactions and outcomes sometimes occur. These can have both desirable and undesired consequences for the scientist. Some examples of these interactions will be given, which are associated with quite diverse technical topics, ranging from press and radio interviews covering work on the soundscape of a threatened species (Ceratotherium simum simum, the southern white rhinoceros), to a radio interview on the acoustics of coffee roasting that included a surprise guest, to an underwater photo shoot with a National Geographic photographer covering research on an underwater noise abatement system. Some guidelines will be presented that aim to minimize the undesired outcomes.
The city of the future—Noise initiative in the “Year of Science 2015”
Authors: Fiebig André , Schulte-Fortkamp Brigitte , Genuit Klaus
Published: May 2016

In the context of the German Year of Science 2015, the issue noise in cities was addressed by means of a special initiative in order to raise noise awareness and to stimulate public participation. The “Sound of the City” initiative taking place within the framework of the Year of Science 2015 was organized and supported by the Federal Ministry of Education and Research (BMBF). By using different media, people were invited to report on how their cities sound. They were encouraged to upload audio recordings of their acoustical environments, to relate the sounds to the respective places and to describe the sounds and their perception. In general, the participants should consider sounds, which they typically associate with their cities. This action led to a comprehensive data base of audio files, which all have in common that the sounds bear a particular meaning for the participants. In a subsequent study, all submitted sounds were subject to a detailed analysis to investigate from different viewpoints the distinctive features of the sounds. The paper will present the results of the analyses and discuss the findings with respect to the potential of such public participation in the field of community noise.
Analysis of 500 noise ordinances
Authors: Blomberg Leslie D.
Published: May 2016

The noise ordinances for the 500 largest communities in the United States were collected and analyzed to determine the various techniques, metrics and criteria communities use to regulate noise (such as sound pressure level, nuisance, disturbing the peace, plainly audible, minimum distance, time of day, etc.). A survey of a random sample of those communities was conducted to determine the effectiveness of the noise regulation techniques, metrics, and criteria.
An abbreviated history and recent developments regarding community noise and soundscape management in New Orleans
Authors: Woolworth David S.
Published: May 2016

New Orleans has one of the most complicated soundscapes of the cities of America, and with it a veritable gumbo of people and their opinions about sound and the city. Recent efforts to revise the ordinance and reduce sound levels from the Vieux Carre Entertainment District met with an encouraging response from residents and business owners alike, yet failed in City Council. The New Orleans Health Department has begun a program of proactive education of entertainment workers in the last year. This paper will touch on the origins of the city soundscape, early regulations, and then discuss in greater detail a summary of the recent developments in soundscape management.
A spacetime finite element method for coupled acoustic fluid-structure interactions
Authors: Miller Scott T. , Hanford Amanda D.
Published: May 2016

The spacetime discontinuous Galerkin (SDG) finite element method is applied to problems of acoustic propagation. The spacetime discontinuous Galerkin are a family of discontinuous finite element methods for hyperbolic systems of equations. They utilize an advancing front mesh generation procedure that allows local “patches” of elements to become decoupled from the global solution domain through causality. Causal space-time meshes enable a locally implicit solution procedure with provably linear computational complexity. Mesh adaptivity is shown to effectively resolve propagating waves and minimize dispersion error. Numerical results demonstrate the effectiveness of the proposed solution method, including achieving optimal convergence rates. Time domain simulations of several canonical acoustic problems are presented.
Uncertainty quantification, turbulent scattering, and random sampling in outdoor sound propagation calculations
Authors: Wilson D. K. , Pettit Chris L. , Hart Carl R. , Ostashev Vladimir E.
Published: May 2016

Although the fundamental physics of sound propagation outdoors (e.g., absorption, ground interactions, refraction, and scattering) are well understood, modeling capabilities are typically inadequate to capture the many intricate interactions with the atmosphere, ground, and natural and man-made terrain features. Furthermore, environmental data are rarely available at the sub-wavelength resolution needed to accurately predict the sound field in the audible range, in a deterministic sense. Fortunately, advances in computing capabilities and statistical sampling methods provide new opportunities for quantifying the inherent uncertainties of sound propagation predictions. Among the sampling techniques considered in this presentation are ordinary Monte Carlo sampling, Latin hypercube sampling, stratified sampling based on meteorological classes, importance sampling, and adaptive importance sampling. When uncertainties in the atmospheric and ground properties dominate, importance sampling is found to converge to an accurate estimate with the lowest calculation time. When random turbulent scattering dominates, the sampling method has little impact. Efficient and accurate approaches to calculating sound level statistics and quantifying uncertainty result from simultaneously sampling over frequency, source/receiver position errors, uncertain atmospheric profiles and ground properties, and random processes such as scattering by turbulence and vegetation.
Development of a simulation for supersonic aircraft signature propagation through turbulence
Authors: Stout Trevor A. , Sparrow Victor W.
Published: May 2016

For the next generation of quiet supersonic civilian aircraft, minimizing the acoustic signature is important. To inform the design process, a model of the effect of shock wave propagation through the atmosphere is required. For such a model to be accurate, both the weak nonlinear effects on the supersonic signature and the distortion due to atmospheric turbulence could be important. To best predict the variability of waveforms heard at multiple locations on the ground, a propagation simulation requires multiple random realizations of the turbulent field. In the present model, a finite difference implementation of the two-dimensional, nonlinear KZK propagation equation is combined with a statistical turbulence model to simulate shock wave propagation through the atmosphere. For this initial work, a KZK simulation for focused sources developed at the University of Texas by Y. Lee was modified and extended for atmospheric propagation. [Work supported by NASA via a subcontract from Wyle.]
Sound synthesis methods of fire flame sound for predicting hidden images
Authors: Jo HyunIn , Afzal Rehan H. , Muhammad Imran , Jeon Jin Y.
Published: May 2016

A methodology is proposed and investigated for realistically synthesizing aerodynamic sounds, such as fire sounds based on a graphically generated animation of fire. The proposed technique, “bandwidth extension method,” is a physically based combustion sound model for synthesizing low frequency flame sounds from a visual flame simulation, which runs at low temporal sampling rates. The spectral bandwidth approach uses noise matching combustion sound spectra, whereas the data-driven texture approach uses input flame sound recordings. Various simulations of fire animations are presented, and a comparison is provided of small- and large-scale phenomena for plausible synthesized and recorded flame sounds of various flames.
A modal time-domain method for modeling dispersive and dissipative linear waves
Authors: Botts Jonathan , Savioja Lauri
Published: May 2016

A modal time-domain method is developed for simulating linear dispersive and dissipative waves in 3D geometries. Two of the principle challenges in modeling large acoustic systems are fitting models into computer memory and managing numerical wave speed errors; both prevent modeling of large problems and high frequencies. To address these issues, a framework is developed for solving linear wave equations on a structured subdivided domain using exact frequency-dependent time integration. From the perspective of modeling sound in rooms, the method is shown to accurately capture propagation losses due to air absorption, dispersive bending waves in panels, lossy propagation in porous media, and dispersionless propagation over large distances. This approach enjoys exact time integration for many PDE, but such accuracy comes at the cost of highly-structured grids and non-trivial boundary conditions. Advantages and shortcomings are discussed relative to problems of practical size and interest.
Investigating the role of the medial olivocochlear reflex in selective attention
Authors: Beim Jordan A. , Oxenham Andrew J. , Wojtczak Magdalena
Published: May 2016

Selective attention can dramatically attenuate the cortical responses to unattended stimuli relative to attended stimuli. The mechanisms behind this attenuation and their locus in the auditory pathways are not yet understood. Recent animal work suggests that changes may begin to occur as early as the cochlea itself, potentially through the medial olivocochlear (MOC) reflex. Since measuring MOC activity directly is too invasive to be done in humans, otoacoustic emissions (OAEs) are used to examine changes in cochlear function. Previous investigations of attention-related efferent effects on cochlear processing using OAEs have generally found small and inconsistent effects. The previous lack of effects could be due in part to shortcomings in OAE and MOC-reflex measurement methodology. A new experimental paradigm designed to overcome these shortcomings was used here to examine the effects of selectively attending to visual or auditory stimuli. Participants directed attention to either low-frequency tones, high-frequency tones, or visual stimuli to complete a task with each stimulus while OAEs were recorded using the same low-frequency tones. Initial results have revealed an average decrease in emission magnitude of 8.5 dB when participants attended to the visual stimulus compared with the low-frequency tones, suggesting substantial attentional effects on cochlear responses.
A model of the cochlear apex and structure for study of mechanism and response characteristics
Authors: Alkhairy Samiya , Shera Christopher
Published: May 2016

We provide a model of the cochlear apex that is geared towards studying: cochlear function represented by common response characteristics (e.g., sharpness of tuning), governing mechanisms, inter-relations between the response characteristics, inter-relations between the traveling wave and point admittance effective mechanics, and the relationship between response characteristics and mechanism. The model currently used for some of these ends is an uncoupled resonant simple harmonic oscillator. However, this framework is inconsistent with current knowledge in the field. Hence, an alternative framework must be provided for these purposes. To these ends, in this paper, we construct a general parametric model of the cochlear that represents the Organ of Corti as a single partition in a box fluid model. The model provides closed-form expressions for responses—specifically membrane velocity and fluid pressure—and the corresponding response characteristics. Development of the model includes construction of effective mechanics, construction of responses and their characteristics, and validation. We find that our model provides a suitable representation of data, by using auditory nerve fiber Wiener-Kernel data to approximate mechanical responses. Also, we show that the model may be extrapolated beyond its primary purposes for use as a computationally efficient cochlear front-end to auditory aid devices and speech processing programs.
Effect of sub-tectorial space fluid dynamics on cochlear energy dissipation and inner hair cell mechano-transduction
Authors: Prodanovic Srdjan , Gracewski Sheryl M. , Nam Jong-Hoon
Published: May 2016

In the mammalian cochlea, the mechano-transduction of the inner hair cell (IHC) stereocilia occurs in a micrometer-thick fluid space between the tectorial membrane and the reticular lamina. Using a computational model of the cochlea, we analyzed how the sub-tectorial space (STS) fluid mechanics affect cochlear power dissipation and IHC mechano-transduction. Based on the simulations of a single IHC stereociliary bundle in the STS (Prodanovic et al., 2015), the fluid-induced forces of the STS were reduced to simple equations. The reduced STS response was combined with a whole cochlear model consisting of: organ of Corti structural mechanics, cochlear fluid dynamics, and outer hair cell electro-physiology. Energy dissipation in the cochlea was quantified for three categories: macro-fluidic dissipation along the cochlear scalae, micro-fluidic dissipation in the STS, and other dissipation in the organ of Corti. The phase of IHC mechano-transduction current with respect to the basilar membrane displacement was dependent on stimulating frequency and location.
Frequency cueing and top-down processes in the perceptual segregation of simultaneous tone
Authors: Shen Yi , Louthan Brooke E.
Published: May 2016

Discriminating the properties of two simultaneously presented pure tones could be challenging even when the two tones are distant in frequency, potentially due to the tones being perceptually grouped into a single auditory object. In the current study, two tones 1.1 octaves apart were presented monaurally into the same ear, only one of which was amplitude-modulated at a depth of 100% and a rate of 10 Hz. Listeners selected the amplitude-modulated tone from the pair, and performance thresholds were estimated in terms of the presentation duration required to carry out the task. Moreover, the experiment included conditions in which the frequency of one of the tones was cued by a precursor tone, presented to the ipsilateral or contralateral ear. For ipsilateral precursors, when the precursor was relatively long (400 ms), the presence of precursor improved threshold from the no-precursor condition independent of the gap duration between the precursor and the tone-pair. On the other hand, when the precursor was relatively short (100 and 200 ms), the threshold improvement was relatively small for short gap duration. The facilitation effect of the precursor was observed for gap duration as long as 1 s, suggesting the involvement of top-down processes. For contralateral precursors, the facilitation effect was much reduced.
Complex pitch perception via vocoder simulations of cochlear-implant processing
Authors: Mehta Anahita H. , Oxenham Andrew J.
Published: May 2016

Melodic pitch perception in cochlear implants (CIs) is limited at least in part by spectral resolution, which in turn is limited by the number of spectral channels as well as interactions between adjacent channels. Future technical improvements may lead to greater numbers of functional channels within CIs; however, the target number of channels required to extract the fundamental frequency from a harmonic sound is not known. The present study used noise-vocoded simulations of CI processing to parametrically study melodic pitch perception, with other potential cues, such as temporal-envelope rate and lowest spectral component, removed. The number of spectral channels was parametrically varied, along with the degree of channel interaction. In contrast to earlier studies, preliminary results suggest that 32 channels are not sufficient to elicit the perception of complex pitch, even in the absence of any significant channel interactions. Even when pitch perception was possible with higher numbers of channels, performance was degraded by introducing varying amounts of channel interaction. The results suggest that spectrally based pitch is unlikely to be generated in CI users without a substantial change in technology and/or site of stimulation. [Work supported by NIH grant R01DC005216.]
Release from masking in cochlear-implant listeners and its relationship to spectro-temporal resolution
Authors: Croghan Naomi B. , Smith Zachary M.
Published: May 2016

Release from masking is commonly observed in normal-hearing listeners when fluctuating interferers mask speech perception less than steady interferers at the same signal-to-noise ratio. In contrast, studies of cochlear-implant listeners have historically failed to find masking release with fluctuating maskers. Here, we provide new insights into the relationship between spectro-temporal resolution and release from masking in cochlear-implant and simulated cochlear-implant listeners. Varying degrees of current spread were simulated in normal-hearing listeners using a tone vocoder. Speech reception thresholds were measured with four different interferers: a tone complex, speech-shaped noise, four-talker babble, and a single competing talker. A dynamic spectral ripple detection test was conducted to measure psychophysical spectro-temporal resolution. Results show that overall speech perception was correlated with spectro-temporal ripple detection thresholds. However, some maskers were more sensitive to spectro-temporal resolution than others. Subjects in both groups demonstrated release from masking between the speech-shaped noise and the single competing talker conditions, and the degree of release varied with spectro-temporal ripple sensitivity. These findings shed new light on previous cochlear-implant results, suggesting that individual cochlear-implant listeners with high spectro-temporal resolution may benefit from the temporal fluctuations in certain noise types.
Relationship of working memory to the effect of listener training on pitch and rhythm perception
Authors: Guzman Sandra J. , Milone Julian , Meinke Kenneth , Shafiro Valeriy , Sheft Stanley
Published: May 2016

Experience and training can affect discrimination of tonal sequences. Recent work has demonstrated differences in processing multidimensional tonal sequences defined both by pitch contour and sequence rhythm. With groups defined by skill level on a pattern reconstruction task, a significant interaction between group and sequence-task condition suggested a difference in the manner of integration of pitch and rhythm information, with the poorer performing group showing greater integration across dimensions. Current work investigated the effect of training over sessions on pitch and rhythm processing of four-tone sequences by trained musicians and audio-arts students experienced in critical listening. Sequence tones either had a fixed duration (212 ms) with frequency randomly selected from a logarithmically scaled distribution (400–1750 Hz), a fixed frequency (837 Hz) with a randomly selected logarithmically scaled duration (75–600 ms), or a random frequency and duration. In initial conditions, the task was to assemble sequence elements to recreate the target sequence, whereas the later conditions required subjects to ignore extraneous changes in one dimension while reconstructing the target dimension. Trends suggest that training improves performance. Ongoing work is examining the relationship between performance on a number-letter sequencing task and integration of the pitch and rhythm information in tonal sequences.
Interactions between front-back confusion and visual capture in summing localization
Authors: Montagne Christopher , Zhou Yi
Published: May 2016

Ambiguity in binaural timing and level information often causes front-back confusions in sound localization. This experiment investigated the extent to which front-back confusions are modulated by concurrent visual stimuli. 15-ms duration noise stimuli were presented over two loudspeakers positioned at ±45o in front or behind a listener with a delay between them of −1—1 ms in steps of 0.5 ms, thus evoking summing localization. These sound stimuli were presented with or without light-flash stimuli at three different frontal locations. In comparison to audio only trials, when visual stimuli were also presented front-back confusion decreased for sound stimuli presented in front and increased for rear-presented auditory stimuli. This effect was greater for phantom sound sources than single speaker controls. These results suggest that visual cues influence the perceived location of a sound source when it is outside the field of vision. Further, the phantom sound sources presented using “summing localization” may offer less robust localization cues than physical sound sources, resulting in greater front-back confusion and stronger visual capture. Acoustic analyses of binaural and spectral cues are conducted to identify potential causes of the differences in FBC rates between single speaker and phantom sound sources.
A binaural model using equalization/cancellation and simulated head movements to localize and extract one speaker from a mixture
Authors: Deshpande Nikhil , Braasch Jonas
Published: May 2016

This model takes a mixture of two simultaneous speech signals at unique azimuth positions to extract either speaker using the equalization/cancelation (EC) method. Head-related transfer functions are used to spatialize the two sound sources. The model localizes the sources by analyzing interaural time differences and then virtually rotates its head to find the position for the best signal-to-noise ratio. Next, the model segments the mixed speech signal in time and frequency bins, and uses an EC algorithm in each bin to compensate the target signal from the mixture. From the residual non-cancelled energy, it generates a binary map and overlays this on the spectrogram. The ability of the model to cancel out the target signal determines the bins where the target is actually present. The signal is then reconstructed in time and frequency, leaving only one desired target signal. The model achieves signal-to-noise ratios of up to 80 dB. [This material is based upon work supported by the National Science Foundation under Grant Nos. 1320059 and 1539276.]
Enhanced auditory spatial performance using individualized head-related transfer functions: An event-related potential study
Authors: Wisniewski Matthew G. , Kenzig Stephanie M. , Romigh Griffin D. , Thompson Eric R. , Iyer Nandini , Simpson Brian D. , Rothwell Clayton
Published: May 2016

Head-related transfer functions (HRTFs) capture location dependent alterations to a sound caused by a physical interaction with a listener's head, shoulders, and outer ears. Sounds rendered with a listener's own HRTF can be localized with accuracy comparable to real sources; however, because anthropometric features vary across listeners, rendering sounds with non-individualized HRTFs can severely degrade localization of virtual sound source location, especially in elevation. Here, we were interested in identifying event-related potential (ERP) features associated with the benefit of employing individualized HRTFs. Thirty “runs” of 250 ms white-noise bursts (6–12 bursts long) with identical virtual elevations (0°–90°, 10° increments) were presented back-to-back within a block. Listeners were instructed to press a button whenever the elevation changed (i.e., at the start of each run). Elevation change detection was enhanced in an Individualized compared to a non-Individualized HRTF condition. ERPs to first bursts of a run showed larger amplitude P3s in the Individualized HRTF condition. Differences in P3 amplitudes between conditions were positively correlated with behavioral benefits gained from employing an individualized HRTF. That effects occurred for the P3 suggests that at least part of the benefit obtained from using individualized HRTFs reflects post-sensory processes.
Native and non-native intuitions on the phonology of English and French binomials
Authors: Green Viola
Published: May 2016

Binomial locutions are a well-known case of structural iconicity. By binomial locutions we understand formations that have the shape of A conjunction B (1a), or A-B (1b): (1). a. English: bread and butter, wear and tear; French: dire et juger, ni foi ni loi b. English: wishy-washy, helter-skelter; French: pêle-mêle, clopin-clopant The word order in such locutions has been claimed to be motivated by certain constraints on the ordering of the two elements (Cooper and Ross 1975, Birdsong 1995). The main objective of this study is to investigate several specific phonological segmental constraints and the sensitivities that native and non-native speakers of English and French exhibit for these constraints. This is proposed to be tested with a computer-based judgment task, with pairs of nonsensical expressions, structured in such a way that one expression obeys a specific constraint, and the other expression disobeys it. The task of the participants is to listen to such pairs and to indicate which of them they like better by using a 6-point scale. According to the preliminary results, native English speakers tend to be sensitive to most of the phonological constraints in various degrees, while native French speakers are indifferent to most constraints tested.
Rapid reduction of listening effort resulting from predicting speech processing, and delays associated with cochlear implantation
Authors: Winn Matthew
Published: May 2016

Speech communication involves not only the recognition of words, but also processing and prediction resulting from those words. This study explored the question of whether prediction guided by semantic context reduces physiological listening effort, and whether this process is as quick and effective in people who use cochlear implants (CIs). To examine this issue, pupil dilation was used as a time-varying index of effort during sentence perception by CI users and listeners with normal hearing. NH listeners also heard spectrally degraded vocoded versions of the stimuli, which consisted of high-and low-context sentences. For NH listeners, context resulted in rapid effort reduction for normal speech; predictable sentences yielded reduced responses even before stimulus offset. For degraded stimuli, this effect was not observed until after the stimulus was over, suggesting that listeners normally process and take benefit from context in real time, but poor signal quality delays that process. For CI listeners, effort reduction from context was generally not as early or as large as that for NH listeners. These effects all persisted even when intelligibility was perfect, suggesting that word and sentence recognition scores could mask difficulties in functional language use, like timing and prediction in speech comprehension.
Speech recognition performance of listeners with normal hearing, sensorineural hearing loss, and sensorineural hearing loss and bothersome tinnitus when using air and bone conduction communication headsets
Authors: Manning Candice A. , Mermagen Timothy J. , Scharine Angelique A.
Published: May 2016

Military personnel are at risk for hearing loss due to noise exposure during deployment (Norin et al., 2011). Despite mandated use of hearing protection, hearing loss and tinnitus are prevalent due to reluctance to use hearing protection. Bone conduction (BC) headsets can offer good speech intelligibility for normal hearing (NH) listeners while allowing the ears to remain open in quiet environments and the use of hearing protection when needed. Tinnitus sufferers often show degraded speech recognition; however, it is unclear whether this is a result of decreased hearing sensitivity or increased distractibility. It has been suggested that vibratory stimulation of BC might ameliorate tinnitus; however, there is currently no research to support or refute this claim (Hoare, et al., 2014). Speech recognition of words presented over AC and BC headsets was measured for three groups of listeners: NH, sensorineural hearing impaired, and/or tinnitus sufferers. Three levels of speech-to-noise (SNR = 0,−6,−12) were created by embedding speech items in pink noise. Better speech recognition performance was observed with the BC headset regardless of hearing profile and speech intelligibility was a function of SNR. Discussion will include study limitations and the implications of these findings for those serving in the military.