bluuebunny/crossref_metadata_2025 huggingface dataset:
Parameter estimation of acoustic scattering echoes of underwater targets using sparse representation approach
Authors: Meng Xiangxia , Li Xiukun , Jakobsson Andreas
Published: November 2017

The acoustic scattering echo of an underwater target usually consists of multiple overlapped components. The time delay of each reflection is of great importance to estimate the size of the target. Herein, a sparse approach is presented to obtain the estimation of time delays with high resolution and accuracy. The parameters are determined using a dictionary with many more elements than expected reflections, with each dictionary element being found as the convolution of the transmitted signal and a potential impulse. The estimation problem is then converted into a convex optimization problem, which is then solved efficiently using the alternating direction method of multipliers (ADMM) framework. The estimation accuracy depends on the grid of the dictionary. To obtain high resolution, a dictionary refinement technique is employed. To model the time-varying nature of the signal amplitudes, we further estimate the temporal envelope of the signal using a weighted combination of splines. Using this technique, the algorithm can estimate both the time-delay and amplitude of a reflection simultaneously, without the need of prior information about the number of components. The method can be applied for the separation of overlapped components and high-resolution estimation of multi-angle echoes.
Scattered signal distributions, parametric uncertainties, and Bayesian sequential updating
Authors: Wilson D. K. , Hart Carl R. , Pettit Chris L. , Breton Daniel J. , Nykaza Edward T. , Ostashev Vladimir E.
Published: November 2017

A variety of probability density functions (pdfs) have been proposed for scattered signals, which have varying analytical advantages and ranges of physical applicability. We discuss here situations modeled by a compound pdf, in which a basic pdf, attributable to the underlying scattering process, has uncertain parameters or is modulated by variability in the environment. The parameters of the modulating pdf are termed hyperparameters. Some previous examples of compound formulations include the K-distribution, for which strong scattering (exponential pdf) is modulated by a gamma pdf for the mean signal power, and scattering by intermittent turbulence, for which strong scattering is modulated by a log-normal pdf for the structure-function parameter. We describe some alternative formulations, including strong scattering modulated by a gamma pdf for the inverse mean power, and Rytov (log-normal) scattering modulated by a normal pdf for the log-mean of the signal. These lead to relatively simple marginalized signal power distributions (Lomax and log-normal, respectively). Furthermore, the conditional scattered signal pdf may be viewed as a likelihood function in which the modulating pdf is the Bayesian conjugate prior. Hence the hyperparameters of the modulating process can be refined by simple sequential Bayesian updating as additional transmission data become available.
Estimation and equalization for shallow water communication channel using geometric encoding of channel multipath
Authors: Sen Gupta Ananya
Published: November 2017

The shallow water acoustic channel is well-known to exhibit rapid fluctuations in its impulse response, which is challenging to estimate and compensate for in real time. In particular, the moving ocean surface and static sea bottom reflect the acoustic signal in unpredictable ways to create rapidly time-varying multipath arrivals. The talk will focus on the nexus of shallow water acoustic propagation paths and how multipath can be discovered and exploited to improve shallow water acoustic communications. In particular, the talk will review sampling strategies for the time-varying shallow water acoustic channel and propose novel geometric encoding techniques that exploit non-uniform channel sampling strategies. We will also demonstrate how geometric encoding can be harnessed for real-time channel estimation as well as semi-blind channel equalization. Results based on experimental field data in recent work as well simulation results will be presented.
A comparison of speech coherence index and measured speech intelligibility
Authors: Szuts Tobi A. , Schwenke Roger W.
Published: November 2017

Perceptual tests were taken in real and simulated spaces to determine whether Speech Coherence Index (SCI) predicts human performance better than Speech Transmission Index (STI). SCI is a proposed method of estimating speech intelligibility during event conditions, that is, in real time with program material. The complex valued coherence function is used to estimate the signal-to-noise ratio on a per frequency basis, and is calculated with short time windows at high frequencies and longer time windows at low frequencies to mimic the multi-resolution nature of human hearing. SCI has been shown to track STI very closely under simplified conditions. Under more realistic conditions, SCI is more sensitive to reverberant energy and is always less than STI. Under certain conditions, such as long source to listener distance or low SNR, SCI predicts significantly lower intelligibility values than STI.
Results from the summer sound lab: Exploring acoustical options for a multiuse space on campus
Authors: Butko Daniel , Maggia Zachary , Abdallah Collin , Trout Lindsey
Published: November 2017

This paper summarizes the progress of an active multiphase acoustical research project emphasizing implementation of adaptive interactive acoustical responses in multiuse spaces to transform unhealthy learning environments. A multiuse space on campus, which suffers from poor speech intelligibility as a result of excessive reverb and flutter echo revealed through finish materials, room volume, and shape, functions as an architectural sound lab and location for data collection. The project, launched Spring 2017, will span multiple phases and disciplines for data collection, design, prototyping, validation, and construction. Faculty and students are collecting and analyzing acoustical data, adding to a literature review and database of comparable acoustical challenges and results, and validating findings in both computer and physical model form. Collected data will lead researchers to design applications for adaptive and resilient learning environments with minimized acoustical distractions and improved speech intelligibility. Their work will culminate in a final full-scale built form, providing scholarly merit applicable to similar spaces and/or functions. Established industry partnerships will provide development of physical panel-based prototyping, followed by acoustical testing, full-size fabrication, and installation for public interaction and academic validation.
Bone conducted sound in a dolphin’s mandible: Experimental investigation of elastic waves mediating information on source localization
Authors: Reinwald Michael , Marchal Jacques , Boschi Lapo , Grimal quentin
Published: November 2017

Marine mammals, such as dolphins, use audition as a tool to navigate and hunt. It is widely accepted that the main auditory pathway for sound reception in a dolphin’s skull is through the lower jawbone and the connected fatty tissues—both possibly acting as a waveguide. Elastic waves traveling inside the mandible therefore likely contain information on the position of sound sources. The objective of the work was to investigate to which extent elastic wave signals in a mandible of a common dolphin (Delphinus delphis) can be used to localize a source. Experiments were conducted in a water pool by placing a sound source emitting pulses in the range of 10–100 kHz at different angles in the horizontal plane of the mandible. The elastic waves propagating in the mandible were measured at two positions close to the hypothetical ears by piezoelectric discs glued to the bone. We evaluated energy directivity patterns, interaural level differences, and applied a time-reversal localization algorithm to simulate acoustic source localization of the sound source. The findings should give insight into the directivity of the auditory pathway of sound in a dolphin’s mandible and will be substantiated by 3D simulations in future work.
Quantification of fast pinna motions in rhinolophid and hipposiderid bats
Authors: Yin Xiaoyan , Qiu Peiwen , Müller Rolf
Published: November 2017

As part of their biosonar behaviors, rhinolophid (family Rhinolophidae) and hipposiderid bats (family Hipposideridae) both show conspicuous motions of their outer ears (pinna). These motions coincide with pulse emission and echo reception in time and could hence have a functional relevance for the encoding of sensory information. However, a quantitative in-depth characterization of these motions is still needed to derive detailed hypotheses for their function. To accomplish this, dense sets of landmark points have been placed on the pinna to provide for dense spatial coverage of its surface over the course of a motion cycle. Occlusion-free stereo tracking of the landmarks was accomplished with an array of four high-speed video cameras. Customized methods based on motion prediction have been used to track landmark points across video frames. The results have been used to construct accurate, continuous estimates of pinna surface motion. These estimates reveal that the pinna surface is subject to heterogeneous patterns of displacements and velocities within each motion cycle. Experiments with simplified robotic reproductions to understand the acoustic implications of these pinna surface motions are currently in progress. Once the signal transformations that result from the pinna motions are understood, the question of functional relevance can be addressed.
The trait-based approach as a powerful tool to study the bio-geo seafloor system
Authors: Törnroos Anna
Published: November 2017

One of the major causes of heterogeneity on the seabed is the biology. The presence of organisms creates voids and frameworks within and on the sediment, and their behavior may layer or sort the entire seafloor. Making use of the biological information would be powerful for improving acoustics. Likewise, embracing, to a greater degree, acoustic techniques and measurements to understand the biology would be favorable. However, to tackle this bio-geo diversity in a cross-disciplinary way requires a common language and approach. Here, I present and propose the trait-based approach as a way forward. Because there are simply too many species to describe and include in one model, reducing this complexity is essential and can be done by considering individuals characterized by a few key characteristics, or traits. Relevant biological traits span morphology, behavior and life-history of organisms and can be applied on single individuals and scaled up to whole communities, incorporating the density of organisms. By exemplifying the progress in benthic ecology, I outline where we currently stand, possible key traits of value for both fields and ideas on how to progress.
Relating functional diversity of infauna and sediment geoacoustic properties
Authors: Clemo W. Cyrus , Dorgan Kelly M.
Published: November 2017

Marine sediments cover most of the seafloor and vary in physical structure from unconsolidated gravel or sand grains to cohesive, gel-like muds. Sediments also provide a habitat to diverse and abundant animals (infauna). Infauna are impacted by but can also affect the sediment’s physical and biogeochemical properties and fluid flow through and across the sediment. Through activities such as burrowing, feeding, and construction of tubes and rigid body parts, many infauna act as ecosystem engineers, directly and indirectly creating and changing their habitats. Characterization of infauna using functional groups based on how their activities affect their sediment environments can simplify the broad diversity of infauna. For example, some infauna create habitat structure in addition to modifying surface topography through tube construction. Others change sediment properties through bioturbation (animal-induced particle mixing) and bioirrigation (fluid mixing) as they burrow. Structure creation and bioturbation/irrigation can affect sediment geotechnical properties such as porosity, bulk density, grain size heterogeneity, fracture toughness, and stiffness. Changes in these properties can influence acoustic wave speed, attenuation, and backscatter. Thus, acoustics tools can be used to observe and quantify animal-sediment interactions relatively noninvasively by relating the activities of different functional groups with changes in acoustic properties of sediments.
Do environmental stress-induced changes in faunal composition and bioturbation affect sediment geoacoustic properties? A test case in the Gulf of Mexico dead zone
Authors: Briggs Kevin , Richardson Michael , Shivarudrappa Shivakumar
Published: November 2017

Four sites on the continental shelf off Louisiana, each subjected to different historical exposures to low concentrations of bottom-water dissolved oxygen, are investigated in terms of their macrobenthos species composition, sediment physical properties, and sediment geoacoustic properties (sound speed, attenuation, and impedance). From macrobenthos species composition, feeding type is identified, which allows categorization of some bioturbation activity as either dilation or compaction of sediment. Dilation and compaction should affect sediment properties of bulk density and porosity, which are significant predictor variables of geoacoustic properties. Different levels of oxygen stress correspond with statistically separable macrobenthos assemblages, abundance and diversity of biogenic structures (burrows and voids), and ratios of dilators to compactors. Sediment sound speed and attenuation values measured in subcores from box cores are compared at each of the four sites with different faunal composition and average bottom-water dissolved oxygen concentrations to test the long-term (historical) effects of different bioturbation regimes on geoacoustic properties. Sediment acoustic properties are regressed on sediment physical properties and compared with established empirical fits from a worldwide database to identify possible anomalies. The impedance of surficial sediment is measured at each site with the Acoustic Sediment Classification Profiler to examine possible large-scale (side-wide) effects on geoacoustic properties.
Time-dependent seafloor roughness simulations using a coupled spectral ripple-biological decay model
Authors: Penko Allison , Calantoni Joseph
Published: November 2017

Ever changing hydrodynamic conditions in the nearshore continuously affect biological communities and sediment features on the seafloor. Seafloor sediments have complicated interactions with the co-existing biological flora and fauna on the seabed. For example, ripple formation by waves and ripple degradation from biological activity are opposing forces occurring continuously. Simulating this complex natural environment is challenging due to these dynamic interactions of processes that span across a wide range of length and time scales. Existing seafloor models are often based on equilibrium conditions and neglect any change due to biological effects. Additionally, typical equilibrium ripple models provide only geometric dimensions, not a roughness spectrum necessary for acoustic applications. We present a time-varying spectral seafloor model, NSEA, that predicts the spatial and temporal evolution of seafloor roughness accounting for both the evolution and degradation of ripples due to hydrodynamics and biology. Model predictions are compared to high-frequency sector-scanning sonar data collected off the coast of Panama City, FL, during the Target and Reverberation Experiment (TREX13) and at the US Army Corps of Engineers Field Research Facility in Duck, NC. The sector-scanning sonar imaged ~15 square meters of the seafloor every 12 min for up to four weeks in depths up to 20 m.
Local suppression of bioturbation and its acoustic consequences
Authors: Hefner Brian T. , Kargl Steven G. , Williams Kevin
Published: November 2017

Seafloor roughness in shallow waters can be both spatially and temporally dynamic. While wind-driven waves and bottom currents can generate bedforms such as ripples on sand sediments, bottom-feeding fish tend to limit the lifetime of these anisotropic features. This greatly reduces the time during which high frequency sonars can exploit the ripples to coherently penetrate the sediment at subcritical angles. Sonar performance prediction in these environments therefore relies heavily on sediment transport models to generate roughness predictions that accurately reflect changes on these time scales. The competition between the hydrodynamics and biology of the environment can be further complicated by the natural introduction of materials which can locally suppress the bioturbation. Two examples are discussed here: The first comes from the Sediment Acoustics Experiment in 2004 where a storm deposited a layer of mud over some areas of seafloor protecting the bedforms from fish. The second is from the recent Target and Reverberation Experiment where there is evidence that spatially-varying shell content can also reduce the effects of bioturbation. The consequences for sonar performance in these two cases are discussed. [Work supported by the U.S. Office of Naval Research and the Strategic Environmental Research and Development Program.]
Ultrasonic stimulation and metabolic stress in neuronal systems
Authors: Cressman John R. , Gertz Monica , Chitnis Parag V.
Published: November 2017

We report on computational and experimental investigations into the effects of high-frequency focused ultrasound stimulation on neuronal tissue. We simultaneously measuring local field potentials as well as extracellular oxygen and potassium concentrations in hippocampal brain slices to investigate physiological responses, including metabolic demand, during ultrasonic stimulation. To better interpret our observations, we utilized computational models that incorporate dynamics for transmembrane ionic and osmotic flows, membrane fluctuations, and metabolism. Our experiments and models suggest that ultrasonic stimulation can produce substantial ionic redistribution that leads to a significant metabolic burden.
High resolution modulation of human brain circuits using transcranial focused ultrasound
Authors: Legon Wynn
Published: November 2017

Current non-invasive electric and electromagnetic non-invasive neuromodulatory approaches have proven effective for inducing transient plastic changes in human cortex. However, these technologies have poor spatial resolution and suffer from a depth-focality tradeoff. Transcranial focused ultrasound (tFUS) is an emerging non-surgical low-energy technique for inducing transient plasticity in sub-cortical and cortical areas with high spatial resolution and adjustable focus. tFUS has been successfully employed in small and large animal preparations and our work has also demonstrated tFUS to be effective for human cortical and subcortical neuromodulation. Here, we will discuss tFUS current approaches as well as challenges and future directions for this technology as a tool for neuroscience research and human brain mapping and potential clinical applications.
Urban design with noise in mind—A model for future ASA outreach workshops for city planners and decision makers
Authors: Standlee Kerrie G.
Published: November 2017

In early 2009, the Acoustical Society of America funded the development of materials that could be used to introduce urban planners and decision makers to the concept of using soundscaping as a tool in land-use planning. After several months of discussion among interested persons, a symposium outline was generated and speakers were solicited to develop materials that would address specific topics considered important in training urban planners. The materials were developed and first used at a symposium co-sponsored by the ASA and the City of Portland during the ASA May, 2009 meeting in Portland, Oregon. The materials were again presented at a symposium co-sponsored by the ASA and the City of Baltimore during the ASA April, 2010 meeting in Baltimore, Maryland and finally at a symposium co-sponsored by the ASA and the City of Seattle during the ASA May, 2011 meeting in Seattle, Washington. This paper presents a summary of the materials used at the three symposiums and discusses how the material can continue to be used as an ASA outreach event at future meetings around the country.
Quietness as a commons: Integrating soundscape in urban planning for the environmentally just city
Authors: Radicchi Antonella
Published: November 2017

Today, urbanization and environmental pollution represent major issues of the urban planning agenda and one of the most relevant challenges is constituted by planning environmentally and socially just cities to protect human health and ensure quality of life and well-being. To achieve this goal, noise pollution and the scarcity of quietness in cities have also to be taken into account. In Europe, the importance of quiet areas has been first recognized by the 2002 Environmental Noise Directive and, since then, numerous projects have been developed by the EU Member States to define a common methodology to protect quiet areas. Notwithstanding, according to the European Environment Agency, there is still the need for in-depth research in the field. This paper argues that integrating soundscape in urban planning processes, through the paradigm of “quietness as a commons,” could significantly contribute to fill this gap of knowledge. This assumption is discussed by presenting a novel citizen-driven methodology to analyze, assess and plan urban quiet areas, implemented in a pilot study in Berlin. In detail, this paper illustrates the methods applied, the findings and the first draft of planning guidelines developed with the community to protect existing quiet areas in the pilot area.
The advantage of binaural recording for soundscape assessment
Authors: Genuit Klaus
Published: November 2017

In the beginning, binaural recording was used for music productions. For more than 40 years, applications are being intensively used in the automotive industry to optimize vehicle interior sound. Only a binaural recording system like an artificial head enables listeners using calibrated equalized headphones to perceive hearing events which are very realistic to the original sound field. Nowadays, within the scope of soundscape standardization ISO 12913, recommendations are being discussed regarding the use of binaural technology for recording environmental sounds, where in the past normally only single microphones were used. For an overall estimation of the total sound pressure level, this may be sufficient, but in a complex sound situation, like soundscapes with several different sound sources at different locations, the selectivity of the human hearing is only given properly by binaural listening. This paper will explain the technology of binaural recording and playback systems and its advantages in comparison with other sound recording systems.
Infrasound from small explosions from near to intermediate ranges
Authors: De Jesus Diaz Luis , Costley Richard D. , McComas Sarah , Simpson Christopher , Johnson James , Hayward Chris
Published: November 2017

An experiment was performed near the U.S. Army Engineer Research and Development Center (ERDC) site near Vicksburg MS on May 2014. Explosive charges were detonated and the shock and acoustic waves were detected with pressure gauges, infrasound sensors, and seismometers stationed at various distances from the source, from 3 m to 15 km. One objective of the experiment was to compare the effectiveness of different wind filter strategies. Toward this end, several sensors were deployed near each other, approximately 8 km from the site of the explosion. These sensors used different types of wind filters, including different length of porous hoses, a bag of rocks, a foam pillow, and no filter. Signal-to-noise estimates made from signals recorded with these different sensors will be used to evaluate the effectiveness of the different strategies. A second objective was to compare the infrasound and seismic signals recorded with collocated infrasound sensors and geophones. Results from this experiment will be presented. Permission to publish was granted by Director, Geotechnical & Structures Laboratory.
On the influence of the jet stream variations on infrasonic propagation
Authors: Willis Maxwell B. , Waxler Roger M. , Hetzer Claus
Published: November 2017

The jet stream is an eastward flowing wind jet seen around 10 km with its largest magnitude in the winter months, lessening in the summer. Its direction, while predominantly easterly, can vary from northeast to southeast on a day-to-day basis. It can produce ducting of infrasonic signals when its speed is of sufficient magnitude. Infrasonic signals were observed on a network of sensor arrays from a series of explosions detonated throughout the year. Each series consisted of 3 explosions, 1 series for each season of the year. Sensors were deployed in arrays of 4 sensors per array. The network consisted of 4 lines of arrays extending in the westerly, easterly, northeasterly, and southeasterly directions. These arrays were located at distances ranging from 20 km to 80 km from the source. The data from each array was analyzed to determine if infrasonic signals from the explosions were detected. A propagation model was produced for each event using a parabolic equation and an atmospheric profile corresponding to the time of each event. Correlations between the observations and the direction of the jet stream are investigated.
Sound propagation above a flat ground with random spatially varying properties
Authors: Dragna Didier , Blanc-Benon Philippe
Published: November 2017

The acoustic properties of ground surfaces vary in space. Usually, these variations are not accounted for in predictions of outdoor sound propagation for two main reasons. First, they are not known as it is costly to obtain finely sampled spatial measurements of these ground properties. Second, there is no existing simple and quick-to-compute analytical solution for a ground with a spatially-varying admittance, contrary to the well-documented case of a ground with a homogeneous admittance. This imperfect knowledge of the ground characteristics leads to uncertainties about the sound pressure level. This paper aims at characterizing these uncertainties. Propagation of acoustic waves over the ground with a spatially-varying surface admittance is therefore considered. Using the diagram technique, the average Green's function is determined. An asymptotic expression in the form of a Weyl-Van der Pol formula is obtained at long range and at grazing incidence. Modifications of the reflection coefficient and of the surface wave contribution due to randomness are analyzed. Numerical simulations using a linearized Euler equations solver are then carried out. Comparison of the mean pressure obtained from ensemble-average over 200 realizations and from the analytical solution is performed. Finally, the mean intensity and intensity fluctuations are investigated.
Efficient modeling of long range impulse sound propagation in three dimensions
Authors: Cosnefroy Matthias , Cheinet Sylvain , Ehrhardt Loic , Juvé Daniel , Dragna Didier
Published: November 2017

Sound characteristics close to the ground strongly depend on the atmospheric and ground properties in terms of amplitude, shape, and time of arrival. Time-domain numerical modeling is able to accurately account for outdoor sound propagation and is valuable to decipher the interactions between the refractive, scattering, and ground effects. It remains computationally challenging for three-dimensional long range simulations. A high-order parallel Finite-Difference Time-Domain solver with the moving frame approach is presented, featuring accurate time-domain impedance boundary conditions and very efficient convolutional perfectly matched layers to artificially truncate the computational domain. The design of the absorbing boundaries is based on a stability analysis of the time integration scheme and is shown to optimize the absorption properties for grazing waves. The model allows for accurate propagation of impulse sounds in 3D over several hundreds of meters and up to 1000 Hz using a personal laptop with a simulation duration of a few hours. The numerical predictions are compared to experimental measurements under different weather conditions, with a special focus on the sensitivity to the mean vertical wind profile and the ground properties.
Performance of Green’s function retrieval methods for various sound source distributions: Application to outdoor acoustic propagation
Authors: Denis Max , Collier Sandra L. , Noble John , Alberts W. C. Kirkpatrick , Ligon David , Sim Leng , Reiff Christian G. , James Deryck D.
Published: November 2017

In this work, Green’s function retrieval methods for an outdoor acoustic propagation channel are presented. Green’s function retrieval methods by multidimensional deconvolution and crosscorrelation are compared for different source distributions. Of particular interest is the accuracy of the retrieved Green’s function of an arbitrary sound source with that of an impulsive sound source. Also, the signal-to-noise ratio of both methods will be investigated. To this end, outdoor acoustic experiments are conducted in a clearing and wooded area in southern Maryland. Results will be obtained for various source-receiver ranges up to 400 m.
Numerical analysis on the effect of the sea surface roughness on the acoustic transmission loss in the atmosphere
Authors: Turo Diego , Ryan Teresa J. , Judge John , Vignola Joseph F.
Published: November 2017

Atmospheric sound propagation over the sea surface is affected by several factors including wind, temperature profile, and sea state. Preliminary numerical studies using a Crank-Nicolson parabolic equation solution approach have demonstrated that sea roughness introduces excess transmission loss. This excess loss induced by the sea roughness can be represented instead by a flat surface with a compensatory effective impedance. Calculation of transmission loss for the flat surface is computationally more efficient but requires the evaluation of the effective impedances for any given sea state. In this study, a 2-D finite-difference time-domain solver is used to determine the effective impedances for several sea states. The effect of sea roughness on transmission loss is then quantified by using the Crank-Nicolson parabolic equation.
Deturbing supersonic signatures
Authors: Doebler William , Sparrow Victor
Published: November 2017

The process of deturbing (removing effects of turbulence from) experimentally measured sonic boom pressure waveforms from aircraft would provide a baseline sonic boom signature. This baseline signature could be used to calculate perception metrics that may be part of a supersonic aircraft noise certification standard. The traditional deturbing process has been shown to remove turbulence reasonably well from experimentally measured N-wave sonic boom pressure waveforms whose tail shock generates the atmosphere’s impulse response. N-wave booms such as that from Concorde were deemed unacceptable and prohibited for over land operations due to their startling nature and due to public annoyance. As a consequence, newly designed low-boom aircraft are being tailored for lower amplitude sonic booms that will not have any strong shocks. Since a tail shock is needed to generate the atmospheric impulse response for traditional deturbing, new deturbing techniques are needed. Two methods are presented using cross correlation averaging and frequency domain filtering for determining a baseline supersonic signature for computing sonic boom metrics. [Work supported by the FAA. The opinions, findings, conclusions and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]
Auditory object formation from background noise improves speech perception
Authors: Lander-Portnoy Maury , Zevin Jason
Published: November 2017

Auditory object formation allows listeners to isolate a speech stream from a complex acoustic environment. While most studies focus on foregrounded speech, here we focus on whether listeners can form auditory objects from background noise to aid in speech perception. We use an open-set word recognition task with fluctuating speech-shaped-noise maskers, created by randomly interrupting the noise in each 125 ms window with a long (100 ms) or short (25 ms) silence. On each trial, three maskers were played, with the word occurring during the third. We previously showed that participants perform significantly better when the patterns repeat, compared to when the first two maskers differed from the third. Only the ordering of long or short within preceding patterns differs. To examine whether this advantage is due to auditory object formation, we leverage previous studies showing that inserted silences interfere with object formation. We insert 433 ms silences between patterns and observe defeat of the advantage we previously observed. We therefore attribute the advantage in the repeated masker condition to formation of an auditory object from background noise. Moving forward, we will manipulate other parameters affecting object formation and observe their affect on speech perception in noise.
Distribution of spectral modulation transfer functions in a young, normal-hearing population
Authors: Eddins David A. , Hoover Eric , Eddins Ann C.
Published: November 2017

Common measures of auditory spectral shape perception include notch-noise masking methods to estimate auditory filter shape and width (i.e., equivalent rectangular bandwidth or ERB) and spectral modulation detection to estimate across-channel spectral processing. The notch noise masking method has been widely used and the distribution of ERBs in a young, normal hearing population is well established. The spectral modulation detection method is growing in popularity yet the distribution of spectral modulation transfer functions among young normal hearing people is unknown. Here, we report the distribution of spectral modulation detection thresholds for spectral modulation frequencies from 0.25 to 8 cycles/octave for 49 young, normal hearing listeners who inexperienced in performing psychoacoustic listening tasks. The carrier was Gaussian noise with a passband from 400 to 3200 Hz and −24 dB/octave rolloff outside the passband. The presentation level was 80 dB SPL. The results reveal the typical bandpass sensitivity to spectral modulation with a minimum near 2.0 cycles/octave. Thresholds at each frequency are tightly distributed across the population and normative values are computed including mean, median, and corresponding confidence intervals. These reference values can be very useful for future investigations involving normal controls or patient populations and when comparing among previously published datasets.
Comparison of scoring methods for spatial release from masking for speech based on analysis of psychometric function slope
Authors: Hoover Eric , Diedesch Anna , Gallun Frederick J. , Eddins David A.
Published: November 2017

The ability to benefit from the spatial separation of talkers in a multi-talker environment is critical to speech communication. A headphone-based test of spatial release from masking for speech (SR2) has been shown to be sensitive to differences between young, healthy listeners and listeners with various auditory deficits. Existing studies relied on a simplistic method to score SR2, comparing the number of correct responses in conditions of collocated and spatially-separated background talkers. Psychometric functions were fit to trial data compiled across multiple studies in order to evaluate if an alternative scoring method could improve diagnostic power. We hypothesized that differences in informational masking between collocated and spatially separated conditions would result in a difference in condition-specific slope estimates, thus leading to a relationship between scoring method and diagnostic power. Results showed a small but significant difference in slope between conditions, consistent with expectations, but the difference between scoring methods was not clinically significant. This information will be used to guide the development of a portable, rapid implementation of SR2 for clinical and research applications. [Funding provided by NIH R01 DC015051.]
Establishing the response of low frequency auditory filters
Authors: Rafaelof Menachem , Christian Andrew , Shepherd Kevin P. , Rizzi Stephen A. , Stephenson James
Published: November 2017

The response of auditory filters is central to frequency selectivity of sound by the human auditory system. This is true especially for realistic complex sounds that are often encountered in many applications such as modeling the audibility and annoyance of sound, voice recognition, noise cancelation, and the development of advanced hearing aid devices. The purpose of this study was to establish the response of low frequency (below 100 Hz) auditory filters. Two experiments were designed and executed; the first was to measure subjects’ hearing threshold for pure tones (at 25, 31.5, 40, 50, 63, and 80 Hz), and the second was to measure the Psychophysical Tuning Curves (PTCs) at two signal frequencies (Fs= 40 and 63 Hz). Experiment 1 involved 36 subjects while experiment 2 used 20 subjects selected from experiment 1. Both experiments were based on a 3-down 1-up 3AFC adaptive staircase test procedure using either a variable level tone or variable level, narrow-band, noise masker. A summary of the results includes masked threshold data in the form of PTCs, the response of auditory filters, their distribution across subjects, and comparison with similar recently published data.
Sociophonetic trends in studies of Southern English
Authors: Thomas Erik R.
Published: November 2017

Studies of Southern English have largely kept pace with advancements in sociophonetics in other parts of the world. They have expanded away from single-point studies of vowel nuclei to cover such topics as vowel-inherent spectral change, intonation, consonantal acoustics, and neurolinguistic coding of phones, especially with regard to ethnic identification. The ethnic diversity of the South, with African Americans, Latinos, enclaves of Asian Americans, and other groups such as Cajuns, facilitates growth in these new directions. Among the current linguistic trends of which sociophoneticians are staying abreast are the expansion of Latinos, social divergence within the African American population, and rapid dialect leveling among urban white Anglos. Integrating these developments with other advancements in sociolinguistics has proved more difficult. Empirical studies have incorporated various sociological methods with regard to social networks, but researchers are only now beginning to utilize them in conjunction with current phonetic techniques. There is also a need to examine wider arrays of phonetic variables in studies.
Case Study: Body Composition Periodization in an Olympic-Level Female Middle-Distance Runner Over a 9-Year Career
Authors: Stellingwerff Trent
Published: November 2017

This case study features an Olympic-level female middle-distance runner implementing a science-based approach to body composition periodization. Data are emerging to suggest that it is not sustainable from a health and/or performance perspective to be at peak body composition year-round, so body composition needs to be strategically periodized. Anthropometric (n = 44), hematological, other health measures, and 1,500-m race performances (n = 83) were periodically assessed throughout a 9-year career. General preparation phase (September to April) featured the athlete at ∼2–4% over ideal competition phase body weight (BW) and body fat (%), with optimal energy availability being prioritized. The competition body composition optimization phase (May to August) included creating an individualized time frame and caloric deficit with various feedback metrics (BW, performance, and hunger) to guide the process. There were significant seasonal fluctuations in anthropometric outcomes between phases (47.3 ± 0.8 vs. 48.3 ± 0.9 kg BW; 53.6 ± 7.8 vs. 61.6 ± 9.7 mm International Society for the Advancement of Kinanthropometry sum of 8 [So8] skinfolds; p < .01), and a significant correlation of decreasing So8 during the peak competition period over her career (r = −.838; p = .018). The range of body composition during the competition period was 46.0–48.0 kg BW and a So8 range was 42.0–55.9 mm. There were also significant positive correlations between slower 1,500-m race times and increasing So8 (r = .437; p < .01), estimated fat mass (r = .445; p < .01), and BW (r = .511; p < .0001). The athlete only had two career injuries. This case study demonstrates a body composition periodization approach that allowed for targeted peak yearly performances, which improved throughout her career, while maximizing training adaptation and long-term athlete health through optimal energy availability.
Sprint Running Performance and Technique Changes in Athletes During Periodized Training: An Elite Training Group Case Study
Authors: Bezodis Ian N. , Kerwin David G. , Cooper Stephen-Mark , Salo Aki I.T.
Published: November 2017

Purpose: To understand how training periodization influences sprint performance and key step characteristics over an extended training period in an elite sprint training group. Methods: Four sprinters were studied during 5 mo of training. Step velocities, step lengths, and step frequencies were measured from video of the maximum velocity phase of training sprints. Bootstrapped mean values were calculated for each athlete for each session, and 139 within-athlete, between-sessions comparisons were made with a repeated-measures analysis of variance. Results: As training progressed, a link in the changes in velocity and step frequency was maintained. There were 71 between-sessions comparisons with a change in step velocity yielding at least a large effect size (>1.2), of which 73% had a correspondingly large change in step frequency in the same direction. Within-athlete mean session step length remained relatively constant throughout. Reductions in step velocity and frequency occurred during training phases of high-volume lifting and running, with subsequent increases in step velocity and frequency happening during phases of low-volume lifting and high-intensity sprint work. Conclusions: The importance of step frequency over step length to the changes in performance within a training year was clearly evident for the sprinters studied. Understanding the magnitudes and timings of these changes in relation to the training program is important for coaches and athletes. The underpinning neuromuscular mechanisms require further investigation but are likely explained by an increase in force-producing capability followed by an increase in the ability to produce that force rapidly.
Trend Analysis of 20 Years of FIM Road Racing Grand Prix Motorcycle World Championship
Authors: D’Artibale Emanuele , Rohan Maheswaran , Cronin John B.
Published: November 2017

Purpose: The technological advancements in motorcycle road racing have ensured the evolution of motorcycle performance; however, it is unknown whether these advancements have resulted in increased speed and therefore risk. To better understand the top level of this sport and inform future regulations, performance-related strategies, and safety procedures, this study aimed to (1) analyze and describe how the performance characteristics of the top class of the Fédération Internationale de Motocyclisme Grand Prix motorcycle world championship (GPWC) have changed with time and (2) quantify potential interactions between performance data (ie, crashes, speed, and environmental conditions). Methods: Variables such as top 10 riders’ speed of racing, crashes, starting position of winner, participants, and environmental conditions were collected from official race reports from 1997 to 2016. Data standardization was also ensured by including only dry competitions in the analysis. Results: The mean racing speed ranged from a minimum of 155 (7.27) km·h−1 (year 2000) to a maximum of 165 (6.48) km·h−1 (year 2015). Linear mixed-model analysis revealed that the variables year and class significantly influenced changes in mean speed (faster racing). Per race, 12–14% of starters (95% confidence interval) suffered a crash. No significant associations were found between crashes and mean speed, ground temperature, air temperature, or air humidity. Conclusions: The speed of dry racing of the top class of the GPWC has increased over a 20-y span. Motorcycle circuit racing riders should consider the importance of being prepared to cope with crashing events to minimize chances of injury.
Association of Gastrocnemius Muscle Stiffness With Passive Ankle Joint Stiffness and Sex-Related Difference in the Joint Stiffness
Authors: Chino Kentaro , Takahashi Hideyuki
Published: November 2017

Passive ankle joint stiffness is affected by all structures located within and over the joint, and is greater in men than in women. Localized muscle stiffness can be assessed by ultrasound shear wave elastography, and muscle architecture such as fascicle length and pennation angle can be measured by B-mode ultrasonography. Thus, the authors assessed localized muscle stiffness of the medial gastrocnemius (MG) with consideration of individual variability in the muscle architecture, and examined the association of the muscle stiffness with passive ankle joint stiffness and the sex-related difference in the joint stiffness. Localized muscle stiffness of the MG in 16 men and 17 women was assessed at 10° and 20° plantar flexion, neutral anatomical position, and 10° and 20° dorsiflexion. Fascicle length and pennation angle of the MG were measured at these joint positions. Passive ankle joint stiffness was determined by the ankle joint angle–torque relationship. Localized MG muscle stiffness was not significantly correlated with passive ankle joint stiffness, and did not show significant sex-related difference, even when considering the muscle architecture. This finding suggests that muscle stiffness of the MG would not be a prominent factor in determining passive ankle joint stiffness and the sex-related difference in the joint stiffness.
A Case for Sensorimotor Simulation as a Basis for the Animate–Inanimate Distinction in Infancy
Authors: Hegele Mathias , Seyfried Friedrike
Published: November 2017

In this opinion paper, we aim to delineate the development of the person–object differentiation in visuomotor behavior as established during the first two years of life, which can be conceived as a precursor for the broader distinction between animate and inanimate entities, which in turn form the basis of the more inclusive biological–nonbiological distinction (Poulin-Dubois, Lepage, & Ferland, 1996). We then discuss embodied sensorimotor simulation, which allows us to use the self as a model for perceiving objects in our environment, as a potential mechanism underlying this distinction.