bluuebunny/crossref_metadata_2025 huggingface dataset:
Region, gender, and within-category variation in American English voiced stops
Authors: Elston Abigail H. , Blake Katherine , Berkson Kelly , Herd Wendy , Cariño Joy , Nelson Max , Strickler Alyssa , Torrence Devan
Published: May 2016

The two-way voicing contrast in American English stops—particularly in initial position—is often described as a long-lag (e.g., long positive VOT for /p/) versus short-lag (e.g., short positive VOT for /b/) distinction, with less frequent instances of lead voicing (e.g., negative VOT for /b/) attributed to individual variation. Systematic within-category gender and region differences have been reported, however, with more closure voicing found for male than for female speakers (Ryalls, Zipprer, and Baldauff, 1997), and more fully voiced closures for /b/ in female speakers from North Carolina than those from Wisconsin (Jacewicz, Fox, and Lyle, 2009). With this in mind, we investigate the interaction of gender and region in the prevoicing of word-initial voiced stops by comparing the VOTs of male and female speakers from Indiana and Mississippi. Participants were recorded reading three repetitions of a pseudo-randomized list of words including bot, dot, and got. Regional—but no gender—differences were found: speakers from Mississippi produced stops with negative VOT more often (~35% of the time) than speakers from Indiana (~15%), suggesting that southern varieties of English are indeed more heavily prevoiced than other varieties of English.
Stylistic variation in children’s vowel production
Authors: Jacewicz Ewa , Fox Robert A. , Deatherage Jill M.
Published: May 2016

The monophthongization of the diphthong [ai] to [a] is possibly the most stereotyped feature of Southern American English. This feature can be observed to varying degrees across the American South. Although monophthongization represents an important social symbol in the South, its pervasiveness has begun to recede in recent generations. This sound change has been brought on by multiple factors including population mobility, education, and urbanization, which have promoted acceptance of a more standardized variety of American English, including diphthongal realizations of [ai]. The current study examines the change in progress toward [ai] in 20 children aged 8–10 from western North Carolina in three different speaking styles: citation-form words, read sentences, and informal, unscripted talks. In addition to acoustic analysis, stylistic variation was evaluated by 20 central Ohio listeners (10 males and 10 females). Participants were asked to listen to individual words and to rate the degree of perceived monophthongization on a seven-point scale. Results showed an increase in perceived monophthongization from citation forms to informal talks. Compared to girls, boys had a higher occurrence of the monophthongal variants and lower occurrence of the full diphthongs across all production types. Discussion will focus on the advancement of the sound change.
Canadian raising in Fort Wayne, Indiana
Authors: Strickler Alyssa , Berkson Kelly , Davis Stuart
Published: May 2016

The phenomenon often referred to as Canadian Raising, wherein speakers raise the diphthongs /aɪ/ and /aʊ/ to [ʌɪ] and [ʌʊ], respectively, when preceding voiceless sounds, is attested not only in Canada but also in places in the Northern periphery of the U.S. (e.g., Ann Arbor and the Upper Peninsula, in Michigan). Raising has also been documented in locations distant from the border, such as Philadelphia. The current study examines the spread of raising farther south from Michigan into northeast Indiana, specifically Fort Wayne. Acoustic analysis of preliminary data from Fort Wayne area speakers was conducted to determine whether raising indeed occurs and to explore the effect of contextual factors such as speaker sex, age, and prosodic structure. The results confirm that while this raising does in fact happen around Fort Wayne, there is an age effect: younger speakers (<25 yr) show raising across the board in the expected environments but older speakers (>60 yr) do not. This suggests that vowel raising is a relatively new characteristic of Fort Wayne English.
Dissociating contributions of talker gender and acoustic variability for spectral contrast effects in vowel categorization
Authors: Assgari Ashley , Mohiuddin Asim , Theodore Rachel , Stilp Christian
Published: May 2016

Speech categorization is influenced by spectral contrast effects (SCEs), the perceptual magnification of spectral differences between successive sounds. Through SCEs, preceding acoustic contexts can bias categorization of following sounds away from reliable spectral properties. Recent findings (Assgari & Stilp, 2015 JASA) show that SCEs in vowel categorization can be modulated by talker characteristics: a clear SCE when the preceding context was 200 sentences spoken by a single talker was diminished when the context featured 200 talkers. This result was attributed to variability in mean pitch of the preceding sentences. However, neither mean sentence pitch nor talker gender was explicitly controlled, which challenges identification of the locus of the talker effect. The current study examined whether gender and pitch variability yield separable contributions to SCEs. Listeners heard precursor sentences then categorized a target vowel from an /ɪ/ to /ɛ/ continuum. Sentences were processed to add a modest low-F1 or high-F1 spectral peak to encourage “eh” or “ih” responses, respectively. Critically, talker gender was crossed with pitch variability in these sentences. Results will isolate the property responsible for attenuating SCEs if gender and pitch variability have dissociable effects. Failure to observe this pattern suggests similar effects of these properties on SCEs.
Gender and rate effects on speech intelligibility
Authors: Johnson Eric M. , Ferguson Sarah H.
Published: May 2016

Older adults seeking hearing help often complain of particular difficulty understanding female voices. This contrasts with studies using young listeners with normal hearing in which female talkers have been found to be generally more intelligible than male talkers (e.g., Bradlow et al., 1996). Could some factor in addition to talker gender be causing older adults to have increased difficulty understanding female voices? Speech that has been time-compressed has been shown to be less intelligible than unprocessed speech (e.g., Gordon-Salant and Friedman, 2011), but few data exist to show whether an increased presentation rate causes an equal loss of intelligibility for male and female talkers. The present study will explore whether an increased playback rate has a greater negative effect on the intelligibility of speech produced by female versus male talkers. Subjects will listen to sentences produced by two female and two male speakers from the Utah Speaking Style Corpus presented at either their original rate or at an increased rate (1.5 times faster) and type out what they heard. The resulting data will show whether, for young normal-hearing listeners, an increased rate of speech affects the intelligibility of female talkers more than it affects the intelligibility of male talkers.
Perception of voice gender in cochlear implant simulations of children's speech
Authors: Guest Daniel R. , Kapolowicz Michelle R. , Hossain Shaikat , Montazeri Vahid , Assmann Peter F.
Published: May 2016

Previous studies [Assmann et al., J. Acoust. Soc. Am. 135, 2424 (2014) and Assmann et al., J. Acoust. Soc. Am. 138, 1811 (2015)] investigated normal-hearing listeners’ ability to discriminate gender and age in children’s speech. The speech stimuli were /hVd/ syllables produced by 140 speakers, ages 5 through 18, and processed using the STRAIGHT vocoder to simulate a change in speaker gender. Experimental conditions involved swapping the fundamental frequency contour (F0) and/or the formant frequencies (FF) to the opposite-sex average within each age group. The present study extended these previous experiments by presenting the stimuli to normal-hearing listeners through a cochlear implant simulation implemented as a sine wave vocoder. Supporting findings reported at previous meetings, swapping F0 has a larger effect on perceived gender than swapping FF for older voices, and single-parameter changes (swapping either F0 or FF), had relatively small effects on older male voices but pronounced effects on older female voices. Overall, the present findings indicate that gender recognition is more difficult in a cochlear implant simulation. Furthermore, gender recognition in a cochlear implant simulation is particularly difficult with ambiguous voices, such as those of young children.
Field measurements of interface waves and geoacoustic characterization of near surface sediment and soil
Authors: Giard Jennifer , Potty Gopu R. , Miller James , Baxter Christopher , Bradshaw Aaron
Published: May 2016

There is a need for rapid and nondestructive sensing of near-surface shear properties of the ground and seafloor. Our approach is to measure interface wave dispersion and invert these measurements to extract a shear wave speed profile. Field measurements of interface waves using geophones and accelerometers will be presented. A laser Doppler vibrometer (LDV) will also be incorporated in the suite of sensors for the measurement of wave properties. Data from these sensors will be compared to understand the coupling of the sensors into the soil or sediment and its effect on the measurements. Geoacoustic and geotechnical properties will be estimated using the interface wave data. The uncertainty and resolution of the estimates in different sediment/soil types will be explored. The Interface Wave Testing Facility at the University of Rhode Island will also be used to understand the surface wave propagation characteristics in different type of sediments/soils. [Work supported by Army Research Office and the Office of Naval Research.]
Geoacoustic inversion based on particle velocity
Authors: Dall'Osto David R. , Dahl Peter H.
Published: May 2016

An approach to geoacoustic inversion using a non-dimensional vector quantity, known as circularity, is discussed. This quantity corresponds to the difference in phase and magnitude of the vertical and horizontal components of particle velocity, and is also the normalized curl of the active intensity vector. As such, it is highly dependent on the phase, amplitude, and arrival angle of interfering multipath arrivals, with value as a function of source depth that depends on both frequency and bottom type. We first show results from the Targets and Reverberation Experiment (TREX) which took place off Panama City, where frequencies in the range of 1–4 kHz are used to study sandy sediments [Dall’Osto et al., J. Acoust. Soc. Am. 139, 311–319, 2016]. The approach is next applied hypothetically at lower frequencies for which fewer modes are supported in the waveguide, and to different seabed conditions to demonstrate how a range of sediments from sand to mud are distinguished.
Sediment characterization from normal incidence bottom loss at the GLISTEN sea test
Authors: Isakson Marcia J. , Piper James , Banks Roger
Published: May 2016

The GLider Sensors and payloads for Tactical characterization of the ENvironment (GLISTEN) sea test was conducted off the west coast of Italy in August of 2015. Led by the Centre for Maritime Research and Experimentation (CMRE), the effort included seven other international organizations including the Applied Research Laboratories from The University of Texas at Austin (ARL:UT). The mission of the sea test was to improve and understand long-range acoustic methods of environmental characterization in shallow waters. As part of the test, a team from ARL:UT deployed a remotely operated vehicle (ROV) which collected normal incidence bottom loss data from 6 to 20 kHz along with video and laser line profiling data. These data were taken along the propagation paths of the CMRE low-frequency transmission loss experiment. In this presentation, results will be shown from the bottom loss measurements for a variety of sediments that included both layering and entrained gas pockets. The acoustic data will be compared with models that include such frequency dependent effects as interface roughness and volume scattering. [Work supported by ONR, Ocean Acoustics.]
Spatial variability of sediment roughness and its effect on reverberation
Authors: Hefner Brian T.
Published: May 2016

As part of the environmental characterization supporting the Target and Reverberation Experiment in 2013 (TREX13), the Seafloor Laser-line Scanner (SLS) was deployed to measure sediment roughness at locations throughout the experiment site. The SLS uses structured light to create a two-dimensional digital elevation map of the seafloor over a 0.3 × 3.5 m area. This map is processed to determine the seafloor roughness power spectrum which is used to model backscatter from the seafloor. While a relatively shallow site for TREX13 was chosen to limit the area within which environmental characterization was required, there was significant variability in the sediment roughness which could not be sufficiently measured in the time available. To overcome this difficulty, data from a 400 kHz multibeam backscatter survey collected by de Moustier and Kraft have been combined with the SLS measurements to infer the roughness throughout the site. Although the reverberation modeling focuses on scattering wavenumbers that affect the 2–4 kHz acoustic measurements, the 400 kHz backscatter strengths are correlated to the spectral strengths at the mid-frequency wavenumbers of interest. The implications of these results for reverberation modeling as well as the limits of this approach will be discussed. [Work supported by ONR.]
Generative acoustics in architecture
Authors: Schilb Emily , Ermann Michael , Rife David , Hulva Andrew
Published: May 2016

The researchers share three studies in parametric, generative, and iterative architectural acoustics. (1) A real-time parametric model shapes a geometrically complex ceiling plane with grips in order to visualize first-order reflections so that early arriving strong reflections may be directed to the audience and late-arriving echoes may be avoided. (2) A ray-tracing software model pivots door openings so that a coupled volume concert hall can be calibrated to establish the “sweet spot” range of aperture sizes that are more likely to produce a double-sloped sound decay. (3) A custom-designed auralization software simulates sound transmission loss so that designers may hear the (relative) noise isolation of different assemblies.
Elucidation of acoustical phenomena through the re-tooling of comprehensive acoustical simulations
Authors: van der Harten Arthur W.
Published: May 2016

In its 8 years available to the general public, the open source acoustical simulation tool Pachyderm Acoustic for Rhinoceros has been used not only for prediction of room quality and noise level, but in a variety of other ways which help to clarify the physical behavior of sound in space. Since a scripting interface for Ironpython was released in 2011, and a grasshopper interface in 2015, Pachyderm has earned a place in the growing field of customizable workflows. Its geometrical and numerical tools have been re-purposed for customized visualizations, real-time analysis, search algorithms, and even sculpture. This talk exhibits some of the most interesting work done by re-tooling Pachyderm Acoustic to-date, and attempts to speculate on how it may be used in the future, as designers with more knowledge of acoustics begin to emerge in the workplace.
Statistical considerations of early-stage design by using computer-based tools in architectural acoustics
Authors: Vorlaender Michael , Lu Shuai
Published: May 2016

Room simulation techniques require input data of the room model and the boundary conditions. In an iterative early-stage design process, the general room shape and the boundary conditions correspond to the perceptual parameter space such as reverberation time, strength, clarity, etc. The influence of specific settings in the algorithmic details such as the number of rays, the temporal resolution, the filter bandwidth will be demonstrated by calculating room impulse responses under the condition of variation of such settings. Furthermore, the statistics of the input variables of the general shape result in certain degrees of freedom for the absorption and scattering coefficients. It is discussed how a design space could be defined, which describes the probability for achieving the desired room acoustic performance as a function of the general room shape and boundary conditions.
Lost in translation, easing communication through the use of digital modeling
Authors: Kanter Shane J. , Miller Gregory , Mayell Marcus
Published: May 2016

Daily communication between Acoustician, Architect, facility users, building owners, and consultants paves a road riddled with several opportunities for miscommunication. Although many design team members have honed their auditory senses, many of us communicate most effectively through the use of visual graphics and diagrams. Computer aided design, including the use of moving images, has not only become a tool for analysis but also allowed for more effective communication to educate and influence important design decisions. Parametric modeling tools allow consultants to develop analysis and communication tools early on and throughout the design of architectural elements. Two recent applications of the digital modeling process include the new orchestra shell at the Lyric Opera in Chicago and a 1000 Seat Convening Hall. Digital tools used to model and analyze acoustic performance have been imperative while working through the challenges embedded within each project. In both cases, these tools have helped overcome design and communication challenges among the team, leading to a result that meets the unique needs of each space.
Noise sources from the industrialization of the ocean
Authors: Stocker Michael
Published: May 2016

Increasingly technology is opening up hostile and challenging marine environments for industrial exploitation. This is occurring in the energy sector with fossil fuel exploration and extraction operations and developing wind and hydrodynamic energy projects. It is also occurring with the deep-water expansion of other extraction industries such as minerals mining and fishing. All of these operations and enterprises are introducing loud and complex noise sources into marine bioacoustic habitats. This presentation will be an overview examination of existing and developing noise sources that are a consequence of the industrialization of the outer continental shelf and high seas.
Underwater sound directionality of commercial ships
Authors: Gassmann Martin , Wiggins Sean M. , Hildebrand John A.
Published: May 2016

The underwater sound radiated by commercial ships is an unintended by-product of their operation and one of the most significant contributors to man-made noise at low frequencies in the ocean. To estimate the directionality of underwater sound radiated by current commercial ships, a seafloor array of five high-frequency acoustic recording packages (HARPs) deployed to 1 km depth with a maximum horizontal aperture of 1 km was used. As a ship of opportunity passed over the HARP array, the directions from the ship to each HARP along with the corresponding source levels were estimated for each ship location. Ships were tracked via satellites (Automatic Identification System—AIS) and acoustically by a frequency domain beamformer that was implemented for one of the HARPs configured with a volumetric hydrophone array (2 m maximum aperture). The directionality estimates of contemporary commercial ships exhibit significant stern-bow asymmetries among other quantitative characteristics that will be discussed.
The effect of operational measures on shipping sound in the North Sea
Authors: Binnerts Bas , de Jong Christ
Published: May 2016

From studies into marine biology, it is known that the behavior of marine mammals and fish can be influenced by the ambient underwater sound level. In busy seas like the North Sea in Europe, sound from shipping traffic is largely responsible for the low frequency part of the ambient sound. In this work, possibilities to regulate the underwater radiated sound of ship traffic are investigated. This involves measures that look at traffic flows and operational use of the vessels, to determine what can be done to reduce the shipping sound levels in certain marine areas. Three types of operational measures are considered: (1) the effect of spatial planning (for example, changing the location of shipping routes), (2) the introduction of a radiated sound limit for vessels in a certain area, and (3) the introduction of a speed limit for vessels in a certain area. The proposed measures have been analyzed on their effect and effectiveness, by means of numerical analysis. Calculations have been performed for a generic ship traffic flow, based on actual recorded AIS data from a North Sea shipping lane, using a speed depended model for the source level of different ship types and a sound propagation model.
A case study in Canada: Exploring research challenges of industrial wind turbines and health
Authors: Krogh Carmen M. , Aramini Jeffery
Published: May 2016

The topic of adverse health effects associated with industrial wind turbines (IWT) is controversial and debated worldwide. Some residents living in proximity to wind energy facilities report symptoms of sleep disturbance, annoyance, headaches, ear pain/discomfort, mood disorders, stress, cardiac and blood pressure effects, reduced quality of life, and other adverse effects. In some cases, research initiatives have been the result of individuals’ complaints. The research is challenged in part by the complexities and numerous variables associated with this subject. A range of IWT research approaches, sometimes in combination with each other, has been used including self-reporting surveys, investigations and acoustical measurements. On July 12, 2012, Health Canada announced its large scale cross-sectional randomized epidemiological wind turbine noise and health study. The research was conducted by Health Canada in two Canadian provinces. Health Canada indicated its study had limitations, would not be definitive, and would not permit any conclusions to be made with respect to causality. This presentation will explore some of the inherent challenges of studying health effects associated with wind energy facilities and will consider the role of those individuals reporting adverse health effects.
Industrial wind turbines and adverse health effects: Where we are, where we need to go, and the need for regulations and predictive models to recognize human physiology
Authors: Nissenbaum Michael A.
Published: May 2016

Since our initial study was published (Nissenbaum et al., 2012), work in several areas of human physiology has begun to elucidate the precise mechanisms by which sleep disturbances result in adverse health effects, over both short and longer durations. These include impaired neuronal connections in the learning brain, altered genetic expressions impacting the immune system, and correlations between poor quality sleep and MRI-measured atrophy of the brain over a mean period of 3.5 years. Additionally, fMRI has demonstrated brain responses to sounds with frequencies as low as 8 Hz. At lower frequencies, somatosensory mechanisms are now thought to play a role, in addition to auditory. Local regulations regarding noise (Soundscape) limits and methods of measurement were designed prior to current understandings of human sensory and reactive physiology. Instrumentation and modeling geared towards satisfying those regulations are by implication lacking because they do not capture or predict physiological responses to IWT noise. According to the principles of soundscape, and given the subtleties of human physiology, humans remain the best instruments available for detecting objectionable noise and identifying adverse health effects. Regulations, measurement methods, and predictive models must adapt to current understandings of human physiology to best protect human populations.
Effects caused by sounds at low frequencies
Authors: Fiebig André , Schulte-Fortkamp Brigitte , Bray Wade , Genuit Klaus
Published: May 2016

A central tenet of the Soundscape concept is that humans immersed in sonic environments are as “new experts” reliable communicators, whose reports and descriptions of sound and its effects must be taken seriously. As a first step, different experiments focusing on wind turbines coupled with detailed questionnaires were carried out to study the link between specific characteristics of wind turbine noises and annoyance reactions. It seems as if this will enable to determine the benefit of the Soundscape approach for investigated low frequency noise phenomena. The challenge of validating and resolving widespread and growing reports of health, physiological and behavioral effects apparently from new environmental infrasound can be met through coupling soundscape with parallel scientific techniques not limited to acoustic measurements. The soundscape concept has an incipient role to connect and approach the resolution of this complex issue. Such an augmented soundscape approach centering on the sensitivity of human beings is as important and applicable to responses to effects from sound as it is to responses to directly audible sound. This is a new kind of merged sound quality and public health issue combining acoustic, psychoacoustic, and medical aspects. Its resolution depends on a combined soundscape-mediated approach.
Patient Centered Medicine and Soundscape—A bridge between clinicians and acousticians
Authors: McMurtry Robert Y.
Published: May 2016

The Patient Centred Method (PCM) and Soundscape have much in common including their emergence about 60 years ago based on the work of Balint and Kryter, respectively. Both place the patient or person at the center of management of clinical illness or noise annoyance. PCM requires that the patient perceive that they have experienced meaningful care, communication, and common ground in clinical encounters. The evaluation focuses on the patient’s life context and their perception of disease or the “illness experience.” When PCM is accomplished the result is higher satisfaction, better outcomes of chronic diseases, fewer tests and referrals, and attendant lower costs (Stewart et al. 2000). Soundscape, a term coined by Shafer in 1977 also places the person in center, in the context of their sonic environment, emphasizes their perception of noise as the “New Experts” (Bray 2012). According to Bray, exposed people are “objective measuring instruments whose reports and experiences must be taken seriously and quantified by technical measurements.” This paper will explore the congruence of PCM and Soundscape and the applicability to environmental noise assessments. The necessity of this approach in evaluating the impact (e.g., PTSD) on those exposed to wind turbine acoustical energy will be explored.
Wind farm infrasound—Are we measuring what is actually there or something else? (Part 2)
Authors: Cooper Steven E.
Published: May 2016

In predigital acoustics, low frequency analysis used analog narrow band filters and cathode ray oscilloscopes for special problems leading to the general use of peak values. Analog filters have time constants that can affect the derived rms values requiring caution where high crest factors are involved. Modern narrowband digital analysis based on a FFT of the time signal extracts the periodic function that occurs in the time domain that are then displayed as discrete peaks in the frequency domain. FFT analysis of turbines show discrete infrasound peaks at multiples of the blade pass frequency in addition to sidebands in the low frequency range spaced at multiples of the blade pass frequency. Are these signals actually there or are they a product of modern day analysis. Is the infrasound signature a clue to a different area of investigation? In Jacksonville, Part 1 presented the complexity of the investigations and showed how the raw Pascal data are lost when converting to SPL and then A-weighting. Part 2 presents the results of different filtering techniques for different wind farms.
An evaluation of how nightly variations in wind turbine noise levels influence wrist actigraphy measured sleep patterns
Authors: Michaud David S.
Published: May 2016

Health Canada’s Wind Turbine Noise and Health Study assessed self-reported and objective measures of sleep on a sub-sample of the study’s 1238 participants. The data analysis indicated that calculated long term outdoor wind turbine noise (WTN) levels up to 46 dBA did not have a significant influence on the evaluated measures of sleep (Michaud et al., 2016, Sleep 39, 97–109). A more refined analysis is being conducted to assess wrist actigraphy measured sleep patterns in relation to nightly variations in wind turbine operations. Variations in turbine operations (i.e., RPM and electrical power) were used to calculate WTN levels in 10-min intervals and time-synchronised with sleep watch data collected in 1-min epochs. The 10-min sound levels and daily sleep diaries (relied upon to adjust for closed or open windows) were used to estimate indoor A-weighted WTN levels. The correction factor used to obtain indoor sound levels was derived from a series of field measurements designed to investigate the outdoor to indoor sound pressure level difference on a representative sample of dwellings. The analysis is restricted to participants living between 0.25 and 1 km from wind turbines (116 males and 159 females). At these distances, WTN levels are the highest making it more likely to detect potential WTN impacts on sleep. Results will be presented for multiple measures of sleep in 10-min intervals and nightly averages for up to seven consecutive sleep nights.
Wind turbine acoustic analysis should be performed to minimize the potential for adverse impacts on life-quality for neighbors
Authors: Rand Robert W. , Ambrose Stephen E.
Published: May 2016

Wind turbine environmental assessments should be expanded to include evaluating infrasonic, low-frequency, and A-weighted noise levels. Modern instruments and microphones can measure three simultaneous, band-pass measurements: dBL, dBC, and dBA. This paper will evaluate these band-pass measurements and discuss potentials for predicting potential adverse public responses.
Integrated extinction, or total scattered energy, as a linear sum of individual contributions in acoustic multiple scattering
Authors: Norris Andrew
Published: May 2016

Multiple scattering (MS) involves interaction between scatterers with the result that the scattered field is not simply the sum of the separate responses. In fact, it is generally a very nonlinear process, particularly at high frequencies. It is therefore surprising that there are circumstances for which the total energy of the scattered acoustic wave is simply the sum of the individual contributions. Total scattered energy, also known as the integrated extinction, is defined as the integral of the scattering cross-section with respect to wavelength for a given direction of incidence, and is therefore a measure of the scattering over all frequencies. Two conditions are necessary, one at zero frequency and the other at infinite frequency. They are, respectively, (i) that all scatterers have effective static compressibility and density equal to the background properties, and (ii) that the wavefront in the forward direction associated with MS does not precede the incident wavefront. Examples will be given showing how both conditions can be achieved with regular and irregular arrays of elastic shells. This linear MS result is particular to acoustics, as compared with electromagnetic waves in vacuo. [Work supported by ONR.]
The effective material properties of a composite elastic half-space
Authors: Abrahams Ian D. , Parnell William J.
Published: May 2016

A classical problem in applied mathematics is the determination of the effective properties of a composite material by looking at its reflection and transmission properties. This model discussed here is an elastic half-space containing randomly distributed voids—to obtain its “average” material properties (i.e., the effective density and elastic moduli) we consider elastic waves incident from a homogeneous half-space onto the inhomogeneous material. We restrict attention to dilute dispersions of inclusions, and therefore, results are obtained under the assumption of small volume fraction. We look at several aspects of this problem, as times allows. First, we discuss how predictions derived from the non-isotropic Foldy or the Waterman-Truell multiple-scattering theories (MSTs) in the low-frequency limit are equivalent to results found by an asymptotic integral equation (homogenization) method developed by the authors [1]. Second, the effect of nonlinear pre-stress on each void, and hence on the averaged material properties, is considered [2]. And third, some comments are offered regarding higher order effects and the closure assumption (e.g., the quasi-crystalline approximation). [1] W. J. Parnell, I. D. Abrahams, and P. R. Brazier-Smith, Quart. J. Mech. Appl. Math. 63, 145–175, 2010. [2] T. Shearer, W. J. Parnell, and I. D. Abrahams, 471, 20150450, 2015.
Effects of age and hearing loss on coding frequency and amplitude modulation
Authors: Whiteford Kelly L. , Kreft Heather A. , Oxenham Andrew J.
Published: May 2016

Is phase-locking to temporal fine structure (TFS) selectively affected by hearing loss or ageing? This question has clinical relevance because audiometric measures may be insensitive to TFS deficits linked to auditory neuropathy/dyssynchrony and synaptopathy (“hidden hearing loss”). Previous work has suggested that slow-rate FM is coded via phase-locking to TFS, whereas fast-rate FM is converted to amplitude modulation (AM) via cochlear filtering. This hypothesis was tested by correlating performance in slow- and fast-rate FM with performance in tasks known to reflect TFS coding (interaural-time-difference detection, ITD) and cochlear filtering (forward masking patterns). Subjects with clinically normal hearing at low frequencies between the ages of 20 and 80 years were tested, with approximately 10 subjects per decade. Effects of low- and high-frequency hearing loss were also examined, while controlling for age. Although correlations were found between all measures of FM and AM, no clear specific effect of age was found on TFS coding (independent of AM coding). Preliminary results with hearing-impaired listeners suggest an effect of cochlear filtering that may not be specific to the fast-rate FM detection. Overall, the results do not provide strong evidence for TFS-specific deficits with either age or hearing loss. [Work supported by NIH grant R01DC005216.]
Spike-timing and mean-rate coding of the temporal fine structure and envelope cues in real words
Authors: Bruce Ian C. , Wirtzfeld Michael R.
Published: May 2016

A number of studies over the past decade have argued for the importance of temporal fine structure (TFS) cues for the perception of consonants. However, recent investigations indicate that TFS cues from consonants may largely be converted into envelope (ENV) cues by narrowband cochlear filtering, such that these cues are conveyed by the mean-rate response of auditory nerve fibers rather than spike-timing cues. However, these studies used nonsense VCV syllables, and this result may not generalize to real words in which the patterns of ENV and TFS cues may be substantially different, and in which lexical context may play a role. In this study, we used a computational model of the auditory periphery and neural-based speech intelligibility predictors to investigate the TFS and ENV representation of real words from the NU-6 database. Spike-timing and mean-rate cues were evaluated for “auditory chimaeras” created from this database, in which the TFS of one signal is mixed with the ENV of another. The results indicate that the chimaera processing has a bigger impact in general on the mean-rate representation of phonemes than on the spike-timing representation, and inclusion of the spike-timing cues gives better predictions of phoneme perception. [Funded by NSERC of Canada.]
Psychophysiological responses to listening to speech in intermittent noise
Authors: Francis Alexander L.
Published: May 2016

Listening to speech in noise can be effortful, and the presence of background noise may in itself provoke physiologically measurable stress. Typical laboratory tests of speech perception in noise often present masked stimuli in trials separated by silence, in effect starting and stopping an otherwise constant background noise multiple times over the course of an experiment. While these interruptions might reduce listener stress by providing momentary respite from an aversive stimulus, intermittent noise might also increase stress by repeatedly inducing automatic physiological responses to the noise onsets. Here, I present the results of an experiment contrasting these possibilities. Younger (age 18–36) and older (age 60 + ) listeners heard sentences presented in speech-shaped noise at 0 dB SNR while physiological responses linked to stress and arousal (skin conductance, heart rate, fingertip pulse amplitude, and facial electromyography) were recorded. Two roughly 15-min blocks of noise, each containing 36 unique sentences, were presented. In the interrupted noise condition the noise was silenced for 5 s shortly after each sentence while in the uninterrupted condition the noise continued unabated. Behavioral measures of listening task performance and physiological measures collected during listening and speaking will be presented, and implications for future research will be discussed.
Effects of elevated amplitude modulation discrimination threshold on simultaneous amplitude modulation rate discrimination
Authors: Anderson Sean R. , Kan Alan , Litovsky Ruth Y.
Published: May 2016

Cochlear-implant (CI) users struggle to understand speech in difficult listening environments partly because they have limited access to auditory cues that allow for perceptual segregation between target and competing sounds. Because CI speech coding strategies optimize the encoding of envelope cues to promote better speech intelligibility, envelope may be an important cue for source segregation in CI users. Recent work has suggested that access to amplitude modulation (AM) depth and rate varies according to location of electrodes in the cochlea, and that turning off electrodes that yield poorer AM sensitivity may improve speech reception. The purpose of this study was to investigate the role of AM sensitivity in the ability of listeners to use AM rate information in multiple electrodes. It was hypothesized that electrodes with higher AM thresholds, which were simulated in normal-hearing listeners, would limit listeners’ ability to segregate AM rates. Subjects discriminated between pairs of stimuli that varied in AM rate relative to a reference rate. Stimulus pairing was within- or across-ears. Results suggest that AM insensitive electrodes impair CI users’ ability to discriminate AM rates, which may limit source segregation using envelope cues in complex listening environments. [This work was supported by NIH-NIDCD R01 DC003083 (Litovsky).]
Effects of a precursor on amplitude modulation detection are consistent with efferent feedback
Authors: Almishaal Ali , Jennings Skyler G.
Published: May 2016

The acoustic waveform of speech is characterized by slowly varying amplitude fluctuations (i.e., envelope) and an accurate representation of the envelope is essential for speech understanding. The post-cochlear representation of the contrast between peaks and valleys of the envelope (peak-to-valley contrast) may be reduced by cochlear compression. This study tested (1) whether amplitude modulation (AM) detection thresholds are consistent with cochlear compression and (2) whether the introduction of a precursor before the carrier results in improved AM thresholds, consistent with a decompressed cochlear response via the medial olivocochlear reflex (MOCR). In the no precursor condition, AM thresholds worsen at mid-levels, consistent with reduced peak-to-valley contrast from cochlear compression. In the precursor condition, AM thresholds improved at low modulation frequencies and mid-to-high levels, consistent with a reduction in cochlear amplifier gain and decompression of the cochlear input/output function via the MOCR. These findings suggest the MOCR may play a role in the perception of other amplitude-modulated stimuli, such as speech.
How well do measures of the precedence effect based on clicks predict performance for long-duration stimuli?
Authors: Pastore M. Torben , Braasch Jonas
Published: May 2016

Despite multiple reflections off nearby surfaces, listeners often localize sound sources based primarily upon the first arriving, direct sound. This is called the precedence effect. Much has been learned about the precedence effect using transient clicks, but the vast majority of everyday sounds are relatively long in duration. Recently, Pastore and Braasch (JASA, 2015) tested the effects of increased lag intensity on localization dominance for longer, 200-ms duration stimuli with 20-ms cosine-squared ramps. Assuming that interactions at the onset of lead-lag stimuli are primarily responsible for the precedence effect, it has been suggested that the binaural cues important to the precedence mechanism are the same for clicks and longer-duration noise stimuli. To test this hypothesis, we presented lead-lag stimuli composed of 1-ms, rectangular clicks, as well as 41-ms and the previously used 200-ms long noise bursts. Five, lead-lag delays between 1 and 5 ms were tested for lead/lag level differences of 0-, --4-, and --8-dB. Results and statistics clearly show that the classic click stimuli and long-duration stimuli do not yield the same performance for the conditions tested in these experiments, especially when lag level is increased. [Research supported by NSF 1320059.]
Backward masking and tonal audibility before and after a noise burst
Authors: Sears Robert , Smith Silas , Yonovitz Al
Published: May 2016

This study reports on the perceived position of the tonal signal during a threshold tracking procedure. The stimulus was a 1000 Hz sinusoid tone. The inter-stimulus (ISI) interval varied from 2 ms to 64 ms. The noise stimulus was a 70 dB HL band-limited white noise. The subject tracked threshold (2 dB steps). In these experiments, ten normal hearing subjects (18–30 years) were presented the stimulus before the noise burst. Moving through a critical ISI value, the stimulus becomes inaudible after a further reduction in ISI, the stimulus is detected but appears to follow the noise. This finding supports a hypothesis that the tonal signal may be modulated by physiological loci by changing the ISI and the tonal intensity.
Development of subcortical pitch representation in three-month-old Chinese infants
Authors: Jeng Fuh-Cherng , Lin Chia-Der , Hollister Grant R. , Sabol John T. , Mayhugh Garrett N. , Wang Tang-Chuan , Wang Ching-Yuan
Published: May 2016

This study investigated the development of subcortical pitch processing, as reflected by the scalp-recorded frequency-following response, during early infancy. Thirteen Chinese infants who were born and raised in Mandarin-speaking households were recruited to partake in this study. Through a prospective-longitudinal study design, infants were tested twice: at 1–3 days after birth and at three months of age. A set of four contrastive Mandarin pitch contours were used to elicit frequency-following responses. Frequency Error and Pitch Strength were derived to represent the accuracy and magnitude of the elicited responses. Paired-samples t tests were conducted and demonstrated a significant decrease in frequency error and a significant increase in pitch strength at three months of age compared to 1–3 days after birth. Results indicated the developmental trajectory of subcortical pitch processing during the first three months of life.
Particulate damping media and isolation of ground-borne vibrations
Authors: Tavossi Hasson M.
Published: May 2016

Ground borne vibration can be dissipated by attenuation, absorption, frictional, and viscous damping before being transmitted to the buildings, by means of a suitable particulate media below the structure. We show that the band-pass behavior of particulate media for mechanical vibrations can also result in significant attenuation of vibrations for frequencies on either side of the pass-band. Sample particulate structures are subjected experimentally to the longitudinal and shear waves of different amplitude and frequencies, generated by electro-mechanical shakers vibrating in different directions. The amount of vibration damping by attenuation, resonance absorption, frictional and viscous dissipations are determined experimentally. The pressure wave and shear-waves, generated experimentally by the electro-mechanical shakers, are combined to simulate realistic ground borne vibrations. Damping media consisting of composite materials with different elastic properties are tested as tuned absorbers. The goal is to determine the damping characteristics for most efficient absorption of vibration, of different intensity and frequency. The results can be used to design tuned dampers for specific ground borne vibrations and determine material characteristics for dissipation of ground borne vibrations at large scale.
Measurements of the reduction in ground vibration levels from wave barrier trench
Authors: LoVerde John J. , Dong David W.
Published: May 2016

Where buildings are adjacent to railroad tracks, there are limited practical applications for controlling the transmission of train vibration. In critical listening spaces like auditoria or government buildings, isolation of the building structure is sometimes undertaken. However, this option is not attractive for most commercial or residential development due to the attendant costs and complications. For these properties, one option for reducing levels of ground vibration is to dig a trench between the tracks and the project to act as a wave barrier. Construction of a deep trench presents a wide variety of construction challenges, and the application of this method has been rare within the United States due to the lack of regulations and sensitivity that might demand such an approach. The authors recently had a project where a wave barrier (trench) was applied, which provided the opportunity to observe the construction of the trench and to measure the resulting reduction in ground vibration levels before and after the installation. Various aspects of this process are discussed.
Using the sounds of nuclear power
Authors: Smith James A. , Heidrich Brenden J. , Agarwal Vivek , Heibel Michael D. , Smith Robert W. , Garrett Steven L.
Published: May 2016

The generation of sound by heat has been documented as an “acoustical curiosity” since a Buddhist monk reported the loud tone generated by a ceremonial rice-cooker in 1568. Over the last four decades, significant progress has been made in understanding “thermoacoustic processes,” enabling the design of thermoacoustic engines and refrigerators. We have developed and tested a thermoacoustic engine that exploits the energy-rich conditions in the core of a nuclear reactor. The heat engine is self-powered and can wirelessly transmit the temperature and reactor power by generation of a pure tone which can be detected outside the reactor. We report here the first use of a fission-powered thermoacoustic engine capable of serving as a performance and safety sensor in the core of a research reactor and present data from two hydrophones in the coolant (far from the core) and an accelerometer attached to a structure outside the reactor. These measurements confirmed that the frequency of the sound produced indicates the reactor’s coolant temperature and that the amplitude (above an onset threshold) is related to the reactor’s operating power level. These signals can be detected even in the presence of substantial background noise generated by the reactor’s fluid pumps. [Work supported by Idaho National Laboratory and Westinghouse Electric Co.]