bluuebunny/crossref_metadata_2025 huggingface dataset:
A moving target? Comparing within-talker variability in vowel production between native and non-native English speakers across two speech styles
Authors: Rogers Catherine L. , Gordon Amber , Pizarro Melitza
Published: September 2012

Non-native English speakers may show greater variability in speech production than native talkers due to differences in their developing representations of second-language speech targets. Few studies have compared within-talker variability in speech production between native and non-native speakers. In the present study, vowels produced by four monolingual English speakers and four later learners of English as a second language (Spanish L1) were compared. Five repetitions of six target syllables (“bead, bid, bayed, bed, bad” and “bod”), produced in conversational and clear speech styles, were analyzed acoustically. Fundamental and formant frequencies were measured at 20, 50 and 80% of vowel duration. Standard deviations computed across the five repetitions of each vowel were compared across speaking styles and talker groups. Preliminary data analyses indicate greater within-talker variability for non-native than native talkers. Non-native talkers’ within-talker variability also increased from conversational to clear speech for most measures. For some native talkers, within-talker variability was smaller for vowels with near neighbors in the vowel space than for vowels with more spectrally distant neighbors. This correlation was stronger in clear speech for talkers who showed a significant clear-speech intelligibility benefit in production in a related study. Implications for theories of vowel production will be discussed.
Processing reduced speech across languages and dialects
Authors: Warner Natasha L. , Brenner Daniel , Tucker Benjamin V. , Sung Jae-Hyun , Ernestus Mirjam , Simonet Miquel , Gonzalez Ana
Published: September 2012

Normal, spontaneous speech utilizes many reduced forms. Consonants in spontaneous speech frequently have a different manner or voicing than would be expected in clear speech (e.g. /d/ and /ŋ/ in “you doing” both being realized as glides or /dȝ/ in “just” as a fricative), and near or complete deletions are also common (e.g. the flap in “a little”). Thus, listeners encounter and must process such pronunciations frequently. When speakers and listeners do not share the same dialect or native language, such reductions may hinder processing more than for native listeners of the same dialect. The current work reports a lexical decision experiment comparing listeners’ processing of reduced vs. careful stops (e.g. /g/ in”baggy” pronounced as an approximant or as a stop), by several groups of listeners. Results show that listeners from both Arizona and Alberta, Canada can recognize speech by an Arizona speaker with reduced stops, but they recognize the words more easily when stops are clearly articulated. Speech style of the preceding frame sentence has little effect, suggesting that both groups can process the stops regardless of whether surrounding context leads them to expect reduced stops. Additional data from second-language learners and bilingual listeners is currently being collected.
Evidence of Spanish undershoot in a Mexican-American community
Authors: Dean Arika B.
Published: September 2012

Previous phonetic work on Spanish vowels has suggested that undershoot does not occur in the Spanish vowel system. Quilis & Esgueva (1983) suggested that Spanish vowels were static with little to no articulatory variation. This study contributes to a growing body of phonetic research attempting to disprove these claims. The data comes from audio interviews conducted in a predominantly Hispanic community in Pearsall, Texas. Acoustic analysis is conducted on all vowels in the Spanish vowel range (/i/, /e/, /a/, /o/, /u/), and each token is measured from the midpoint of the vowel nucleus, as well as onset and offset. Subjects are Spanish speakers of different age, sex, language competency, and socioeconomic status. In response to Lindblöm’s (1963) assertion that stress is more significant than duration in determining undershoot, this study raises that question again and finds that stress is more statistically significant than duration in the Spanish undershoot process, contrary to Lindblöm’s findings. These results also contradict Willis (2005), who found that duration influences the F1 value for Spanish vowels. The effects of English substrate influence are considered, and the vowels of monolingual Mexican Spanish speakers are analyzed, providing a control against the speakers in the Pearsall community.
The production and perception of English stops in a coda position by Thai speakers
Authors: Lerdpaisalwong Siriporn
Published: September 2012

This paper reports results from a pilot study on the production and perception of English stops in a coda position by native speakers of Thai with different length of residency (LOR) in the US. This study explores three important issues in second language (L2) acquisition: typological markedness (Eckman, 1997), the relationship between production and perception of speech sounds (Flege, 1988 and 1999), and the length of learning L2 sounds (Flege 1999). There were 13 Thai-speaker participants whose LORs ranged from 1 year to 23 years. They participated in two tasks: sentence reading in a production task, and sentence listening in a perception task. Preliminary results show that participants produced all English voiced stops less accurately than voiceless stops. However, in the perception task, only /g/ was perceived less accurately than voiceless stops. The speakers perceived /b/ better than /k/ and perceived /d/ better than /p/ and /k/. The more accurate the speakers can perceive the sounds, the better they can produce it. The Thai speakers with a longer LOR perceived and produced English stops in the coda position more accurately than those with a shorter LOR. The results found raise our awareness of to which sounds should be paid special attention and the benefit of enough language input. Also, the study suggests the pattern of English stops acquired by native speakers of Thai in both production and perception processes.
Acoustic correlates of stop consonant voicing in English and Spanish
Authors: Dmitrieva Olga , Shultz Amanda A. , Llanos Fernando , Francis Alexander L.
Published: September 2012

In English, fundamental frequency at the onset of voicing (onset f0) co-varies with the Voice Onset Time (VOT) of initial stops and provides an additional perceptual cue to the phonetic feature of voicing, especially when VOT is ambiguous. However, aerodynamic and physiological explanations of the onset f0/VOT relationship suggest that onset f0 should correlate with voicing only in languages such as English that contrast short lag (voiceless unaspirated) with long lag (voiceless aspirated) consonants, and not in languages such as Spanish that contrast prevoiced with short lag stops. Previous perceptual research supports this prediction: Spanish speakers with little English experience do not incorporate onset f0 in making voicing decisions, suggesting lack of a correlation in their ambient language. In contrast, Spanish speakers with extensive experience with English show an English-like pattern of onset f0 use, suggesting that exposure to the English pattern of covariation has influenced their perceptual weighting of these two cues. The present study compares the distribution and correspondence between VOT and onset f0 in syllable-initial bilabial stops ([b] - [p]) in Spanish and English. Implications for the typology of voicing contrasts and perceptual strategies for sound categorization in non-native language environments are discussed.
Perception of place-of-articulation contrasts of English word-final consonants in connected speech by Japanese and Korean second language learners
Authors: Ito Kikuyo , Hyun JungMoon
Published: September 2012

An extension of a previous study examining Japanese listeners’ perception of place contrasts of English word-final stops in connected speech (Ito, 2010) was carried out by administering the same experiment to Korean listeners. Stimuli embedded in a carrier sentence and produced in fast casual speech were presented in a three-alternative forced choice identification test, adopting minimal triplets (e.g., sip-sit-sick, bib-bid-big, Kim-kin-king) followed by an adverb starting with /p/, /t/, or /k/. Data for 24 Korean listeners were compared with the previous data for 24 Japanese and 24 American English (AE) listeners. Whereas Japanese listeners had exhibited severe difficulty in perceiving place contrasts of nasal and voiceless stops, Korean listeners were expected to have much less perceptual difficulty on those contrasts because of the different L1 phonological rules of final stops. Results revealed that Koreans’ response accuracy was much higher than that of Japanese on voiceless stops (Korean 82%, Japanese 67%, AE 90%) and nasal stops (Korean 96%, Japanese 66%, AE 98%), conforming to the predictions. The contrasting performance between Korean and Japanese listeners on nasal stops was especially remarkable, strongly supporting the notion that Japanese listeners’ difficulty in perceiving place contrasts of word-final nasals is due to their L1phonological rules.
Effects of acoustic and linguistic aspects on Japanese pitch accent processing
Authors: Wu Xianghua , Kawase Saya , Wang Yue
Published: September 2012

This study investigates the hemispheric processing of Japanese pitch accent by native and non-native listeners. The non-natives differ in their first (L1) and second (L2) language experience with prosodic pitch, including Mandarin (tonal L1) and English (non-tonal L1) listeners with or without Japanese learning experience. All listeners completed a dichotic listening test in which minimal pairs differing in pitch accent were presented. Overall, the results demonstrate a right hemisphere lateralization across groups, indicating holistic processing of temporal cues as the pitch accent patterns span across disyllabic domain. Moreover, the three pitch accent patterns reveal different degrees of hemispheric dominance, presumably attributable to the acoustic cues to each pattern which involve different hemispheric asymmetries. The results also reveal group difference, reflecting the effects of linguistic experience. Specifically, the English listeners with no Japanese background, compared to the other groups, exhibit greater variance in hemispheric dominance as a function of pitch accent difference, showing a greater reliance on acoustic cues when linguistic information is lacking. Together, the findings suggest an interplay of acoustic and linguistic aspects in the processing of Japanese pitch accent but showing a more prominent acoustic influence. [Research supported by NSERC.]
Orthography modulates lexical recognition in a second language
Authors: Shea Christine E.
Published: September 2012

We use a cross-modal masked priming paradigm to investigate a) whether orthography is always activated during lexical recognition and b) when activated, whether orthography influences the perception of allophonic variants by adult L2 learners. L1 Spanish and L2 Spanish learners (n=60) were exposed to written Spanish primes with ‘b’ ‘d’ or ‘g’ in intervocalic position. In Spanish, the positional phones corresponding to these orthographic symbols are voiced fricatives [β Ð v̥]; in English they are voiced plosives. In the matched prime trials, written primes were paired to auditory targets with the expected voiced fricative (lado ‘[laÐo] ‘side’). For the unmatched prime trials, the auditory target had medial plosives ([lado]. Orthographic prime durations were either 33ms (implicit, Condition 1) or 67ms (explicit, Condition 2). Accuracy and reaction times were registered on lexical decision to the auditory target. Preliminary RT results indicate a three-way interaction among group, trial type (matching or unmatching) and prime condition. Follow-up tests revealed a significant difference for the L2 listeners for prime conditions: significantly longer RTs were registered for the ‘matching’ trials when the orthographic prime was visible (Condition 2). These results suggest that L2 lexical recognition is modulated by orthographic information when it is explicitly available.
Pulse compression in striation processing—Acoustic invariant as seen in the time domain
Authors: Hursky Paul
Published: September 2012

The acoustic invariant is well known to produce broadband interference or striation patterns in spectrograms. These have been used for a variety of applications, including geo-acoustic inversion and target tracking, in both passive and active settings. The processing to extract parameters from these broadband interference patterns has typically been performed on the spectrograms. However, spectrogram striations have energy that is spread across a wide band. This paper will present a time domain approach, in which the striations are pulse-compressed via a correlation process, before extracting the parameters of interest. Narrowband signals pose an interesting conundrum for striation processing - they are typically much stronger iin level than the underlying broadband interference pattern, and can be mistaken for striations, thus corrupting the parameter extraction. As in time delay estimation, pre-whitening is needed to suppress narrowband components. At the same time, the narrowband components best reveal the underlying interference pattern, albeit in a very narrow band, because they are of such high SNR. We will discuss how to exploit this information content as well.
Empirical and collocation-point methods for estimation of acoustic field and array response probability density functions
Authors: Hayward Thomas J. , Oba Roger M.
Published: September 2012

Recent research has investigated the representation of acoustic field uncertainties arising from uncertainties of the acoustic environment, with emphasis placed either on the representation of the acoustic field as a random process or on estimation of the acoustic field probability density function (pdf) at a given receiver location. The present work introduces two methods for estimating acoustic field and array response pdfs. The first method is based on the computation of the empirical characteristic function (ECF) of the acoustic field, derived from a random sample in the acoustic parameter space and computation of the corresponding acoustic fields. The acoustic field pdf estimate is obtained as the Fourier transform of the ECF. The second method is based on approximation of the characteristic function using collocation-point methods, which are based on orthogonal-polynomial approximations of the mapping from the parameter space to the acoustic field. Both methods are investigated in two examples: (1) a stratified shallow-water model with two-dimensional uncertainties of sound speed and attenuation coefficient; and (2) a shallow-water model with sound-speed fluctuations in the water column defined by a time-stationary internal wave field. Sampling requirements and convergence of the pdf estimates are investigated for both methods and compared. [Work supported by ONR.]
Mode coupling due to bathymetric variation
Authors: White Charles E. , Clark Cathy A. , Potty Gopu
Published: September 2012

In shallow water the assumption of range independence fails in conditions of rapidly-varying bathymetry and/or horizontal sound speed. In these environments, the modes of vibration of the acoustic wave equation become coupled, with a transfer of energy between adjacent modes occurring upon traversing a horizontal change of environment. In this talk, we will consider some simple applications of mode conversions due to variable bathymetry. Results will be compared to closed form propagation solutions in constant-slope wedge environments. The ultimate goal of this research is the development of a fully non-adiabatic range-dependent mode solution which retains analytical integrity while executing in a time window that is tactically useful for warfare applications.
Long-range tracking of bowhead whale calls using directional autonomous seafloor acoustic recorders
Authors: Mathias Delphine , Thode Aaron M. , Kim Katherine H. , Blackwell Susanna B. , Greene Charles R. , Macrander Michael A.
Published: September 2012

Since 2007 “Directional Autonomous Seafloor Acoustic Recorders” (DASARs) have been deployed at five sites across a 280 km swath of the Beaufort Sea continental shelf to record bowhead whale (Balaena mysticetus) calls during their autumn migration. Composed of an omnidirectional pressure sensor and two horizontal directional sensors measuring particle motion, DASARs provide information for determining the bearing to a sound source. In previous analyses, bearings obtained from multiple DASARs within a single site have been used to localize calls, with a maximum baseline separation of 21 km between instruments. Here, we use data collected from two different sites to exploit a 45 km instrument separation for tracking bowhead whale calls detected under low ambient-noise situations in 2009 and 2011. These data sets have been manually analyzed to extract a series of calls from individual whales swimming from one site toward another. The fact that the tracking method does not require relative arrival time information makes matching calls between these widely separated shallow-water recordings practical. Both empirical and numerical transmission loss models are used to investigate the relationship between animal orientation, source level, and the presence of harmonics.
Compound manipulation of micro-particles using a single device:Ultrasonic trapping, transporting, and rotating
Authors: Jia Kun , Yang Keji , Chen Jian , Meng Jianxin
Published: September 2012

Ultrasonic manipulation is widely used as a noncontact technology and recently small particles rotating on a vibrating substrate has been observed. In this report,a novel methodology which compounds the procedures of ultrasonic trapping, transporting and rotating micro-particles in fluid using a single device is investigated. Irregular micro-particles in a standing wave field experience both acoustic radiation force and torque, which drive the particles to pressure nodes and keep them in a balance posture. A prototype device has also been built according to this theory, which six phase-controlled piezoelectric transducers whose sound beam axes are arranged with an angle of 60 deg in the x-y plane are used to generate ultrasonic standing waves with arbitrary node. The transducers are divided to two groups, so the wave field can be rotated by switching between the two groups. The synthesized sound field is scanned using a needle hydrophone and 200 μm irregular SiO2 particles are used to perform the compound manipulation ability of our device. The experimental results show good agreement with the theoretical calculation and the possible reason accounting for the small deviations is also discussed. This method may provide more complex and elaborate applications in micro-assembling and cell biomechanics.
Collocation analysis of higher mode coupling in waveguides with discontinuous cross-section
Authors: Ginsberg Jerry H.
Published: September 2012

Standard techniques for analyzing transmission and reflection at discontinuities in a waveguide use weighted residuals to match modal series on each side of the junction. Convergence of the model equations generally is slow, which led Homenticovschi and Miles [JASA, 128 (2010) 628-638] to introduce a renormalization technique. Such a formulation does not lend itself well to implementation of a general computational algorithm. Slow convergence of the standard approach a consequence of using weighted residuals, which is a smoothing process, to interrogate a discontinuity. Evidence of this may be found in the analysis of scattering from cylinders having a discontinuous surface impedance [Ginsberg, JASA, 92 (1992) 1721-1728]. That work showed that a weighted residual formulation converges slowly, whereas a proper description of the field, including the singular nature of the velocity at the discontinity, is obtained from a collocation solution that satisfies the surface boundary condition at a discrete set of points. The present work uses standard modal series to represent the signal in each side of the discontinuity. The junction conditions of the waveguide are satisfied at a dscrete number of points. The rate of convergence will be assessed for a variety of schemes for selecting the collocation points, and the implementation of the formulation as part of a computational algorithm of networks will be discussed.
Fostering research in a general education acoustics course
Authors: Hoekje Peter L.
Published: September 2012

The general education science course often is the last science course an undergraduate takes. Liberal arts core requirements may include the goal that students come to understand or appreciate the nature of science and its impact on society. Incorporating research experience may be desirable, but has its challenges in a course for the non-major. A basic toolkit for student inquiry gives the capabilities for sound editing and analysis, filtering, sound level monitoring, sound and music synthesis, vowel and speech analysis, musical instrument design, and room acoustics analysis. These tools are available as low cost or free software. A course design compromise must be reached between delivery of content and support of student inquiry. However, a class of forty pursuing independent research projects in acoustics makes a rewarding experience for both instructor and students!
An integrated lecture-laboratory approach to teaching musical acoustics
Authors: Piacsek Andrew A.
Published: September 2012

At Central Washington University, "Physics of Musical Sound" (PHYS103) is an introductory level course that satisfies a General Education Breadth requirement in the lab-based science category. Enrollment is capped at 40 students, of which 10-15 are typically music education majors. From 1998 to 2010, this five-credit course was taught in a traditional lecture format: four 50-minute lectures and a two-hour lab each week. Starting in 2011, the course was reformatted into three two-hour periods. The objective was to incorporate inquiry-based learning strategies adopted from physics education research. The two-hour meeting time provides flexibility to structure the class with a combination of lecture, tutorial, group problem solving, and experiment. Computational resources, including sound analysis software and online interactive simulations, are heavily utilized. Example activities will be described and lessons learned from the transition to the new format will be discussed.
Ultrasonic scattering for inverse characterization of complex microstructures
Authors: Rokhlin Stanislav I.
Published: September 2012

This paper overviews resent theoretical and experimental results for inverse characterization of duplex polycrystalline microstructures from measurements of ultrasonic attenuation and backscattering. The duplex microstructures are formed by elongated regions of clustering crystallites with preferred orientations and are typical for titanium alloys. New insights into the dependences of the backscattering and attenuation on frequency and averaged ellipsoidal grain radii are obtained. In particular the dominant effect of the averaged ellipsoidal radius in the direction of wave propagation, instead of the ellipsoidal cross-section, is shown. Also the opposite effect on attenuation and backscattering of grain size in the direction of wave propagation is demonstrated by theory and experiment. Both attenuation and backscattering depend on effective elastic properties of clusters, their size and orientation and the measurement system parameters. It is shown that for material property inversion it is advantageous to decouple elastic and geometrical properties by a special series of measurements and data inversion: first determine grain geometry and size from relative directional and/or attenuation-to-backscattering ratio measurements; this is followed by absolute attenuation and backscattering measurements to obtain the crystallite orientation distribution function in the clusters.
Acoustic scattering from weakly coupled porous media
Authors: Denis Max , Chandra Kavitha , Thompson Charles
Published: September 2012

In this work, wave propagation and multiple acoustic scattering from porous media are examined. For a highly porous media, the inertial coupling between solid and fluid phases can be small. In such a case the dilatational and acoustic motions will be weakly coupled. The controlling factor is the ratio of effective inertial mass density of the porous media and the fluid mass density. Using Biot’s analysis as the starting point, the dilatational and acoustic motions, as well as the scattered pressure that ensues are evaluated. The Kirchhoff-Helmholtz integral equation is used to this end. The integral equations are evaluated using a series expansion in terms of derived acoustic contrast properties. Using the local Padé approximant procedure detailed in [The Journal of the Acoustical Society of America, 128(5) EL274-278 (2010)]. Of particular interest, are high contrast media and wavelengths comparable to the average scatterer size.
Diffuse ultrasonic backscatter measurements for monitoring stress in rail
Authors: Walentine Devin T. , Kube Christopher M. , Turner Joseph A. , Fateh Mahmood
Published: September 2012

Recent research in polycrystalline materials, both theoretically and experimentally, has demonstrated a dependence of diffuse ultrasonic backscatter (DUB) on applied stress. This dependence has been used to develop a measurement device for monitoring longitudinal stress in continuous welded rail (CWR). However when moving this research from the laboratory setting to field applications many additional challenges are encountered with respect to the experimental method. In this presentation, results from initial field experiments are presented. This work is performed on a switch track from a railroad mainline to a short line railroad siding. Comparison between DUB measurements and actual stress in the rail is accomplished through the use of four stress modules (based on standard strain gauge technology) that were installed at four different locations along test site. In these field tests, DUB experiments using two orthogonal shear waves are investigated. Procedures to mitigate errors in our experiments and techniques to refine the measurement for more accurate results are discussed. These field experiments highlight the utility of this approach with respect to practical and financial considerations for determining induced stresses in CWR. [Research supported by FRA.]
Elastic wave propagation in coated pipelines
Authors: Kirby Ray , Zlatev Zahari , Mudge Peter
Published: September 2012

Guided elastic waves are commonly used in the non-destructive evaluation of oil and gas pipelines. In order to protect pipes from environmental damage a viscoelastic coating such as bitumen is often applied. Viscoelastic coatings do, however, attenuate travelling waves and it is not uncommon in a coated pipe for the signal reflected from a defect to be attenuated to the extent that it is no longer discernable above the background noise. Thus, viscoelastic coatings significantly impact on the effectiveness of non-destructive testing in pipelines, both in the ability to resolve defects but also in the length of pipeline that may be tested. In order to obtain a better understanding of guided wave propagation in coated pipes, a numerical model is presented here that seeks to analyse the propagation of torsional and longitudinal modes in a coated pipe with simple axisymmetric defects. Reflection coefficient predictions are compared with experimental data for a pipe coated with bitumen and good agreement is observed between the two, although only after first undertaking a curve fitting exercise to identity appropriate values for the phase speed and attenuation of bulk torsional waves in the viscoelastic material.
Simultaneous measurement of local longitudinal and transverse wave velocities, attenuation, density, and thickness of a layer by using point-focus ultrasonic spectroscopy
Authors: Chen Jian , Bai Xiaolong , Ju Bingfeng , Meng Jianxing
Published: September 2012

This paper presented an ultrasonic technique for simultaneous determination of the complete set of acoustical and geometrical properties of a layer embedded between two known materials using point-focus ultrasonic spectroscopy, which provides a high lateral resolution. The theoretical model of the two-dimensional spectrum Rt (θ, ω) of the layer is calculated as a function of six parameters of longitudinal and transverse velocities cl, ct, attenuation αl, αt, density ρ and thickness h, which fully determined the layer properties. The experimental spectrum Re (θ, ω) can be measured by V(z, t) technique. A two-step algorithm is presented to decompose the searching process of parameters from one six-dimensional to two three dimensional spaces. The sensitivity of the two-dimensional spectrum to individual properties and its stability against experimental noise are studied. The full set properties of a 250 μm thick stainless steel plate immersed in water are determined. The proposed technique used a point focus transducer, which makes the set-up simple and reliable. It allows measurement of the local properties of the layer and enables precision material characterization.
Voicing in English revisited: Measurement of acoustic features signaling word-medial voicing in trochees
Authors: Toscano Joseph C. , McMurray Bob
Published: September 2012

A great deal of work in speech has argued that invariant acoustic cues do not exist, leading many researchers to conclude that listeners use specialized representations, such as talkers’ inferred gestures, instead. Other work has emphasized that many phonological distinctions are signaled by multiple cues; Lisker (1986, Language and Speech, 29, 3-11), for example, lists 16 cues to voicing. Yet, few studies have measured the reliability of multiple cues and asked whether combining them may provide a solution to the lack of invariance. Here, we present measurements of 12 potential cues to the voiced/voiceless distinction in stops (including many of those reported by Lisker, 1986) and use a statistical modeling approach to determine which ones distinguish the two categories and how reliable those cues are. We recorded two-syllable non-words (/sVCVs/) with one of six consonants (/b,p,d,t,g,k/) and one of four vowels (/a,æ,i,u/). We found that talkers used multiple cues, but that cues varied in their usefulness. In addition, a classifier trained on the cues was able to accurately identify voicing categories. We argue that by harnessing information from multiple cues, listeners can overcome ambiguity in individual cues in specific utterances, allowing them to recognize speech across talkers and phonological contexts.
“Talker normalization” effects elicited with no change in talker
Authors: Vitela A. Davi , Lotto Andrew J. , Story Brad H.
Published: September 2012

For more than fifty years, it has been known that listeners’ perception of a target speech sound may shift as a result of a change in speaker of a preceding carrier phrase. The predominant theories explaining this phenomenon suggest that the listener must be extracting information specific to the speaker - either generating speaker-specific acoustic-phonemic mapping or an estimate of the dimensions of the speaker’s vocal tract. To the extent that these processes derive representations that are specific to a speaker, one would not expect shifts in target perception when the apparent speaker remains unchanged. This prediction was explicitly tested by appending targets to different carrier phrases produced by the same speaker. Speaker characteristics were controlled by using an articulatory synthesizer that allows one to specify the source and dimensions of the vocal tract. Significant shifts in target perception were readily obtained, even when the speaker remained the same. These results suggest that these shifts are not tied to talker identity or anatomy but to more general aspects of the context acoustics. [Work supported by NIH-NIDCD.]
Efficient coding of redundancy among formant frequencies in vowels
Authors: Stilp Christian , Kluender Keith
Published: September 2012

Stilp and colleagues (Proc. Natl. Acad. Sci. [2010]; JASA [2011]; PLoS One [2012]) demonstrated that auditory perception rapidly and automatically exploits redundancy among acoustic attributes in novel complex sounds. When stimuli exhibited robust covariance between acoustic dimensions (attack/decay, spectral shape), discrimination of sound pairs violating this pattern was initially poorer than that for sound pairs respecting the pattern. While results support efficient coding of statistical structure in the environment, evidence of its contribution to speech perception remains indirect. The present effort examines perceptual organization adhering to statistical regularities in speech sounds. Vowel stimuli (/ɑ/, “ah”) were synthesized to reflect natural correlation between formant frequencies across talkers; as vocal tract length decreases (from men to women to children), formant center frequencies increase (here F 1-F 2 varied; others held constant). Listeners discriminated vowel pairs that either obeyed this correlation (16 pairs) or violated it (1 pair) in randomized AXB trials without feedback. Performance replicated results with nonspeech sounds. Vowels that violated natural redundancy between formant frequencies were discriminated poorer than vowels that obeyed this pattern. Results encourage an efficient coding approach to speech perception, as redundancy among stimulus attributes is exploited to facilitate perceptual organization and discrimination. [Supported by NIDCD.]
Importance of sentence-level and phoneme-level envelope modulations during vowels in interrupted speech
Authors: Fogerty Daniel
Published: September 2012

Speech interrupted by noise has been used as a simplified case for listening to speech in the presence of a fluctuating masker. The present study investigated the importance of overall vowel amplitude and intrinsic vowel amplitude modulation to sentence intelligibility. Eight young normal-hearing listeners participated in the experiment. Sentences were processed according to three conditions that replaced vowel segments with noise matched to the long-term average speech spectrum. Vowels were replaced with (1) low-level noise that distorted the overall sentence envelope, (2) segment-level noise that restored the overall syllabic amplitude modulation of the sentence, and (3) segment-modulated noise that further restored faster temporal envelope modulations during the vowel. Results demonstrated incremental benefit with increasing resolution of the temporal envelope. An additional seven listeners participated in a separate experiment that replaced vowels with a vowel masker instead of noise. The vowel masker was modified to have a flattened fundamental frequency at the mean of the replaced segment. The vowel masker either had a standard temporal envelope or was modulated by the envelope of the replaced vowel. Listeners who heard vowel maskers performed more poorly than those who heard noise maskers. No benefit of segment modulation was observed with the vowel masker.
Effects of noise on adults' word learning
Authors: Han Min Kyung , Storkel Holly L. , Cox Casey
Published: September 2012

Neighborhood density, the number of similar sounding words, and phonotactic probability, the likelihood of occurrence of a sound sequence, influence word learning by adults in quiet listening conditions. Specifically, Storkel, Armbruster, and Hogan (2006) found that adults learned high density words and low probability words more accurately. This study examined how neighborhood density and phonotactic probability influence adults’ word learning in noisy conditions. Fifty-two college students learned nonwords varying in neighborhood density and phonotactic probability at either +8 dB SNR or 0 dB SNR, and learning was measured in a picture naming task. Results showed a significant interaction of density, probability, and noise level. At +8 dB SNR, no effects were significant. At 0 dB SNR, density interacted with probability, showing better learning when density and probability converged. In other words, for low probability words, learning was better when density was also low (i.e., low-low optimal), whereas for high probability words, learning was better when density was also high (i.e., high-high optimal). These results indicate that noise dampens the effects of probability and density in a moderately noisy condition (i.e., +8 dB SNR) and requires a convergence of probability and density in the noisiest condition (i.e., 0 dB SNR).
Optimizing receiver and source positioning in the ocean: Lessons from nature
Authors: Michalopoulou Zoi-Heleni
Published: September 2012

Extracting information from the ocean using acoustic signals as well as detecting and localizing sources is critical for both defense and environmental applications. Accurate parameter estimation strongly relies on optimal positioning of sources and receivers, whose locations are often the function of the ocean waveguide. Observing marine-mammal vocalizations, one notices that preference is given to transmission and reception at particular depths. A simple sound propagation analysis indicates that use of the specific locations may optimize sound reception. We can make similar choices with man-made systems, calibrating the locations of deployed sound transmission/reception equipment, with optimal detection and estimation in mind. [Work supported by ONR.]
Speech enhancement by maintaining phase continuity between consecutive analysis frames
Authors: Mehmetcik Erdal , Ciloglu Tolga
Published: September 2012

The aim of speech enhancement algorithms is to increase the quality and intelligibility of noise degraded speech signals. Classical algorithms make modifications in the magnitude spectrum of the noise degraded signal and leave the phase spectrum unchanged. Leaving the phase spectrum unchanged relies on the results of the early listening tests, in which it is concluded that a better phase estimation does not have a significant effect on speech quality. However, a poor phase estimate causes a noticeable distortion in the reconstructed signal. In this work a new phase estimation method (in the voiced segments of speech) is proposed. This method is then incorporated into classical (magnitude based) enhancement algorithms and a new enhancement method is put forward. The performance of the proposed enhancement method is tested with the ITU-T standard PESQ measure and the results are presented.
Seismo-acoustic propagation near thin and low-shear speed ocean bottom sediments
Authors: Collis Jon M. , Metzler Adam M. , Siegmann William L.
Published: September 2012

Accurate and efficient parabolic equation solutions exist for complex propagation environments with elastic sediments. Certain ocean acoustic environments (such as harbors or estuaries) can feature a seafloor interface consisting of partially consolidated sediments, which can be described as a transitional solid. These complex sediments are generally thin, with low-shear wave speeds, and can cause numerical instabilities to arise in parabolic equation solutions. These instabilities make it difficult to obtain accurate solutions. In the low-shear limit, this problem can be treated as a multiple-scale problem. In this talk, such an ocean environment is modeled as a water layer overlying a thin transitional solid sediment layer over an elastic basement. An elastic parabolic equation approach is developed using asymptotic solutions for the displacements in the transitional solid, which are then incorporated into existing seismo-acoustic parabolic equation solutions by explicitly enforcing fluid-solid and solid-solid interface conditions across the transitional-solid interfaces. Solutions are benchmarked against existing elastic parabolic equation and normal mode solutions for accuracy.
Effects of seismic source and environment parameters on elastic bottom parabolic equation solutions
Authors: Frank Scott D. , Collis Jon M. , Odom Robert I.
Published: September 2012

Recently, two-types of elastic self-starters have been incorporated into parabolic equation solutions for range-dependent elastic bottom underwater acoustic problems. These source fields generate parabolic equation solutions that can be used to study development of oceanic T-phases via the process of downslope conversion. More general range-dependence has also been shown to scatter elastic wave energy into water column acoustic modes which then propagate as T-phases. In certain circumstances, sources in the elastic bottom can also cause interface waves at the ocean bottom that contribute to the ocean acoustic field. Both types of waves can propagate long distances and could be source mechanisms for unexplained acoustic signals recorded near the sea floor and below the ray-theoretic turning point. Parabolic equation solutions will be used to study effects of parameters such as frequency, source location, and source type on T-phase and interface wave generation and propagation.[Work supported by ONR.]
The effects of mode structure on coherence in shallow water propagation
Authors: Wylie Jennifer , DeFerrari Harry , Lourenco Felipe
Published: September 2012

In an ideal shallow water propagation channel the sound field is accurately described by normal modes and the mode structure is predictable with clean separated modes. However the real ocean environment is rarely ideal, and variations in bottom bathymetry and water column sound speed are usually present. When fluctuations are small and on the order of a fraction of an acoustic wavelength the sound field propagation is deterministic and any mode pattern deviations are small and slow and the phase response is linear. Here the propagation is considered phase coherent and spatial and/or temporal averaging will produce gain. When the fluctuations increase to the order of ½ to 1 acoustic wavelength the mode patterns becomes distorted such that slow linear fluctuations in phase can no longer describe the propagation. Here coherence is reduced and in some cases completely lost. A unifying theory will be presented linking mode pattern deviations and coherence. PE models will be used to predict mode structure and individual mode correlation will be computed with the ideal case. These mode correlations will be used to estimate temporal and spatial coherence and the results will be compared with data from three shallow water experiments.
Airflow resistance—A comparison between international and american test methods
Authors: Kovacik Marek
Published: September 2012

This paper presents the results of a study to determine differences between two test methods that purport to measure airflow resistance. Airflow resistance can be used to determine the acoustical absorption characteristics of materials. In ASTM C522-03(R2009) method, the air is supplied at a steady rate and the pressure difference across the test specimen is measured. In the ISO 9053/EN 29053 B method, a low frequency acoustic wave is produced by a moving piston. The pressure change measured inside the testing apparatus is directly related to airflow resistivity. In a recent round robin, sponsored by ASTM, samples of various densities were tested using the ASTM method. Airflow resistance was also measured with a Norsonic 1517 Airflow Resistance Measurement System following the ISO method. Differences between methods, effects of sample orientation, and other causes of uncertainty will be presented.
Temporal coherence in Budgerigars (Melopsittacus undulatus)
Authors: Neilans Erikson G. , Dent Micheal L.
Published: September 2012

Auditory scene analysis has been suggested as a universal process that exists across all animals. Relative to humans, however, little work has been devoted to how animals isolate sound sources to create auditory objects. Frequency separation of sounds is arguably the most common parameter studied in auditory streaming, yet it is not the only factor. Elhilali et al. (2009) found that in humans, synchronous tones are heard as a single auditory stream, even at large frequency separations, compared to asynchronous tones with the same frequency separations, which are perceived as two sounds. These findings demonstrate how both timing and frequency separation of sounds are important for auditory scene analysis. It was unclear how animals, such as budgerigars (Melopsittacus undulatus), would perceive synchronous and asynchronous sounds. Budgerigars were tested on the perception of synchronous, asynchronous, and partially overlapping pure tones and budgerigar contact calls. Budgerigars segregate partially overlapping sounds in a manner predicted by computational models of streaming. However, overlapping budgerigar contact calls are more likely to be segregated than pure tone stimuli with the same temporal overlap. These results emphasize the necessity of using complex communication signals when examining complex sound perception processes such as auditory scene analysis.
Abdominal magnetic resonance elastography
Authors: Yin Meng
Published: September 2012

Many disease processes, both focal and diffuse, cause marked changes in cell and tissue mechanical properties. Magnetic resonance elastography (MRE) is a magnetic resonance imaging-based technique for quantitatively assessing the mechanical properties of tissues based on the propagation of shear waves. Multiple studies have demonstrated MRE can be successfully implemented to assess abdominal organs with many potential applications, from detecting diffuse disease processes to characterizing tumors. The first clinical application of MRE to be well documented is the detection and characterization of hepatic fibrosis, which systematically increases the stiffness of liver tissue. In this diagnostic role, it offers a safer, less expensive, and potentially more accurate alternative to invasive liver biopsy. Emerging results also suggest that measurements of liver and spleen stiffness may provide an indirect way to assess portal hypertension. Preliminary studies have demonstrated that it is possible to use MRE to evaluate the mechanical properties of other abdominal structures, such as the pancreas and kidneys. Steady technical progress in developing practical protocols for applying MRE in the abdomen and the pelvis provides opportunities to explore many other potential applications of this emerging technology.
Focused, radially polarized shear wave beams in tissue-like media
Authors: Spratt Kyle S. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F.
Published: September 2012

In the past decade there has been a surge in the optics literature regarding the unique characteristics of focused, radially-polarized light beams. Of particular interest is the existence of a longitudinal component to the electric field in the focal region of the beam, of comparable amplitude to the radial component and yet with a smaller beamwidth [cf. Q. Zhan, Adv. Opt. Photon. 1, 1-57 (2009)]. In the linear approximation there exists a direct analogy between these light beams and radially-polarized shear wave beams in incompressible elastic media, and hence we may interpret the results found in the optics literature as applying to low-frequency shear waves propagating through tissue-like media. When considering nonlinear effects, however, the fact that the gradient of the field experiences a larger gain due to focusing than the field itself implies that the shear wave case is more susceptible to nonlinear behavior than its optical analog. Second-harmonic generation in the focal region of a focused, radially-polarized shear wave beam in a soft solid is investigated. [Work supported by the ARL:UT McKinney Fellowship in Acoustics and by NIH DK070618.]