bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of a finite-difference acoustic propagation model of transcranial ultrasound
Authors: Bouchoux Guillaume , Bader Kenneth B. , Korfhagen Joseph J. , Raymond Jason L. , Ravishankar Shivashankar , Abruzzo Todd A. , Holland Christy K.
Published: September 2012

Adjuvant ultrasound exposure improves rtPA thrombolysis in stroke patients. Transmission of 120-kHz ultrasound through the temporal bone is efficient but exhibits skull-dependent distortion and reflection. Numerical models of acoustic propagation through human skull based on computed tomography (CT) data have been developed. The objective of our study was to validate a finite-difference model of transcranial ultrasound quantitatively. The acoustic fields from a two-element annular array (120 kHz and 60 kHz) were acquired in four ex-vivo human skulls with a calibrated hydrophone (10 kHz-800 kHz frequency range). The spatial distributions of the acoustomechanical properties of each skull were obtained from CT scans and used for simulations. Predicted acoustic fields and waveform shapes were compared with corresponding hydrophone measurements and were in good agreement. Transmitted wave amplitudes were systematically underestimated (14%) and reflected wave amplitudes were overestimated (30%). The acoustic impedance of each skull was likely underestimated from the CT scans. However, high correlation between predictions and measurements (R<+>2<+>=0.93 and R<+>2<+>=0.88 for transmitted and reflected wave amplitudes, respectively) demonstrates that this model can be used quantitatively for evaluation of 120-kHz ultrasound-enhanced thrombolysis. This work was supported by NIH-RO1-NS047603.
Plumbing the depths of Ligeia: Considerations for acoustic depth sounding in Titan's hydrocarbon seas
Authors: Arvelo Juan I. , Lorenz Ralph
Published: September 2012

Saturn’s moon Titan is the only satellite in our solar system with a dense atmosphere and hydrocarbon seas. The proposed Titan Mare Explorer (TiME) mission would splashdown a capsule to float for 3 months on Ligeia Mare, a several-hundred-kilometer wide sea near Titan’s north pole. Among TiME’s scientific goals is the determination of the depth of Ligeia, to be achieved with an acoustic depth-sounder. Since Titan’s surface temperature is known to vary around 92 K, all instruments must be ruggedized to operate at cryogenic temperatures. This paper’s contributions include an approach to infer key acoustic properties of this remote environment, their influence on the development of a cryogenic depth sounder, and on an approach to infer the transducer’s response, sensitivity and performance when unable to perform in-situ calibration measurements or to replicate key environmental conditions. This effort was conducted under the auspices of the Civilian Space Independent Research and Development program from the Johns Hopkins University Applied Physics Laboratory.
Acoustophoresis in gases: Effect of turbulence and geometrical parameters on separation efficiency
Authors: Robert Etienne , Imani Jajarmi Ramin , Steibel Markus , Engvall Klas
Published: September 2012

Advanced particle manipulation techniques based on acoustophoresis have been developed in recent years, driven by biomedical applications in liquid phase microfluidics systems. The same underlying physical phenomena are also encountered in gases and hold great potential for novel particle separation and sorting techniques aimed at industrial and scientific applications. However, considering the physical properties of gases, optimizing the performance of flow-through separators unavoidably requires an understanding of the re-mixing effect of turbulence. In the work presented here we have investigated the effect of turbulence intensity on the separation efficiency of a variable frequency acoustic particle separator featuring a rectangular cross-section with adjustable height. This allows the creation of a standing wave with a variable frequency and number of nodes. The air flow is seeded with alumina particles, 300 nm nominal diameter, and the excitation source is an electrostatic transducer operated in the 50-100 kHz range. In addition to flow and acoustic parameters, the separation efficiency is investigation as a function of geometric parameters such as the parallelism of the resonator walls and the matching between the channel height and the excitation frequency. The measurements made using laser doppler anemometry and light scattering provide guidance for the design of separator configurations capable of advanced separation and sorting tasks with sub-micron particles.
Selected theoretical and numerical aspects of fast volume and surface integral equation solvers for simulation of elasto-acoustic waves in complex inhomogeneous media
Authors: Bleszynski Elizabeth , Bleszynski Marek , Jaroszewicz Thomas
Published: September 2012

Comparative analysis is considered of two fast FFT-matrix-compression based elasto-acoustic integral equation solvers, employing volumetric and surface formulations, and designed to analyze sound propagation inside a human head; in particular to examine mechanisms of energy transfer to the inner ear through airborne as well as non-airborn path-ways, and to assess effectiveness of noise-protection devices. Verification tests involving the fast surface and volume integral equation solvers are carried out comparing their predictions with those following from an analytical solution of field distribution in an elasto-acoustic layered sphere.Resultsiare presented of representative numerical simulations of acoustic energy transfer to the cochlea for a human head model containing a detailed geometry representation of the outer, middle, and inner ear. The geometry model consists of: (1) the outer surface of the skin surrounding the skull and containing (2) the outer ear represented by its exterior surface, the surface of the auditory canal, and the tympanic membrane modeled as a finite-thickness surface, (3) the middle ear consisting of the system of ossicles and supporting structures, (4) the skull described by its external surfaces and including (5) a set of surfaces representing the inner ear (boundaries of the cochlea, the vestibule, and the semi-circular canals). *This work is supported by a grant from US Air Force Office of Scientific Research.
A modeling and simulation suite for design of buried object scanning sonars
Authors: Lee Hunki , Noh Eunghwy , Been Kyounghun , Ahn Hongmin , Moon Wonkyu , Ohm Won-Suk
Published: September 2012

In this talk we highlight a work in progress, concerning the development of a comprehensive modeling and simulation (M&S) suite for design of buried object scanning sonars. The M&S suite is expected to cover almost all aspects of physical and engineering acoustics involved in the design process, ranging from transducers, sound propagation, sediment acoustics, backscattering by buried objects, to sonar image processing. The overview of the M&S suite is given along with a preliminary demonstration in the context of a cylindrical object buried in sandy sediment. [This work was conducted in the Unmanned Technology Research Center (UTRC) sponsored by the Defense Acquisition Program Administration (DAPA) and the Agency for Defense Development (ADD) in the Republic of Korea.]
Elastic properties of coarse grained lead-free solder alloys
Authors: Gladden Josh R. , Tennakoon Sumudu
Published: September 2012

Because of health and environmental concerns about lead, lead-free solder alloys in most consumer electronics have been required in the European Union since 2006. Many of these alloys are prone to mechanical failure over time, leading to less reliable circuitry. The source of these failures is not well known and many have conjectured that the coarse grained alloys become more brittle over time when exposed to elevated temperatures (~100 °C). Our group, in collaboration with Cisco Systems, has recently studied the effects of aging on the mechanical properties of Sn-Ag-Cu (SAC) solder alloys using using both resonant ultrasound spectroscopy (RUS) and conventional pulse-echo methods. With grain sizes on the order of 100's of microns, the heterogeneity of these alloys present a particular problem for RUS and interpretation of pulse-echo data. Resonance data exhibiting the effect of the heterogeneity will be presented and discussed. Elastic moduli derived from pulse-echo methods as a function of temperature and isothermal aging time will also be shown.
Wave number filtering on a finite periodically supported plate: Implications on the vibration field, radiated power, and validity of SEA
Authors: Haberman Robert
Published: September 2012

Preston Smith published and presented a number of papers on wave propagation and sound radiation from periodically supported plates. An excellent reference is, “Radiation from Periodically Supported Fluid-Loaded Plates”, BBN Report No. 3999, January 1979. In these papers he identifies the physics of Bloch wave radiation, coherent scattering from ribs and spatial attenuation. As an extension to Preston’s work, the problem of propagation of a local isotropic wave field on a finite periodically supported plate is considered. The specific question to be addressed is: do the rib supports provide wave number filtering of the isotropic field as it propagates throughout the plate-stiffener system? This question is answered via a series of analytical and finite element models. The implications on radiated power and validity of the SEA isotropic vibration field assumption will be discussed.
A review of recent advances in vibro-acoustic system response variance determination in statistical energy analysis: A tribute to Preston Smith, Jr
Authors: Koch Robert M.
Published: September 2012

Since the pioneering work of Preston Smith, Jr. and Richard Lyon in 1959 in the development of the theory of Statistical Energy Analysis (SEA), followed by many others in the 1960’s on through today, the US Navy has utilized the important SEA vibro-acoustic simulation approach for high frequency self- and radiated-noise predictions of a multitude of undersea vehicles and systems. As a tribute to Preston Smith, this talk will review the current state of research in the determination of the variance/probability distribution about the mean response of a system modeled in SEA. While the subject of system response variance (or confidence interval) has obviously been of interest since the inception of this energy-based statistical method, there has been significant recent research in the literature advancing this area that is worth reviewing. As an additional acknowledgement of Preston Smith’s later important work in the area of underwater cylindrical shell acoustics, the current presentation will also revisit the canonical structural acoustic problem of a point-excited, finite cylindrical shell with fluid loading and compare SEA-derived radiated noise level predictions with a variety of different classical analytical and modern day numerical approach solutions (e.g., FEA, EFEA/EBEA, closed form plate and shell theory solutions).
A range recursive algorithm for random sum acoustic propagation loss prediction
Authors: Clark Cathy Ann
Published: September 2012

The work of P. W. Smith, Jr. includes prediction of the averaged impulse response for sound transmission in a shallow-water channel. His predictions are most applicable in situations for which cycle mixing with range results in randomization of phase interference between modes. In this talk, a calculation of random summation propagation loss for these types of conditions is presented. An integral expression approximating the normal mode sum is reformulated through a change of variable to an integral with respect to cycle number. The resultant formulation leads to a recursive relation in the range variable which enables calculations to be simplified significantly. The integral formulation is shown to successfully reproduce propagation loss with range by comparison to measurements in a number of environments.
Monitoring of corrosion in pipelines using guided waves and permanently installed transducers
Authors: Lowe Michael J. , Cawley Peter , Galvagni Andrea
Published: September 2012

Guided Wave Testing (GWT) of pipelines for the detection of corrosion has been developed over about 20 years and is now a well established method worldwide, used mostly in the oil and gas industry. The established approach is as a screening tool: GWT is used to detect the presence of significant reflectors which are then examined locally in detail using conventional methods of NDE. To date most of the equipment has been developed for deployment solely at the time of test. However recent developments include permanently-attached transducers which can be left in place after testing, for example to allow easier access for future testing at difficult locations such as buried pipes. This is enabling a new approach, in which improved sensitivity may be achieved by detecting changes with respect to earlier reference signals, and also continuous monitoring which may follow degradation during service. The presentation will include a summary of the GWT method and discussion of current research for monitoring.
Estimation of adhesive bond strength in laminated safety glass using guided mechanical waves
Authors: Reis Henrique
Published: September 2012

Laminated safety glass samples with different levels of adhesive bond strength were manufactured and tested using mechanical guided waves. The adhesive bond strength of the test samples was then also evaluated using the commonly used destructive testing method, i.e., the pummel test method. The interfaces between the plastic interlayer and the two adjacent glass plates are assumed to be imperfect and are modeled using a bed of longitudinal and shear springs. The spring constants were estimated using fracture mechanics concepts in conjunction with surface analysis of the plastic interlayer and of the two adjacent glass plates using atomic force microscopy and profilometer measurements. In addition to mode shape analysis, the phase and energy velocities were calculated and discussed. The guided wave theoretical predictions of adhesion levels using energy velocities were validated using the experimental pummel test results. From the attenuation dispersion curves, it was also observed that the S1 mode exhibits attenuation peaks in specific frequency ranges, and that the attenuation of these peaks is sensitive to the interface adhesion levels. Results show that this guided wave approach is useful in the nondestructive assessment of adhesive bond strength in laminated safety glass.
Incorporating expected sparsity of damage into ultrasonic guided wave imaging algorithms
Authors: Michaels Jennifer E. , Levine Ross M.
Published: September 2012

Many imaging methods employing ultrasonic guided waves are based upon delay-and-sum algorithms whereby echoes scattered from sites of damage are constructively reinforced after signal addition. Resolution of the resulting images depends upon such factors as the underlying array geometry, spectral content, knowledge of the propagation environment, and incorporation of phase information. For plate-like structures of engineering interest, geometrical features such as edges, cut-outs and fastener holes contribute to signal complexity and can cause significant image artifacts, which hinders detection and localization of actual damage. However, it is reasonable to make the a priori assumption that damage is spatially sparse. If this assumption is properly incorporated into imaging algorithms, then the resulting images should also be sparse and thus be easier to interpret. Several algorithms are developed and implemented that are based upon sparse reconstruction methods, and their performance on both numerical and experimental data is evaluated in terms of image quality and computational efficiency.
Modeling of nonlinear guided waves and applications to structural health monitoring
Authors: Nucera Claudio , Lanza di Scalea Francesco
Published: September 2012

Research efforts on nonlinear guided wave propagation have increased dramatically in the last few decades because of the large sensitivity of nonlinear waves to structural condition (defects, quasi-static loads, instability conditions, etc...). However, the mathematical framework governing the nonlinear guided wave phenomena becomes extremely challenging in the case of waveguides that are complex in either materials (damping, anisotropy, heterogeneous, etc...) or geometry (multilayers, geometric periodicity, etc…). The present work develops predictions of nonlinear second-harmonic generation in complex waveguides by extending the classical Semi-Analytical Finite Element formulation to the nonlinear regime, and implementing it into a highly flexible, yet very powerful, commercial Finite Element code. Results are presented for the following cases: a railroad track, a viscoelastic plate, a composite quasi-isotropic laminate, and a reinforced concrete slab. In these cases, favorable combinations of primary wave modes and resonant double-harmonic nonlinear wave modes are identified. Knowledge of such combinations is important to the implementation of structural monitoring systems for these structures based on higher-harmonic wave generation. The presentation will also present a specific application of nonlinear guided waves for the monitoring of thermal stresses in rail tracks to prevent buckling.
Ultrasonic waves for the inspection of underwater waveguide structures
Authors: Pistone Elisabetta , Rizzo Piervincenzo
Published: September 2012

The non destructive inspection of immersed structures is popular as it minimizes unexpected and costly failures of important marine structures. In this paper we present a non-contact laser/immersion transducer technique for the inspection of underwater waveguide structures. The technique uses laser pulses to generate leaky guided waves and conventional immersion transducers to detect these waves. To prove the feasibility of the proposed methodology, a laser operating at 532 nm is used to excite leaky guided waves in a plate subjected to different damage scenarios. The plate is immersed in water at constant temperature and damage is first simulated using different weights located in the region of interest, i.e. between the point of the laser illumination and the immersion transducers. Damage is also simulated by engraving a series of notches on the face of the plate exposed to the probing system. The waveforms are then processed using the joint time-frequency analysis of the Gabor wavelet transform, statistical features and advanced signal processing techniques to identify and locate the presence of the defects. The findings show that the probing system and the signal processing algorithm used are able to detect differences between pristine and damaged conditions.
Defect visualization in pipes using a longitudinal guided wave mode
Authors: Lee Hyeonseok , Park Hyun Woo , Sohn Hoon
Published: September 2012

Recently, defect visualization techniques based on guided waves have been developed for pipe inspection. This study advances existing defect visualization techniques in two ways: (1) a fiber-guided laser ultrasonic system, which can operate under high radiation and temperature environments, is used to generate and measure broadband guided waves, and (2) a longitudinal mode instead of a torsional mode is used to detect axial cracks and wall thinning. Using optical fiber probes installed along a circumferential direction of a pipe with equal spacing, a pure longitudinal mode, L(0,2), is launched by axisymmetrically exciting a pipeline structure. The generated L(0,2) subsequently interacts with scattering sources such as defects or pipe boundaries and generate reflected L(0,2) and higher-order modes, L(n,2), (n>0). The reflected modes, L(0,2) and L(n,2), are measured in a pulse-echo manner using the same fiber probes and synthetically processed. By back propagating the dispersive L(0,2) and L(n,2) modes in time and space, this study reconstructs dispersion-compensated L(0,2) and L(n,2) at the scattering sources and thereby visually locates the defects. Numerical simulation and experimental studies are performed to validate the effectiveness of the proposed technique.
Comparing L1 and L2 phoneme trajectories in a feature space of sound and midsagittal ultrasound tongue images
Authors: Sano Keita , Yaguchi Yuichi , Wilson Ian
Published: September 2012

To support the development of pronunciation training systems for non-native (L2) speakers, past research has proposed visualization of a speaker's tongue using ultrasound as feedback showing differences between L2 and native (L1) speakers. However, there has been little or no quantitative assessment combining temporal variation of speech sounds and ultrasound tongue images. We propose a mining method to analyze such temporal differences between L1 and L2 speakers. We firstly construct two eigenspaces: one made from feature vectors of speech sounds using Spectrum Vector Field (SVF) and the other from ultrasound tongue images using Histogram of Oriented Gradients (HOG). Next, we compare the movements of L1 and L2 trajectories. Furthermore, we model the connection of phonemes by finding tongue shapes from adjacent speech sounds, and we indicate the differences between L1 and L2 speakers to make a clear intermediate representation from the feature space. In our experiment, we analyze the differences between L1 and L2 pronunciation by focusing on the temporal trajectories of the feature space. These trajectory differences between L1 and L2 speakers’ speech sounds will be presented. We will also present the feature space of ultrasound tongue images that indicate the intermediate tongue shapes mentioned above.
Perception of speech-in-noise for second language learners and heritage speakers in both first language and second language
Authors: Blasingame Michael , Bradlow Ann R.
Published: September 2012

This study asks whether speech recognition by bilingual listeners in each of their two languages follow complementary or supplementary patterns. Previous studies showed that early bilinguals are disproportionately affected by adverse listening conditions in L2 (Mayo et al., 1997; Shi et al, 2010; Bradlow & Alexander, 2007), but did not measure performance in L1. The current study extends these results using bilingual performance under adverse listening conditions in both languages to determine whether reduced use of the dominant language by relatively well-balanced bilinguals affects performance in L1 as well as L2. We examine two groups of English-Spanish bilinguals: Spanish learners (SL) and Spanish heritage speakers (SHS). Although both English dominant, crucial differences between these groups are L1 (SL=English, SHS=Spanish) and L1-L2 balance (SL=large imbalance, SHS=relatively balanced). Both groups were presented with sentences in English and Spanish in which final keywords varied on three factors: speech style (clear versus plain/conversational), contextual predictability (high versus low), and signal-to-noise ratio (easier versus harder). Results show SHS do not pattern like monolinguals in either language, yet average performance across both languages is higher than SL. This result suggests the overall system SHS maintain is “larger” than SL, but may be more susceptible to noise.
Idiosyncrasy and generalization in accent learning
Authors: Sumner Meghan , King Ed
Published: September 2012

People understand speech well, despite pronunciation variation. Perceptual learning, where listeners are trained with acoustic features ambiguous between two phonemes and subsequently shift their perceived phoneme boundary, is one way listeners may compensate for variation (Norris et al 2003). These perceptual shifts, however, seem idiosyncratic to one speaker (Eisner & McQueen 2005, Kraljic & Samuel 2005), rarely generalizing to new speakers. We propose that lack of generalization is due to lack of experience mapping phonemes to specific continua; previous work uses continua like [s]-[f], whose midpoints rarely occur in speech. Ambiguous tokens that are never heard in real speech may be perceived as specific to the speaker used in training, preventing generalization. Use of a continuum occurring in accented speech, such as the mapping of English tenseness onto vowel duration, allows manipulation of the idiosyncrasy of the mapping. We train 13 listeners on an idiosyncratic duration mapping (lax to short duration, tense to ambiguous duration) and 11 on an Italian accent pattern (lax to ambiguous duration, tense to long), and test generalization to a different speaker. Listeners generalize the Italian accent, and generalize away from the idiosyncratic pattern. This suggests listeners generalize likely accents, treating unlikely patterns as idiosyncratic.
Functional significance of the acoustic change complex, mismatch negativity, and P3a for vowel processing in native-English listeners and late learners of English
Authors: Martin Brett A. , Shafer Valerie , Wroblewski Marcin , An Lee Jung
Published: September 2012

The acoustic change complex (ACC), mismatch negativity (MMN), and P3a all provide indices of the neural processing of the types of acoustic changes that underlie speech and language perception. The goal of this study was to compare neural correlates of vowel processing for contrasts that have been shown to be easy to perceive in native-English speakers but more difficult for native-Spanish speakers. Processing of a vowel change from /I/ to /E/ was compared in a group of late learners of English and a group of monolingual English listeners (n = 15 per group). Preliminary analyses suggest differences in processing of the vowel change from /I/ to /E/ across the groups. Monolinguals processed the vowel change more rapidly and more accurately than bilinguals. The obligatory response to vowel onset showed a larger N1 for the bilinguals compared to the monolinguals. In addition, group differences were obtained in mean global field power (MMN and P3a were longer for bilinguals) and topography (current source density showed group differences for ACC P2 component, MMN, and P3a). Therefore, ACC, MMN and P3a all showed the effects of native language experience; however, these effects were not identical for each component.
Phonemic processing in compensatory responses of French and English speakers to formant shifted auditory feedback
Authors: Mitsuya Takashi , Samson Fabienne , Ménard Lucie , Munhall Kevin G.
Published: September 2012

Past studies have shown that speakers modify their vowel formant production when auditory feedback is altered in order to make the feedback more consistent with the intended sound. This behavior was thought to minimize acoustic error overall; however, Mitsuya et al. (2011) showed different magnitudes of compensation for altered F1 across two language groups depending on the direction of perturbation. Their results seem to reflect how the target vowel is represented in relation to other vowels around it. From this observation, they proposed that compensation is to maintain perceptual identity of the produced vowel, requiring some phonological processes for error reduction. Yet, the results might have been specific to the language groups examined, and/or unique to F1 production. To generalize Mitsuya et al.’s hypothesis, the current study examined 1) different language groups and 2) F2 production. We compared compensatory behavior of F2 for /ɛ/ among French speakers (FRN) and English speakers (ENG) with decreased F2 feedback. With this perturbation, the feedback sounded like /œ/, which is phonemic in French but not in English. The preliminary data suggest that FRN compensated in response to smaller perturbations and showed greater maximum compensations than ENG.
Quantifying the consonantal voicing effect: Vowel duration in an Italian–American community
Authors: Beller-Marino Ylana , Bradley Dianne
Published: September 2012

Cross-linguistically, vowel duration preceding voiced consonants is greater than that preceding voiceless consonants, all else equal (Chen 1970, Mack 1982). Notably, this consonantal voicing effect is larger for English, a presumed instance of language-specific phonological enhancement of a basic phonetic process. The current study asks whether bilingual speakers maintain separate durational settings, and compares consonantal voicing effects across languages in two participant groups: foreign-born Italian speakers who acquired English as young adults, and US-born speakers from the same community who had simultaneous childhood exposure to Italian and English. The complete materials set employed familiar words, e.g., English rib/rip; Italian cubico/cupola, and sampled systematically over vowel height and consonantal place; data reported are drawn from the high-vowel materials subset only. For targets uttered within language-appropriate carrier phrases, both groups exhibited the consonantal voicing effect in each language; both also exhibited the same interaction with language, producing reliably larger effects in English, suggesting that language-specific settings were attained. But crucially, where foreign-born speakers produced a purely phonetic effect in Italian, US-born speakers suppressed phonological enhancement only partially. These findings, plausibly reflecting a degree of interplay between phonologies, are discussed in terms of the circumstances of language learning.
American Chinese learners' acquisition of L2 Chinese affricates /ts/ and /tsh/
Authors: Liu Jiang , Jongman Allard
Published: September 2012

Many studies on L2 speech learning focused on testing the L1 transfer hypothesis. In general, L2 phonemes were found to be merged with similar L1 phoneme to different degrees (Flege 1995). Few studies examined whether non-phonemic phonetic categories such as consonantal clusters in L1 help or block the formation of new phonetic categories in L2. The current study examined the effect of L1 English consonantal clusters [ts] (e.g., the ending of the plural noun ‘fruits’) and [dz] (e.g., the ending of the plural noun ‘foods’) on learning L2 Chinese affricates /ts/ and /tsh/. We studied duration and center of gravity (m1) of L2 Chinese affricates /ts/ and /tsh/ produced by native Chinese speakers, novice American Chinese learners and advanced learners. In terms of duration, both learner groups showed contrast between L2 /ts/ and /tsh/, which is similar to native Chinese speakers’ production. However, for m1, only the advanced learner group showed contrast between L2 /ts/ and /tsh/, which is similar to native speakers’ production while the novice learner group did not show m1 contrast between the two L2 affricates. The duration result can be accounted for by the existence of durational difference between L1 English [ts] and [dz] whereas the lack of m1 contrast between the two L2 affricates for the novice learner group can be accounted for by the absence of m1 difference between L1 English [ts] and [dz].
Modeling learning of the English voicing contrast by Spanish listeners living in the United States
Authors: Llanos Fernando , Francis Alexander L. , Dmitrieva Olga , Shultz Amanda A. , Chapman Rachel
Published: September 2012

The importance of cue covariation in phonetic learning is explored through four experiments investigating perception of stop consonant voicing. Spanish and English show different uses of voice onset time (VOT; the time between consonant burst release and vocalic voicing onset) in cuing voicing perception. English contrasts short lag (<20 ms) with long lag (>20 ms) stops, whereas Spanish contrasts prevoicing (<0 ms) with short lag (>0 ms) stops. Secondary cues may also differ. In English, VOT and onset f0 (fundamental frequency at voicing onset) are positively correlated, and onset f0 plays a role in voicing perception. In Spanish these properties may not be as strongly correlated, meaning that onset f0 may be less relevant to voicing perception. As predicted, Spanish listeners tested in Spain showed a 0 ms VOT boundary with little use of onset f0, whereas English listeners tested in the US showed a 20 ms boundary with moderate use of onset f0. Significantly, Spanish listeners tested in the US showed an English-like VOT boundary, but made even greater use of onset f0 than did English listeners. Computational Hebbian modeling suggests a role for differences in each groups’ experience with specific patterns of VOT/onset f0 covariation.
Featural enhancement of Spanish word-initial stops in clarifications of misheard words
Authors: Schertz Jessamyn L.
Published: September 2012

In an experiment exploring phonetic featural enhancement in Spanish, native speakers were asked to read words aloud, then repeat them when a supposed automatic speech recognizer “guessed” incorrectly (e.g. subject says “basta,” computer displays (in Spanish) “Did you say ‘pasta’?”, subject repeats “basta”). In a previous experiment with the same paradigm, English speakers exaggerated VOT in the second repetition (longer prevoicing for voiced and longer aspiration for voiceless stops) when the incorrect guess was a minimal pair in voicing with the target word. Spanish speakers also had longer prevoicing durations for voiced stops, but unlike English speakers, showed no change in VOT for voiceless stops; in fact, VOT was shorter in the clarification, though not significantly. The differences in how speakers of the two languages manipulated the stops reflects cross-linguistic differences in the phonetic components of the stop contrast. Additionally, Spanish speakers produced fricatives for some of the word-initial voiced stops. Although Spanish voiced stops are realized as fricatives in many environments, they are not expected to be lenited following a pause. The results of this study confirm that speakers use inventory-specific featural manipulations to clarify contrasts, and demonstrate unexpected variability in post-pausal voiced stops in this dialect of Spanish.
Perception and production of second language sound inventory by English-speaking learners of Korean
Authors: Park Hanyong
Published: September 2012

This study investigates the perception of L2 sound inventory and its comparison with L2 production by eleven adult English-speaking novice learners of Korean in a classroom setting. We examined the perceptual identification and production accuracy of Korean consonants and vowels: eight monophthongs /i e ɛ ī u o ʌ ɑ/ both in isolation and following /p t k/ contexts, and fourteen consonants /p p’ ph t t’ th s s’ c c’ ch k k’ kh/ with /ɑ/ in word-initial position. Overall results indicated that most learners were better at production than perception. Such tendency was more apparent for consonants (except /s/) than vowels, for many learners exhibited a high performance in both perception and production of vowels. Results also showed that learners with more accurate production tended to exhibit more accurate perceptual identification. However, such observation applied only to vowels. Further, learners often had difficulty in both production and perception for the same vowels. Findings suggest rate differences in L2 sound learning; learning takes longer in perception than in production, and in consonants than in vowels. Findings also suggest that production-perception link is stronger in L2 vowel development, at least in the case of English speaking learners of Korean.
Factors affecting the perception of foreign-accented speech by native and non-native listeners
Authors: Tamati Terrin N.
Published: September 2012

Previous research has shown that several factors influence the perception of foreign-accented speech. Beyond talker-related factors, such as native language, length of residency, and age of acquisition, other factors, such as listener experience, listening context, and lexical characteristics, play an important role. To futher investigate these issues, the current study explored the perception of foreign-accented speech by native speakers of American English and Korean learners of English. In an accent rating task, listeners evaluated English sentences produced by native and non-native speakers (Korean and Mandarin) for strength of accent. Sentences contained three key words that varied by lexical frequency (high or low) and phonological neighborhood density (high or low). The same listeners also completed a sentence recognition task with a similar set of materials in which they listened to sentences and typed in the words they recognized. Results showed that lexical frequency and neighborhood density, overall, significantly influenced perceived accentedness and recognition accuracy for both groups. However, these effects were mediated by the native language of the talker and listener. These findings support previous research showing lexical frequency and density effects in the perception of foreign-accented speech and suggest that these effects may interact with talker and listener background.
Processing interactions between segmental and suprasegmental information in English and Mandarin Chinese
Authors: Lin Mengxi , Francis Alexander L. , Llanos Fernando , Dmitrieva Olga , Chapman Rachel
Published: September 2012

In this study, a Garner selective attention task is used to identify cross-linguistic differences in attention to vowels, consonants and tones. In previous research, Tong et al. (2008) reported that, in Mandarin Chinese, consonantal and vocalic variability interfered more with tone processing than vice versa (asymmetric integrality), in contrast with the findings of earlier studies (Lee & Nusbaum, 1993; Repp & Lin, 1990). However, while these earlier studies examined both English and Mandarin Chinese listeners, Tong et al. (2008) did not study English speakers because of cross-linguistic differences in tone discrimination. The present study extends this work to examine interactions between these properties in English as well as Mandarin Chinese, using stimuli in which the consonantal, vocalic and tonal differences are linguistically meaningful in both languages, and normalizing for cross-linguistic differences in discriminability. It is predicted that Chinese results will replicate those of Tong, et al. (2008), while English listeners may show more symmetric integrality between segmental and tonal information than in previous studies since these pitch contours are prosodically meaningful and corrected for discriminability. Results will be discussed with respect to the role that linguistic knowledge plays in determining processing dependencies between segmental and suprasegmental information.
Information-based performance measures for model-based estimation
Authors: Sullivan Edmund J.
Published: September 2012

Classical estimation is conventionally evaluated via the Cramer-Rao Lower Bound on the estimate. When prior information is available, Bayesian estimation can be used if this information is available in statistical form. However, when the prior information is in the form of a physical model, such as in a tracking scheme, it is not clear how much improvement will be provided, since it is not in statistical form. Here it is shown how this problem can be dealt with using the Fisher information matrix by introducing the model into a Kalman estimator. Since the state error covariance provided by a steady-state Kalman estimator is the inverse of the Fisher matrix, it directly provides a statistical measure of the information provided by the model. Then by relating the Fisher information matrix to the Kullback-Liebler distance, it is shown how the Fisher matrix is scaled to provide its information in bits. The model can then be evaluated as to how much information it provides to the estimator. An example using a moving towed array as a bearing estimator will be presented. It will be quantitatively shown that inclusion of the array motion in the estimator will improve the estimation performance
Exploiting differences in underwater acoustic signal and noise distributions to improve signal detection in low signal-to-noise ratio
Authors: Pyzdek Andrew T. , Culver R. L. , Bissinger Brett E.
Published: September 2012

Traditional models for acoustic signals and noise in underwater detection utilize assumptions about the underlying distributions of these quantities to make algorithms more analytically and computationally tractable. Easily estimated properties of the signal, like the mean amplitude or power, are then calculated and used to form predictions about the presence or absence of these signals. While appropriate for high SNR, quantities like the mean amplitude may not give reliable detection for SNR at or below 0 dB. Fluctuation based processors, utilizing additional statistics of received pressure, offer an alternative form of detection when features of the received signal beyond changes in mean amplitude are appreciably altered by the presence of a signal. An overview of fluctuation based processing will be given, with a focus on the underlying statistical phenomena that grant this method efficacy. Work sponsored by the Office of Naval Research in Undersea Signal Processing.
Coherent processing of shipping noise for ocean monitoring
Authors: Lani Shane W. , Sabra Karim G. , Roux Philippe , Kuperman William , Hodgkiss William
Published: September 2012

Extracting coherent wavefronts between passive receivers using cross-correlations of ambient noise may provide a means for ocean monitoring without conventional active sources. Hence applying this technique to continuous ambient noise recordings provided by existing or future ocean observing systems may contribute to the development of long-term ocean monitoring applications such as passive acoustic thermometry. To this end, we investigated the emergence rate of coherent wavefronts over 6 days using low-frequency ambient noise (f < 1.5 kHz) recorded on two vertical line arrays-separated by 500m- deployed off San-Diego CA in ~200m deep water. The recorded ambient noise was dominated by nonstationary distributed shipping activity with the frequent occurrence of loud isolated ships. Noise data were first processed to mitigate the influence of these loud shipping events in order to primarily emphasize the more homogenous and continuous background ambient noise in the frequency band. Furthermore, the coherent noise field propagating between the VLAs was beamformed using spatio-temporal filters to enhance the emergence rate of specific coherent wavefronts. This presentation will discuss various strategies for the selection of these spatio-temporal filters (either data-derived or model-based) in order to improve the continuous tracking of these coherent wavefronts over 6 days.
Estimation of a broadband response with dilation process compensation at very low signal to noise ratios
Authors: Gendron Paul J.
Published: September 2012

Challenges of estimating broadband acoustic response functions at low signal to noise ratio (SNR) are due to both their varying sparsity and the varying spatio-temporal dynamics of each acoustic arrival. Acoustic responses can be quite sparse over the delay-Doppler-angle domain exhibiting large regions that are relatively quiet. The arrivals may share significant Doppler processes due to platform motion or may be driven independently by boundary interactions. Because of this estimation must be adaptive across delay-Doppler and angle with any single fixed estimator inadequate. One means of constructing such an estimator is to view each angle-Doppler-frequency slot as either ensonified or not. A mixture model can be employed for this purpose to describe the behavior of the acoustic response over received signal duration, aperture, and bandwidth. The posterior mean is derived and shown to be soft shrinkage operator of the conventional Wiener filtered coefficients under each of the components of the mixture. This estimator can be employed for bulk dilation estimation as an alternative to a phase locked loop. The posterior variance is derived and compared conventional Wiener filtering. The resulting adaptive structure is applied to M-ary orthogonal signaling sets taken in diverse shallow water environments at very low SNR. This work was supported by the Naval Innovative Science and Engineering Program and the Office of Naval Research.
A comprehensive study of the Bellhop algorithm for underwater acoustic channel modelings
Authors: Huang Xiaopeng
Published: September 2012

Ray tracing is one of the most conventional methods for modeling underwater acoustic sound propagation, and the Bellhop algorithm is a highly effcient ray tracing program, written by Michael Porter as part of the Acoustic Toolbox. In this abstract, based on the introduced Bellhop algorithm, we select several typical underwater acoustic environments so as to study how to model their channels and analyze their channel properties. Simulation results will investigate the following aspects of channel modeling and perperties: ray tracing, eigen-ray tracing, coherent transmission loss, channel impulse reposne, coherence time. In addition, simulation results will compare the performance difference with variant environmental parameters, such as sound speed anomaly and wavy surface.
Information content of an acoustic field propagating in an ocean waveguide
Authors: Finette Steven
Published: September 2012

It is intuitively clear that, in some sense, waves carry “information” concerning both their source characteristics and their interaction with boundaries and/or sound speed inhomogeneity in the propagation path. This presentation addresses the issue of how one can estimate the maximum rate that an acoustic field can transfer information in an ocean waveguide, based on the properties of wave propagation. Information theory is the natural framework for addressing this question, relating wave propagation and communication concepts; it is applied here for the example of a Pekeris waveguide. Using properties of the propagation operator, information-theoretic arguments applied to the propagated field allow for the transfer of information along independent communication channels in the waveguide and an explicit expression for the channel capacity is obtained. The latter represents an upper bound on the error-free transfer of information from a source to a point in the waveguide by use of the propagated field. Work supported by the Office of Naval Research.
Modeling uncertain source depth in range-dependent environments
Authors: James Kevin R. , Dowling David R.
Published: September 2012

Efficient and accurate estimation of the uncertainty in a transmission loss calculation is important for tactical applications of underwater acoustic propagation calculations. Uncertainty in source depth can contribute significantly to the overall transmission loss uncertainty. The unique relationship between source depth and transmission loss motivates a different approach to uncertainty estimation than that used for other environmental and sound-channel parameters. Prior research has shown that in a range-independent environment, source depth uncertainty can be efficiently modeled using the principles of reciprocity. This presentation describes a new approach to uncertainty estimation in range-dependent environments, based on the assumption that the relationship between source depth and transmission loss is approximately governed by the adiabatic approximation on a local scale. Transmission loss predictions are taken from RAMGEO results to solve for the unknowns in the resulting approximate formulation. By modeling the relationship between source depth and transmission loss, approximate uncertainty bounds can be generated for transmission loss predictions. Results are provided for simple up-sloping and down-sloping range-dependent environments, for frequencies from 100 Hz to several kHz, and for ranges of several kilometers. [Sponsored by the Office of Naval Research, Code 322OA.]