bluuebunny/crossref_metadata_2025 huggingface dataset:
Diagnostic performance comparison of the Chartis System and high‐resolution computerized tomography fissure analysis for planning endoscopic lung volume reduction
Authors: Gompelmann Daniela , Eberhardt Ralf , Slebos Dirk‐Jan , Brown Matthew S. , Abtin Fereidoun , Kim Hyun J. , Holmes‐Higgin Debby , Radhakrishnan Sri , Herth Felix J.F. , Goldin Jonathan
Published: February 2014

Background and objective

Endobronchial valve (EBV) therapy is optimized in patients who demonstrate little or no collateral ventilation (CV). The accuracy of the Chartis System and visual assessment of high‐resolution computerized tomography (HRCT) fissure completeness by a core radiology laboratory for classifying CV status was compared by evaluating the relationship of each method with target lobe volume reduction (TLVR) after EBV placement.

Methods

Retrospective HRCT fissure analysis of a study population who underwent catheter‐based measurement of CV followed by complete occlusion of the targeted lobe by EBV. Accuracy, sensitivity, specificity, positive predictive value and negative predictive value of the HRCT fissure analysis and the catheter‐based measurement of CV for predicting TLVR was determined.

Results

Accuracy for correctly classifying TLVR with EBV was similar for Chartis System and HRCT fissure analysis (74 vs 77%). The sensitivity and specificity of the Chartis measurement were 86% and 61% and those of HRCT fissure analysis 75% and 79%. Patients with TLVR ≥350 mL had statistically significant improvement in respiratory function, exercise performance and quality of life measures.

Conclusions

When evaluating patients for likelihood of successful EBV therapy, the Chartis System CV assessment and HRCT fissure analysis appear to have comparable accuracy. Both techniques were found to be beneficial for EBV procedure planning.
Lymphangiosarcoma in 12 dogs: a case series (1998–2013)
Authors: Curran K. M. , Halsey C. H. C. , Worley D. R.
Published: February 2014

Lymphangiosarcoma (LAS) is an uncommon malignant neoplasia arising from lymphatic endothelium; little information exists regarding therapy. Single institutional retrospective review for canine LAS histopathology diagnoses over a 15‐year period yielded 12 dogs. Ten dogs were presented for a mass and/or swelling at cervical, trunk or limb regions. Prior to diagnosis, 10 dogs received empiric wound therapy. Cytology performed in 10 consisted of mild inflammation. Survival ranged from 60, 168 and 876 days for three dogs with palliation; 90 days with prednisone in one; 182 days with chemotherapy in one; 240, 267, 487, 630 and 941 days for five receiving surgery; and 574 days for one receiving surgery, radiation and chemotherapy. One dog is alive with recurrence at 243 days following surgery and carboplatin chemotherapy. Clinical improvement existed in LAS dogs receiving multimodal therapies. Early tissue biopsies are recommended for progressive oedematous lesions of unknown origin.
Two-terminal vertical memory cell for cross-point static random access memory applications
Authors: Tong Xiaodong , Luo Jun , Wu Hao , Liang Qingqing , Zhong Huicai , Zhu Huilong , Zhao Chao
Published: February 2014

In this work, the authors propose a 4F2 (F is the length of half pitch) memory cell with a vertical PNPN structure (silicon device with 4 layers doped with p-type, n-type, p-type and n-type dopants, respectively) to increase static random access memory (SRAM) integration density compared to the traditional 6T SRAM cell with an area of 90 ∼ 150F2. Thanks to the simple two-terminal configuration, the cross-point structure with proposed cell can be used in memory design, to achieve the highest density in planar complementary metal oxide semiconductor (CMOS) technology and to be implemented potentially in future three-dimensional integration. Experimental results demonstrate that the fabrication of proposed memory cell is compatible with CMOS process, little impact by process variation and reliability issues. Calibrated simulations display that the proposed cell can be programmed at nanosecond level speed with acceptable power consumption in most memory applications.
Stage acoustics as affected by an array of apertures incorporated into the orchestra shell of a stagehouse coupled auditorium
Authors: Summers Jason E. , Shimizu Yasushi
Published: February 2014

A number of performance halls incorporate into their design a volume (or ‘‘chamber’’) surrounding the stage platform and coupled to the stage platform through the orchestra shell. Bass Performance Hall utilizes this design concept, while incorporating into the orchestra shell an array of apertures backed by adjustable doors. Measurements have been made to assess the impact of the adjustability of these doors on the soundfield of the stage platform. Consideration was given to both the early and late portions of the soundfield. Variations in impulse response derived measures, in the spectra of early reflections, and in the coupling behavior are presented. These are examined in view of existing models for the reflection and transmission properties of apertures and for the decay of coupled spaces. [Research supported by the Bass Foundation.]
Consideration of the propagation loss of the direct sound with change in seat conditions
Authors: Shimizu Yasushi
Published: February 2014

Reviewing excess attenuation of the direct sound by seats in concert hall acoustics gives the propagation loss by the performers absorption on the stage platform and diffraction of the front seats as well as seat dip effect in low frequency spectrum. Scale model experiments with 1/10 scale model in anechoic chamber were conducted at YAMAHA Acoustic Research Laboratories, Hamamatsu, focusing on propagation loss by (1) diffraction due to various geometrical conditions of the seating row in front of the listening position and (2) attenuation by the seat rows in front of the listening point. The results show the excess attenuation in middle and high frequency spectra. The optimum height between two adjacent seating rows is more than 1.3 feet and the number of seat rows are less than five seats. Normalized SPL referenced to SPL measured at 6.6 feet over the listening point is presented to be effective for evaluating excess attenuation. Concert Hall at Niigata Performing Arts Center was designed with consideration of these scale model experiments. Measurement data of normalized SPL and power spectra of orchestra sound in this hall are presented. 2284,2284
A five-channel microphone system for detecting 3-D acoustic image sources
Authors: Choi Chulmin , Kim Lai-Hoon , Doo Se-Jin , Oh Yang-Ki , Jeong Dae-Up , Sung Koeng-Mo
Published: February 2014

Measuring three-dimensional behavior of early reflections in a sound field has been an important issue in auditorium acoustics, since they are found to be strongly correlated with the subjective experience of spatial impression in rooms. A conventional way of detecting the direction and relative amplitude of reflections is to utilize a four-channel microphone system. This system, however, has the inherent possibility of missing some important reflections while exploring the early part of reflections. A new measurement system, which has five microphones on the apex of a tetrahedron and at the center of gravity, is proposed in the present work. The proposed system enables us to find more early reflections accurately, which previous four-channel microphone systems might miss. A peak detecting pair matching algorithm, which gives dominant peaks of impulse response automatically by typical iteration, was adopted, since we should find exact peak positions of measured impulse response in order to calculate source positions accurately. In the present paper, the theoretical backgrounds and features of the five-channel microphone system are presented. Also, some results from experiments using the system are discussed. Experimental results clearly show the advantage of the five-channel microphone system over the conventional four-channel microphone system. [Work supported by Korean Research Foundation Grant KRF-1999-1-310-004-3.]
An experiment in the use of resilient materials in orchestra riser design
Authors: Hoffman Ian B. , Talaske Richard H. , Harrison Byron W.
Published: February 2014

An experiment was assembled under extremely limited time and space constraints to investigate the acoustic effect of resilient materials in orchestra riser design. The riser was a portable, box-type riser for assembly on a flat concert platform, not a lift-type riser. The primary goal of the inquiry was to maximize lateral vibration transfer through the riser (from celli, basses, etc.) without detrimentally affecting airborne sound radiation from the riser. A portion of a full-scale riser was mocked up, including sections of differing elevation. Various design configurations of the riser allowed experimentation with and without resilient materials, and with resilient materials placed at different positions within the riser structure. The experiment was conducted within a reverberant volume. The riser was excited by mechanical shakers and by a cello, independently. Vibration measurements were captured using accelerometers on the riser, and airborne sound pressure levels were captured by a distant microphone. Initial results suggest that the use of resilient materials in certain configurations can considerably increase lateral vibration transfer through the riser (as compared to rigid construction), without significant compromise to airborne radiation from the riser.
Acoustic scattering by a buried object with a compliant top in a rigid porous material
Authors: Velea Doru , Waxler Roger , Sabatier James M. , Hickey Craig J.
Published: February 2014

Recently, a method for the detection of landmines buried a few inches below the surface of the ground has been developed at the University of Mississippi. This method utilizes acoustic-to-seismic coupling and measures the particle velocity of the insonified ground surface on- and off-target with a Laser Doppler Vibrometer. As part of the on-going theoretical effort to explain the measurements, this paper is concerned with acoustical scattering from an object buried in a rigid porous half-space. The object is assumed to be a rigid right circular cylinder with the exception that its top can move in the vertical direction in a pistonlike fashion with a mechanical resonance at around 100 Hz. A boundary element method has been employed to predict the on-target/off-target particle velocity ratio. Comparisons with observations are made. [Work supported by the U.S. Army Communications-Electronics Command Night Vision and Electronic Sensors Directorate.]
Acoustic landmine detection: Poroelastic model and elastic wave models
Authors: Zeng Yanqing , Liu Qinghuo
Published: February 2014

Acoustic waves can be a viable tool for the detection and identification of landmines and unexploded ordnance (UXO). Design of acoustic instruments and interpretation and processing of acoustic measurements require accurate numerical models for acoustic wave propagation in heterogeneous soil with buried objects. Two numerical models will be compared in this work: the soil is treated as an elastic material in the first model, and as a poroelastic material in the second model. A multidomain pseudospectral time-domain method is used for the elastic model, while a finite-difference method is used to solve Biot equations in the poroelastic model. Acoustic wave response of a buried landmine is investigated with both methods. When the soil is treated as a fluid-saturated poroelastic medium, additional attenuation is automatically introduced via the relative motion between solid frame and pore fluid. Thus the poroelastic model is presumably a more accurate model; however, the elastic model requires less computation time. This work will study several important scenarios such as landmines buried in dry sand, in wet sand, and in mud. A comparison between results of the PSTD model and results of the poroelastic model is performed to characterize the regime of validity for the elastic model.
3-D multidomain PSTD for elasticity
Authors: Zeng Yanqing , Liu Qinghuo
Published: February 2014

A 3-D numerical modeling scheme is developed in general curvilinear coordinates by using a multidomain pseudospectral time-domain (PSTD) method. The computational domain is naturally divided into subdomains of piecewise homogeneous, curvilinear quadrilaterals conforming to the problem geometry. These curvilinear quadrilaterals are then mapped onto a unit square, where the spatial derivatives are approximated by the Chebyshev PSTD method. Characteristic conditions and physical boundary conditions are used to patch the solution between adjacent subdomains. A newly developed unsplit perfectly matched layer (PML) is used to absorb outgoing waves at the computational edge. This multidomain PSTD algorithm allows natural incorporation of curved boundaries into the numerical scheme, thus providing more increased flexibility and accuracy than the conventional finite-difference method. The numerical scheme is validated by analytical solutions and by other numerical methods. Applications of this multidomain PSTD method will be shown for acoustic landmine detection.
The perceptual interaction between the pitch and timbre of musical sound
Authors: Marozeau Jeremy P. , de Cheveigné Alain , McAdams Stephen , Winsberg Suzanne
Published: February 2014

The perceptual dependency of the timbre of musical sounds on their fundamental frequency (F0) was examined through two timbral dissimilarity experiments. In Experiment 1, subjects judged timbral dissimilarity between pairs of stimuli produced by 12 musical instruments equal in F0, duration, and loudness. There were three sessions, each at a different F0 (B2, Db3, Bb3). In Experiment 2, the same stimuli were presented in pairs with a constant difference in F0. Two sessions corresponded to two different intervals (B2-Db3 and B2-Bb3). Subjects were instructed to ignore pitch difference. The results are interpreted in terms of an evolution of timbre space as a function of F0. Experiment 1 produced dissimilarity matrices that were similar at different F0s, suggesting that the relative positions of instruments within the timbre space varied little with F0. Experiment 2 produced dissimilarity matrices that were symmetrical, suggesting further that F0-dependent displacements within the timbre space are small. Patterns of dissimilarity were similar with or without an F0 difference, showing that subjects could ignore a constant difference in pitch when making timbral dissimilarity judgments. Results suggest that the perception of timbre is relatively independent of pitch and can be abstracted across differences in F0 under these conditions.
Infants’ perception of transposed melodies
Authors: Kim Daniella A. , Werner Lynne A.
Published: February 2014

It has been suggested that infants are similar to adults in their perception of tone chroma, in the perceptual similarity of notes in octave relationships [Demany and Armand (1984)]. In music, note pitches are defined by height (frequency distance) and chroma (key). The current study further examines this question. Seven- to nine-month-old infants’ perceptions of transpositions of six-note tonal melodies were measured using an observer-based procedure. Once given a background melody subjects were trained to respond to an entirely different training melody and not to a simple transposition. Once that discrimination had been learned, transposed versions of the background melody were introduced. If infants perceive tone chroma as adults do, they should learn this discrimination more quickly for an octave transposition. In fact, infants learned to ignore a transposition by a fifth more quickly than transpositions by an octave. The implication is that infants found melodies that were transposed by a smaller distance in frequency as more perceptually similar to the background melody than they did for the octave transposition. A possible conclusion is that octave transpositions of whole melodies have special perceptual status for infants of this age range. [Work supported by NIDCD Grant No. DC00396.]
Auditory streaming without spectral cues
Authors: Grimault Nicolas , Bacon Sid P. , Micheyl Christophe
Published: February 2014

Spectral features are powerful cues in the perceptual organization of sound sequences. The ‘‘peripheral channeling’’ explanation of stream segregation predicts that the perception of fusion or fission in sequences, in a repeating ABA format, depends on the degree of spectral overlap of the A and B sounds. Nevertheless, previous studies have shown that other factors can also affect auditory stream segregation. Sequences of fully unresolved complex tones, bandpass filtered in the same frequency region, have been shown to perceptually split apart into two streams when the fundamental frequencies of the complexes are widely separated [Grimault et al., J. Acoust. Soc. Am. 108, 263–271 (2000)]. In the present experiment, normally hearing adults heard rapid alternations of a pair of flat-spectrum, sinusoidally amplitude-modulated broadband noise bursts. These noise bursts were segregated based on differences in modulation rate, as determined with a constant stimulus procedure as well as with a procedure in which segregation responses were collected continuously while the modulation rate of B was swept up or down during a block of trials. [Work supported by Fondation pour la Recherche medicale and NIDCD.]
Perceptual learning and attentional cues in nonsimultaneous masking
Authors: Rose Marina M. , Hartley Douglas E. H. , Moore David R.
Published: February 2014

This study investigated training effects in three nonsimultaneous masking conditions, and the possible role of an attentional cue. Three groups of six participants trained on seven consecutive days on either (i) backward masking (BM, 0-ms delay), (ii) combined forward and backward masking with a short inter-masker delay (10-ms, FBS) or (iii) combined forward and backward masking with a long inter-masker delay (110-ms, FBL). The signal was a 10-ms, 1-kHz tone pip, and the masker was a 300-ms, 1.6-kHz wide noise (40 dBSPL/Hz), centered at 1 kHz. Training sessions had 15 runs (30 presentations/run), using a 2AFC, maximum-likelihood procedure. The FBS condition showed the highest amount of masking, followed by the BM and FBL conditions, respectively (p<0.05). A small but significant improvement was found between training days when all three groups were combined (p<0.001). Pre-training data showed, for most subjects, lower FBL than BM thresholds. This could indicate that the first noise burst in the FBL condition did not mask the signal, but rather acted as a temporal and attentional cue, helping to ‘‘listen at the right time.’’ [Work supported by the National Health Service, the Wellcome Trust, and the Medical Research Council.]
The impact of labeling versus detection training on performance in an asynchrony-detection task
Authors: Mossbridge Julia A. , Wright Beverly A.
Published: February 2014

It is not clear which training methods yield the fastest improvement on perceptual skills. To address this issue, performance on a detection task was compared following training on a labeling or detection task. The labeling task was to determine, for each presentation, whether the onsets of two tones were synchronous or asynchronous. Tone onsets were separated by one of six durations. The detection task was to determine which of two presentations contained tones with asynchronous onsets. The duration between tone onsets was varied adaptively to establish the asynchrony-detection threshold (79% correct detections). In both tasks, the tonal frequencies were 0.25 and 4 kHz. Labeling-trained listeners (n=11) had detection thresholds lower than those of untrained controls (n=6) following just 600 labeling trials (p=0.008). In contrast, detection-trained listeners (n=6) had detection thresholds lower than controls only following 3660 detection trials (p=0.027), 2160 trials on the asynchrony-detection task plus 1500 trials on related temporal-acuity tasks. Thus, labeling training appears to improve performance on an asynchrony-detection task more quickly than detection training itself. By increasing our understanding of perceptual learning processes, these data may aid the treatment of individuals with disorders in auditory perception. [Work supported by NIDCD.]
Specificity of learning in an auditory asynchrony-detection task
Authors: Wright Beverly A. , Fitzgerald Matthew B. , Mossbridge Julia A.
Published: February 2014

The ability to determine whether the onsets of two tones at different frequencies are asynchronous is a measure of temporal acuity. Learning in this asynchrony-detection task and its generalization to untrained frequencies and temporal-acuity tasks was explored. For six listeners, asynchrony-detection thresholds for tones at 0.25 and 4 kHz improved from 79 to 20 ms with 4320 training trials. A z-score analysis revealed that trained listeners learned significantly more than untrained controls on the trained condition, but only slightly or no more than controls on: (1) the trained task at two sets of untrained frequencies (0.5 and 1.5 kHz, 0.75 and 1.25 kHz), and (2) three untrained temporal-acuity tasks at the trained frequencies (offset asynchrony detection, onset temporal order, and offset temporal order). This generalization pattern parallels that seen when the trained task was to determine the onset order of two tones [B. A. Wright and J. A. Mossbridge, J. Acoust. Soc. Am. 107, 2882 (2000)]. Thus, learning in both asynchrony-detection and temporal-order tasks appears to be mediated by task-specific, frequency-dependent mechanisms. By increasing our understanding of temporal-acuity mechanisms and their plasticity, these data may guide the treatment of related hearing disorders. [Work supported by NIDCD.]
Unsigned coding of stimulus change
Authors: Hafter Ervin R. , Gallun Erick , Bonnel Anne-Marie , Edwards Brent , Viemeister Neal
Published: February 2014

Various studies have pointed to a special importance for stimulus transients in such diverse areas as the overshoot in masking and onset dominance in sound localization. Evidence that the internal representation of transience may be unsigned is found in cases where listeners readily detect a change in the ongoing stimulus without successfully identifying the direction of that change. We will review these results and present new data on sensitivity to change without sign in such dimensions as frequency and lateral location. Unusual sensitivity to transience has implications for the perception of natural scenes, where change per se may represent the code for simple alerting signal. [Work supported by grants from NIH, DC00087 and DC00683.]
Are cognitive processes involved in the perceived degree of urgency of auditory warning signals?
Authors: Guillaume Anne , Pellieux Lionel , Chastres Veronique , Drake Carolyn
Published: February 2014

Studies on the perceived degree of urgency of auditory warning signals have demonstrated that the greatest sense of urgency is created by sequences with a high fundamental frequency, many irregular harmonics, and fast sequence rate (Edworthy et al., 1991). However these effects disappeared when subjects were under high workload. In order to further investigate the cognitive processes involved, listeners’ perception of two sets of warning sounds were tested: one constructed following Edworthy’s indications, and a second composed of real alarms currently used by the French airforce. A first group of listeners evaluated the perceived degree of urgency between pairs of alarms. A second group quantified the perceived difference between the two alarms. A multidimensional analysis demonstrated that the spatial distribution of the constructed alarms was similar for both tasks. However, for the real alarms, a different pattern was observed: Some alarms were classified as nonurgent although their acoustical characteristics would have indicated a high-urgency classification. The conclusion is that the perceived degree of urgency is determined by both low-level perceptual factors and more complex cognitive processes involving long-term memory and personal experience.
A documentation of phonetic detail in onset-embedded words
Authors: Crosswhite Katherine , Masharov Mikhail , McDonough Joyce M. , Tanenhaus Michael
Published: February 2014

As part of a study of online processing of onset-embedded words, we documented phonetic-level properties of speech production, such as duration differences, that may cue for word identification, segmentation and/or lexical access. Forty nouns (20 pairs like cap/captain, doll/dolphin) were placed in sentences in three frames (nuclear, prenuclear, and utterance-final position). Each sentence was read, then pronounced from memory by eight speakers randomly ordered. In keeping with previous research, instrumental analyses revealed strong effects of syllable count on vowel duration [Klatt, J. Phonetics 7, 279–312 (1979)] and initial consonant VOT [Lisker and Abramson, Lang. Speech 10, 1–28 (1967)]. A similar effect on initial consonant duration was also found. These effects were stable across speakers, words and contexts, suggesting they may be available as cues to overall word length in online segmentation. To test this, the noun pairs of one speaker were cross spliced to produce congruous and incongruous tokens, and presented to listeners in a ‘‘visual world’’ eyetracking paradigm [Allopenna et al., J. Mem. Lang. 38, 419–439 (1998)]. We will report on whether beneficial durational cues of congruous tokens and/or potentially misleading incongruous cues had more influence on online word segmentation of our subjects. [Work supported by NIH and NSF.]
Similarities in acoustic modeling for /r/ and /l/
Authors: Espy-Wilson Carol Y. , Boyce Suzanne E.
Published: February 2014

It is well known that acoustically American English /r/ and /l/ show similar F1 and F2 values, with /l/ showing a high F3 and /r/ showing a low F3. Stevens [Acoustic Phonetics, 1998] models tip-down bunched /r/ and light /l/ with similar tongue configurations and lateral acoustic paths around the tongue. Two major articulatory differences in this model are the more forward position of the tongue/palate contact for /l/ vs /r/ and the longer constriction for bunched /r/ vs /l/. Ong and Stone [Phonoscope 1 (1998)] note that the /l/ and /r/ in their data showed very similar pharyngeal volumes, accounting for the similarity in F1–F2 patterns for these segments. In this paper, we explore the possibility that these variants of /r/ and /l/ share acoustics mechanisms for generating F1 and F2, and that the difference in F3 for /l/ vs /r/ arises primarily from palatal constriction length and front cavity shape.
Temporal trading relationship between singletons and geminates in different vowel contexts
Authors: Al-Khairy Mohamed
Published: February 2014

Length is phonemically contrastive in both consonants and vowels in Arabic. The goal of this study is to examine whether a trading relationship exists between the duration of singletons and geminates in the environment of short and long vowels in Arabic. Preliminary results based on duration measurements of 48 tokens of word-medial bilabial stop singletons and geminates spoken by four speakers suggested that, as expected, geminates are always longer (2.6 times on the average) than singletons. Long vowels are always longer (2.45 on the average) than short vowels. A trading relationship, however, exists between consonant and vowel durations. First, short vowels became significantly shorter when occurring before geminates. This is true only when the vowel following the geminate is also short. Second, geminates preceding short vowels are significantly longer (3.2 vs 2.3 times on the average) than geminates preceding long vowels. To see if these preliminary results also hold true for other types of stop consonants in Arabic, more data will be collected. Similarities and differences in the trading relationship between these consonants and vowels will be examined. Cross-language comparisons regarding the trading relationship between singletons and geminates, and their neighboring vowels will be discussed.
Quality of front vowels before /r/
Authors: Clark Michael J. , Hillenbrand James M.
Published: February 2014

The vowels /i/ and /I/ are not contrastive before /r/ in American english, and the phonetics literature is equivocal about which symbol to use for the nucleus in words such as beer. Similarly /e/ and /ε/ are not contrastive before /r/, and the literature contains varied references to one or the other in words such as bear. Trained listeners disagree about representing the vowel in /r/-final words. Ten men and ten women recorded monosyllables containing /i,I,e,ε/, with initial /b/ and /h/ and with no final consonant or with final /d/ and /t/. For example, the /b/-initial high front series was bee, bead, beet, bid, bit. Additionally an /r/-final set (beer, bear, hear, hair) was recorded. Acoustic measurements included the first two formants. Formants for /i,I,e,ε/ in /d/-final and /t/-final syllables (and for /i,e/ in open syllables) were typical of those measured in an earlier study of subjects from the same region. The high front vowel in /r/-final syllables (beer and hear) showed formant values intermediate between /i/ and /I/, but closer to /i/. The mid front vowel (in bear and hair) fell entirely within the range seen for /e/. Listening tests using synthetic vowels and backward versions of the original syllables will be discussed. [Work supported by NIH.]
Duration and rate effects on English vowel identification by native Spanish listeners
Authors: Gottfried Terry L. , Berman Adam M.
Published: February 2014

Several American English vowel contrasts are specified by co-varying formant frequency and duration information. Listeners alter their vowel identification according to speaking rate, apparently making judgments about relative vowel duration. Two series of spectral continua were previously created from natural speech, ‘‘beat-bit’’ and ‘‘pat-pet,’’ varying F1 and F2, and syllable duration [Berman et al., J. Acoust. Soc. Am. 105, 1402 (1999)]. These syllables were inserted into sentence contexts of two rates (normal and fast). Longer syllable duration led to more ‘‘beat’’ and ‘‘pat’’ responses; faster rate contexts also led to more ‘‘beat’’ and ‘‘pat’’ responses. The present research tested native speakers of Spanish on their use of duration and rate context in English vowel identification. Despite the absence of Spanish vowel contrasts based on duration, native Spanish listeners were significantly affected by syllable duration and sentence rate in their identification of the ‘‘beat-bit’’ contrast. They also showed a significant duration effect for ‘‘pat-pet,’’ but the magnitude of this duration effect was significantly smaller for these non-native listeners than for native listeners, and there was no significant effect of sentence rate. With less English experience, non-natives might show even smaller effects of duration and sentence rate.
Center of gravity effects in the perception of virtual formant transitions
Authors: Iyer Nandini , Jacewicz Ewa , Feth Lawrence L. , Fox Robert A.
Published: February 2014

When F2 and F3 of vowels are separated by up to 4.3 Barks (6.3 ERBu) and amplitude modulated to change their spectral centroid over time, listeners perceive a transition similar to that in two-formant diphthonglike vowels [Lublinskaja, 1996]. This study replicates Lublinskaja’s finding relating to Russian vowels and extends its application to the consonant-vowel (CV) transitions in /wi/ and /ju/ in English. Stimuli were two-formant or three-formant CVs generated by an upward (/wi/) or downward (/ju/) transition of F2 over the frequency range Δf=100−800 Hz, in steps of 100 Hz. For the three-formant CVs, F2 and F3 were separated by the same Δf as in the two-formant CVs, and their amplitudes were modulated so as to move the spectral centroid up or down. The differences in amplitude between F2 and F3 were either 10 dB or 20 dB. The stimuli were 88 ms in duration. Listeners identified the stimuli in a one-interval, forced-choice identification procedure. Results for the English CV combinations are discussed in relation to the findings reported in Lublinskaja’s study. [Research supported by a grant from The Ohio State University College of Social & Behavioral Science to L. Feth and an INRS Award from NIH to R. Fox.]
Perception of relative formant amplitude for /i/ and /I/ in English
Authors: Jacewicz Ewa
Published: February 2014

This work investigates listeners’ sensitivity to variations in the intensity of F2 and F4 for the English /i/-/I/ distinction using four-formant synthetic vowels. Two nine-step /i/-/I/ continua were synthesized with the amplitudes of F2 and F4 increasing or decreasing in steps of 2 dB. During 2AFC discrimination tasks, listeners were able to detect the 2-dB difference for both formants. /i/ was perceived as more natural with decreasing intensity of F2 and as less natural with increasing intensity of F2. The opposite was observed for /I/. Stepwise intensity changes of F4 were perceived as a difference in timbre for both vowels but not as a difference in naturalness. These data suggest that, perceptually, the patterns of relative formant amplitude provide information about the naturalness of /i/ and /I/ in English. The selective auditory sensitivity to the differential contribution of the intensities of F2 (variation in naturalness) and F4 (variation in timbre) is manifested when the 2-dB difference is detected for both frequency peaks. [Work supported by an INRS Award from NIH to R. Fox.]
Statistical analysis of acoustic Green’s functions in a shallow ocean environment
Authors: Chapin Sean R. , Ioup George E. , Ioup Juliette W. , Smith George B.
Published: February 2014

Knowledge of statistical properties of acoustic Green’s functions can assist in the development of effective blind deconvolution algorithms for enhancing the detection and classification performance of active and passive sonar systems. One hundred synthetically generated Green’s functions have been produced representing the acoustic propagation of signals in a given shallow ocean environment. Fourier analysis is performed on the Green’s functions and various statistical properties are calculated in both the time and frequency domains, including examination of properties such as the mean, variance, and the third- and fourth-order moments in both domains. Statistics are also generated for the entire ensemble of Green’s functions as a function of time and frequency. A similar statistical analysis is conducted on the autocorrelation of each of the Green’s functions in both domains. Synthetic noise-free signals are produced by convolving the Green’s functions with representative source signals. Statistical analysis is performed on the resulting signals in both domains for comparison to the results obtained using the Green’s functions alone. Results include large phone-to-phone variations in kurtosis of the Green’s functions and ensemble average kurtosis increasing sharply with time and decaying to zero. [Research supported by ONR.]
Time-reversal operator applied to broadband active sonar
Authors: Fromm David M. , Gaumond Charles F.
Published: February 2014

The decomposition of the time reversal operator (DORT) is a single-frequency technique that isolates scatterers using a system of multiple sources and receivers [Prada et al., J. Acoust. Soc. Am. 99, 2067–2076 (1996)]. The application of this technique to a broadband active sonar system is shown through simulations in a realistic oceanic environment using RAM PE and a coherent reverberation model. A broadband signal containing reverberation, noise, and a target return is simulated. The broad bandwidth allows point targets or clutter to be isolated in range. The returns of interest are then time windowed, Fourier transformed, and DORT processing is applied. By propagating the eigenvectors of the time reversal operator to create time reversal images, the character of the return can be evaluated. [Research sponsored by ONR.]
Iterative deconvolution for source recovery from multipath degraded signals
Authors: Larue James P. , Ioup George E. , Ioup Juliette W. , Smith George B.
Published: February 2014

Known ocean propagation Green’s functions can be used to recover an estimate of the source in underwater acoustic passive detection. Good estimates of the source improve the performance of classification algorithms. Since convolution models the propagation, deconvolution using the Green’s function as the impulse response produces an estimate of the source. In the presence of moderate amounts of noise, deconvolution methods degrade due to the extreme noise sensitivity of the process. Iterative deconvolution has been shown to be more robust in the presence of noise than some other techniques due to the effect of a gradually changing window that need not be pushed to convergence. Iterative techniques are more difficult to apply for oscillatory data than for non-negative data because conservation of area does not provide a robust normalization. Iterative deconvolution techniques are tested for noise performance in source recovery and compared to other methods. [Research supported by ONR.]
Matched field processing classification
Authors: Abawi Ahmad T. , Schey Phil , Hodgkiss W. S.
Published: February 2014

Matched field processing (MFP) has traditionally been performed using vertical line arrays. During the Shallow Water Cell Experiment SWellEx-96, which was conducted off the coast of San Diego in the spring of 1996, it was shown that MFP could also be done using horizontal line arrays (HLA). The MFP correlation using the 250-m long HLA used in this experiment was large enough for detection, but because of the high sidelobes, classification by depth was not possible. However, simulations predicted that the sidelobe levels for an approximately 500-m long HLA would be small enough to make classification by depth possible. To verify this prediction, the SWellEx-99 experiment was conducted in spring of 1999. During this experiment, which was conducted in approximately 200 m of water, a number of large (∼500 m) horizontal line arrays were deployed. A J15-3 source, which transmitted multi-tone signals at various levels, was towed along various tracks. In this paper, data from the SWellEx-99 experiment are used to examine the detection and classification performance of adaptive matched field processing on large horizontal line arrays.
Robust adaptive beamforming for hydrodynamic self-noise rejection
Authors: Premus Vincent E. , Kogon Stephen M.
Published: February 2014

White noise gain (WNG) is a metric widely used in the radar community for limiting the degree of adaptivity of an adaptive beamformer (ABF). Constraining adaptation of an ABF algorithm has two key effects: (1) protection against self-nulling associated with steering vector mismatch, and (2) limitation of white noise gain associated with squinting a beampattern to place a null on a mainlobe interferer. Hydrodynamic self-noise, or cable strum, commonly manifests itself as a source of mainlobe interference for passive acoustic towed horizontal line arrays. Cable strum is the result of vibrations excited in the array body by vortex shedding in the presence of flow. Strum is particularly detrimental on beams near endfire and typically exhibits very high dynamic range. As such, it requires an aggressive adaptation strategy for its effective removal. In this work, a white noise gain constraint for the rejection of cable strum is derived based on the scaled orthogonal projection approach of Cox et al. [IEEE Trans. ASSP 35 (1987)]. Tradeoffs involved in balancing strum rejection performance against mismatch-induced signal self-nulling are examined. [Sponsored by the Dept. of the Navy, under Air Force Contract No. F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and not necessarily endorsed by the U.S. Air Force.]
An experimental investigation on a direct blind equalizer for underwater acoustic multiple FIR channel
Authors: Liu Jianmin , Wang Yingmin , Cao Xiangrui , Zhang Zhengqi
Published: February 2014

A blind equalizer removes the distortion caused by intersymbol interference (ISI) without the need for training sequences. In order to get the complete phase information of the ISI, high-order statistics have to be used to find the equalizer taps. However, L. Tong et al. have shown that most channels can be identified from the second-order cyclostationary statistics through fractionally spaced equalizers. This result has stimulated considerable research activities in fractionally spaced channel identification and equalization. In this paper a single-input multi-output (SIMO) channel blind equalizer for an underwater acoustic communication system is considered. A direct blind equalization scheme was investigated by simulations, which is a novel unsupervised adaptive equalizer and was suggested by J. Labat first for single-input single-output (SISO). An interactive matched processing (MP) is added for the SIMO case. The work verified the prediction that the linear equation form of the direct blind equalizer lends itself naturally to adaptive solutions and optimum combinations of the equalizer outputs and improved performance over existing algorithms in terms of mean-square error and probability of error in the equalized data.
Signal processing for acoustic surveillance of the land environment
Authors: Ferguson Brian
Published: February 2014

Surveillance systems that rely on the propagation of sound in the atmosphere are not constrained by electromagnetic line of sight and offer the advantages of being passive, lightweight, compact and covert. Such systems are unattended in their operation and are often deployed in remote areas. To demonstrate the scientific principles that underpin the operation of such systems, various narrow-band and broadband signal processing algorithms are applied to real acoustic data from both single and multiple sensors. In one example, the acoustical Doppler effect enables the flight parameters and blade-passage frequencies of turboprop and rotary wing aircraft to be estimated from the time-frequency signal analysis of spectrogram data. In another example, the acoustical Lloyd’s mirror effect is used to extract the flight parameters of a jet aircraft. Other examples deal with the application of generalized cross-correlation processing to the detection, localization and tracking of aircraft, ground vehicles and weapon fire. Wideband cross-correlation with differential Doppler compensation is required for the acoustic tracking of high-speed sources when the sensors are widely separated and phase tranform prefiltering is required to suppress the ambigouous peaks in cross-correlograms caused by the presence of strong narrow-band lines in the source spectra of air and ground vehicles.
Backscattering from empty and water-filled tilted cylindrical shells due to leaky helical flexural waves: Comparison and ray theory
Authors: Blonigen Florian J. , Marston Philip L.
Published: February 2014

For tilt angles smaller than the meridional ray coupling condition previously investigated [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998)], helical rays on empty and water-filled steel shells can significantly enhance the backscattering. These contributions are compared and modeled in the present work. Such contributions in the water-filled case are found to be weaker in amplitude, which is to be expected since additional energy is lost through radiation leaked to the inner fluid. A modified ray theory taking into account the increased radiation damping was compared with experimental results for the earliest helical wave arrival, yielding satisfactory agreement. However, the energy lost to the interior of the shell may be at least partially recovered, as internal rays can excite additional leaky waves on the shell. Contributions from rays with one internal chord inside the cylinder were superposed with those of the first helical wave, and the resulting backscattering amplitude was nearly that of the air-filled case for the first helical wave alone. This shows that we may regard the ray theory for the empty shell as an upper bound for corresponding amplitudes observed in the water-filled case. [Work supported by ONR.]
Effect of bottom ripple on detection of a buried object using shallow-grazing-angle underwater sonar
Authors: Lim Raymond
Published: February 2014

Sound penetration into the seafloor at shallow (subcritical) sonar grazing angles has been a topic of much discussion lately because measured levels can be much higher than expected based on simple propagation models assuming a flat seafloor. A popular mechanism for explaining this penetration is based on diffraction of energy into the bottom by seafloor roughness. For objects buried in the bottom, this holds the promise for enhanced long range detection with sonar as long as the backscatter by the roughness itself does not overpower the echo from the object. Here the detectability of a sphere buried under roughness in the form of anisotropic wave-induced ripple is investigated by modifying a scattering solution that combines a stochastic perturbative description of the roughness with a deterministic description of the sphere response. [See Lim et al., J. Acoust. Soc. Am. 107, 1246–1262 (2000).] Comparison with predictions for an isotropic, power-law seafloor roughness at a given rms amplitude demonstrates greater high frequency detection capability with rippled seafloors over a wide range of illumination angles relative to the ripple direction. Comparisons with experimental data are also discussed. [Work supported by ONR.]
Measurements of the acoustic properties of bubbly liquids and partially voided polyurethane solids in the resonance regime
Authors: Wilson Preston S. , Roy Ronald A. , Carey William M.
Published: February 2014

Complete understanding of sea-surface scattering, shallow water volume scattering, and bottom interaction requires the understanding of frequency-dependent acoustic propagation in bubbly media. Because of the high attenuation encountered at and near the range of resonance frequencies associated with bubble size distribution, experimental measurements in this regime are difficult, and for many specific cases, have not been obtained. Using an impedance tube method similar to one previously described [J. Acoust. Soc. Am. 106, 2291(A) (1999)], measurements of the acoustic impedance of bubbly fluids in the vicinity of individual bubble resonance have been obtained. The measurement procedure will be briefly summarized, and contrasted with the previously reported method. Results obtained over a range of frequencies and void fractions with known size distributions will be presented and compared to existing theory. In addition, the acoustic behavior of partially voided polyurethane spheres and plates has been studied using the present impedance tube method. Evidence for collective oscillation of these structures will be shown. [Work supported by ONR.]