bluuebunny/crossref_metadata_2025 huggingface dataset:
Korean stops and affricates: Acoustic and perceptual characteristics of the following vowel
Authors: Cho Taehong
Published: October 2005

Despite numerous studies on lax, aspirated, and fortis stops in Korean, few have reported on the role of the following vowel in consonant perception. This paper examines the degree to which vowels convey the phonation characteristics of the preceding obstruents, with a hypothesis: Native speakers utilize vowel’s quality in perceiving the preceding obstruents. This study includes (1) acoustic analyses of VOT, F0, intensity build-up, and vowel length and (2) the perception test, where subjects were instructed to indentify CV syllables using stimuli with consonant portions completely removed. The acoustic analyses indicate that the acoustic characteristics associated with vowels pattern systematically with preceding obstruents (e.g., systematic difference in vowel length). In the perception test, subjects correctly identified the missing consonant 78% of the time, supporting the hypothesis. The probability was higher for the fortis than for the aspirated obstruents: Obstruents with longer VOTs spread less acoustic information into the following vowels, suggesting that the nature of VOT is possibly ‘‘voiceless vowelness.’’ Most wrongly identified aspirated obstruents were misperceived as fortis ones, confirming that the aspirated and the fortis consonants share some acoustic features (e.g., higher F0, rapid intensity buildup). The overall results indicate that following vowels play a pivotal role in consonant perception.
Production and perception of consonant coarticulation in Taiwanese
Authors: Peng Shu-hui
Published: October 2005

Taiwanese coda stop consonants are unreleased, so that their place of articulation tends to be confused with that of the initial consonant of any following syllable. This traditionally is described as place assimilation–i.e., categorical feature change. Recent phonetic theories suggest an alternative description in terms of a continuous variation in degree of coarticulatory overlap between consonants. This study investigates the production and perception of coda consonants before different following onset consonants. Productions by six subjects were analyzed using electropalatographic (EPG) and acoustic measurements. Perception was examined using the concept formation paradigm. Preliminary data suggest that apparent place assimilation in Taiwanese is a noncategorical gestural coarticulation. The latency of the second gesture with respect to the first decreased as speech rate increased, so that gestural reduction was found in the production of every subject in normal and fast speech rates. The dental gesture was deleted more frequently than the velar gesture. In the perception test, the identification of coda place became worse as the latency of the second gesture decreased, so that the coda’s gesture was overlapped more by the following onset gesture.
Aerodynamic evidence of preconsonantal stop lenition in Taiwanese
Authors: Hsu Chai-Shune K.
Published: October 2005

Taiwanese word-final stops lenite intervocalically. In addition, regressive place assimilation occurs optionally in casual speech. It has been suggested that gestural reduction is the crucial articulatory mechanism in place assimilation [J. Jun, UCLA Ph.D. dissertation (1995)]. Based on previously developed methods and interpretations [D. Silverman and J. Jun, Phonetica 51, 210–220 (1994)], oral pressure experiments were conducted to assess whether gestural reduction obtains before a stop consonant in Taiwanese. Data for all nonhomorganic consonant clusters containing a labial constituent were analyzed. Results of pressure measured behind the lips suggest that both oral and nasal word-final stops at all three places of articulation may reduce before a word-initial stop consonant. Reduction was found to be variable, but nonlabials reduce before labials more readily than labial reduction before nonlabials. Variable gestural overlap was also detected in consonant clusters. Word-final gestural reduction is suggested to be a general process, occurring both intervocalically and preconsonantally, but perceived as ‘‘lenition’’ intervocalically and ‘‘assimilation’’ preconsonantally.
Techniques for improved stop and nasal consonant discrimination
Authors: Loizou Philipos C. , Dorman Michael F. , Spanias Andreas S.
Published: October 2005

The automatic recognition of stop and nasal consonants is known to be a difficult recognition task. This paper presents various techniques that can be used to improve the discrimination of stop and nasal consonants. An improved spectral representation for stop consonants is proposed, which unlike other feature representations, emphasizes the mid-to-high regions of the spectrum. A subspace projection approach, which is used as a preprocessing step in a hidden Markov model based system, is also proposed for improved nasal discrimination. This approach finds a transformation matrix which maps the original nasal observation onto a subspace such that the ‘‘distance’’ between the nasals is maximized on the subspace. Two statistical distance measures are investigated for finding the transformation matrix, namely the divergence and the Bhattacharyya measures. Results on stop and nasal consonant recognition will be presented using the subspace approach and the improved spectral stop representation.
Clicks in a Chinese nursery rhyme
Authors: Nathan Geoffrey S.
Published: October 2005

Clicks (speech sounds produced by velaric suction) have been reported in a number of African languages but have never been reported elsewhere in the world. However, several Chinese dialects have been discovered to use clicks in a special children’s version of a traditional nursery rhyme. This paper reports on the nasalized palatal clicks found in two different renditions of this nursery rhyme. The clicks replace normally occurring syllable-initial velar nasals in this special version, which apparently functions as a tongue-twister in those dialects that display this behavior. The clicks are completely integrated within the syllable structure of the words that they occur in, and sound quite similar to those found in Xhosa and !Kung. The paper will present articulatory descriptions and acoustic analyses of the clicks, and there will be an audio tape available for those who wish to hear the data. Some speculation on the origins and functions of the clicks will be presented.
Individual differences and the acquisition of new phonetic categories
Authors: Case Pamela , Tuller Betty
Published: October 2005

Adults’ acquisition of non-native phonetic categories occurs within the context of an individual’s existing phonology. The present work examines (1) the process of acquiring a new phonetic category, (2) the impact of the new phonetic category on nearby, previously existing categories, and (3) transfer of learning to novel contexts. Monolingual American English speakers were required to learn the Hindi voiced, unaspirated, dental stop consonant. First, listeners were asked to identify and judge the goodness of stimuli on two synthetic continua spanning a range from Hindi dental to American English alveolar stop consonants. One continuum was voiced, the other voiceless. In addition, listeners judged the similarities between all possible pairs of stimuli on each continuum. After this perceptual mapping procedure, subjects participated in a two-alternative, forced-choice training program using only voiced stimuli. Progress was monitored throughout training. Following training, the mapping procedure was repeated with both the voiced and voiceless continua. Results are discussed from the theoretical perspective of the nonlinear dynamical approach to learning and transfer in motor behavior presented by Zanone and Kelso [in Swinnen, Heuer, Massion, & Casaer, 461–490 (1994)] and with respect to Best’s perceptual assimilation model and Kuhl’s perceptual magnet effect. [Work supported by NIDCD and NIMH.]
A phonetic study of stress in Korean
Authors: Jun Sun-Ah
Published: October 2005

Stress in Korean (Seoul) has been controversial for many years: Some linguists believe there is word-level stress and others do not. Among those who believe that word-level stress exists, there has been controversy regarding its location: the first or second syllable (H. Lee, 1973), the second syllable (Huh, 1985), or the final syllable (Choi, 1935). Even though it has been shown that there is no fixed acoustic property of stress, researchers have found that stress is detectable based on duration, amplitude and F0 [Fry (1958), Lea (1977), Beckman (1986)]. By examining these prosodic features, this paper investigates whether there is stress in Korean and, if so, what its domain and location are. Words with a reiterated syllable, /na/ or /ta/, were uttered by native Seoul speakers in different prosodic positions. The preliminary results show that Korean stress is not a word-level but a phrase-level stress: The location of the stressed syllable depends on its position in an accentual phrase (Jun, 1993). In addition, the stress falls on either the first or the second syllable of the phrase depending on the number of syllables in the phrase, syllable weight, and the position of the phrase in the sentence.
Modeling the articulatory dynamics of two kinds of stress
Authors: Cohen K. Bretonnel , Beckman Mary E. , Edwards Jan , Fourakis Marios
Published: October 2005

A study reported at an earlier meeting of this Society examined fine-grained timing cues to three levels of stress by comparing jaw kinematics in intonationally accented syllables (with full vowels), unaccented syllables (with full vowels), and completely stressless (reduced-vowel) syllables. For all four speakers in the study, measured values for movement duration, displacement, and peak velocity were consistently largest in the accented syllables and smallest in the reduced-vowel syllables. This study examines the relationships among these kinematic measures using two different models of the underlying gestural dynamics. The first generated shorter (less stressed) syllables by decreasing the latency of the closing gesture relative to the opening gesture without changing the targeted gestural speed or displacement. The second generated shorter syllables by changing the targeted gestural speed, but decreasing targeted displacement more, so as not to increase the predicted velocities. The first model generated predicted durations, which were closer to the observed distribution of durations among the three stress types, whereas the second generated predicted displacements that were closer to the observed distribution of displacements. Neither generated the observed distribution of velocities, suggesting that a hybrid model is necessary.
Variational approaches in the nonlinear theory of fluid-permeable elastic continua
Authors: Grinfeld Michael G. , Norris Andrew N.
Published: October 2005

A new nonlinear governing system for poroelastic fluid-permeable media in Eulerian variables is derived on the basis of Hamilton’s principle for reversible effects and the Onsager–Sedov approach for irreversible effects. The classical (Murnaghan-like) equations of nonlinear elasticity, as well as the governing equations of the ideal and Navier–Stokes fluids, appear to be some special cases of the general governing system. It is well known that the Navier–Stokes equations for compressible fluids provide a correct self-consistent basis for studying a wide variety of nonlinear effects in fluids. The authors believe that the governing system proposed here provides the same opportunities for various nonlinear effects in poroelastic fluid-penetrable media. In particular, it allows one to study the internal structure of shock waves and flutterlike phenomena among others. [Work was supported by ONR.]
Elastic nonlinearity in rock: On the relative importance between higher-order elastic constants and hysteresis
Authors: Van Den Abeele Koen , Johnson Paul , Ten Cate James
Published: October 2005

Rocks are extremely elastically nonlinear, even at strain as low as 10−7. Recent simulations of dynamic elastic pulsed wave experiments and comparison with static and resonance test predictions revealed that the physical mechanism for nonlinearity in rocks cannot be attributed to higher-order nonlinear coefficients alone. Static stress-strain tests and resonance measurements show in addition an undeniable hysteretic behavior of stress and modulus versus strain. Therefore, hysteresis has been introduced into the dynamic nonlinear wave equation by means of a discontinuous term in the modulus. The new theoretical model is based on four parameters: the first and second nonlinearity constants, attenuation, and hysteresis strength. In doing so, rich harmonic spectra and nonlinear waveforms observed in dynamic pulse mode experiments can be simulated using realistic values of higher-order elastic constants and hysteresis. Furthermore, the model provides characterization criteria for rock types depending on the relative importance of hysteresis and nonlinearity parameters. Chalk, for instance, can have large first and second nonlinearity parameters, because it shows a rich harmonic spectrum but no hysteresis. On the other hand, the nonlinear spectra of several sandstones can be attributed almost entirely to the first nonlinear coefficient and to hysteresis. [Work supported by DOE/OBES/UCal.]
Identification of rhythmic forms of speech production
Authors: Cummins Fred
Published: October 2005

An experiment was conducted to elicit stable forms of rhythm in spoken English. Stimuli were constructed, each of which consisted of a repeated series of the words take and cards. While the interval from one take to the next was a constant (1.5 s), the timing of cards relative to this interval was systematically varied. Subjects were instructed to repeat the phrase takeapackofcards, so that the relative timing of take and cards matched that of the stimulus. After some time, the stimulus was switched off, and subjects attempted to maintain the prescribed timing pattern on their own. Although there were eight target timing patterns in the stimuli, the obtained distribution of subjects’ productions was trimodal rather than octomodal. The three modes are hypothesized to correspond to three stable, preferred forms of rhythmic production for this phrase. These data strongly suggest that there is an observable rhythmic basis to English speech production. [Supported by ONR.]
Response to ‘‘Comments on ‘Reflection from a corrugated surface revisited [J. Acoust. Soc. Am. 96, 1116–1129 (1994)]’ ’’
Authors: Chesneaux Jean-Marie , Wirgin Armand
Published: October 2005

The comments of Kazandjian [J. Acoust. Soc. Am. 98, 1813–1814 (1995)] concerning the paper [J. Acoust. Soc. Am. 96, 1116–1129 (1994)] are discussed, notably those concerning the equivalence of the Rayleigh and extinction methods, the identity and convergence of perturbation series deriving from these methods, and the pertinence of numerical computations as indicators of the validity of theoretical predictions.
The effect of signal onset/offset envelope on underwater detection thresholds of a harbor seal (Phoca vitulina)
Authors: Turnbull S. D. , Terhune J. M.
Published: October 2005

The effects of signal onset/offset envelope on the underwater hearing thresholds of a harbor seal (Phoca vitulina) were measured. Pure-tone, 540-ms pulses at 2, 4, 8, and 16 kHz were presented as test signals. An ANOVA revealed that there were no significant differences between repeated threshold measures for abrupt onset/offset signal envelopes versus slow onset/offset signal envelopes [F=4.380, d.f.=(1,18), p≳0.05]. Seal vocalizations which have an abrupt onset/offset may be serving a short-range communicative function by helping the listener determine the direction of a nearby sender.
Where are we now? A 30-year perspective
Authors: Killion Mead C.
Published: October 2005

At one time, most of the things known about hearing aids were wrong. The resulting hearing aid designs often made it more difficult to hear in noise rather than less: In 1970, Tillman etal. reported a 20-dB degradation in the signal-to-noise ratio corresponding to a 50% word-recognition score. The situation has improved because of improved components and especially because of an improved understanding of what a hearing aid can do to help [or make things worse, such as ‘‘filtering out the noise,’’ which unavoidably results in the loss of valuable speech cues as well (Villchur, 1993)]. Most modern hearing aids can provide improved hearing in noise, and some of them can handle high-level noise and music without audible distortion. One design is being successfully used in concerts by members of major symphonies. Nonetheless, even the best—and best fitted—hearing aids typically leave their wearer with a deficit of at least 2–3 dB in tolerable signal-to-noise ratio (mild-moderate loss), often 6–8 dB (moderate loss), and sometimes much more. Objective improvements in signal-to-noise ratio appear needed to close the gap.
Time-frequency display of loudspeakers and electroacoustic impulse response data using cycle-octave wavelet transforms
Authors: Keele D. B. (Don)
Published: October 2005

A cycle-octave time-frequency display is created by plotting the magnitude of the wavelet transform, using a Morlet complex Gaussian wavelet, on a log-frequency scale versus time in number of cycles of the wavelet’s center frequency. This type of display is quite well suited for plotting the decay response of wideband systems, such as the impulse response of a loudspeaker or room, because the time scale is long at low frequencies and short at high frequencies. If the response of typical filters are poltted on this type of display, the resultant 3-D responses are independent of the filter’s center frequency, i.e., the decay response shape of a particular filter remains the same as it’s center frequency is shifted up and down in log frequency. It can be shown that the wavelet transform of a system’s impulse response is equivalent to an aggregate of the tone-burst responses of the system evaluated at equal-percentage-spaced frequencies, where the appropriately scaled and time-reversed mother wavelet acts as the tone-burst excitation signal.
Backscattering from a baffled finite plate strip with fuzzy attachments
Authors: Russell Daniel A. , Sparrow Victor W.
Published: October 2005

A formulation for predicting the effect of fuzzy attachments on the response of a master structure was originally provided by the fuzzy structure theory of Soize. An extension of Soize’s theory was recently developed by Pierce et al. (ASME 1993 Winter Meeting, New Orleans, LA). This new formulation is applied to a finite plate strip simply supported in an infinite rigid baffle. An incident plane-wave pulse is incident upon the plate and the effect of the fuzzy attachments on the target strength is determined. The primary effect of a large number of 1-DOF fuzzy attachments is an apparent added mass and an apparent added damping to the plate. Both of these effects depend directly on the mass distribution of the 1-DOF attachments with respect to their natural frequencies. A representative distribution is considered. It is found that if the most probable natural frequency of the fuzzy attachments coincides with a plate resonance, the amplitude at the target frequency is significantly reduced, the amount of reduction increasing as the total mass of all attachments increases. Plate resonances above the target frequency are shifted upward, and those below are shifted downward.
The development of frequency resolution in humans as revealed by the auditory brain-stem response recorded with notched-noise masking
Authors: Abdala Carolina , Folsom Richard C.
Published: October 2005

Studies of tuning in infants have reported that auditory brain-stem response (ABR) tuning curves generated using low-frequency probes are adultlike by 3 months of age while high-frequency tuning curves remain immature [Folsom and Wynne, J. Acoust. Soc. Am. 81, 412–417 (1987)]. Behavioral studies have similarly reported adultlike low-frequency psychoacoustic tuning curves by 3 months with high-frequency tuning curves immature until approximately 6 months of age [L. Olsho, Infant Behav. Dev. 8, 371–384 (1985); Spetner and Olsho, Child Dev. 61, 632–652 (1990); Schneider et al., J. Exp. Psych.: Human Percept. Perform. 16, 642–652 (1990)]. Prior to this experiment, there have been no ABR studies of the development of frequency resolution for infants older than 3 months. In this study, notched-noise tuning functions were constructed from wave-V amplitude data for 3-month-old, 6-month-old, and adult subjects. Tone-pip stimuli at 1000, 4000, and 8000 Hz (50 dB nHL) were presented simultaneously with notched-noise masking centered at frequencies related to the tone-pip frequency (1/3-oct intervals above and below the probe frequency). By plotting wave-V amplitude across notched-noise center frequency, isointensity tuning functions were generated for the three subject groups at the three probe frequencies. Auditory filter width (Q) and slope (dB/oct) were measured from each notched-noise tuning function in order to quantify degree of tuning. Consistent with previous studies, results showed that 3-month-old infants do not have adultlike tuning for high-frequency stimulation (8000 Hz). In contrast, by 6 months of age, tuning-function width (Q) is adultlike for both high- and low-frequency probes. These results, combined with previously reported evidence that the human cochlea is fully tuned at birth [Abdala et al., submitted to Hear. Res. (1995); Bargones and Burns, J. Acoust. Soc. Am. 83, 1809–1816 (1988)], suggest that immaturities in the auditory-neural system contribute to the broad high-frequency tuning consistently observed in 3-month-old human infants.
The minimum lung pressure to sustain vocal fold oscillation
Authors: Lucero Jorge C.
Published: October 2005

In previous experimental studies it has been observed that the minimum lung pressure to sustain vocal fold oscillation after its onset is lower than the threshold pressure needed to initiate it. This phenomenon is studied analytically using a previous body-cover model of the vocal folds and applying the describing function method to the general case of large amplitude oscillations. It is shown that the phenomenon is a consequence of the nonlinear characteristic of the effective aerodynamic damping introduced by the air pressure acting on the vocal folds. The results predict a value for minimum sustaining pressure equal to half the threshold pressure for a rectangular prephonatory glottis, which is in the order of experimental results.
Finite element modeling of isotropic elastic porous materials coupled with acoustical finite elements
Authors: Kang Yeon June , Bolton J. Stuart
Published: October 2005

In this paper the development of a two-dimensional elastic-absorption finite element model of isotropic elastic porous noise control materials is described. A method for coupling elastic-absorption finite elements with conventional acoustic finite elements is also presented for the cases when the interface between the adjacent air space and the foam is either unfaced or sealed by a membrane. The accuracy of the acoustic/elastic-absorption model has been verified by comparing its predictions with analytical solutions for the case of wave propagation in a foam-filled waveguide. Further, the finite element model has been used to investigate the effect of edge constraints on the surface normal impedance of a foam sample in a standing-wave tube. As expected, edge constraints were found to stiffen the foam acoustically at low frequencies.
Full field tomographic reconstruction of sound fields using TV holography
Authors: Espeland Morten , Lo/kberg Ole J. , Rustad Rolf
Published: October 2005

A vibrating sound source causes periodic variations of the refractive index in the surrounding medium. A light wave passing through the sound field will experience a corresponding variation of its path length which can be measured by interferometric techniques like TV holography. One TV-holography recording represents the integrated optical pathlength in one direction. The sound source is rotated to record cross sections of the field as seen from different directions. By tomographic backprojection of these recordings, afterward the amplitude and phase of the sound field in any plane of the volume are reconstructed.
Spectral statistics for systems with ray splitting
Authors: Oerter Robert N. , Ott Ed , Antonsen Thomas M. , So Paul
Published: October 2005

A finite reverberant system having a discontinuity in some physical parameter will exhibit the splitting of ray trajectories in the high-frequency limit. It is known that this ray splitting can increase the amount of chaos in the ray trajectories [Couchman etal., Phys. Rev. A 46, 6193 (1992)]. This increase of chaos is expected to reveal itself in the eigenfrequency spectrum as a shift away from Poisson statistics and toward the Gaussian orthogonal ensemble (GOE) statistics of random matrix theory. Numerical results are presented that confirm the predicted shift in the spectral statistics. [Work supported by ONR and DOE.]
Hot spots in the newborn vowel space
Authors: Aldridge Michelle A. , Kneeppel Katrena L. , Bower T.
Published: October 2005

The vowels /i/, /y/, /u/, and /unrounded u/ define one surface of the vowel space, whether defined in articulatory or acoustic terms. Adults can give goodness ratings to vowels from the space surrounding prototypic vowels, the prototypic vowels typically obtaining the highest ratings. Does this reflect unlearned structural sensitivities or some averaging process during life? Is it true in newborns? Attractiveness or ‘‘goodness’’ was measured by how long newborns listened to first presentation of a set of vowel stimuli. The longer the listen, the better the newborn perceived that vowel to be. The edges of the surface defined by /i/, /y/, /u/, and /unrounded u/ was broken into 40 steps. Twenty newborns (7–33 h) were presented with 21 stimuli defining two edges of the vowel surface, five infants begining at each corner of the vowel surface. The corner, prototype vowels are preferred over intermediates; even /y/ and /unrounded u/ which do not occur in Texas. However, /i/ and /u/, which do occur in Texas, do elicit more listening than the other two corner vowels. Unlearned, structural sensitivities have been affected by experience in infants as young as 7 h of age.
Advanced acoustic signal detection and localization with lower-order statistics
Authors: Tsakalides Panagiotis , Nikias Chrysostomos L.
Published: October 2005

The importance of extending the statistical signal processing methodology to the so-called alpha-stable farmework is apparent. First, scientists and engineers have started to appreciate alpha-spectra and the elegant scaling and self-similarity properties of stable distributions. Additionally, real life sonar applications exist in which impulsive ocean channels tend to produce large-amplitude, short-duration interferences more frequently than Gaussian channels do. The stable law has been shown to successfully model noise over certain impulsive channels. In this lecture, new robust techniques are proposed for source detection and localization in the presence of noise modeled as a complex isotropic stable process. First, optimal, in the maximum likelihood sense, approaches are presented and the Cauchy beamformer is introduced. Also, subspace methods based on fractional lower-order statistics are developed for sonar applications where reduced computational cost is a crucial design parameter. Finally, simulation experiments demonstrating the performance of the proposed methods are presented.
The mechanical effects of focused shock waves on tissuelike structures
Authors: Sturtevant Bradford , Howard Danny
Published: October 2005

Shock waves focused to strengths sufficient to fracture kidney stones in extracorporeal shock wave lithotripsy (ESWL) injure soft tissue. In a complex organ like the kidney, the injury occurs in a sequence of processes beginning with the mechanical stimulus during or shortly after the passage of the shock wave, followed by a complex series of bio-mechano-chemical responses, terminating with altered function and histology of the organ. This paper presents preliminary results of an invitro study of the initial mechanical stimulus. A planar nitrocellulose membrane of order 10 μm thick immersed in liquid is used as a simple model of tissue membrane. Use of thoroughly degassed water, glycerin, and castor oil at the focus of an electrohydraulic lithotripter controls cavitation, and addition of 20-μm-diam hollow glass spheres to the test liquid simulates the acoustic nonuniformity of tissue. In water, small (∼1-mm diameter) circular punctures are generated by bubble collapse after only one or two shock waves. In noncavitating, uniform liquids the membrane only fails after of order 100 shock waves, by cavitation. With the addition of acoustic nonuniformity in order to increase shear induced by the shock, a different mode of failure occurs; the membrane fails in long (∼1 cm) tears after about 20 shocks. [Work supported by NIH Grant P01 DK43881-01A3.]
A minimum variance unbiased estimator for resolving blurred beamformed images corrupted by signal-dependent speckle noise
Authors: Makris Nicholas C.
Published: October 2005

A variety of methods currently exist for resolving the ambiguity and blurring introduced by beamforming ocean acoustic line array measurements of ambient noise [R. A Wagstaff, J. Acoust. Soc. Am. 63, 863–869 (1978)] and reverberation [N. C. Makris, J. Acoust. Soc. Am. 94, 983–993 (1993)]. However, these methods are not necessarily optimal because they assume that the measured data are deterministic, whereas in actuality they are stochastic. An optimal estimator for resolving such blurred beamformed images produces the minimum variance possible and is unbiased in its output. Estimation theory is used to derive such a minimum variance unbiased (MVU) estimator and to determine bounds on the resolution of such blurred images. The fields measured by the array are assumed to obey circular complex Gaussian random (CCGR) statistics, which have previously been shown to describe a wide variety of ocean acoustic field measurements from towed-array reverberation, to both horizontal and vertical ambient noise. Given CCGR fields, the resulting beamformed images are corrupted with signal-dependent noise known as speckle. Coherence theory for CCGR fields is used to express the MVU estimator for resolving blurred images in terms of the temporal coherence of the received fields and the measurement time.
Omega-to-the-one-third term in dispersion relation for acoustic pulse propagation through turbulence
Authors: Pierce Allan D.
Published: October 2005

The author’s earlier formulation of pulse propagation through turbulence required a somewhat adhoc separation of the effects of large scale and small scale turbulence with the selection of a cut-off turbulent wave number kc that separates the two regimes. A neater-cleaner formulation proceeds with the premise that the frequency dispersion of pulses is caused by that part of the turbulence spectrum which lies in the inertial range originally predicted by Kolmogoroff. The acoustic propagating wave’s dispersion relation has the acoustic wave number being of the form k=(ω/c)+F(ω), where c is a spatially averaged sound speed and where, for mechanical turbulence, the extra term F(ω) must depend on only the angular frequency ω, the sound speed c, and the turbulent energy dissipation ε per unit fluid mass and per unit time. If the turbulence is weak, then the quantity F(ω) has to be of second order in the portions of the turbulent fluid velocity in the intertial range, so, following Kolmogoroff’s reasoning, it must vary with ε as ε2/3. Simple dimensional analysis then reveals that F(ω) is Kε2/3c−7/3ω1/3, the latter factor being as announced in the title of this abstract, and K being a universal dimensionless complex constant. A similar result holds for thermal turbulence. The analysis showing that the separating-out of the effects of turbulence in the inertial regime is in fact possible yields K=−0.37eiπ/3. The dispersion is typically small, but has an accumulative effect that leads to a sizable pulse distortion over large propagation distances. [Work supported by NASA Langley Research Center.]
Processing of log and linear ripple spectra
Authors: Yost William A.
Published: October 2005

Two sets of experiments were conducted involving spectra with sinusoidal ripples of amplitude versus frequency. For one set of stimuli the sinusoidal spectral ripple was on a linear frequency scale while for the other set the ripple was on a log frequency scale. For both sets of stimuli ripple frequency and ripple phase were varied. In experiment I, listeners were asked to determine if a change in ripple stimuli was a ripple frequency change or a ripple phase change. They were also asked to differentiate between log and linear ripples. Except for a few conditions, listeners were unable to differentiate between linear and log ripples and between spatial frequency and spatial phase changes. In experiment II, listeners were asked to discriminate between ripple spectra and flat spectra. The ripple spectral depth required for discrimination was approximately the same for both log and linear ripples. The results will be discussed in terms of suggestions that the auditory system performs a type of spatial frequency analysis similar to that performed by the visual system. [Work supported by NIDCD and AFOSR.]
Evaluation of a computationally assisted low-frequency calibration technique in an acoustic tank
Authors: LeDoux Claude A. , DuBord Regina M.
Published: October 2005

Acoustic tank calibration of transducers using low-frequency pulsed sinusoidal inputs (below 500 Hz) in water has generally been impossible, due to strong, variable signal reflections from the tank walls and air–water interface that corrupt measurements before the transducer response reaches steady state. Since the large tank size needed to overcome this difficulty is impractical, a computational scheme has been investigated for predicting these steady-state responses. Specifically, Prony’s method, applied to the echo-free portion of a response signal, has been employed to generate a mathematical signal model which theoretically can be used to extrapolate the response to any later time, as suggested by Beatty etal. [J. Acoust. Soc. Am. 63, 1782–1794 (1978)]. An experimental assessment of this approach, performed in the Naval Undersea Warfare Center acoustic tank, as well as experimental justification of its validity, will be presented.
Theoretical modeling of nonlinear surface waves
Authors: Hamilton M. F. , Il’inskii Yu. A. , Zabolotskaya E. A.
Published: October 2005

Nonlinear effects in surface waves, like those in bulk elastic waves, are enhanced dramatically by microinhomogeneous features such as cracks and grains that are common in rocks. Since surface waves experience less geometrical spreading loss than bulk waves, nonlinearity can be even more pronounced than in bulk waves. A brief review of theoretical models for studying nonlinear surface wave propagation will be presented. The models are based on the theory developed by Zabolotskaya [J. Acoust. Soc. Am. 91, 2569–2575 (1992)] for nonlinear Rayleigh waves in isotropic solids. In subsequent articles published in the Journal the theory was used to study harmonic generation, waveform distortion, and shock formation in plane waves, cylindrical waves, and diffracting surface wave beams. Radiation from both time harmonic and pulsed sources was investigated. Reported values for second- and third-order elastic moduli were used to calculate coefficients of nonlinearity for a number of rocklike materials. The theoretical model was recently extended to encompass nonlinear Stoneley, Scholte, and Lamb waves, and to include effects of anisotropy and piezoelectricity. Most experiments reported on nonlinear surface waves are associated with the development of nonlinear SAW devices in the 1970s. Several of these experiments will be revisited, and new interpretations of the measurements will be offered. [Work supported by NSF, the Office of Naval Research, and the Schlumberger Foundation.]
Theoretical approaches for computing FAT spreads
Authors: McCammon Diana F.
Published: October 2005

FAT (frequency, angle, and time) spreading is approached theoretically through the Helmholtz integral equation for scattering from random rough surfaces. Using the Kirchhoff approximation, angle spread is readily found to be related to the probability of surface slopes. Various approximate evaluations are discussed for modeling time spread, from numerical ray tracing to integrals over pulse shapes. Solving for the half-power points of the intensity shows the link between angle and time spread. Frequency spread functions are discussed, illustrating the difficulty of using Fresnel phase approximations for higher-order corrections to the Doppler shift.
Application of describing-function theory to a flow-excited resonator
Authors: Kook Hyungseok , Mongeau Luc
Published: October 2005

A theoretical model based on a describing-function theory [T. D. Mast and A. D. Pierce, J. Acoust. Soc. Am. 97, 163–172 (1995)] was applied to the problem of a flow-excited Helmholtz resonator with a complex geometry. The lumped acoustic parameters and flow parameters required in the model were determined both from empirical data and from existing analytical models. Detailed comparisons were made between experiments and theory in order to validate the approach. The results show that the theory provides an alternative to computationally intensive CFD models for predicting the main acoustic characteristics of the resonator system.
Nonlinear coupling between the surface and volume modes of an oscillating bubble
Authors: Mao Yi , Crum Lawrence A. , Roy Ronald A.
Published: October 2005

An experimental study was conducted of the nonlinear coupling between the surface and volume modes of an oscillating bubble. Through this coupling, the surface modes of a bubble can produce monopole sound radiation, which has a higher radiation efficiency than the surface modes. A hydrophone and a hypodermic needle, connected to an air supply, were submerged in water in a small (7.1×7.1×7.7 cm3) sealed cell that was also connected to a regulated vacuum system for control of the ambient pressure. The sound radiation produced by releasing a bubble from the needle was monitored by a hydrophone and displayed on a digital oscilloscope. Two high-speed video cameras simultaneously recorded the radial motion of the bubble and the sound radiation trace as displayed on an analog oscilloscope. At low ambient pressures (i.e., a few cm Hg), it was observed that after the bubble creation sound died out, a sound of the same frequency but with a lower and relatively constant magnitude followed. Therefore, it is believed that these subsequent acoustical emissions are evidence of the coupling between the surface and the volume modes of the bubble. Observation of a constant phase angle between the surface oscillations of the bubble and the radiated sound suggests a causal relationship.
Acoustic parameters of nasalized vowels in hearing-impaired and normal-hearing speakers
Authors: Chen Marilyn Y.
Published: October 2005

One of the more prevalent abnormalities that contribute to reduced intelligibility in the speech of hearing-impaired speakers is inadvertent nasalization. Acoustic analysis of the speech of hearing-impaired children and nasalized vowels of normal-hearing adults indicate the presence of an extra pole-zero pair between the first and second formants and a reduced first-formant prominence. The difference between the amplitude of the first formant and the amplitude of the extra peak, A1-P1, was shown to be a promising measure that correlates with listener judgments of the degree of vowel nasality in utterances of hearing-impaired and normal-hearing children. To obtain further validation of these parameters as measures of nasality, A1 and P1 were systematically manipulated in synthetic utterances. The results of perceptual experiments with a number of synthesized words (of the form bVt) showed somewhat different relative importance of the two parameters, depending on the vowel. High correlation of A1-P1 with the average nasality perception judgments was found for each of the stimuli except those for which the first formant was very close to the extra peak frequency. A procedure was developed for correcting the value of A1-P1 to normalize for different vowels, based on the frequencies of the first two formants.
On equivalence of locally active models of the cochlea
Authors: de Boer Egbert
Published: October 2005

In the literature on locally active models of the cochlea several forms of the model have been worked out in which elements of the organ of Corti are assumed to produce acoustical energy. In these models use is made of a secondary resonance or a place-dependent delay to achieve activity over a limited part of the length of the basilar membrane, and outer hair cells are postulated as sources of energy production. In the present paper it will be shown that several of these models are formally equivalent. That means that they can be reduced to a standard form, and that the only difference resides in the choice and meaning of the parameters. The results of the analysis serve to facilitate the analysis of function and structure in cochlear models containing sources of local activity. In particular, questions of positive versus negative feedback, and the parts played by resonance and impedance-level differences can be resolved unambiguously. The treatment can be extended to models with higher dimensionality, and can also serve to obtain insight in nonlinear phenomena occurring in cochlear models.
Discrimination of changes in the spectral shape of two-tone complexes
Authors: Versfeld Niek J. , Houtsma Adrianus J. M.
Published: October 2005

Discrimination experiments were performed for changes in the amplitude of two-tone complexes. Thresholds were measured, among other things, as a function of bandwidth and center frequency. Usually, the overall intensity was roved in each and every presentation to prevent subjects from using loudness cues. The results show that changes in the spectral shape of broadband two-tone complexes can be perceived with and without a roving intensity level. For narrow-band signals, attempts have been made to explain the results in terms of the EWAIF model [Feth, Percept. Psychophys. 15, 375–378 (1974)]. This model could account for the data for signal bandwidths of 1 semitone or less. Modified EWAIF models did not yield better predictions. Thresholds for a change in the spectral shape were measured as a function of sensation level. The ‘‘near-miss’’ to Weber’s law was not observed. This result is consistent with excitation pattern models.
A computational model for signal processing by the dorsal cochlear nucleus. II. Responses to broadband and notch noise
Authors: Blum Jacob J. , Reed Michael C. , Davies John M.
Published: October 2005

In a previous paper a computational model was developed which was shown to account for most of the essential features of the variety of experimentally observed response maps of type-IV cells in the dorsal cochlear nucleus to pure tones. In the present study, the responses of the same model DCN to broadband noise and notch noise are investigated. It is shown that the previous model qualitatively accounts for the observed responses to these more complex sounds. Predictions of the model for inverted notches and for the behavior of type-IV cell output as notch center is varied for different amplitudes are presented. It is shown that the model is suitable for feature detection of auditory signals and an expansion is given as to how this ability arises from the properties of the stellate, type-II, and type-IV cells and the variations in the connectional patterns that were previously shown to account for the response patterns of type-IV cells to pure tones.
Weakly nonlinear waves and acoustic streaming produced by a vibrating strip flush with a plane wall
Authors: Furuyama Shinji , Inoue Yoshinori
Published: October 2005

The weakly nonlinear propagation of a two-dimensional wave, which is radiated into a half-space from a sinusoidally vibrating strip mounted on a plane wall, is studied theoretically. It is supposed that the wavelength of radiated waves is of the same order as the width of the strip, and that the acoustic Reynolds number is sufficiently large. The entire propagation process, from generation of sound to the stage where the amplitude of a sawtooth wave is saturated, is analyzed in the leading-order approximation. In a near field, linear wave theory is valid to first approximation. The asymptotic form of its time-averaged acoustic intensity can have sidelobes in addition to a central lobe. Acoustic streaming occurs near the strip in the next order, whose flow pattern differs according to a normalized frequency which is less or greater than a critical frequency. In the far field, a simple-wave equation is exactly solved and the subsequent evolution into the sawtooth wave is examined using the equal-areas rule. These two-dimensional waves may be regarded as cylindrical waves with directivity. At greater distances, the amplitude saturation becomes independent of direction.
Detection of speech targets under the divided attention manipulations
Authors: Tseng Chin-Hsing , Tsao Feng-Ming
Published: October 2005

Divided attention tasks were designed to test the following hypothesis: When two dimensions of a single speech stimulus are simultaneously attended to for target detection, one dimension can be processed faster than the other if the former has a higher information value. Targets were (1) a given vowel or any vowels produced by a given speaker, or (2) a given plosive or a specified lexical tone embedded in a syllable, or (3) a specified lexical tone embedded in disyllabic noun or a name for man-made objects. The target occurrence probabilities for the two dimensions were set at 0.10 vs 0.40, 0.25 vs 0.25, or 0.40 vs 0.10 in a given block of trials. Chinese-speaking college students participated in these experiments. It was found that the target detection latency varied inversely with target occurrence probability for either dimension under all these manipulations. A clear performance trade-off pattern was observed for each manipulation; that is, as one dimension received more attention, the processing of the other became less efficient. These results demonstrated that attention can be divided between dimensions of ‘‘speech processing space’’ as cued by the information value. [Work supported by NSC, ROC.]
Low-frequency, direct-path acoustic reverberation near the Mid-Atlantic Ridge
Authors: Caruthers Jerald W. , Novarini Jorge C.
Published: October 2005

In 1991 and again in 1993, the Acoustic Reverberation Special Research Program (ARSRP) of the Office of Naval Research conducted low-frequency acoustic reverberation experiments just west of the Mid-Atlantic Ridge. To support analyses of these measurements, the ARSRP also conducted geological and geophysical surveys of the region, resulting in nearly full-coverage bathymetry gridded to a resolution of 200×200 m. Direct-path reverberation data have been modeled successfully using Lambert’s law applied to the local grazing angle determined from the high-resolution bathymetry. Excellent agreement of this simple model with data shows clearly that, for this region, knowledge of the 2-D seafloor morphology at the proper scale determines the ability to predict reverberation. For a model such as Lambert’s law, which glosses over the details of seafloor microroughness or texture at the scale of the acoustic wavelength (λ = 6 m), the bathymetry scale that is critical is shown to be an order of magnitude or two above the acoustic scale. Lambert coefficients for the region varied depending on sedimentation and local geomorphology. For this region, explaining the success of Lambert’s law and its regional differences might serve as a goal of more detailed theoretical efforts into scattering at the microscale. [Work supported by ONR.]