bluuebunny/crossref_metadata_2025 huggingface dataset:
On explaining intrinsic vowel duration differences: An electromagnetic midsagittal articulometer (EMMA) study
Authors: Turk Alice , Matthies Melanie , Perkell Joseph , Svirsky Mario
Published: October 2005

The purpose of this study is to determine whether intrinsic vowel duration differences arise from an explicit timing control strategy or solely from the distance an articulator travels. Presumably, a difference in control strategy would be reflected in a change in the relation of peak velocity to distance traveled, or in the amount of time position is maintained. An EMMA system was used to track movements of points on the tongue and jaw during the production of /dVs/ (V=/e, E, æ, a, inverted vee/) tokens in a constant frame at two different speaking rates. Measurements were made of target position, distance traveled, and peak velocity for each gesture toward and away from the vowel target. Preliminary results from one speaker suggest that the duration of articulatory movement can be well predicted by articulatory distance and peak velocity alone. Furthermore, all of the unreduced vowels measured in the study showed a similar relationship between peak velocity and displacement, suggesting that the same control strategy was used for all of them. [Work supported by NIH.]
On the perceptual characteristics of ‘‘speech gestures.’’
Authors: Carré René , Chennoukh Samir , Divenyi Pierre , Lindblom Björn
Published: October 2005

The notion of ‘‘speech gesture’’ or ‘‘phonetic gesture’’ has been developed as a theoretical construct during the past few years. For present purposes, the term is specified as a ‘‘phonologically significant task defined on the vocal tract area function.’’ A given task generally involves the coordination of the movements of several articulators. It appears reasonable to expect speech gestures to have perceptual characteristics like the following: (a) Within certain limits, the time course of speech gestures is not important; (b) within certain limits, the precise synchronization of two, or more, gestures (e.g., constriction displacement and lip opening) is also unimportant; (c) vowel reduction is a natural consequence of speech gesture characteristics. The commands of the distinctive region model were studied as possible speech gestures. Preliminary tests show, as hypothesized, that there are no significant perceptual differences (a) when the shape of a gestural transition is changed to be linear, quadratic, logarithmic, or cosine; (b) when the time separation between two gestures varies from −30 to +30 ms; (c) when gestural dynamics (transitional rate of change) is kept constant but the target is not reached (because of movement undershoot).
The articulatory kinematics of two levels of stress contrast
Authors: Cohen K. Bretonnel , Beckman Mary E. , Edwards Jan , Fourakis Marios
Published: October 2005

Intonation pattern and syllable duration are thought to be the most salient perceptual cues to phrase stress. However, intonation is an inherently ambiguous cue, since not all English pitch accents involve higher pitch on the accented syllable, and because there are stress contrasts at a lower level, where stress cannot be equated with accentuation. Duration, too, is ambiguous, since it can cue other prosodic contrasts, such as phrasal position. This study examines finer-grained timing cues to stress. A strain-gauge system was used to examine jaw opening and closing movements in /popen ayep/ sequences in intonationally accented full-voweled syllables, unaccented full-voweled syllables, and completely stressless (reduced-vowel) syllables produced by four speakers. Measured values for movement duration, displacement, and velocity were consistently larger in accented than in unaccented full-voweled syllables. However, these differences were nowhere near as large as the differences between full- and reduced-vowel syllables. Reduced syllables also had steeper velocity-displacement relationships, suggesting a durational difference at the level of gestural dynamics as well. However, no such consistent difference was observed between accented and unaccented full-voweled syllables. These results support the notion that stress contrasts are not uniformly interpreted in the phonetics at different levels.
The IPA problem
Authors: Ladefoged Peter
Published: October 2005

Every few years it is appropriate to review our knowledge of the phonetic structures of the world’s languages and try to assess how many different speech sounds there are. Problems arise because it is not easy to say whether two sounds occurring in different languages are the same or not. Two sounds are definitely different if they distinguish words within a language. But if they occur in different languages this test cannot be used. This is the basis of the IPA problem. The International Phonetic Association tries to provide a way of symbolizing every distinct speech sound, but it cannot tell whether two sounds are potentially distinct when they have been observed only in different languages. The data from recent phonetic studies indicate that there are limitless ways in which the sounds of one language can differ from another, but that the number of parameters along which sounds can vary is fairly small. In most cases the variation in the sounds that occur in different languages is the result of the use of a different value of one of the parameters, rather than the use of some novel parameter that has not been observed in other languages.
High vowel devoicing in Turkish
Authors: Jannedy Stefanie
Published: October 2005

Jun and Beckman (ICSLP94) explain vowel devoicing in Japanese and Korean in terms of gestural overlap [Browman and Goldstein, LabPhon1 (1990)]; the glottal gestures for preceding and following voiceless consonants overlap to a greater or lesser extent with the glottal gesture for high vowels. The devoicing of the four short high Turkish [i barred eye y u] can be explained by the same model which predicts that vowels are more likely to undergo devoicing if they are short and the adjacent voiceless consonants have strong and large glottal opening gestures. This study evaluates influencing factors such as precedingandfollowingenvironment, rate, stress, and syllabletype. Subjects read 210 words positioned utterance initially in a carrier phrase at three rates. Faster rates and lack of stress facilitated devoicing most. As in Japanese and Korean, there were more devoiced vowels before following stops than before following fricatives, since vocal fold vibration ceases gradually before fricatives, but abruptly before stops. Devoicing also occurred in utterance-initial position. This result is less easy to interpret in terms of the model, since only the following laryngeal gesture can overlap with the vocalic gesture. More devoicing occurred in open syllables, where vowels are significantly shorter in Turkish.
Control of lip closure in stop consonant production
Authors: Löfqvist Anders , Gracco Vincent L.
Published: October 2005

Studies applying mechanical perturbations to the lower lip and the jaw have shown a trade off between movements of perturbed and unperturbed articulators in making the lip closure for a bilabial stop. While this concept is attractive, evidence for such trading relationships in normal speech has remained elusive, partly due to methodological problems. This study examines the vertical positions of the upper and lower lip at closure for bilabial stops. An electromagnetic transduction system was used to track receivers on the upper and lower lips, and the lower incisors for transducing jaw movements. The speech material consisted of VCV sequences where the first vowel was /a/, the middle consonant /p,b/, and the second vowel /i,a/; stress occurred on the second vowel. Preliminary results from three subjects showed upper lip positions at closure to occur over a range of 0.3 cm; the range for lower lip positions was 0.5 cm. Examination of 40 tokens for each subject revealed a positive relationship between upper and lower lip positions at closure, with correlation coefficients ranging from 0.5 to 0.7. The results will be discussed in relation to theories of speech motor control. [Work supported by NIH.]
An analysis of the variation of vocal tract configurations in continuous speech utterances
Authors: Kaburagi Tokihiko , Honda Masaaki
Published: October 2005

This paper studies the variation of vowel and consonant articulation to examine the invariant features of phoneme-specific vocal tract configurations. The establishment of these features may be one of the goals of organizing articulatory movements, and they can be useful in constructing models of those movements. Articulatory data were gathered with a magnetic position-sensing device that traced the position of receiver coils placed on the lower jaw, upper lip, lower lip, and tongue in the midsagittal plane. Experiments were performed using (a) V1V2V3, (b) V1V2V3V4V5, (c) V1CV2, and (d) CV1CV2CV3CV4CV5 contexts, where Vi was a combination of vowels /a,i,u,e,o/ and C was one of consonants /p,t,k,b,d,g/. A Japanese male subject uttered these sequences at several speeds with different stress. Articulatory data were sampled when the vocal tract constricted for vowels or when the vocal tract closed for plosive consonants: For each vowel and consonant, 200 data frames were sampled on average from the whole data set of about 150 000 frames (10 min). The variability of the vocal tract configuration was then quantitatively analyzed for each phoneme by calculating the variation of each measurement point from its average position. The variation was very small when the vocal tract closed or constricted, especially in the traversal direction. How phoneme context, utterance speed, and stress affect the vocal tract configuration was also investigated.
Acoustic scattering from fluid-loaded elastic shells: A Gaussian beam approach
Authors: Yang Yang , Norris Andrew N. , Couchman Luise S.
Published: October 2005

Acoustic scattering problems from fluid-loaded elastic shells are usually formulated in terms of surface Helmholtz integrals. The numerical evaluation of these integrals is very time consuming, especially at high frequencies. A new method is proposed here for the computation of the scattered fields. The basic idea is to use ray methods to first represent the supersonic surface fields. The surface integral is then represented as a summation of individual integrals along Gaussian beams. Each integral is approximated as a line integral along the center ray of the beam, and finally, the acoustic far field is obtained by asymptotically evaluating each line integral at its stationary points. The asymptotic expression for the membrane wave part is uniform and valid at all the observation angles. The difficulties of dealing with caustics and infinite sets of rays do not arise in the present formalism. This approach allows the acoustic response to be easily calculated without resorting to two-point ray tracing or surface Helmholtz integrals. It is therefore numerically fast. The numerical results agree well with the available exact solution and the pure ray results on a spherical shell for kfa≳10, where kf is the fluid wave number. [Work supported by ONR and NRL.]
Perceptual evaluation of articulatory movement recovered from acoustic data
Authors: McGowan Richard S. , Rubin Philip E.
Published: October 2005

A method involving task dynamics and a genetic algorithm [see McGowan, Speech Commun. 14, 19–48 (1994)] was used to recover articulation from the speech acoustics of a human subject. Six utterances from a single subject were chosen to test the applicability of the proposed method to human beings: /ga/, /gi/, /da/, /di/, /ba/, and /bi/. The first three formant trajectories of the natural utterances were extracted and used to represent the acoustic data. A genetic algorithm was used in constrained optimization of task-dynamic parameters applied to the Haskins Laboratories articulatory synthesizer, ASY. The articulatory movements recovered in this manner were assessed using perceptual tests of the resulting speech generated by ASY and by a visualization of the resulting ASY articulation.
Asymptotic determination of the eigenfrequencies of a sphere in a fluid
Authors: Gaunaurd G. C.
Published: October 2005

Starting from a phase-matching principle that is the acoustical analog of the Bohr–Somerfeld–Wilson quantization rule of the old ‘‘quantum theory,’’ it is analytically shown how to asymptotically obtain the eigenfrequencies of an insonified sphere immersed in a fluid. This technique was first illustrated by J. B. Keller [cf. Ann. Phys. 4, 180–188 (1958)] and it has been extended by many authors, notably L. B. Felsen and J. M. Ho, who have renamed it the ‘‘ray-acoustic algorithm.’’ It is shown here how the acoustical counterpart of this quantum principle leads to a resonance condition for the (external) eigenfrequencies of a sphere (rigid, soft, or to some extent, elastic) that exactly coincides with F. W. J. Olver’s (1954) classical asymptotic formula for the (complex) zeros of the spherical Hankel functions. The poles of the scattering amplitude of an elastic sphere fall into two great families, one depending on shape, and the other on elastic composition. The asymptotic spacings in between the shape-dependent zeros in the (complex) ka plane are shown to reduce to a uniform value, obtained earlier by numerical means, which manifests itself in all the (RST) ‘‘background’’ curves of the sphere. [Work supported by NSWC-DD IR Program.]
Computer model simulations of reverberation from the ARSRP acoustics experiment
Authors: Chin-Bing Stanley A. , Murphy Joseph E.
Published: October 2005

Detailed reverberation measurements were made from the mid-Atlantic ridge region during the 1993 Acoustics Experiment, Acoustic Reverberation Special Research Program (ARSRP). The reverberation scenario (designated as ‘‘Seg 076’’) that ensonified a segment of sedimented seafloor overlying an anelastic subbottom has been examined. Computer simulations of the reverberant field were generated and compared with the ARSRP measured reverberation. Time domain and cw computer simulations were made using high-resolution ocean acoustic–seismoacoustic computer models. Several realizations of the rough range-dependent sediment and sub-bottom were used (from the Webb–Jordan sediment distribution model and the Goff–Jordan fractal seafloor/basement model). Computer simulations allowed ‘‘numerical experiments’’ to be performed whereby parts of the environment were changed or eliminated. Simulation results that help identify those seafloor regions responsible for the reverberant returns are presented. [Work supported by ONR, Acoustic Reverberation SRP, and the High Performance Computing DoD Shared Resource Center: U.S. Army Corps of Engineers Waterways Experiment Station (CEWES) HPC Center, Vicksburg, MS.]
Simulations of the 1993 ARSRP deep ocean seafloor scattering experiments using h
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t—An adaptive wave propagation regime simulation technique
Authors: Robertsson Johan O. A. , Levander Alan , Holliger Klaus
Published: October 2005

A new general hybrid technique, HARVEST (hybrid adaptive regime viscoelastic simulation technique), to solve the 2-D acoustic/viscoelastic equations for problems which encompass different wave propagation regimes, such as the relatively smooth water column and the highly heterogeneous seafloor in deep ocean seafloor scattering experiments, is presented. A Gaussian beam method is used to propagate the source field through a vertically heterogeneous water column to the scattering region near the seafloor. This extrapolated source field is inserted into a viscoelastic finite-difference method used to compute the complex acoustic/anelastic interaction of the wave field with the rough seafloor. The backscattered field is extrapolated to a receiver array distant from the scattering locale by means of the Kirchhoff integral. HARVEST is employed to simulate ocean acoustic reverberation data collected during the 1993 ARSRP (Acoustic Reverberation Special Research Program) Acoustics Cruise. HARVEST is found to successfully reproduce ocean acoustic data within the confidence limits imposed by knowledge of seafloor morphology and material properties. The nature of scattering targets is interpreted from acoustics data in terms of synthetic HARVEST simulated data. In particular, rough basement that barely protrudes the sediment cover may cause strong returns in the backscattered field.
Shallow-water acoustic experiment in the Strait of Sicily Area: Preliminary results
Authors: Berkson J. M. , Kristensen A. , Max M. , Yates T. W. , Vermillion G. M.
Published: October 2005

Shallow-water acoustic and geoacoustic measurements were made in the southwest margin of the Adventure Bank area of the Strait of Sicily in a region having about 120-m water depth and a generally smooth calcareous sand seafloor. Concurrent propagation and reverberation experiments were conducted using horizontal and vertical array receivers with both broadband explosive and controlled narrow-band sources. Propagation is frequency dependent with minimum transmission loss at long range occurring in the frequency band 200–800 Hz. Overall reverberation envelope of duration was about 60 s and includes both diffuse returns and arrivals from major bathymetric features. [Work supported by ONR.]
Backscattering data analysis using multiple constraint beamforming
Authors: Li D. , Tang D. , Frisk G. V.
Published: October 2005

Using a vertical receiving array to measure bottom backscattering is clearly advantageous over the single receiver configuration. In the single receiver case, one uses arrival time information and the assumption that the scatterers are on the seafloor to obtain backscattering strength as a function of grazing angle; a vertical array, on the other hand, can be steered in various desired directions without invoking the aforementioned assumption. However, sediment stratification causes reflections in the normal direction, which are generally much stronger than the scattered signals at oblique angles. If one uses conventional beamforming, the reflected signals in the normal direction may therefore contaminate the signals received at oblique angles through sidelobe leakage. Therefore a multiple constraint beamforming technique is applied which substantially reduces the sidelobe level in the normal direction and enables one to measure backscattering strength at oblique angles. This technique is employed in the analysis of a deep ocean backscattering data set, and it is found that sediment inhomogeneities rather than seafloor roughness are the primary cause of backscattering. [Work supported by ONR.]
Average acoustic field in shallow water I: Active sonar performance prediction
Authors: Zhou Ji-Xun , Zhang Xue-Zhen , Rogers Peter H. , Caille Gary W.
Published: October 2005

The seabed dominates the shallow-water acoustics problem, but bottom properties and bottom scattering mechanism are usually poorly known. Detailed interference patterns in shallow water are thus not always physically meaningful for engineering applications. A simple analytical expression averaged over frequency or space can sometimes give better insight into some physical problems. In this presentation, an average angular power spectrum method for calculating shallow-water sound propagation, reverberation, noise, and spatial coherence is briefly introduced. The method is based on normal-mode and ray-mode analogies and originally appeared in Chinese papers which are not available in English [Zhou, Acta Acoust. Sin. 5, 86–99 (1980); Acta Ocean. Sin. 1, 212–217 (1979)]. Taking active sonar performance prediction as an example, analytical expressions for range/depth dependences of the sound propagation, average reverberation intensity, and echo-reverberation ratio will be given for several typical cases, including Pekeris shallow water, wedged continental shelf, and negative gradient waveguide. [Work supported by ONR.]
Variational model for the radiation impedance of class IV transducers
Authors: Robinson Harold C. , McLaughlin Elizabeth A.
Published: October 2005

In a previous paper [H. C. Robinson, J. Acoust. Soc. Am. 95, 2833 (A) (1994)], a variational method for determining the modal radiation impedance of baffled transducer arrays, based on the radiated power, was presented. In this paper, these variational methods will be extended to include unbaffled arrays of radiators with arbitrary spatial orientation. The surface velocity of each of the radiators is represented by invacuo eigenmode expansions, while the surface pressure is given by expansions in suitable trial functions. The arbitrary orientation of the array elements will be represented by transforming the surface velocities and pressures using Euler angles. As a specific example, the case of two coplanar class IV flextensional transducers will be examined in detail. The invacuo eigenmodes of a single element will be determined using finite element methods and parametrized in elliptical cylindrical coordinates (ξ,η,z). The surface pressure trial functions will be judiciously chosen functions of (ξ,η,z) as well. The behavior of the modal radiation impedances as a function of dimensionless separation distance kd, as well as of relative orientation, will be investigated. Comparisons of the results to equivalent circuit models and experimental data will be presented. [Work sponsored by ONR.]
The combined finite element and hybrid-type infinite element analysis for complex structure underwater transducers
Authors: Yoon Jong-Rak , Kim Chun-Duck
Published: October 2005

A numerical method for evaluating the electroacoustical characteristics of a complex structure of transducer immersed in an infinite acoustic medium is adopted. The mechanical, electrical, and acoustical response of the transducer in the finite region is modeled by the finite element method; the Sommerfeld radiation condition to the infinite region is modeled by the hybrid-type infinite element method, and the boundary between both regions is formulated with compatibility of the acoustical admittance in both regions. The numerical results, which include the elastic response, the radiation impedance, and the input electrical admittance, are given for a single piezoelectric cylinder and a coaxial two piezoelectric cylinder array with various polyurethane windows. The technique allows one to interpret and to optimize design parameters such as geometrical shape and mechanical properties of structure components, electrical characteristics of piezoelectric elements, etc.
Bond graph model for one-dimensional heat conduction for modeling of piezoelectric ceramic vibrators including thermal effects
Authors: Moon Won-kyu , Busch-Vishniac Ilene J.
Published: October 2005

A new bond graph model for conduction heat transfer is developed and applied to consideration of thermal energy balance in the piezoelectric thickness vibrator. In formulation of the model, the mechanical and electrical effects are included, so it can be applied directly to the temperature-dependent thickness vibrator. Although the analysis is applied to the one-dimensional case only, the method can be used for general heat conduction problems. For the purpose of evaluation of the new method, the model predictions for one-dimensional heat conduction excluding other variable effects are compared with the results of the analytic solutions in simple cases. The simulation illustrates the validity and the accuracy of the model.
Nonscattering of sound by sound resulting from a head-on collision of two plane-wave pulses
Authors: Westervelt Peter J.
Published: October 2005

Two arbitrary pulses p2(t−c−10x) and p1(t+c−10x) each of width c0τ pass through one another at x=0, generating a differential surface mass rate source density dσs(t,x)=qs dx where qs=Ad(p1p2)/dt and A= (ρ0c40)−1[2 + ρ0c0−2(d2p/dρ2)ρ0]. The equation for the scattered pressure ps is d2ps/dx2−c−20 d2ps/dt2= −q̇s and its solution is ps(x’,t)=∫dps=(c0/2)∫dσs= (c0/2)∫qs(x,t’)dx, t’ being the retarded time; thus, (ps)± = (c0/2)A∫±c0τ/2x’[d(p1p2) t=t’±/dt]dx, where + is chosen when x’<x, − when x’≳x, and t±’ = t ± c0−1(x’− x).

Suppose x’≳c0τ/2 then x’ lies outside the interaction zone, it is found that (ps)−= (c20A/4)(p2p1+ṗ2∫t−∞p1dt)=0 unless p1 has a nonzero average which is possible for plane waves but it is assumed that this is not the case [L. D. Landau and E. M. Lifshitz, FluidMechanics (Addison-Wesley, Reading, MA, 1959), p. 267]. In the event x’<−c0τ/2x’ again lies outside the interaction zone and (ps)+= (c20A/4)(p1p2+ṗ1∫t−∞p2 dt)= 0. Within the interaction region −c20/2<x’<c0τ/2 so that ps=(ps)+ +(ps)−=(c20A/4)(2p1p2 +ṗ2∫t−∞p1 dt+ṗ1∫t−∞p2 dt), which is precisely the result obtained previously [P. J. Westervelt, J. Acoust. Soc. Am. 94, 1774 (A) (1993)], recalling that p1 is here a plane wave; thus in the earlier result pm=p1/2. The zero scattering results obtained here conflict with nonzero results obtained by Trivett and Rogers [J. Acoust. Soc. Am. 71, 1114 (1982)] in a related problem, which most likely stems from spurious sources arising from discontinuities similar to those that plagued Ingard and Pridmore-Brown.
Experimental difficulties in measuring the scattering of sound by sound
Authors: TenCate James A.
Published: October 2005

The question of whether one sound beam can interact with another at nonzero angle and scatter nonlinearly generated sound outside the mutual interaction region has been debated since the 1950s. Experimental work on this problem has left the question unresolved. This presentation describes experimental difficulties associated with measuring scattered sound produced by real diffracting primary beams. Optimal conditions for observing scattered sound, as outlined by Berntsen etal. [J. Acoust. Soc. Am. 86, 1968 (1989)] and by Darvennes and Hamilton [J. Acoust. Soc. Am. 87, 1955 (1990)], are reviewed in relation to the design of our own experiments. Our experiments were performed with either two uniform circular sources in water (megahertz frequencies), or with one circular source and the other a shaded source with lower sidelobes. A variety of primary frequency ratios, interaction angles, and other parameters were considered. Comparison of the primary beam patterns with measured sum and difference frequency field patterns reveals the difficulty in identifying which components of the latter correspond to ‘‘scattered’’ sound. It is concluded that two Gaussian-type sources with exceedingly good sidelobe suppression are needed to perform a reasonable experiment. [Work supported by the Packard Foundation and ONR.] a)Present address: Earth and Environmental Sciences Division, Mail Stop D443, Los Alamos National Laboratory, Los Alamos, NM 87545.
Analytical method for describing the paraxial region of finite amplitude sound beams
Authors: Hamilton Mark F. , Khokhlova Vera A. , Rudenko Oleg V.
Published: October 2005

The paraxial region of finite amplitude sound beams in lossless fluids is studied theoretically. Both focused and unfocused beams are considered. A special analytical method which combines the parabolic approximation (KZ equation) with nonlinear geometrical acoustics (NGA) is developed to model nonlinear and diffraction effects near the axis of the beam. The corresponding system of nonlinear equations describing waveform evolution is derived. For the case of an initially sinusoidal wave radiated by a Gaussian source, an analytical solution of the coupled equations is obtained along the axis of the beam. The solution is expressed in both the time and frequency domains. In the high-frequency limit, classical simple wave solutions are recovered (plane-wave solution for unfocused beams and spherical wave solution for focused beams). In the limit of weak nonlinearity, the quasilinear axial solutions of the KZ equation for the fundamental and second-harmonic components are recovered. The analytical solution is in good agreement with numerical solutions of the KZ equation for a wide range of ratios between the focal length, Rayleigh distance, and shock formation distance. Harmonic propagation curves, waveform distortion, focusing amplification factors, and other characteristics are calculated. [Work supported in part by NATO and ISF.]
A study of the role of diffraction in the behavior of focusing step shocks using NPE-type equations and a finite difference program
Authors: Piacsek Andrew A.
Published: October 2005

A finite difference solution to an NPE-like equation is used to study the linear and nonlinear behavior of focusing step shocks in regions where caustics are formed. The initial condition is a nominally plane step pulse with a hyperbolic tangent rise profile of thickness lsh; the wavefront has a single ripple of length scale Lwf, concave towards the direction of propagation. When ε=lsh/Lwf is much less than unity, the linear numerical simulation showed that the shock behaves nearly according to geometric theory. Several different values of ε were investigated, verifying the linear theory predictions of normalized amplitude ∼ε−1/4 at the cusp [J. Hunter and J. Keller, Wave Motion 9, 429–443 (1987)]. Numerical solutions are also obtained for three cases of nonlinear propagation with dissipation. In addition to ε, the distinguishing parameters are shock amplitude and dissipation. It is observed that for cases in which nonlinearity is stronger relative to diffraction and focusing, the wavefront forms a cusp at a later time, caustics are less pronounced, and the (normalized) rise time is shorter. Implications of these results on the effect of caustics on sonic boom rise times is discussed.
Modification of the spectral method for describing nonlinear acoustic waves containing shocks
Authors: Khokhlova Vera A. , Sapozhnikov Oleg A.
Published: October 2005

Numerical simulations of finite amplitude sound waves become particularly time consuming in the case of strongly distorted waveforms that contain shocks. To improve the efficiency of time domain numerical codes, weak shock theory can be used to separate the description of the shock fronts from the evolution of the continuous segments of the wave. The idea of the present work is to modify the spectral method by taking into account the known asymptotic behavior of high-frequency components in shock waves. Use of asymptotic results permits the number of spectral components retained in the numerical computations to be reduced. A finite set of coupled equations for the spectral amplitudes, which approximates the infinite set of spectral equations corresponding to an exact formulation, is obtained for the simple wave equation. This reduction is achieved by introducing asymptotic expressions for the high-frequency components in sawtoothlike waves. Several model problems are studied. It is shown that less than 15 harmonics require numerical calculation in order to obtain an adequate description of the evolution of an initially sinusoidal wave to a sawtoothlike waveform. [Work supported by ISF and the Russian Fund for Fundamental Investigations.]
Neural network modeling of a dolphin’s sonar discrimination capabilities
Authors: Andersen Lars N. , Rasmussen A. René , Au Whitlow W. L. , Nachtigall Paul E. , Roitblat Herbert
Published: October 2005

The capability of an echo-locating dolphin to discriminate differences in the wall thickness of cylinders was previously modeled by a counterpropagation neural network using only spectral information of the echoes [W. W. L. Au, J. Acoust. Soc. Am. 95, 2728–2735 (1994)]. In this study, both time and frequency information were used to model the dolphin discrimination capabilities. Echoes from the same cylinders were digitized using a broadband simulated dolphin sonar signal with the transducer mounted on the dolphin’s pen. The echoes were filtered by a bank of continuous constant-Q digital filters and the energy from each filter was computed in time increments of 1/bandwidth. Echo features of the standard and each comparison target were analyzed in pairs by both a counterpropagation and a backpropagation neural network. The backpropagation network performed better than the counterpropagation network, and the use of both time and frequency domain features resulted in better performance than if only time or frequency domain features were used. [Work supported by ONR, Grant No. ONR N00014-93-1378.]
Generation of streaming and rarefaction of the gas in the far field of the weakly nonlinear plane waves
Authors: Yano Takeru , Inoue Yoshinori
Published: October 2005

The propagation of weakly nonlinear plane waves emitted from a harmonically oscillating plate into an ideal gas of semi-infinite extent is considered under the condition that the energy dissipation is negligibly small everywhere except for discontinuous shock fronts. Recently, the authors have numerically shown that, in the case of strongly nonlinear waves, contrary to the result of the conventional weakly nonlinear theory, streaming due to shocks occurs in the direction of wave propagation and thereby the gas near the source is rarefied as time proceeds [Y. Inoue and T. Yano, J. Acoust. Soc. Am. 94, 1632–1642 (1993)]. In the present paper, the evolution of the weakly nonlinear waves including shocks is determined up to O(M2), where M is the acoustic Mach number (M≪1). In this order, the wave profile develops to an asymmetrical sawtoothlike one in the far field and weak streaming is excited in the region beyond the shock formation distance. For M≲0.2, the results quantitatively agree with those in the previous work. Furthermore, by taking into account both the production of entropy and the generation of reflected wave at each shock front, the physical mechanism is clarified for the rarefaction of the gas in O(M3).
Prediction of the time-averaged pressure distribution for finite amplitude standing waves
Authors: Chen Reh-lin , Sparrow Victor W.
Published: October 2005

A finite difference numerical approach to studying two-dimensional nonlinear wave propagation was recently developed [V. W. Sparrow and R. Raspet, J. Acoust. Soc. Am. 90, 2683–2691 (1991)]. In this talk the approach is modified and applied to a one-dimensional finite amplitude standing wave in a rigid tube. The numerical method can solve for lossless, weakly nonlinear waves in the tube including all second-order nonlinearities from the continuity equation, momentum equation, and the equation of state. The acoustic pressure in the time, space, and frequency domains and the time-averaged acoustic pressure distribution are all determined. Generation of harmonics of the fundamental frequency along with the development of a nonzero, time-averaged pressure are seen from discrete Fourier transforms of the numerical results. The results for the time-averaged pressure distribution are compared to recent analytical predictions [C. P. Lee and T. G. Wang, J. Acoust. Soc. Am. 94, 1099–1109 (1993)]. The results show agreement between the present work and that of Lee and Wang when the nonlinearities from both the momentum equation and equation of state are included. A slightly different result is obtained when one also includes nonlinearity from the continuity equation.
Evolution equations for nonlinear Rayleigh wave propagation
Authors: Hamilton M. F. , Il’insky Yu. A. , Zabolotskaya E. A.
Published: October 2005

Time domain evolution equations are derived for nonlinear Rayleigh wave propagation along the free surface of an isotropic solid. The evolution equations are expressed in different forms: one for the horizontal displacement component, and one for a complex displacement variable. Both equations are derived from spectral equations published earlier [Zabolotskaya, J. Acoust. Soc. Am. 91, 2569 (1992)]. To simplify the derivation of equations for the displacement variables, not all components of the nonlinearity coefficient matrix are retained. However, the terms which are retained possess the same mathematical properties (symmetries in the frequency domain, singularities in the time domain, and others) as the terms that are not taken into account. Moreover, with appropriate definition of the shock formation distance, it is shown that numerical solutions based on the simplified equations yield close agreement with numerical solutions based on the complete nonlinearity matrix. The nonlinear terms in the new evolution equations are expressed as time derivatives and Hilbert transforms of the displacement variables. Waveforms calculated with the time domain evolution equations are shown to agree with results based on the original frequency domain equations. [Work supported by the Packard Foundation, ONR, and NSF.]
Observations of nonlinear effects associated with ice cracks
Authors: Ostrovsky Lev A. , Ekimov Alexander , Korotkov Alexey , Lebedev Andrey , Sutin Alexander M.
Published: October 2005

The hypothesis that cracks in ice may provide anomalously strong acoustic nonlinearity is experimentally verified. Two series of experiments were performed. One of them was done insitu, on a freshwater lake covered by a 40-cm-thick ice. Flexural waves were excited in ice by a vibrator in frequency range 0.2–2 kHz and received by accelerometers. Air temperature was −5 and +3 °C for two different series of measurements. A high level of nonlinearity was registered. In particular, a pronounced subharmonic signal was generated which testifies for parametric instability. The second experiment was performed in laboratory conditions, when a ‘‘crack’’ was created artificially, as a contact between two pieces of ice. We studied modulation of ultrasound (about 26 kHz) by low-frequency (30–90 Hz) vibrations. For vibration acceleration amplitudes up to 0.1 and 0.3 g a pronounced modulation spectrum appeared; moreover, modulation frequency subharmonics were observed in this case. Some theoretical considerations of the effects observed are also given. It is believed that nonlinear effect can be effectively used for Arctic ice characterization. a)Now at Univ. of Colorado, CIRES, ETL/ERL/NOAA, 325 Broadway R/E/ET, Boulder, CO 80303.
Diffusing light photography of solitons and capillary-wave turbulence
Authors: Wright W. , Budak R. , Putterman S.
Published: October 2005

The attenuation of light propagating through a slab of water (containing a dilute concentration of polyballs) is approximately proportional to its thickness. Application of this insight to the local elevation of a fluid surface has enabled us to use photography to determine the instantaneous global topography of the surface of a fluid in motion. Use of diffusing light enables us to obtain images that are free of the caustics which plague shadowgraphs. Applications include breather solitons and wave turbulence which results from the nonlinear interaction of a broadband spectrum of high amplitude surface ripples. Measurements indicate that as the amplitude of excitation of the surface of water is increased the wave number of the capillary motion displays a transition to a broadband spectrum. The temporal response of a single pixel yields the power spectrum of the surface height as a function of frequency ‘‘f.’’ The numerous harmonics which can be seen at low amplitude merge at high amplitude into a broadband spectrum which goes as 1/f3. This technique should permit the measurement of turbulent parameters which go beyond the purported range of current theories. [Work supported by US DOE Division of Engineering and Geophysics and NASA Microgravity.]
Experimental study of streaming in acoustic resonators
Authors: Jankovsky Joseph C. , Holt R. Glynn , Apfel Robert E.
Published: October 2005

Anomalous rotations of solid and liquid drops have been observed in resonant chambers in both 1g and in the microgravity environment of space in the Drop Physics Module (DPM) aboard the United States Microgravity Laboratory (USML-1) mission in 1992. The observed torques are produced by acoustic streaming, typically in the nondegenerate plane where rotations are undesired, and have been attributed to an imbalance in the paired driver amplitudes. To quantify the torque exerted on the inclusion, measurements were made using suspended and levitated spherical samples with single and paired driver configurations. Experiments were conducted in both degenerate and nondegenerate planes to study the effects of orthogonal coupling. Absorption effects of active and passive drivers are presented, along with asymmetrical driver configurations. The results will be used to control and eliminate unwanted tumbling rotations in the USML-2 DPM experiments to be flown in 1995. [Work supported by NASA through JPL Contract No. 958722.]
Geometrical theory of acoustic scattering by thin elastic shells
Authors: Ho Jin-Meng
Published: October 2005

The sound field scattered by a smooth thin elastic shell immersed in fluid arises largely from specular reflection and acoustic–membrane coupling, unless both source and observer are located near or on the shell. These two contributions have been found to be well described by ray fields for canonical shells in the mid-frequency regime, and hence may be generalized by the principle of localization to accommodate more general geometries. By examining the excitation, propagation, and radiation processes of the supersonic membrane waves on the shell, this paper defines the excitation and radiation coefficients associated with these shell-guided leaky waves as well as the divergence coefficients of the ray tubes characterizing the variation of the wave amplitudes. It extends the concepts of Keller and Karal’s geometrical theory for surface waves [J. B. Keller and F. C. Karal, Jr., J. Appl. Phys. 31, 1039–1046 (1960)]. The explicit evaluation of these coefficients, and therefore the leaky fields, is demonstrated for two classes of shells—cylindrical shells of arbitrary cross section and shells of revolution—based on the knowledge of cylindrical and spherical shell prototypes and differential geometry. The reflected waves are more straightforward and the related coefficients are readily determined. [Work supported by ONR.]
A developmental study of audiovisual speech perception using the McGurk paradigm
Authors: Hockley Neil S. , Polka Linda
Published: October 2005

The development of audiovisual speech perception was examined in this experiment using the McGurk paradigm (McGurk and MacDonald, 1976), in which a visual recording of a person saying a particular syllable is synchronized with the auditory presentation of another syllable. Previous audiovisual speech studies have shown that adult perception is strongly influenced by the visual speech information whereas the perception of young children (5–8 years) shows a very weak influence of visual speech patterns and a strong bias favoring the auditory speech information. In this investigation 46 children in four age groups (5, 7, 9, and 11 year olds) and 15 adults were presented with conflicting audiovisual syllables in which an auditory /ba/ sequence was combined with visual /va/, /θa/, /da/, and /ga/ sequences, respectively. The results indicated that the influence of auditory information decreased with increasing age, while the influence of visual information and the integration of auditory and visual information increased across the age groups. In addition, an adult-like response pattern was observed in only half of the children in the oldest child subject group (10–12 years old) suggesting that the ability to utilize visual speech information continues to develop beyond the age of 12. [Work supported by NSERC.]
Infant dependence on acoustic cue redundancy: Discrimination of the word-final voicing contrast
Authors: Orme Margret A. , Polka Linda
Published: October 2005

Discrimination of a word-final stop consonant voicing contrast, /bid/–/bit/, by adults and infants at two ages (6–8 and 10–12 months) was investigated in a category-change conditioned headturn procedure across three stimulus conditions: full cue (FC), burst and closure cues neutralized (BCCN), and vowel duration neutralized (VDN). Adults performed at ceiling levels for all three conditions. No infant age differences were observed. However, there was some evidence that infants benefitted from the presence of redundant acoustic cues (FC≳BCCN, but FCnot greater thanVDN). Infants performed significantly better with the VDN stimuli indicating that final release burst information is more salient to infants than vowel duration differences for this /bid/–/bit/ contrast. This result differs from findings of prior research on adult and infant perception of such contrasts which showed a prominent use of the preceding vowel duration cue. This finding suggests that vowel duration becomes useful as a cue to final stop voicing with linguistic sophistication. [Work supported by NSERC.]
Sensitivity to the distinctive features of vowels in newborn speech segmentation
Authors: Kaye Kelley L.
Published: October 2005

A previous study investigating the unit of speech perception in newborns [K. L. Kaye, J. Acoust. Soc. Am. 92, 2299(A) (1992)] yielded results suggesting that speech processing in newborns requires both the definition of the multidimensional perceptual space of the utterances in terms of small perceptual units, and the chunking of phenoemes into syllables for cognitive processing in memory. The present study focused on the perceptual process, investigating whether newborns are sensitive to the distinctive features of vowels. A vowel can be characterized by three opposed distinctive features. Using an operant (‖S‖) sucking procedure, one group of newborns received, over earphones, a presentation set with 0 distinctive feature variation, a second group with greater than 0 but less than 1 distinctive feature variation, and a third group with 2 distinctive features variation between the computer synthesized vowels in the set. Results indicated that responding is affected by the number of distinctive features required to define the vowel set, and together these studies indicate that newborns can segment speech in terms of syllables, phonemes, and distinctive features. Distinctive features are normally defined in articulatory terms, yet newborns do not have the appropriate articulatory equipment. The theoretical implications of this will be discussed.
Deficits in linguistic experience delay the development of mature speech perception abilities and of phonemic awareness
Authors: Nittrouer Susan
Published: October 2005

One model of how mature patterns of speech perception develop suggests that the weighting of various kinds of acoustic information changes as a result of experience with a native language. It has further been suggested that this developmental shift in perceptual weighting is related to the development of mature sensitivity to the phonemic structure of one’s native language (i.e., phonemic awareness). Thus it could be predicted that deficits in linguistic experience would delay both the development of mature patterns of speech perception and of phonemic awareness. This preliminary study tested this prediction by administering labeling and phonemic-awareness tasks to two groups of children: those of mid socioeconomic status (SES) and those of low SES. Several studies have shown that parental language directed to low-SES children differs from that directed to mid-SES children in kind and amount, such that low-SES children may be thought of as enduring deficits in linguistic experience. Results showed that low-SES children performed differently from mid-SES children on both experimental tasks, displaying results similar to those of younger, mid-SES children in other studies. These results suggest that linguistic experience plays a role in the development both of mature perceptual weighting schemes for speech signals and of phonemic awareness.