bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning effects for two different speech synthesizers with different speech material
Authors: DePaolis Rory A.
Published: October 2005

This study examined the relationship between the learning effects due to two inexpensive methods of synthesizing speech, formant synthesis (FS) and linear predictive coding (LPC). An experiment using two groups of six subjects listening to either FS or LPC for four consecutive days was conducted. The test material consisted of contextual and nonsense sentences with written clues, contextual sentences without written clues, and the rhyme test. A prose passage was also presented to the subjects. There was no significant difference between the learning curves for the two synthesizers but there was an overall dramatic learning effect, most noticeably from the first to third presentation across all types of speech material. The synthesizers exhibited equality of mean percent correct word scores for all material over the four sessions, excluding day 1, using the nonsense sentences in which the FS device was more understandable. These results are presented graphically with comparisons to other studies using natural and synthetic speech and predictions on the performance of the two synthesizers in noise.
Perception of digitally coded speech under some cognitive load
Authors: Ozawa Kazunori , Logan John S.
Published: October 2005

Perception of meaningful sentences that were encoded by speech coding methods was measured. In order to differentiate and to expand perceptual differences between the speech coding methods for the meaningful sentences, a task of recall for the sentences under cognitive load was adopted. In this experiment, the distractor method of short-term memory [L. R. Peterson and M. J. Peterson, J. Exp. Psychol. 58, 193–198 (1959)] was utilized as the cognitive load to subjects. Pitch predictive multipulse speech coding at 8 kb/s [K. Ozawa and T. Araseki, Proc. ICASSP, 1689–1692 (1986)] and 50 kb/s μ-law PCM were used as speech coding methods. As a reference, uncoded natural speech was also used. A total of 60 Harvard sentences was used as meaningful sentence stimuli. Results showed that the higher the cognitive load, the larger the perceptual differences between uncoded and coded speech, as well as between MPC and PCM. However, differences in error rates among uncoded and coded speech were very small in the case of no cognitive load. The results suggest that this perceptual evaluation method under cognitive load may be a sensitive method that can differentiate perceptual differences in speech quality between coded speech, even for meaningful sentences.
An investigation of the work output of a thermoacoustic prime mover
Authors: Simard Daniel C. , Atchley Anthony A. , Baker Steven R.
Published: October 2005

A thermoacoustic prime mover is a device that exploits an imposed temperature gradient to generate a work output. This work serves to offset dissipative losses and thus improves the quality factor of oscillations. The theory is developed using a quantitative expression for thermoacoustic work as derived by Swift et al. at Los Alamos National Laboratory [J. Acoust. Soc. Am. 78, 767–776 (1985)]. An experiment is described in which the quality factor is measured as a function of temperature gradient. A modified version of the “Hofler” tube is used and the experiment is conducted in argon. The results indicate that the inverse of the quality factor is linear with temperature gradient and are in good agreement with theory. [Work supported by ONR.]
Low Prandtl number gas mixtures as a working fluid in a thermoacoustic refrigerator
Authors: Suzalla M. , Hofler T. , Garrett S. L.
Published: October 2005

Prandtl number (Pr) is the dimensionless ratio of kinematic viscosity to thermal diffusivity, and is about 0.7 for most ideal gases. This value can be lowered significantly by mixing two gas species having molecular weights that are very different, resulting in a minimum Pr of 0.22 for He-Xe mixtures. This can be used to minimize the nuisance effect of viscous shear losses for a thermoacoustic refrigerator as well as for other types of heat engines. The principle of thermoacoustic heat transport will be briefly discussed [J. Wheatley, T. Hofler, G. W. Swift, and A. Migliori, J. Acoust. Soc. Am. 74, 153–170 (1983)]. However, changing the viscosity of the working fluid also changes the details of the acoustic velocity distribution, thereby modifying the basic thermoacoustic heat transport mechanism. Measurements indicate that this effect may be more important than the simple reduction of viscons shear losses. [Work supported by the Office of Naval Research and the Office of Naval Technology.]
Effect of stress on the temperature dependence of sound velocity
Authors: Cantrell John H.
Published: October 2005

The acoustic natural velocity for crystalline solids under stress is expressed directly as a function of the stress and the second- and third-order elastic constants referred to the zero stress state. The temperature dependence of the elastic constants is made explicit by use of the Helmholtz free energy for a system of quantized harmonic oscillators. The resulting expression is used to calculate the temperature derivatives of the sound velocity (dv/dT) as a function of applied stress σ in the solid. It is found that (dv/dT)0−1[(dv/dT)σ − (dv/dT)0] = Kσ, where the subscripted σ denotes evaluation at stress σ and the subscripted zero denotes evaluation at zero stress. The constant K is found to depend explicitly on the third-, fourth-, and fifth-order elastic constants of the crystal. A central-force nearest-neighbor lattice model is used to calculate the fourth- and fifth-order constants from measured values of the acoustic nonlinearity parameters. For these elastic constant data, K (for stress applied perpendicular to the longitudinal wave propagation direction in isotropic solids) is calculated to be 1.8 × 10 −3 MPa−1 for pure aluminum and 6.9 × 10−4 MPa−1 for copper. These results are in good agreement with experimental values obtained for aluminum and copper alloys [K. Salama and C. K. Ling, J. Appl. Phys. 51, 1505 (1980)].
Duration effects on vowel perception
Authors: Besing J. , Collins M. J. , Cullen J.
Published: October 2005

The effect of temporal differences on the identification of vowel tokens was studied using ten normal-hearing subjects. Stimuli were synthetically generated and varied in duration of the steady state, durations of the initial and final transitions, and F1, F2, and F3 location. Listeners were required to identify the given vowel token from a set of ten possible alternatives. The results supported the established effects of duration on the perception of vowels; however, the duration effect was sensitive to the effects of initial and final transition duration and F2 location. These results indicate that alterations in the duration of the initial transition has greater impact than the final transitions. These effects as well as the effects of interactions between steady-state duration, initial and final transition duration, and F1, F2, F3 location will be discussed. [Research supported by NIMH.]
An information-theoretic analysis of acoustic-phonetic and perceptual features
Authors: Jenison Rick L.
Published: October 2005

An information-theoretic approach using vector quantization (VQ) is presented as a framework for quantifying acoustic-phonetic distortion. An optimal codebook derived from 21 CV monosyllables from two speakers was generated for each of a contrasting set of linguistic features. The set of feature-based codebooks served as distortion minimized templates by which an average distortion could be computed for contrasting feature CV databases in quiet and in noise. The discriminating power of the feature codebooks based on a mean-square-error distortion was approximately 90 percent. Consonant confusion matrices were obtained from the CV database in quiet and in noise for five subjects. Transmitted information was computed for the same linguistic features analyzed by vector quantization. Preliminary evaluation of feature transmitted information compared to computed VQ distortion indicates a strong covariance. Further results and implications for distinctive feature systems will be discussed.
A comparison of commercial extracorporeal shock wave lithotripters based on measurements in the acoustic field
Authors: Coleman Andrew J. , Saunders John E.
Published: October 2005

A survey of five, presently available, commercial extracorporeal shock wave lithotripters is reported. As part of the survey, a detailed examination of the acoustic field of the Dornier HM3, Wolf Piezolith 2200, Technomed Sonolith 2000, EDAP LT-01, and Siemens Lithostar was carried out using the same 25-μm, bilaminar PVDF membrane hydrophone. The absolute pressure has been estimated from the voltage waveforms (recorded on a digital scope with a 30-MHz single-shot bandwidth) using the 1-MHz calibration factor for the hydrophone. The peak positive focal pressure at clinically used power settings of the different lithotripters is found to vary in the range 20–115 MPa. The peak negative focal pressure ranges from 3–10 MPa. The width of the focal region (defined as the region in which the peak positive pressure may be greater than 50% of that at the focus) varies from 0.1–2.5 cm. The rise time of the main pressure peak (defined as the time from 10%–90% of the peak positive pressure) is found to vary from less than 30 ns to 500 ns and the full width at a half-maximum of the positive pressure half-cycle from 250–500 ns. The estimated peak positive pressure gain of the different systems range from 10 to above 1000. Some of the parameters reported can be related to the relative clinical performance of the lithotripters. [Thanks to the companies and hospitals who provided the facilities for this survey.]
High-intensity, focused ultrasonic fields
Authors: Bjørnoø Leif
Published: October 2005

The use of extracorporeal shock wave lithotripsy (ESWL) for disintegration of body stones has increased considerably during recent years. A worldwide activity in this field is reflected in a growing number of international publications and in the development and manufacturing of several ESWL machines marketed by companies in Germany and France, in particular. Two main types of ESWL systems are prevailing, the spark gap-based and the piezoelectric disk-based systems. This paper is introduced by a brief reconsideration of the features of pressure waves in water produced by an electrical discharge across a spark gap emphasizing the parameters of significance to pressure wave amplitude and time course. Moreover, a comparison is presented of results obtained using various theoretical models—including the KZK equation—for the calculation of pressure waveform parameters, spatial pressure distribution, etc. involving nonlinearity, diffraction, and absorption in the high-intensity focused ultrasonic fields produced by an ellipsoid as well as a spherical cap focusing geometry. Data from the development of an ESWL of the piezoelectric disk type are reported including demands to transducers and to the electrical discharge circuit. Measured pressure waves in various regions of propagation will be presented. Calibration demands to transducers used for finite-amplitude pressure wave detection including linearity, dynamic range, etc. are emphasized. Finally, a critical assessment is given of the most essential pressure wave parameters, their relation to the focal system data, and their significance to stone disintegration efficiency.
Extracorporeal shock wave lithotripsy: Method, application, and physical foundation
Authors: Grünewald Michael , Koch Heribert , Hermeking Hajo
Published: October 2005

During the last years a new device has been put into the medical health system allowing for noninvasive treatment of kidney and gall stones: the Dornier lithotripter. The principle methods of shock wave generation are discussed, such as underwater spark discharge, dielectric laser breakdown, electromagnetic and piezoelectric method, and their suitability to disintegrate body concrements effectively. For practical applications, careful choice of system parameters has to be made to fulfill all requirements: good stone disintegration and low pain and side effects for the patients simultaneously. Based on the theory of focusing the relevant physical effects like diffraction, nonlinear propagation, and attenuation (absorption) are explored both qualitatively and quantitatively, so far as possible. It will be shown that a full time-dependent profile calculation can be given within simple diffraction theory accounting for a proper description of the dependence of focusing on aperture, including stress and tensile. The relevance of pulse shape forming will be explored. Additionally nonlinear propagation in relation to damping and pulse deformation in soft tissue is important. Within a simple model the propagation of highly unharmonic pulses will be calculated including nonlinear steepening, anomalous tissue absorption, and dispersion.
Cavitation microjets as a contributing mechanism for stone disintegration in ESWL
Authors: Crum Lawrence A.
Published: October 2005

The intense shock waves that are used for stone disintegration in ESWL can readily produce acoustic cavitation in a variety of liquids. It has been discovered that the damage to metal objects placed at the focus of an ESWL can be attributed to the action of liquid microjets produced by collapsing cavitation bubbles [A. J. Coleman et al., Ultrasound Med. Biol. 13, 69–76 (1987)]. Furthermore, Delius has shown that these shock waves can produce cavitation in vivo [Miller et al., J. Acoust. Soc. Am. Suppl. 1 83, S89 (1988)]. In this paper, a general review will be given of the mechanism of microjet formation in cavitation bubbles and arguments made that cavitation plays an important role in stone disintegration. A film will be shown of microjet formation in collapsing cavitation bubbles induced at low acoustic frequencies. [Work supported in part by NIH and ONR.]
A theoretical study of cavitafion generated by an extracorporeal shock wave lithotripter
Authors: Church Charles C.
Published: October 2005

The intense acoustic wave generated at the focus of an extracorporeal shockwave lithotripter is modeled as the impulse response of a parallel RLC circuit. The shock wave consists of a zero rise time positive spike which falls to 0 at 1 μs followed by a negative pressure component 6 μs long with amplitudes scaled to + 1000 and − 167 bars, respectively. This pressure wave drives the Gilmore-Akulichev formulation for bubble dynamics; the zero order effect of gas diffusion on bubble response is included. Results predict that a preexisting bubble in the micron range will expand to over 100 times its initial size, R0, for 240 μs, with a peak radius of 1350R0, then collapse very violently, emitting far UV or soft x-ray photons (black body assumption). Gas diffusion does not appreciably mitigate the violence of the primary collapse, but does significantly increase R0, up to 40 μm, as well as the duration of subsequent ringing, assuming no break up or production of microbubbles. The prediction of x-ray emission is of more academic than clinical concern because relatively few photons will be produced, and renal tissue exhibits a fairly low radio-sensitivity. [Work supported by NIH.]
Arthur H. Benade: The making of a musical acoustics researcher, theorist, and teacher
Authors: Benade Virginia
Published: October 2005

The Rampur State Band, childhood consumption, and repairing World War II aircraft radios are only a few of the influences reported on here as having had some bearing on A. H. Benade's development as a musical acoustician.
Listening to sound in rooms
Authors: Hartmann W. M.
Published: October 2005

Professor A. H. Benade frequently remarked on the paradox involved in listening to musical sounds in rooms. He noted that the transmission path from the sound source to the listener is unreliable; its impulse response and its corresponding frequency response, are irregular, unpredictable, and unstable. Nevertheless, the listener obtains reliable information about the location of the source, about the tone color, and about the transient character. The paradox may be resolved in principle by postulating that the listener's nervous system performs certain temporal summation and differencing operations as well as binaural summation and differencing operations on the internal representation of the sound field. The present talk will review what is known from psychoacoustical experiments concerning these parallel summation and differencing operations with the goal of distinguishing between plausible and implausible models. Most striking has been recent progress on binaural processing where psychoacoustics and electrophysiology appear to be converging on a single model, based upon crosscorrelation in tuned channels. Of particular importance is the precedence effect, which, after 100 years of study, still creates surprises but still wants an adequate definition. [Work supported by the National Institutes of Health.]
Art Benade at the Institut de Recherche et Coordination Acoustique/Musique in Paris
Authors: Causse René
Published: October 2005

This presentation dicusses Art Benade's influence on different instrumental acoustics projects at IRCAM, a musical research institution headed by composer Pierre Boulez. Art Benade was a member of IRCAM's original scientific advisory committee. New performance techniques, such as flute and trombone multiphonics, input impedance measurements of wind instruments and mutes for brasses were among the projects in which Art Benade made contributions, as a theoretical physicist and an adept experimenter, but also as an experienced musical performer and instrument maker. These multifaceted talents enabled him to communicate effectively with composers and performers, to understand musical problems in physical terms (and vice-versa), and to participate in every step of these projects. We will present the most recent results of some of these projects and discuss more particularly a new model of the “wah-wah” mute for the french horn.
Intensity discrimination at three frequencies by means of pulsed- and continuous-tone paradigms
Authors: Turner C. W. , Zwislocki J. J. , Filion P. R.
Published: October 2005

Difference limens (DL's) for the intensity of pure tones were measured with 2AFC pulsed-tone and continuous-tone paradigms at 500, 2000, and 6000 Hz across a broad range of sensation levels (SL's). In the pulsed-tone experiments, the pedestal was gated simultaneously with the increments, whereas, in the continuous-tone experiments the pedestal began 400 ms before the first observation interval, and continued throughout the trial until 400 ms after the termination of the second observation interval. The DL's obtained on five normal subjects were lower for the continuous-paradigm than for the pulsed-tone conditions for all test frequencies and SL's. The difference agrees with physiological results showing that the single-unit neural response to an increment is independent of whether the increment is presented to fibers that are adapted (continous-tone experiment) or unadapted (pulsed-tone) experiment [Smith and Zwislocki, Biol. Cyber. (1975)] and also with the argument that the pulsed-tone paradigm involves the additional requirement of a “memory load” for subjects. However, according to our preliminary findings, the difference does not hold for all hearing-impaired subjects. [Work supported by NIH Grant NS24255.]
Forward-masking properties of multicomponent signals in normal and hearing-impaired subjects
Authors: Kim Munah , Turner Christopher W. , Relkin Evan M.
Published: October 2005

The forward-masking properties of inharmonic complex stimuli were measured both for normal and hearing-impaired subjects. The signal was a single sinusoid of 1000 Hz. Signal threshold was obtained for six different maskers that varied in the number of components. Masking stimuli consisted of 1, 3, 5, 7, 9, or 11 components, logarithmically spaced in frequency surrounding the signal, and were presented at a fixed level of 80 dB SPL per component. An adaptive two-alternative forced choice method was used to determine thresholds. In normal-hearing subjects, the threshold for the signal decreased as the number of components was increased, demonstrating that signals with more components are less effective maskers. Results from hearing-impaired subjects indicated no decrease in threshold with increasing masking components, instead, the thresholds increased as more components were added to the first masker. [Work supported by the Deafness Research Foundation and the Whitaker Foundation.]
Auditory filter width and consonant recognition for hearing-impaired listeners
Authors: Dubno Judy R. , Dirks Donald D.
Published: October 2005

Abnormal frequency resolution is often assumed to contribute to reduced speech recognition by hearing-impaired listeners. However, a strong association between these two conditions secondary to hearing impairment has not been established, perhaps because both are degraded by threshold elevation. Thus, in this experiment, which examined auditory filter effects on consonant recognition, presentation levels of speech stimuli for each subject were selected on the basis of predictions from Articulation Index theory, in order to control for threshold sensitivity differences among the normal-hearing and hearing-impaired listeners. Estimates of filter width for 25 hearing-impaired subjects (calculated from masked thresholds measured in broadband noise as function of the width of a spectral notch) revealed auditory filter widths that increased with the threshold for the probe. Consonant place perception for most hearing-impaired subjects was nearly equivalent to results for normal-hearing listeners when threshold differences were controlled. These results suggest that frequency resolution and speech recognition may coexist as independent consequences of threshold elevation. [Work supported by grants from NINCDS and the Deafness Research Foundation.]
Some parameters of automatic audiometric thresholds
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Threshold measurements were made by two automatic audiometers; (1) continuously variable frequency tracing audiometer with an attenuation step of 0.25 dB; (2) continuously changing discrete individual frequency tracing audiometer with an attenuation step of 1.0 dB. Five trained subjects with bilateral normal hearing, four subjects with unilateral cochlear lesion, and four subjects with unilateral retrocochlear lesion were tested. For both pulsed and continuous tones, there was no observable difference in thresholds between two audiometric measurements for subjects with bilateral normal hearing and for ears with normal hearing in subjects with unilateral hearing impairment. The ears with cochlear lesion indicating abnormal rapid adaptation showed slightly greater separation between pulsed and continuous tone thresholds by continuously variable frequency tracings than by continuously changing discrete frequency tracings. For the ears with retrocochlear lesion indicating abnormal slow type of adaptation, much greater separation was demonstrated by the former. These findings were discussed with and related to parameters affecting thresholds; slow attenuation step in size, threshold at equilibrium (stabilized threshold), and lateral frequency spread of adaptation.
The solution of fluid-structure interaction problem using quadratic, doubly curved finite elements
Authors: Shirron Joseph J. , Schuetz Luise
Published: October 2005

A model to solve coupled fluid—structure interaction problems, such as acoustic scattering from an elastic body, is described. This model uses doubly curved, nine-noded, isoparametric finite elements over which the pressure is taken to vary quadratically. Results from this model are compared with another computer model (NASHUA) that is based on planar finite elements over which the acoustic pressure is assumed to remain constant. Several examples are presented to demonstrate the reduction in the number of elements needed for accurate modeling. Comparison of solution time and accuracy is also given.
Shear wave velocity in surfictal marine sediments: A comparison of in situ and laboratory measurements
Authors: Richardson Michael D. , Muzi Enrico , Troiano Luigi
Published: October 2005

In situ and laboratory measurements of shear wave velocity were compared for a wide variety of shallow-water marine sediment types found in the vicinity of La Spezia, Italy. Both types of measurements utilized pulse techniques, with shear waves generated and received by bimorph ceramic bender elements. Measurements were made between 200 and 1000 Hz. In situ measurements and sediment collections were made by scuba divers to minimize sediment disturbance. Values of shear wave velocity were low (< 100 m/s) for all sediment types sampled. Typical values ranged from 20 m/s in high porosity clays to 50 m/s in sandy sediments. Shear wave velocities measured by in situ and laboratory techniques were not significantly different, suggesting that shear wave velocities measured on carefully collected core samples of surficial sediments need not be corrected to in situ conditions. Apparently, changes in shear modulus, which result from sample disturbance during coring, and changes in pressure and temperature after collection are small compared to the natural variability of surficial sediment shear wave velocity.
The modeling of a shallow-water wedge using complex rays and steepest-descent integration
Authors: Westwood Evan K.
Published: October 2005

A new method for computing propagation loss in a shallow-water wedge with a penetrable bottom will be presented. The method is based on the representation of the total field as a sum of ray fields. Each ray field is expressed as a contour integral over plane waves in the complex θ plane, where θ is incident angle. Saddle points (possibly complex) are found for each ray, and steepest descent path integration is required when the ray strikes the bottom interface near the critical angle. Lateral wave contributions are also included. This model has been applied to the upslope benchmark problems proposed at the 112th Meeting. The results are indistinguishable from those reported by Jensen at the 113th Meeting using Evans' two-way coupled mode model (generally considered to be the most accurate). The computation time for 400 points on a horizontal line is on the order of 5 min. Unlike coupled mode and parabolic equation models, the computation time using this ray model decreases as the frequency is raised. [Work supported by the ONR contract N00014-87-K-0346.]
Transient Green's tensors for a layered solid half-space with different interface conditions
Authors: Ren Shuchu , Hsu Nelson N. , Eitzen Donald G.
Published: October 2005

To understand the influence of the interface conditions on the behavior of transient waves in a structure, the Green's tensor for an isotropic layer overlay on an isotropic half-space is solved using the “generalized ray” expansion technique and Willis inversion method. This inversion method has many advantages over the Cagniard-de Hoop inversion method. First, the displacements rather than the potentials are used and the derivations are greatly simplified; second, self-similar sources are assumed and a detailed discussion of the structure of a complicated algebraic function is avoided; and third, the derivatives of the Green's tensor about spacial coordinates are easily obtained. A FORTRAN code for computation of the Green's tensors was developed. Both the cases of a welded and a liquid coupled interface are considered. Computed results show that changes of the interface condition have a great influence on the behavior of transient waves. For example, when the interface conditions vary from welded to liquid coupled, some of the first few head waves nearly vanish while the first few regular reflected rays keep unchanged. This phenomenon can be used to infer the quality of the interface bond of materials in ultrasonic NDE.
Propagation effects of a transition layer at the ocean/sediment interface
Authors: Collins Michael D. , Chin-Bing Stanley A. , Murphy Joseph E.
Published: October 2005

In this paper, the results of an investigation into the propagation effects of a transition layer in the uppermost portion of the ocean sediment are presented. The layer of sediment directly beneath the ocean bottom is partially saturated with water and is close to the temperature of the water. Due to these saturation and thermodynamic effects, the discontinuity in the speed of sound at the ocean/sediment interface is typically about a half of a percent. Since the deeper layers are insulated from the ocean and are not saturated with water, one would expect the sound speed c0 deep within the sediment to depend only on the depth z below the ocean surface to first order. Thus a reasonable formula for sediment sound speed is cs (z,d) = [αcw (d) − c0(d)]e(d − z)/h + c0(z), where α≅1, cw is the ocean sound speed, d is the ocean depth, and h is the thickness of the transition layer. When attenuation is present in the transition layer, propagation loss increases with h since a thicker transition layer results in longer ray path lengths within the lossy region. [Work supported by ONR and NORDA.]
The outgoing solution of the Klein-Gordon equation and the effects of dispersive sediments on pulse propagation in the ocean
Authors: Collins Michael D.
Published: October 2005

The parabolic equation method, which has been used as a frequency domain tool in underwater acoustics for several years, is also effective for use in the time domain [B. E. McDonald and W. A. Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)]. In this paper, some recent progress in the development of the outgoing solution of the Klein-Gordon equation is described and some calculations are presented. It was found that very small amounts of sediment dispersion result in significant distortion of even the water-borne portion of signals. This surprising finding should help resolve a controversy regarding the relationship between attenuation and frequency in sediments, which has long been accepted to be linear based on several experiments. In a recent paper [Zhou et al., J. Acoust. Soc. Am. 82, 2068–2074 (1987)], a different relationship is proposed based on the analysis of arrival times. Despite the fact that attenuation and dispersion are very intimately related, dispersion is neglected in the analysis. [Work supported by ONR and NORDA.]
The low-frequency reflection coefficient of a gassy sediment
Authors: Gilbert K. E. , Zagar J. R.
Published: October 2005

Narrow-band propagation measurements have been made in a shallow pond with a gas-saturated bottom [L. E. Murray and K. E. Gilbert, J. Acoust. Soc. Am. Suppl. 1 80, S63 (1986)]. A normal-mode analysis of the data was used to extract plane-wave reflection coefficients for the bottom. Between 600 Hz (the cutoff frequency for the first mode) and 2000 Hz, the reflection coefficient R varies approximately linearly with frequency. The end points are R = −0.91 ±0.02 at 600 Hz and R = −0.82 ± 0.02 at 2000 Hz. These values for R are similar to those that have been obtained in broadband experiments [e.g., Jones et al., J. Acoust. Soc. Am. 36, 154–157 (1964)]. Physical mechanisms that may control the low-frequency reflection coefficient of a gassy sediment will be discussed.
Thermopiezoelectric equations of high-frequency vibrations of ceramic shells
Authors: Dökmeci M. Cengiz
Published: October 2005

In view of the author's recent review article [Shock Vib. Dig. 20(2), 3–20 (1988)], this study is carried out for the aim of a systematic and consistent derivation of the governing equations of vibrations of piezocermic shells. First, a variational principle is derived so as to describe all the three-dimensional equations of thermopiezoelectricity. Then, the mechanical displacements, electric potential, and temperature increment of piezoceramic shell are expanded in power series of the thickness coordinate. Next, a system of two-dimensional equations of successively higher-orders approximation is derived for vibrations of thermopiezoelectric shell by use of the variational principle together with the series expansions. The system of equations governs all the types of coupled vibrations of piezoceramic shell [cf. R. D. Mindlin, Int. J. Solids Struct. 10, 625–637 (1974)]. Also, special motions and geometry of piezoceramic shell are indicated. Finally, a theorem of uniqueness is proved for solutions of the governing equations of thermopiezoelectric shell. [Work supported in part by the United States Army through its European Research Office.]
Evaluation of the complex coefficient ŝD33 of thlck film piezoelectric polymers
Authors: Ricketts Donald , Howarth Thomas
Published: October 2005

A model for evaluating ŝD33 is presented using an impact testing technique [J. Acoust. Soc. Am. Suppl. 1 67, S32 (1980)]. In the form of a consolidated bare ring stack, the piezoelectric polymer (PYF2) test specimen is sandwiched between two identical loading masses. A threaded tie rod passes through the center of the entire assembly and is fastened at each end by means of a nut. This arrangement facilitates evaluating ŝD33 as a function of frequency and compressive stress. By impact testing this composite longitudinal vibrator, its resonance frequency (fR) and mechanical storage factor (QM) may be measured. From these measured quantities and the mathematical model of the test resonator, the complex elastic compliance coefficient ŝD33 may be evaluated. The expressions for evaluating the real and imaginary parts of ŝD33 are given. Experimental results obtained at room temperature are presented for ŝD33 versus compressive prestress at two nominal audio frequencies.
Modeling listeners' perception of “silent center” syllables
Authors: Nearey Terrance M. , Andruski Jean E.
Published: October 2005

Recently, Verbrugge and Rakerd [Language and Speech 29, 39–57 (1986)] and Strange and Jenkins [J. Acoust. Soc. Am. Suppl. 1 82, S82 (1987)] have shown evidence that “silent center” CVC syllables (i.e., syllables wherein only the relatively rapid CV and transition portions are preserved, while the relatively steady-state midsections are excised) are well-perceived even when CV and VC portions from different speakers are combined (“hybrid syllables”). This study will present data from analagous experiments with Canadian English, but including both isolated vowels and /bVb/ syllables in an effort to test the degree to which consonantal coarticulation effects (as opposed to vowel-intrinsic properties) are responsible for the high intelligibility of hybrid syllables. The results obtained will be compared with predictions of the pattern recognition model of Nearey and Assmann [J. Acoust. Soc. Am. 80, 1297–1308 (1986)] for Canadian English vowels that exploits vowel-inherent spectral change.
Perceptual effects of attention to phonetic versus “musical” properties of sinewave speech
Authors: Best Catherine T. , Studdert-Kennedy Michael , Manuel Sharon
Published: October 2005

A continuing debate in speech perception research has been whether phenomena such as categorical perception and trading relations are explained by basic psychoacoustic mechanisms or rather by a specialized phonetic mode of perception. Sinewave speech analogs have provided an opportunity to test these alternatives, since the same stimuli can be heard as either distorted speech or nonspeech sounds by different groups of listeners. The psychoacoustic hypothesis would predict similar between-group performance, while the phonetic hypothesis would predict systematic group differences. Several recent findings have favored a distinct phonetic mode in perception of sinewave speech. Best and Studdert-Kennedy [Proc. 10th Int. Congr. Phon. Sci (1983)] used a labeling test with a sinewave-analog /ra/-/la/ continuum, and found that speech-biased listeners performed in a clearly categorical manner, whereas “music”-biased listeners performed near chance. The present research strengthened that finding, by employing AXB identification without overt labels, and AXB discrimination. Control tests with a full-formant /ra/-/la/ continuum and sinewave analogs of their isolated F3 trajectories were included. The two groups performed identically with each control continuum, yet they differed dramatically with the sinewave syllables. In support of the phonetic hypothesis, only the speech-biased listeners systematically classified the stimuli into two clear categories, and showed improved discrimination around the catagory boundary. [Work supported by NIH grant HD-01994 to Haskins Laboratories.]
Can simultaneous presentation of print influence the detection of speech in noise
Authors: Frost Ram , Repp Bruno H.
Published: October 2005

When spoken words are masked by noise having the same amplitude envelope, subjects report they hear the word much more clearly when they see its printed version at the same time. Using signal detection methodology, it was investigated whether this subjective impression reflects a change in perceptual sensitivity or in bias. Signal-plus-noise and noise-only trials were accompanied by matching print, nonmatching (but structurally similar) print, or a neutral visual stimulus. These results revealed a strong bias effect: The matching visual input apparently made the masking noise sound more speechlike, but it did not improve the detectability of the speech. (However, reaction times of correct detections were reliably shorter in the matching condition, suggesting perhaps a subliminal facilitation.) The bias effect was much smaller when nonwords were substituted for the words. Thus it seems that subjects automatically detect correspondences between speech amplitude envelopes and printed stimuli, and they do this more efficiently when the printed stimuli are real words. This supports the hypothesis, much discussed in the reading literature, that printed words are immediately translated into an internal representation having speechlike characteristics. [Work supported by NICHD.]
The interaction of visual place and auditory voicing information during the perception of speech
Authors: Green Kerry P. , Kuhl Patricia K.
Published: October 2005

Previous studies using speeded classification paradigms have been used to test whether the information that underlies the perception of place and voicing is processed in an integral as opposed to a separate fashion. Results of auditory only experiments show that reaction times (RTs) for place classification in a condition in which stimuli vary along both place and voicing (the orthogonal condition) are longer than RTs in a control condition in which stimuli vary only in place. These data are taken in support of the idea that the information underlying place and voicing axe integrally processed. This study was concerned with whether or not place classification would demonstrate the same pattern of results when the place feature was determined by both auditory and visual (the face of the talker) information. To do this, the auditory tokens /ibi/ and /ipi/ were paired with a video display of a talker saying /ibi/ or /igi/, and presented to subjects for speeded classification of place or voicing. Because of the “McGurk effect,” these stimuli were perceived as /ibi, ipi, idi, or iti/. The results showed that RTs for classifying phonetic features in the orthogonal condition were significantly longer than in the control condition. These results were obtained for both place and voicing judgments. Thus auditory-visual results appear to mirror those obtained in previous studies using only auditory stimuli. [Work supported by NIH.]
Distribution of surface-generated noise in a three-dimensional environment
Authors: Perkins John S. , Kuperman W. A. , Ingenito F. , Porter Michael P.
Published: October 2005

Modeling the distribution of noise generated at the ocean surface over a wide ocean area with a spatially variable source level distribution in a three-dimensional (3D) environment requires the capability of efficiently computing the acoustic field from all points on the surface to all points in the ocean. A previously developed noise theory is modified [W. A. Kuperman and F. Ingenito J. Acoust. Soc. Am. 67, 1988–1996 (1985)] and is combined with an approximate numerical technique for computing transmission loss in a 3-D environment based on adiabatic mode theory [M. P. Porter, W. A. Kuperman, F. Ingenito, and A. Piacsek, J. Acoust. Soc. Am. Suppl. 1 81, S9 (1987)]. The wave equation solution of the acoustic field (or its cross-spectral density) from any point to any point (or to any pair of points) reduces to a “spreadsheet” type manipulation of precomputed modal solutions. This 3-D range-dependent numerical scheme is shown to reduce to analytic expressions for the distribution of noise in a horizontally stratified ocean.
An analysis of low-frequency wind-generated ambient noise source levels in the ocean
Authors: Carey W. M. , Kewley D. J. , Browning D. G. , Von Winkle W. A.
Published: October 2005

Historically, the greatest amount of published ambient noise data has been obtained in Northern Hemisphere Oceans. However, principally due to ship noise contamination and lack of directionality, only a limited portion can be used for determining low-frequency and wind-generated ambient noise source levels. Some data have been extracted and combined with the Southern Hemisphere database [A. S. Burgess and D. J. Kewley, J. Acoust. Soc. Am. 73, 201–210 (1983)]. These resulting wind-generated ambient noise source levels are difficult to compare due to differences in the source level definition and descriptions by several investigators. A standard set of source levels is proposed based on a monopole beneath the pressure release surface and an equivalent dipole at the surface. The ambient noise source level data reported in the literature are shown to be in general agreement.
Materials fragmentation by shock waves
Authors: Finlayson B. , Nasr Mohamed , Whelan J. Paul
Published: October 2005

Although extracorporeal shock wave lithotripsy (ESWL) is an important technique, the details of how it works—how shock waves interact with stones to cause disruption—and how to optimize its effect are not known with certainty by practitioners of the art. Three position-dependent mechanisms of disruption were observed. Position dependence was probably due to focusing of the shock wave by an ellipsoidal reflector. Near the focus, the front surfaces of the test objects were roughed (spalated), probably by collapse of cavitation bubbles caused by passage of the shock wave. Also, midspecimen cleavage was seen, presumably caused by back wall reflection tensile stress. Distal to the focus back wall, spalation occurred, possibly due to tension caused by the expanding shock wave. Sieving fraction observations made of the effect of shock waves on “z brick” show that fragmentation has an approximate first-order dependence on the number of shocks and a second-order dependence on the voltage at which the shocks were generated. The multiphase character of the z brick was distinctly revealed in plots of percent fragmentation versus shock number; z brick is not a satisfactory test material, and there is a need for a well-characterized set of test materials.
Cavitation processes induced by weak shock waves propagating in tissue
Authors: Koch H. , Grünewald M. , Hermeking H.
Published: October 2005

Human application of single-cycle focused shock waves requires an intense study of the interaction processes associated with shock wave propagation in biological media. In this connection, shock wave-induced cavitation processes on the scale of a single biological cell are of fundamental importance. On the basis of a model analysis including different propagation media for the bubble-shock wave interaction and various shock wave profiles, possible hazards are discussed and compared with experimental and clinical results.
Fluid-loaded constrained-layer analysis by exact elasticity theory
Authors: Fausett Laurene V. , Dubbelday Pieter S.
Published: October 2005

The constrained-layer damping technique is based on the attachment of an absorbing viscoelastic layer and a stiff constraining layer to the surface of a metal structure to be damped. Starting from the model by F. M. Kerwin [J. Acoust. Soc. Am. 31, 952–962 (1959)], based on thinplate theory for the base plate, a hybrid model of a fluid-loaded plate was developed whereby only the base plate is described by exact elasticity theory [P.S. Dubbelday, J. Acoust. Soc. Am. Suppl. 1 80, S121 (1986)]. A description based on exact elasticity theory for all three layers, without fluid loading, was also formulated [D. W. Fausett, L. V. Fausett, and P.S. Dubbelday, J. Acoust. Soc. Am. Suppl. 1 80, S121 (1986)]. The present study further explores the interaction of viscoelastic damping and fluid loading by a description according to exact elasticity theory of all three layers, combined with fluid loading. For flexural waves, the model shows reasonable agreement with the earlier hybrid model at intermediate frequencies, but discrepancies occur at lower and higher frequencies. These are discussed, and possible mechanisms for the behavior are brought forward. [Work supported by ONR.]
General relationships between acoustic impedance and modal density
Authors: Manning Jerome E.
Published: October 2005

A general formulation of the acoustic impedance is set out using modal analysis. It is shown that the average acoustic resistance can be generally expressed in terms of the modal density of the acoustic space, the bulk compliance of the space, and the average joint acceptance. Examples are given for both simple and complex sources. Although the work presented offers no previously unknown solutions to acoustic radiation problems, it provides a very convenient engineering result that can be used in statistical energy analysis and other related acoustic analysis techniques.
An analytic model of shear and moment interaction of reinforcing ribs with cylindrical shells for acoustic radiation
Authors: Burroughs Courtney B. , Becker Kenneth J.
Published: October 2005

In response to vibratory motion of a cylindrical shell, reactive forces and moments are generated by reinforcing ribs attached to the interior surface of the shell. These reactive forces and moments modify the shell motion and thereby the farfield acoustic radiation from the shell. Equations governing the motion of a rib, modeled as a circular ring, are derived that include normal and circumferential shear forces, and moments applied to the outer edge of the ring where the ring is attached to the inner surface of the shell. Approximate solutions for the impedances of the ring at the outer edge are obtained and used in equations of motion for a point-excited, fluid-loaded, circular cylindrical shell reinforced by periodically spaced ribs.
A simplified model for a beating reed—Preliminary results
Authors: Worman W. E. , Benade A. H.
Published: October 2005

This paper presents early results of a model for the behavior of a musical wind instrument with a beating reed in the case where the air flow is completely blocked for a finite part of each period. The parameters used are appropriate for a clarinet. The method is as follows: (a) Assume a waveform for the transarundal pressure, pin (pressure difference across the reed); (b) calculate the reed position assuming that the reed is a simple harmonic oscillator driven by pin; (c) use the pressure and reed position to calculate the flow into the mouthpiece; (d) use the flow and input impedance of the air column to calculate the transarundal pressure, pout; and (e) adjust the assumed pin so that the calculated pout agrees with it. The results obtained so far allow some general conclusions. The pressure waveform is “squarish,” almost symmetrical, and varies between about zero and twice the blowing pressure. The behavior is independent of system parameters over wide limits and is controlled by energy exchanges that occur when the transarundal pressure is near its minimum.