bluuebunny/crossref_metadata_2025 huggingface dataset:
Split-step/finite-difference and split-step/Lanczos algorithms for solving alternative higher-order parabolic equations
Authors: Yevick David , Thomson David J.
Published: October 2005

Recently Porter and Jensen [J. Acoust. Soc. Am. 94, 1510–1516 (1993)] reported on a seemingly benign propagation problem in which two wide-angle split-step parabolic equations (PEs) performed poorly compared to other PEs. That is, for a source and receiver located within a leaky surface duct, anomalously high transmission losses were predicted for ranges at which the leakage energy is refracted back into the duct. Moreover, both equations displayed greater sensitivity to the choice of reference wave number than the standard PE. In this paper, a new propagation operator is formulated that retains the computational efficiency of the split-step algorithm but is considerably more accurate. Two rapid numerical solution algorithms valid in both two and three dimensions are then introduced and applied to the leaky surface duct. To implement the simplest second-order method a tridiagonal finite-difference system of equations is solved at each range step in addition to the usual split-step Fourier computations. Higher-order procedures instead involve applying the Lanczos algorithm solely to the higher-order terms in the wide-angle expansion, thereby circumventing the convergence difficulties associated with the direct Lanczos evaluation of the Helmholtz propagator [Hermansson et al., IEEE J. Light. Technol. 10, 772–776 (1992)].
Wave shifts, beam shifts, and their role in modal and adiabatic propagation
Authors: Weston David E.
Published: October 2005

On reflection from a plane interface there is a wave shift which in underwater acoustics is often called the effective depth; there is also a beam shift or beam displacement. These shifts are briefly introduced and then the relation between them is spelled out. In application to modal propagation in a range-independent medium, it is shown that a wave shift sum is invariant with respect to depth and provides an eigenvalue equation. Beam shift sums for the cycle distance and cycle time are useful but only approximately invariant, however their ratio defines the truly invariant group velocity. Propagation in a range-dependent medium is analyzed assuming the adiabatic relation; the wave shift sum is now invariant with respect to range as well. This process corresponds to a ray invariant with wave reflections at a fictitious surface defined by the wave shift. A description in terms of beam shifts is more complicated, but shown to be compatible. A simple upslope example is included.
Time domain reflections and diffractions from facet-wedge constructions: Acoustic experiments including double diffractions
Authors: Li Saimu , Chu Dezhang , Clay Clarence S.
Published: October 2005

Reflection, diffraction, and higher order diffractions from a finite width wedge construction on an effectively infinite plane were studied experimentally and theoretically. The construction consisted of a 12.6-cm-width angle iron on dry wall board or sheet rock. The experiments used a spark as a point source with a separated receiver at the same side of the wedge. The reflected pressure signals were well separated in time domain. Higher order diffractions from the apex and troughs of the wedge were observed. The experimental geometry is in the reflections and is different [Medwin et al., J. Acoust. Soc. Am. 72, 1005–1013 (1982)] transmission and shadow geometry. Medwin et al.’s Huygens based constructions were used to compute the double diffraction events.
Utilization of guided elastic waves for the characterization of circumferential cracks in hollow cylinders
Authors: Ditri John J.
Published: October 2005

The scattering of guided elastic waves from a circumferential crack in an isotropic hollow cylinder is investigated analytically using the S-parameter formalism. A general formula, analogous to that of [B. A. Auld, Acoustic Fields and Waves in Solids (Krieger, Malabar, FL, 1990), 2nd ed., Vol. II, p. 200], is derived for the scattered amplitude of an arbitrary mode due to the incidence of an arbitrary mode. The amplitudes are expressed as an integral of the inner product of the crack opening displacement caused by the incident mode and the traction field of the scattered mode. Using a simple approximate form of known elastostatic solutions for the crack opening displacements due to pure tension, a formula is derived for the scattering of guided wave modes of arbitrary circumferential order due to the incidence of axisymmetric wave modes with large wavelength and uniform stress distribution. These results are analyzed and conclusions drawn on the possibility of crack sizing using relatively simple scattering amplitude information.
Coupling finite element and boundary element methods on a mixed solid–fluid/fluid–fluid boundary for radiation or scattering problems
Authors: Dubus Bertrand
Published: October 2005

The coupling between the finite-element and boundary-element methods is presented in which part of the coupling surface is a solid–fluid interface and part a fluid–fluid interface. The equations are derived for the case of quadratic elements on the finite-element side (atila code) and surfaces of uniform velocity on the boundary-element side (chief code). The accuracy of the method is illustrated by two examples: the scattering of plane waves from a fluid sphere and from a spherical Helmholtz resonator.
Measurements of turbulent pressure fluctuations using a buoyant vehicle coated with a thin elastomer layer
Authors: Galib Thomas A. , Katz Richard A. , Ko Sung H. , Sandman Bruce
Published: October 2005

Turbulent pressure fluctuations were measured with piezoelectric pressure transducers which were covered with a 0.125-in.-thick elastomer window on a buoyant vehicle. Model predictions (i.e., corrections) were made to account for the turbulent pressure attenuation through the elastomeric coating and spatial averaging effects of a finite transducer. The corrected results were compared with classic turbulent spectral densities measured by others and found to be in good agreement.
Pattern formation in acoustic cavitation
Authors: Akhatov I. , Parlitz U. , Lauterborn W.
Published: October 2005

A new approach for the theoretical description of structure formation in acoustic cavitation is developed. The model consists of two coupled partial differential equations describing the spatiotemporal evolution of the sound field amplitude and the bubble concentration. Linear stability analysis and numerical simulations of the pattern formation are presented. The relation between this approach and streamer formation is discussed.
Energetic properties of acoustic fields
Authors: Schiffrer Giuliano , Stanzial Domenico
Published: October 2005

From the energy density and the intensity vector of a general acoustic field in the linear adiabatic approximation, the corresponding time-averaged quantities, the active and reactive intensities, are derived and the inherent ambiguities and some of their properties are discussed. The concepts of pressure-velocity phase relation and of velocity of acoustic energy transport are also introduced for a general acoustic field. It is shown that this velocity in modulus cannot exceed the speed of sound, it vanishes only if acoustic pressure p and velocity v are in quadrature, while it reaches its maximal value only if p and v are in accordance, or in opposition of phase.
Shallow-water time series simulation using normal-mode theory in range-independent and range-dependent environments
Authors: Royal Geoffrey S. , Knobles David P. , Koch Robert A.
Published: October 2005

Broadband normal-mode model analyses of propagation in a shallow-water range-independent environment and in a wedge environment are presented. The model is first used to calculate received time series from a point source for a range invariant shallow-water acoustic environment with a constant water sound-speed medium and a penetrable bottom. Range invariant mode model time series are compared to actual experimental data [C. Tindle etal., J. Acoust. Soc. Am. 81, 288–293 (1987)] and to time series that were calculated using a ray model that includes beam displacement [E. Westwood and C. Tindle, J. Acoust. Soc. Am. 81, 1752–1761 (1987)]. The time series from both the mode and ray models agree with each other and with the measured data. In addition, time series from an adiabatic mode model for a shallow-water wedge environment are compared to the experimental results obtained by C. Tindle etal. [Work supported by IR&D Fund at Applied Research Laboratories, The University of Texas at Austin.]
A time-dependent solution of a wave traversing a wedge by a finite length ping ray trace technique
Authors: White Elmer
Published: October 2005

A technique has been developed which demonstrates that an acoustic wave can be simulated using modified ray trace theory for acoustic modeling in shallow water. The resulting time-dependent wave and the transmission loss data closely compares to that benchmarked in the PE Workshop II Proceedings of the Second Parabolic Equation Workshop published in May 1993, edited by S. A. Chin-Bing, D. B. King, J. A. Davis, and R. B. Evans. The solution approximating test case 2, a range-dependent environment demonstrates forward and backscatter characteristics which agree with both PE and normal-mode theory in its behavior patterns. A VCR composite of time images generated by the code trng.f will be shown which demonstrates the sound wave pattern as it traverses a wedge. Transmission loss data are compared to PE generated TL to verify its accuracy.
Finding eigenrays in environments prone to numerical instability and chaos by directly optimizing the travel time integral
Authors: Mazur Martin A. , Gilbert Kenneth E.
Published: October 2005

In classical ray tracing, eigenrays are determined by a ‘‘shooting’’ approach whereby the launch angles of rays are varied until the rays intersect the receiver. In nonseparable range-dependent environments, the ray paths computed by conventional methods are sometimes chaotic, thereby putting a fundamental limit on the accuracy of ray tracing. Previous researchers [M. D. Collins and W. A. Kuperman, ‘‘Overcoming ray chaos,’’ J. Acoust. Soc. Am. 95, 3167–3170 (1994)] have suggested that ray chaos can be overcome by recasting the problem in terms of Fermat’s principle of minimum propagation time. The problem then becomes amenable to so-called ‘‘direct methods’’ of optimization theory. For the specialized duct investigated by Collins and Kuperman we have easily found eigenrays using a simple Rayleigh–Ritz method for directly minimizing the travel time integral. The structure of the ray equations for the duct suggests, however, that the numerical instability may actually be due to ‘‘stiffness’’ rather than chaos. To investigate chaos independently of numerical issues such as stiffness, we consider several nonseparable, range-dependent ducts with known piecewise analytic ray solutions. Results obtained from a shooting method and from Fermat’s principle for several such ducts are presented and discussed. [Work supported by ONR.]
The acoustic wave equation as a finite difference
Authors: Oelze Michael L.
Published: October 2005

The classical wave equation used to describe acoustic phenomena was converted to a finite difference equation. This was done by constraining a sound packet to be in a box of finite length. By using certain mathematical techniques, recursion relations were found which enabled the amplitude of sound to be measured at every point in the box. This form of the equation is useful in modeling certain acoustic phenomena. The finite difference equation is especially useful in calculating wave reflection/transmission phenomena. The classical way of calculating reflection/transmission was by calculating a separate wave for each reflected or transmitted wave. The finite difference equation method cancels the need for many different waves and encompasses all interference from these waves.
Time-domain propagation of signals in a strongly refractive shallow-water waveguide and the extraction of ocean properties
Authors: Sidorovskaia N. A. , Khil’Ko A. I. , Werby M. F.
Published: October 2005

The complex pressure from a point source is calculated over the frequency range between 1 and 5 kHz in steps of 0.2 Hz as a function of depth and range for a strongly ducted shallow-water waveguide. The waveguide is composed of an 80-m water column over a fluid half-space defined by a compressional velocity of 1650 m/s and a density of 1.6 relative to water. Attenuation in the bottom is 0.25 dB/λ. The velocity in the water column varies from 1540 at the surface to 1513 m/s at the bottom where a pronounced gradient exists between 30 and 60 m, with the remaining regions being weakly dependent on depth. A series of time-domain calculations are carried out from the stored frequency data for pulses in terms of (1) pulse widths, (2) central frequency, (3) depth of detection, and (4) range of detection. The central notion is that the pulse amplitude is strongly correlated with depth due to ducting effects. Further, pulse widths and the principle arrival time adds more information on ocean properties such as the velocity profile and some aspect of seafloor geoacoustic characteristics. Unambiguous systematics that suggest a tool useful for extraction of ocean data are reported. [Work sponsored by ONR.]
Nonlinear analysis and classification of speech under stressed conditions
Authors: Cairns Douglas A. , Hansen John H. L.
Published: October 2005

The speech production system is capable of conveying an abundance of information with regards to sentence text, speaker identity, prosodics, as well as emotion and speaker stress. In an effort to better understand the mechanism of human voice communication, researchers have attempted to determine reliable acoustic indicators of stress using such speech production features as fundamental frequency (F0), intensity, spectral tilt, the distribution of spectral energy, and others. Their findings indicate that more work is necessary to propose a general solution. In this study, we hypothesize that speech consists of a linear and nonlinear component, and that the nonlinear component changes markedly between normal and stressed speech. To quantify the changes between normal and stressed speech, a classification procedure was developed based on the nonlinear Teager Energy operator. The Teager Energy operator provides an indirect means of evaluating the nonlinear component of speech. The system was tested using VC and CVC utterances from native speakers of English across the following speaking styles; neutral, loud, angry, Lombard effect, and clear. Results of the system evaluation show that loud and angry speech can be differentiated from neutral speech, while clear speech is more difficult to differentiate. Results also show that reliable classification of Lombard effect speech is possible, but system performance varies across speakers.
Accuracy of quasistationary analysis of highly dynamic speech signals
Authors: Smits Roel
Published: October 2005

In this paper, the accuracy of the analysis of rapidly varying formants using spectrogram and linear prediction is assessed. Analysis of various dynamic signals shows that, when a long analysis window, like 25 ms, is used, the quality of the representation may be impoverished. Obvious unwanted effects are staircaselike formant tracks, flattening-off of formants close to voicing onset, and bending of the formant towards a strong energy concentration in the release burst. The parameters that have the largest influence on the quality of the representation are the length of the analysis window, the transition rate of the formant, the fundamental frequency, and the position and energy of the release burst. It is shown that the most accurate analysis using a quasistationary method is made when windows are positioned pitch synchronously. Finally, a quantitative analysis of the influence of the mentioned parameters provides evidence that no deviations due to the quasistationarity assumption occur when the effective length of the analysis window is not larger than the pitch period. The wideband spectrogram is expected to be a reliable speech-analysis tool because it meets this condition for fundamental frequencies up to 370 Hz.
Lie detection based on phonatory processes
Authors: Pollina Dean A. , Vakoch Douglas A. , Wurm Lee H.
Published: October 2005

Deception has been shown to be associated with changes in the fundamental frequency (F0) of vocalizations. For example, during attempted deception, F0 typically increases [P. Ekman, W. V. Friesen, and K. R. Scherer, Semiotica 16, 23–27 (1976); L. A. Streeter, R. M. Kraus, V. Geller, C. Olson, and W. Apple, J. Pers. Soc. Psychol. 35, 345–350 (1977)]. The current study examines changes in F0 for the identical utterances at two points in time: prior to establishing any belief about the statement, and after having a belief. By analyzing the same phrase at baseline and after the belief manipulation, more precise measurements corresponding to belief can be made than in previous studies.
Advances in underwater acoustic normal-mode computations
Authors: Levinson Scott J. , Sheppard Carol V. , Mitchell Stephen K.
Published: October 2005

Recently, an efficient, numerically robust algorithm for calculating acoustic normal modes was shown to have more than an order of a magnitude improvement in speed while maintaining high accuracy over other algorithms (submitted to JASA by the authors, June ’94). A limitation remains, however, in its dependence on presampled wave numbers in the search for the roots of the characteristic equation (eigenvalues). Since coarse wave-number presampling may result in some eigenvalues remaining undetected, the presampling part of this code is the most time consuming portion—particularly for multichannel environments. We introduce a new approach which overcomes this problem. Analytic derivatives (up to sixth order) are calculated to locally approximate the numerically robust characteristic equation with Pade’ approximants when finding successive eigenvalues. The requirement of wave-number presampling is thereby avoided and eigenvalue root finding is achieved with a superlinear convergence property. Its speed and accuracy will be compared with previous methods for single and multichannel ocean acoustic environments. [Work supported by the Advanced Surveillance Acoustic Prediction System (ASAPS) Development for IUSS Program of the Space and Naval Warfare Systems Command (SPAWAR, PMW 181-1).]
Matched-phase noise reduction
Authors: Orris Gregory J. , McDonald B. E. , Kuperman W. A.
Published: October 2005

A simple method is presented for improving signal-to-noise ratios in noise dominated data, given the shape of the noise spectrum. No a priori information about the signal is required, except that its spectrum be distinct from that of the noise. Under the condition that the noise spectrum is sufficiently well known, a numerical example is given in which a signal may be detected despite a signal-to-noise ratio less than −100 dB.
Mean-scatterer spacing estimates with spectral correlation
Authors: Varghese Tomy , Donohue Kevin D.
Published: October 2005

An ultrasonic backscattered signal from material comprised of quasiperiodic scatterers exhibit redundancy over both its phase and magnitude spectra. This paper addresses the problem of estimating mean-scatterer spacing from the backscattered ultrasound signal using spectral redundancy characterized by the spectral autocorrelation (SAC) function. Mean-scatterer spacing estimates are compared for techniques that use the cepstrum and the SAC function. A-scan models consist of a collection of regular scatterers with Gamma distributed spacings embedded in diffuse scatterers with uniform distributed spacings. The model accounts for attenuation by convolving the frequency dependent scattering centers with a time-varying system response. Simulation results indicate that SAC-based estimates converge more reliably over smaller amounts of data than cepstrum-based estimates. A major reason for the performance advantage is the use of phase information by the SAC function, while the cepstrum uses a phaseless power spectral density that is directly affected by the system response and the presence of diffuse scattering (speckle). An example of estimating the mean-scatterer spacing in liver tissue also is presented.
Estimation of Prandtl numbers in binary mixtures of helium and other noble gases
Authors: Giacobbe F. W.
Published: October 2005

This paper describes two different theoretical methods of calculating Prandtl numbers for mixtures of noble gases at moderate temperatures and pressures. In order to limit the scope and length of this work, only binary mixtures containing helium and one other noble gas (neon, argon, krypton, or xenon) were considered during this study. However, with relatively slight modifications, the methods described in this work for calculating Prandtl numbers should be applicable to other binary noble gas systems. In addition, theoretical gas mixture viscosities and thermal conductivities were compared with the corresponding experimentally measured values at 20.0 °C in order to provide a better assessment of the quality of the Prandtl number calculations. The results of this study should be useful to researchers and design engineers involved in optimizing the operation of acoustic refrigeration systems.
Investigation of Lamb waves for sensor applications in semiconductor processing
Authors: Degertekin F. Levent , Honein Victor , Khuri-Yakub Butrus T.
Published: October 2005

Considering the semiconductor wafers as anisotropic plates, Lamb wave propagation characteristics are related to various parameters dynamically changing during processing. Particularly, the effect of wafer temperature and thin-film growth on phase velocity of zeroth order Lamb waves are analyzed theoretically. These modes are chosen to enable single mode operation in silicon wafers for frequency-thickness product (f*d) less than 3 MHz mm. The surface impedance approach is used in theoretical modeling of propagation in general multilayered anisotropic solid structures. Temperature, thin film, and their combined sensitivity figures are calculated for commonly used structures in semiconductor processing. The results are interpreted to obtain optimum ultrasonic sensor system parameters for certain applications. For example, in case of aluminum films on (100) silicon, antisymmetric mode in 〈100〉 direction shows negligible sensitivity to thin films around f*d=0.8 MHz mm. The same figure for silicon oxide film is 1.57 MHz mm. In a combined measurement, a temperature sensor using these system parameters to measure phase velocity will be minimally affected by thin films, enabling an isolated temperature measurement. Practical implementations of the results in rapid thermal processing environment are also discussed in the paper. [Work supported by SRC.]
Teaching phonetics to undergraduates at the University of Washington
Authors: Hargus Sharon , Davis Katharine
Published: October 2005

In 1993, the Instrumentation and Laboratory Improvement Program of the National Science Foundation awarded $23,960 to the University of Washington (who provided matching funds) for phonetics facilities for undergraduate education. In accordance with NSF guidelines, a summary of the progress to date is presented here. Funds were used to purchase a DOS machine and a Macintosh, which run software including programs for signal processing, speech synthesis, statistics, word processing, and graphics. Also purchased were analog and digital tape recorders, a mixer, microphones, and other speech analysis equipment including a nasometer and an airflow meter. A sound-treated booth in which to do recordings and perception experiments has been built. This laboratory has enabled us to offer a comprehensive course in Linguistic Phonetics at the undergraduate level, and has allowed us to supplement the offerings of other courses. For example, undergraduates in the Dept. of Asian Studies learned about pronunciation in Japanese, students in the English Phonology and Morphology course learned about individual differences in the implementation of phonology, and students in the Language Acquisition course learned about the phonetic characteristics of ‘‘motherese.’’ There are plans for additional equipment which will enable us to teach students about speech perception as well.
Vocal correlates of interpersonal issues
Authors: Vakoch Douglas A. , Pollina Dean A. , Wurm Lee H.
Published: October 2005

Previous studies have related different interpersonal styles to the fundamental frequency (F0) of subjects’ speech. For example, high ratings of pitch have been associated with self-attributions of dominance and affiliation [K. R. Scherer, J. Psychol. Res. 3, 281–298 (1974)], which are two dimensions along which interpersonal issues have been defined [L. E. Alden, J. S. Wiggins, and A. L. Pincus, J. Pers. Assessment 55, 521–536 (1990); L. S. Benjamin, Psychol. Rev. 81, 392–425 (1974)]. Similarly, subjects with greater pitch variability have been judged to be more benevolent [G. B. Ray, Commun. Monographs 53, 266–276 (1986)]. Previous studies, however, have failed to focus on the problematic aspects of interpersonal functioning. The current study reports on the acoustical correlates of six types of interpersonal problems: (1) excessive concern about the evaluations of others, (2) impact of past abuse, (3) dissatisfaction with therapist, (4) excessive responsibility for partner, (5) fear of abandonment, and (6) ineffective interpersonal responses. For females only, a higher mean F0 was predictive of both a greater sense of excessive responsibility for partner (p<0.05) and an increased fear of abandonment (p<0.05).
Forward and backward presentation of Chinese and English speech in the verbal transformation effect
Authors: Chalikia Magdalene H. , Waldstein Rachel , Stech William J.
Published: October 2005

When hearing a word which is continuously repeated, listeners report that the word seems to change into different forms and then vacillates among these forms. This auditory illusion has been called the verbal transformation effect [R. M. Warren, Br. J. Psychol. 17, 249–258 (1961)] and is considered to be caused by the lack of verbal context, produced by the repetition. This study further investigated the role of context in the interpretation of auditory stimulation. Twenty-six listeners heard the individual, continuous, repetition of six stimuli: an English sentence, an English word, and a Chinese word (each played forward and backward). It was assumed that listeners will report verbal transformations with all stimuli except the English sentence, since only this condition contained sufficient contextual cues. Results showed that both forms of the English sentence were treated in the same manner, and that significantly more verbal transformations were reported with the words.
Control experiments on the frequency scale of speech intonation
Authors: Hermes Dik J. , Rump H. H.
Published: October 2005

According to Hermes and Van Gestel [J. Acoust. Soc. Am. 90, 97–102 (1991)], prominences of accent-lending pitch movements in different registers are equal when their excursion sizes are equal on the ERB-rate scale. A reanalysis of their experiments showed that an octave relationship between the high pitch levels in the different registers may have been crucial. In order to test whether this factor influenced the outcome of their experiments, adjustment experiments were performed with stimuli in different low and high registers. The results, supporting the ERB-rate scale hypothesis of Hermes and Van Gestel, showed that the octave relationship had no systematic influence on the results. In an additional experiment, stimuli were resynthesized from a male and a female voice in order to test the effect of the speaker’s natural pitch range. The male and female stimuli gave about the same results. In sum, the effect of pitch excursion on prominence is very robust. An unexpected finding was that, on average, the excursions of the pitch movements in the high register were about 0.15 E (0.5–1 semitone) larger than those of the pitch movements in the low register when lending equal prominence.
Prosodic characteristics of register variation in the read speech of adult native speakers of French
Authors: Levitt Andrea G. , Geoffrion Jeannine
Published: October 2005

Ten female native speakers of French were asked to read two paragraphs in each of three register styles: to a friend (native), to a nonnative speaker (foreigner talk), and to a 1-year-old child (child-directed speech). There were significant differences in the speech rate, number and length of pauses, and mean F0 and F0 range among the three speech styles. Speech rate was significantly different for each of the registers, with foreigner talk the slowest, native speech the fastest, and child-directed speech in between the other two. A similar pattern of significant differences emerged for pause length and number of pauses, again with foreigner talk showing the most pauses and the longest average pause length, native speech showing the fewest and shortest pauses, and child-directed speech in between the other two. Mean F0 was significantly higher for child-directed speech than for the other two registers, which did not differ from one another. The three registers did differ significantly from one another in terms of F0 range, with child-directed speech showing the greatest F0 range, native speech the smallest, and foreigner talk in between the other two. [Work supported by NIH Grant No. 1 R15 HD28173-01.]
Prosodic cues of repetitions in Spanish spontaneous discourse
Authors: Munday Pilar
Published: October 2005

When Spanish speakers repeat words or phrases in discourse, some repetitions are due to false starts or hesitations while others are used for emphasis or clarity. These will be referred to as ‘‘hesitations’’ and ‘‘emphasis’’ repetitions, respectively. Although the purpose of the repetition can often be determined from discourse context or part of speech, this study shows that there are also prosodic cues that serve to distinguish the two types. The speech data consist of all repetitions uttered by a male Colombian speaker over the course of a 1-h spontaneous conversations. The following acoustic information was obtained for each utterance and its repetition: duration, peak amplitude, average amplitude, and duration of any intervening pause. Pauses occur more often and tend to be longer in hesitation repetitions. Contrary to previously reported findings for English, however, a pause is frequently not present. The first element of the hesitation repetition tends to be longer than the second. Amplitude does not appear to differentiate the two types of repetitions. The results suggest that durations is the most important cue for distinguishing between types of repetitions.
Perceptual centers as an index of speech rhythm
Authors: Harsín Charles Andrew , Green Kerry P.
Published: October 2005

One of the obstacles to investigating speech rhythm has been the difficulty in locating the syllabic beat. This study attempts to address that difficulty by using perceptual centers (p-centers) as an index of speech rhythm. P-centers of syllables extracted from natural utterances were determined both by listeners using a method of adjustment procedure and by an acoustic p-center model. The phonetic structure (syllabic onset) and stress patterns of the syllables in the utterances were varied, and the effects of these manipulations on the utterances’ rhythms were investigated. As expected, the p-centers of the syllables varied systematically with their own phonetic structure. Preliminary findings indicate that the p-center of the syllables also changes along with the p-center of the previous or subsequent syllable so as to maintain a relatively constant interval between the two p-centers. The study also examines the effects on rhythm of altering stress patterns, by determining whether unstressed syllables might influence p-centers. The results will be discussed in terms of dynamic constraints which might affect speech production. [Work supported in part by National Multipurpose Research and Training Center Grant No. P60 DC-01409 from the National Institute on Deafness and Other Communication Disorders.]
Prediction of speech transmission quality of wideband and narrow-band telephone handsets using short-time sub-band analysis and psychoacoustic models
Authors: Krebber Winfried
Published: October 2005

A predictor is presented which estimates the mean opinion score (MOS) for a given speech sample from speech and noise transfer characteristics of a specific handset applied to an artificial ear. The critical band rate excitation pattern is computed in 50-ms blocks for original and distorted speech signals and additive room noise. For each block three psychoacoustic parameters are computed: An intelligibility index (I) is evaluated using SNR analysis in each sub-band and considering simultaneous masking effects. Naturalness (N) is estimated by spectral distance between original and distorted speech. A loudness index (L) is derived from loudness (computed similar to ISO532) using a trapezoid function: L decreases if the loudness which is exceeded in 10% of time is lower than 15 sone or higher than 45 sone. The MOS is predicted as a weighted sum of I, N, and L. The prediction results were verified by an opinion test including totally 442 speech samples of several talkers which were filtered simulating typical transfer characteristics of handsets and presented in a noisy environment. Speech level and SNR were varied in a wide range. The comparison proves a good correlation (p=0.93 for all samples and p=0.96 for speech levels below 76 dB SPL).
Analysis of quality factors in synthetic speech produced by rules
Authors: Miyazawa Eri , Nagabuchi Hiromi
Published: October 2005

This paper investigates how various factors affect the quality of synthetic speech produced by rules. Using rules to synthesize speech will be an important technique for providing various telecommunication services in future intelligent networks. The quality of synthetic speech is generally measured by subjectively evaluating the speech from the viewpoint of intelligibility, or by comparing it with the quality of other types of synthetic speech. However, the development of a practical speech synthesis method for use in telecommunication networks requires an overall quality evaluation, including intelligibility and naturalness. The quality should be compared with that of natural telephone speech. To establish an overall quality evaluation method, the effects of several factors on the overall quality (expressed by MOS) of speech synthesized by several Japanese text-to-speech systems are quantitatively compared with the effects of using additive speech-correlated white noise as a natural speech material. Experimental results show that such factors as subject, listening experience, average pitch frequency, and text affect synthetic speech more than natural speech. Quality evaluation characteristics due to these factors are discussed and an overall quality evaluation method for synthetic speech is proposed.
Speech stress classification and feature analysis using a neural network classifier
Authors: Womack Brian D. , Hansen John H. L.
Published: October 2005

Variability in speech production due to task induced stress contributes significantly to loss in speech processing performance. A new neural network algorithm is formulated which classifies speech under stress using the susas stress database. Five spectral parameter representations (Mel, Δ-Mel, Δ2-Mel, Auto-Corr-Mel, and Cross-Corr-Mel cepstral) are considered as potential stressed speech relayers. Eleven stress conditions are considered which include Angry, Clear, Fast, Lombard, Loud, Normal, Question, Slow, and Soft speech. Stressed speech classification using these features is evaluated with respect to (i) pairwise class separability, (ii) an objective measure of pairwise and global feature separability, and (iii) analysis of articulatory vocal tract area functions. Perturbations in speech production under stress are reflected to varying degrees in the five speech feature representations. A neural network classifier over phoneme partitions can achieve good speaker dependent classification performance (80.6%) when stress conditions are combined into six groups of related stress domains. The implication of reliable stress classification will be discussed for applications such as monitoring speaker state, improving naturalness of speech coding, and increasing robustness of speech recognizers in adverse conditions.
Coregistration of received signals with bathymetry using a
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Authors: Lupien Vincent H. , Fricke J. Robert
Published: October 2005

As part of the ARSRP, a software package called Acoustical Ray-Tracing Insonification Software (artist) was developed which performs the coregistration of received signals to areas of the seafloor for direct paths. The transmitting and receiving array beampatterns are projected onto the actual seafloor by ray-tracing to yield two insonification patterns. The (x,y) loci of ray contacts with the seafloor are then triangulated and shadow-zone processed so that the interior of each triangle is inside the illuminated region. Using a bivariate interpolator over each triangle of the insonification patterns, an intersection pattern is generated on a rectangular grid, yielding among other parameters: two-way travel times, TL, beampattern values, and grazing angles. Only the points which lie in the illuminated zones of both the receiver and transmitter are kept. By using another bivariate interpolator over each patch of the intersection pattern, pairs of time contours are generated and for each patch intersected by a contour; the fractional area lying inside the time window is calculated. The final step in the coregistration is to select only those patches which are most loudly insonified for each time window. The patches do not have to be adjacent and the amplitude criteria are user-specified. [Work supported by ONR.]
Modified lead titanate with Eu and Mn for high-frequency ultrasonic transducer
Authors: Suaste E. , Leybón J. , Salazar V. H. , Perez-Martínez O.
Published: October 2005

The conventional materials, such as PZT ceramics, show a high electromechanical coupling factor; however, they must be acoustically matched to tissue in order to facilitate transmission and reception over a broad frequency band. Application of this ceramic in linear arrays entails additional complexity. Each element in an array must be subdivided into several subelements to suppress coupling unwanted lateral modes. Thus piezoelectric ceramics with large electromechanical anisotropies (the electromechanical coupling factor for thickness dilatational vibration Kt is much large than that for planar extensional vibration Kp) have recently come to be developed for use as high-frequency ultrasonic transducer materials. PbTiO3 ceramics modified with alkaline metals or rare earth have been extensively investigated because of their promise as a piezoelectrical materials for high-frequency and high-temperature applications. In Pb[(Co1/2W1/2)0.04Ti0.96]O3 ceramics Yamashita etal. reported that the electromechanical coupling factor for thickness dilatational vibration Kt increasing of poling field but coupling factor for planar extensional vibration Kp was negligibly small. In (Pb0.88Ln0.08)(Ti0.98Mn0.02) ceramics (Ln=La, Nd, Sm, and Gd) Takeuchi etal. found that the Sm ion was excellent in the substitution of the Pb ion to make large electromechanical anisotropy between longitudinal and transverse mode vibration. Electromechanical properties of PbTiO3 ceramics modified by the partial substitution of Eu for Pb and Mn for Ti are examined, and the results are compared with the partial substitution of Sm and other elements of the lanthanides group.
Transit time determination in a one-way ultrasonic measurement system
Authors: Vestrheim Magne , Vervik Steinar , Kanagasundram Murugendran
Published: October 2005

Frequency and time domain analysis are used to study the transit time determination in a one-way ultrasonic measurement system for gases at around 200 kHz. Effects of transducers, diffraction, and interfacing to electronics on pulse forms and transit times are considered. Comparisons are made with experimental results using two transducers mounted in a stabilized acoustic chamber where fluctuations can be reduced so as not to affect amplitude and time measurement accuracies. By utilizing a fitted model for the transmitting responses of the transducers together with measured impedance data and the assumption of reciprocity, a useful modeling of the signal transmission through the system is achieved. The effects of receiving electronics and cabling are also measured and included. The results are used to discuss effects on the transit times for recent precision multibeam ultrasonic flowmeters used in the transport of natural gas, and at resolution and accuracies required in the zero calibration of such meters. [Work performed in cooperation with Christian Michelsen Research, Bergen.]
A phase analysis of an ultrasonic pulse signal for measuring travel time
Authors: Lee Eunbang , Ohtsuki Shigeo
Published: October 2005

A pulse signal has been utilized extensively for estimating travel time in an ultrasonic field. Travel time can be measured by calculating the time difference between transmitted signal and received signal. In a conventional method, time resolution is limited to its pulse width. Also, the received signal has an influence on the transducer characteristic and propagation characteristic and is distorted from the transmitted signal. It is not easy to compare between two different signals for measuring travel time. A technique to analyze the pulse signal by phase for measuring travel time is proposed. This technique can be applied to both a continuous-wave method and an impulse wave method for measuring travel time. The major feature is that the fluctuation of signals dependent on time is displayed in time domain, faithfully. Another feature is a method for identifying different amplitude signals, because this technique is independent of their amplitudes and dc bias. This technique is useful and acceptable for estimating time information such as travel time.
Separation of overlapping reflections for ultrasonic NDE applications
Authors: Patton Richard D. , Marks Patrick C. , Bennett James
Published: October 2005

Since individual layers in a composite material return their own reflections, it is necessary for ultrasonic NDE to separate a received signal into a series of reflections. This becomes more complicated when the layers are thinner than the wavelength of the ultrasonic signal used for testing, resulting in overlapping reflections. The Gauss linearization minimization method was used to separate overlapping reflections [J. V. Beck and K. J. Arnold, ParameterEstimationinEngineeringandScience (Wiley, New York, 1977)]. This algorithm fits a pulse obtained from the pulser receiver to the measured data. Amplitude and time delay estimates are made for each reflection. Multilayer Plexiglas samples with subwavelength thicknesses at 1 but not at 5 MHz were fabricated to verify the performance of the algorithm. Each sample was tested at 1 and at 5 MHz. The algorithm provided curve fits for the 1-MHz data that were almost identical to the theoretical results. The maximum error was 8% and the average error was 2%. Each of the reflections predicted by the curve fits were identified and verified in the 5-MHz data. [Work supported by the Mississippi NSF EPSCoR grant.]
Radiation sensitivity of baffled plates to structural perturbation
Authors: Hahn Steven R. , Ferri Aldo A.
Published: October 2005

The analysis of acoustic radiation and scattering from submerged elastic structures is an important and challenging problem. Often, numerical solutions are hampered by the fact that the acoustic pressure field can be very sensitive to structural detail. In this presentation, a baffled plate submerged in a semi-infinite acoustic medium is used study this sensitive. A finite element description of the structure and a boundary element description of the fluid are used to model the plate-fluid-baffle arrangement. The sensitivity information is obtained by applying perturbation techniques to the matrix equations that arise, yielding exact derivatives of the chosen field variable. Several types of local structural perturbations (point masses, springs, dampers, and ribs) as well as global perturbations (Young’s modulus, density, damping) are considered. The nature of the structural sensitivity is examined and some investigation is made into what types of structural features have the greatest impact on radiation and scattering. Finally, the use of the sensitivity information for engineering and design is discussed.
Structural intensity in an infinite cylindrical shell driven by normal forces
Authors: McDowell Donald J. , Burroughs Courtney B. , Godoy Carlos M.
Published: October 2005

The structural intensity formulation provided by Williams [J. Acoust. Soc. Am. 89, 1615–1622 (1991)] is used to consider the flow of power along an infinite length, thin cylindrical shell driven by a harmonic force applied in the radial direction. Finite element modeling is used to show that the active component of the time-averaged intensity oscillates with respect to the axial coordinate of the shell at a wave number given by the difference between the bending and longitudinal wave numbers. The reactive component of the intensity also oscillates at this rate and is in phase quadrature with the active component. This suggests that the total power at any point along the shell is constant and power is exchanged between wave types. The stored (reactive) power is shown to be associated with circumferential expansions and contractions of the shell.
Balance of energy between scattered and reflected waves resulting from an axial surface wave incident on a discontinuity of a fluid-loaded cylindrical shell
Authors: Means Steven L.
Published: October 2005

There is a branch of the dispersion curve of fluid-loaded cylindrical shells in which fluid mass and an ‘‘effective’’ spring stiffness balance at low frequencies. This leads to a surface wave with a wave number which becomes increasingly close to the acoustic wave number as the frequency tends to zero. When such a surface wave, propagating along the axis of the cylinder, is incident on a shell discontinuity, energy is scattered back along the cylinder’s axis and into the surrounding fluid. The present paper examines the balance of the energy between the reflected and the scattered waves. Comparisons are made with analogous surface waves scattered by a discontinuity of an elastic plate on an elastic foundation.
SEA with exterior fluid loading: An open channeling
Authors: Barbone Paul E. , Crighton D. G.
Published: October 2005

We describe the vibration of a submerged elastic solid within a statistical energy analysis (SEA) framework. We discuss the modal structure of a submerged elastic solid, and contrast it to that assumed in traditional SEA analyses. In particular, submerged solids have higher modal density than their invacuo counterparts, much higher levels of (frequency dependent) damping, and possibly strong coupling between the fluid and solid. Further, modes of submerged structures do not form a complete set, and the energy of oscillation in a fluid/solid mode is often irretrievable, independent of the coupling in the system. These results pinpoint the shortcomings of SEA in addressing exterior fluid loading. We close by identifying research directions for the advancement of SEA toward incorporating exterior fluid loading. [Work supported by ONR.]