bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonaxisymmetric acoustic field excited by a cylindrical tool placed off a borehole axis and extraction of shear wave
Authors: Zhang Bixing , Wang Kexie , Dong Qingde
Published: October 2005

The nonaxisymmetric acoustic field excited by a cylindrical tool placed off the axis of a fluid-filled borehole is investigated. It is shown that the acoustic fields are composed of infinite numbers of the multipole fields with different orders. In cases in which the medium outside the borehole is an isotropic homogeneous elastic solid and a two-phase medium, the dispersion and excitation of the mode waves such as Stoneley waves, pseudo-Rayleigh waves, flexural waves, and screw waves are studied. The full waveforms in the time domain are also simulated and analyzed. It is pointed out that the components of the symmetric and nonsymmetric acoustic fields could be strengthened or weakened by adding and subtracting the two full waveforms logged in some opposite azimuths in a horizontal plane. A method of extraction of the shear wave is presented, and the relationship of the nonsymmetric acoustic field to the shear wave logging is analyzed.
Transient acoustic near field in air generated by impacted plates
Authors: Schedin S. , Wåhlin A. O. , Gren P. O.
Published: October 2005

The transient acoustic near field in air from impacted cantilever plates of two different geometrical shapes and materials is studied using two-reference-beam double-pulsed holographic interferometry. The acoustic waves, observed in two directions simultaneously, are generated by traveling flexural waves in the plates and by the impact process itself. A subsequent phase-stepping procedure is used for quantitative evaluation of the registered two-dimensional projections of the acoustic fields. An interesting observation is the acoustic radiation at the free end of the plate, where sound waves propagate into the air in oblique directions from the plate. At the region right above the free end no acoustic waves are observed. Supersonic flexural waves in the plates generate trace-matched acoustic waves in the surrounding air. Calculations of the corresponding two-dimensional transient acoustic fields are performed. Those are based on an analytical solution of the Kirchhoff plate equation. Calculated results reproduce the character of the observed transient acoustic waves quite well.
Propagation of sound above an impedance plane in a downward refracting atmosphere
Authors: Li Kai Ming
Published: October 2005

An asymptotic analysis has been carried out to study the propagation of sound at long ranges in an arbitrary downward refracting sound-speed profile. It has been shown that the solution can be expressed in a form of the Weyl–Van der Pol formula and the present theory offers an extension for the established theory to the case of a vertically stratified medium. The analysis starts from the full wave equation and the derivation assumes that the ambient properties only depend on the height above an impedance ground and that there is no wind or turbulence in the medium. In addition, the theory also assumes that the sound speed of the atmosphere increases monotonically with height. For such an atmospheric condition, the medium forms a waveguide that enhances the sound levels at long ranges along the ground surface. It is demonstrated that the acoustical path length derived by the asymptotic method is identical to that derived by the analytical ray trace model. Furthermore, the asymptotic method also allows a proper inclusion of the surface wave term rigorously.
Sound propagation over impedance discontinuities with the parabolic approximation
Authors: Robertson J. S. , Schlatter P. J. , Siegmann W. L.
Published: October 2005

Long-range, low-frequency sound propagation over varying terrain conditions is an important problem with both civilian and military applications. This work considers the modeling of cw acoustic signals as they propagate over variable-impedance topography. The NASA implicit finite-difference (NIFD) implementation of the parabolic approximation sound propagation model that incorporates variable-impedance ground surfaces was used. The accuracy of this numerical model is demonstrated with a pair of test problems. An application of the results is used to predict excess attenuation of pure-tone signals whose propagation path includes portions of a flat lake surface.
A Padé approach for eigenvalue identification in underwater acoustic normal mode computations
Authors: Levinson Scott J.
Published: October 2005

Recently, an efficient, numerically robust algorithm for calculating acoustic normal modes called MODELAB was implemented [J. Acoust. Soc. Am. 97, 1576–1585 (1995)]. In this paper, a new approach is introduced and shown to significantly reduce the most computationally intensive aspect of MODELAB: the requirement of fine wave number presampling during the search for eigenvalues. Analytic derivatives (up to sixth order) are efficiently calculated using a new recursion relation for the characteristic equation. The derivatives are used to form Padé approximants, which in turn, are used to locally extrapolate the characteristic equation to find successive eigenvalues. Results indicate that an algorithm using this technique can be more than a factor of five times faster than the MODELAB algorithm, and the new technique is shown to be particularly efficient at near-degenerate eigenvalues, which previously had been the most difficult to identify.
Reflection and transmission coefficients for a layered fluid sediment overlying a uniform solid substrate
Authors: Ainslie Michael A.
Published: October 2005

Simple expressions are found for plane-wave reflection and transmission coefficients for a layered (continuously varying density and sound speed) fluid sediment layer sandwiched between a uniform fluid above (representing the ocean) and a uniform solid substrate below; exact solutions are derived first in terms of the wave functions in the sediment layer, and these are then approximated using Langer’s generalization of the WKB method. The approximate solutions, valid for monotonic but otherwise arbitrary sediment profiles, are evaluated for a class of quasilinear sound-speed profiles and shown to be very accurate for the cases considered; for some special cases they turn out to be exact. Bottom loss predictions are presented for a clay sediment overlying a basalt substrate, examining in particular the influence of different density and sound-speed profiles on the excitation of Stoneley waves at the sediment–substrate boundary.
The effect of distractor frequency on judgments of target laterality based on interaural delays
Authors: Dye Raymond H. , Stellmack Mark A. , Grange Anthony N. , Yost William A.
Published: October 2005

A two-dimensional stimulus-classification paradigm was used to examine the ability of listeners to judge the laterality of an interaurally delayed low-frequency target component presented concurrently with a distractor component. Of primary interest was the effect on performance of the frequency difference (Δf) between the target and distractor. In one set of conditions, the target was fixed at 753 Hz and the distractor was 353, 553, 653, 703, 803, 853, 953, or 1153 Hz (fixed within a block of trials). In a second set of conditions, the distractor was fixed at 753 Hz and the target frequency was 353, 553, 653, 703, 803, 853, 953, or 1153 Hz. The listeners were presented with a target component with an interaural delay that varied from trial to trial, taking on one of ten values, five leading to the left ear and five leading to the right. A distractor component was simultaneously presented with an interaural delay that also took on one of the same ten values. Delays ranged from −90 to +90 μs in 20-μs steps. During a block of 100 trials, each of the possible combinations of target and distractor delay was presented once and only once in a random order.

Listeners were instructed to make left–right judgments based on the target delay. Each condition was repeated ten times, and the slopes of the best linear boundaries between left and right responses were used to derive the relative weights given to the target and distractor. The duration of the signals was 200 ms. Two of the eight listeners weighted the target heavily when the target and distractor were spectrally remote but gave the two components equal weight when the difference in frequency was small. These two listeners yielded similar target weights regardless of which component was designated as the target. One listener gave nearly equal weight to the target and the distractor regardless of Δf. Five of the listeners gave greater weight to the higher of the two frequencies regardless of which was assigned as the target. This high-frequency dominance is explained in terms of cross-correlation functions based on the composite two-tone waveforms.
Vowel-onset detection by vowel-strength measurement, cochlear-nucleus simulation, and multilayer perceptrons
Authors: Kortekaas Reinier W. L. , Hermes Dik J. , Meyer Georg F.
Published: October 2005

An algorithm for detection of vowel onsets in fluent speech was presented by Hermes [J. Acoust. Soc. Am. 87, 866–873 (1990)]. Performance tests showed that detection was good for fluent speech, although the parameter settings had to be modified for application to well-articulated speech. One of the purposes of the algorithm was application to speech by deaf persons, for which it failed completely. In order to improve the algorithm and to make it more generally applicable, two alternative detection strategies have been explored in the present study. These strategies were (a) simulation of transient-chopper responses in the cochlear nucleus and (b) training of multilayer perceptrons. Two large databases of read speech have been used for performance comparison of the original algorithm and the new strategies. The strategy based on simulating cochlear-nucleus responses is found both to result in a higher false-alarm rate than the original algorithm and to be rather level dependent. On the other hand, the performance of a multilayer-perceptron network, trained on mel-scaled spectra, is comparable to the performance of the Hermes algorithm. In more general terms, the results suggest that temporal information on intensity and (rough) spectral envelope are important for human vowel-onset detection behavior. Information on harmonicity can be used as a secondary source of information to avoid detection of mainly unvoiced, nonvowel onsets.
The potential role of speech production models in automatic speech recognition
Authors: Rose R. C. , Schroeter J. , Sondhi M. M.
Published: October 2005

This paper investigates the issues that are associated with applying speech production models to automatic speech recognition (ASR). Here the applicability of articulatory representations to ASR is considered independently of the role of articulatory representations in speech perception. While the question of whether it is necessary or even possible for human listeners to recover the state of the articulators during the process of perceiving speech is an important one, it is not considered here. Hence, the authors refrain from posing completely new paradigms for ASR which more closely parallel the relationship between speech production and human speech understanding. Instead, work aimed at integrating speech production models into existing ASR formalisms is described.
Spontaneous otoacoustic emissions in two gecko species, Gekko gecko and Eublepharis macularius
Authors: Manley Geoffrey A. , Gallo Lothar , Köppl Christine
Published: October 2005

Spontaneous otoacoustic emissions (SPOAE) of the gecko species Gekko gecko and Eublepharis macularius appear as broad spectral peaks (bandwidth 44 to 170 Hz) between 1 and 4.5 kHz that have peak levels of −7 to 10 dB SPL. Most ears showed SPOAE at many frequencies. In some ears, the peaks were superimposed on a broad baseline emission. The instantaneous frequency of any emission varied rapidly within its bandwidth limits and frequencies in the center of the band occurred most commonly, but not with higher levels than frequencies on the periphery of the band. SPOAE were temperature dependent, rising in frequency with an increase in temperature and falling with a decrease in temperature (rate of change from 54 to 107 Hz/°C), with no systematic changes in peak level except that at the temperature extremes, the SPOAE disappeared into the noise. External tones suppressed SPOAE peak level in a frequency-dependent way. Isosuppression tuning curves were V-shaped. In restricted frequency ranges, facilitation also occurred. External tones also caused shifts in the frequency of SPOAE; frequency ‘‘pushing’’ was more common than ‘‘pulling.’’ The maximal frequency shift observed was 313 Hz. In general, the SPOAE characteristics strongly resemble those already reported in the bobtail lizard Tiliqua rugosa.
Parametric modeling and estimation of ultrasonic fields using a system identification technique
Authors: Zhou D. , Peirlinckx L. , Lumori M. L. D. , Van Biesen L.
Published: October 2005

A system identification technique is presented for the parametric modeling and estimation of acoustic fields generated by an ultrasonic transducer. In this technique, the ultrasonic fields are modeled by the superposition of Gaussian beams. The model order, i.e., the number of the Gaussian beams used, and the characteristic coefficients of these Gaussian beams for the superposition depend on the source distribution. An experimental system is built to measure the acoustic fields. From the measured amplitude and phase data, a maximum likelihood estimator is utilized to determine the order and characteristic coefficients of the field model. Once the order and coefficients of the field model are estimated, a complete parametric description of the acoustic fields is then obtained. Using the estimated model, the prediction of the acoustic fields can be made in both forward and backward direction. The predicted and measured fields are then compared to validate the model. The experimental results demonstrate the capability of the technique for the parametric description of ultrasonic fields.
Accuracy of same/different judgments of sequences of complex tones differing in tonal order under various levels of fundamental frequency range, listener training, and type of standard sequence
Authors: Barsz Kathy
Published: October 2005

Same/different judgments of sequences of complex tones differing in tonal order were obtained so that the relationship of performance to the range among the sequential tones’ fundamental frequencies could be measured. Frequency range was defined as the difference between the mean of the two higher fundamental frequencies and the mean of the two lower fundamental frequencies which alternated with them; strengths and weaknesses of this measure are discussed. Data were taken from naive and trained listeners using fixed and random standards. Performance declined as frequency range increased. The performance of listeners trained with a variable standard and in a single condition of the study improved only at the narrowest frequency range; with a fixed standard, this training yielded improvements at a wider frequency range. The performance of listeners trained with a variable standard and in all the conditions improved at the narrow and moderate frequency ranges; with a fixed standard, this training yielded the highest levels of performance measured in each frequency range. The results are discussed in terms of subdivided temporal compounds, auditory attention, and memory for sequences.
Critique: Auditory form and gestural topology in the perception of speech
Authors: Remez Robert E.
Published: October 2005

Some influential accounts of speech perception have asserted that the goal of perception is to recover the articulatory gestures that create the acoustic signal, while others have proposed that speech perception proceeds by a method of acoustic categorization of signal elements. These accounts have been frustrated by difficulties in identifying a set of primitive articulatory constituents underlying speech production, and a set of primitive acoustic-auditory elements underlying speech perception. An argument by Lindblom favors an account of production and perception based on the auditory form of speech and its cognitive elaboration, rejecting the aim of defining a set of articulatory primitives by appealing to theoretical principle, while recognizing the empirical difficulty of identifying a set of acoustic or auditory primitives. An examination of this thesis found opportunities to defend some of its conclusions with independent evidence, but favors a characterization of the constituents of speech perception as linguistic rather than as articulatory or acoustic.
Critique: The potential role of speech production models in automatic speech recognition
Authors: Moore Roger K.
Published: October 2005

This paper presents a critique (by a ‘‘speech technologist’’) of ‘‘The potential role of speech production models in automatic speech recognition’’ by R. C. Rose, J. Schroeter, and M. M. Sondhi which was presented at the 1994 ASA Special Session on ‘‘Speech Recognition and Perception from an Articulatory Point of View.’’ While in general agreement with the points raised in the Rose paper, this article focuses on issues such as (a) whether articulatory information should be ‘‘recovered’’ as part of a recognition process as opposed to that process being ‘‘constrained’’ by articulatory information, (b) how optimum recognition performance is achieved by compromising the ‘‘quality’’ of the underlying generative model, and (c) if recent developments in speech pattern modeling will lead to more powerful generative models of speech. Finally, it is noted that the special session highlighted the fact that a convergence is long overdue between the speech science and speech technology communities toward common (mathematically and computationally based) theories of ‘‘speech pattern processing.’’
Speech perception is hearing sounds, not tongues
Authors: Ohala John J.
Published: October 2005

Three types of evidence are reviewed which cast doubt on claims that recovery of the speaker’s articulations is an inherent part of speech perception: (a) Phonological data (e.g., universal tendencies of languages’ segment inventories, phonotactic patterns, sound changes, etc.) show unmistakably that the acoustic-auditory properties of speech sounds, not their articulations, are the primary determinant of their behavior. (b) Infants and various nonhuman species can differentiate certain sound contrasts in human speech even though it is highly unlikely that they can deduce the vocal tract movements generating the sounds. (c) Humans can differentiate many nonspeech sounds almost as complex as speech, e.g., music, machine noises, as well as bird and monkey vocalizations, where there is little or no possibility of recovering the mechanisms producing the sounds.
Doppler bandwidth dependence on beam to flow angle
Authors: McArdle Andrew , Newhouse Vernon L.
Published: October 2005

The dependence of Doppler bandwidth on transducer beam axis to flow angle for different sample volume geometries is computed, using the Fresnel–Kirchhoff diffraction integral. The computed Doppler bandwidths are shown to agree with experiment. The numerical analyses suggest that a finite Doppler bandwidth exists even for flows parallel to the axis of a continuously transmitting focused transducer, due to the pressure variation along the beam axis.
Interdisciplinary nature of acoustics—Musical acoustics example
Authors: Martin Daniel W.
Published: October 2005

Sound is more than an ‘‘oscillation...in a medium’’ or ‘‘an auditory sensation evoked by the oscillation.’’ From an academic standpoint it involves physical sciences, engineering, life sciences, and art. From an application standpoint it is also related to invention, design, economics, business, and even legislation. These relationships can be described and diagrammed in several different ways. The field of musical acoustics is used as an example of the interaction among the various disciplines.
An integrated model of scattering from an imperfect interface
Authors: Harris John G. , Rebinsky Douglas A. , Wickham Gerry
Published: October 2005

The antiplane shear, SH or scalar problem of scattering from an interface characterized by a narrow region of heterogeneity is considered. An approximate integral representation of the scattered wave fields in terms of a Green’s function for a reference problem, and the stress and momentum polarizations averaged through the thickness of the interface is derived. Providing certain material contrast parameters are O(1), the error in this expression is formally O(kh)2, where k is the wave number and 2h is the thickness of the interface. To find the unknown polarizations we specialize to a model configuration that is periodic over a length scale much greater than the characteristic length scales of the heterogenities in the interface. This allows an exact formulation in terms of an infinite system of algebraic equations. Expressions modeling the reflection and transmission measured by a coaxial, confocal pair of transducers are then derived so that the effects of the transducer can be included in the modeling. These coefficients are calculated in terms of the solution of the algebraic system. Numerical results for several different model interfaces are presented.
Prediction of sound pressure radiated from the open end of a pipe and muffler insertion loss using a single, efficient scheme: Applications to a vacuum pump
Authors: Sridhara B. S. , Crocker Malcolm J.
Published: October 2005

A single, efficient scheme developed by Sridhara and Crocker [J. Acoust. Soc. Am. 95, 2363–2370 (1994)] was used to predict the radiated sound pressure and muffler insertion loss by incorporating a simple logical statement in the computer codes. The scheme was verified through a series of experiments. A 0.06-m-diam loudspeaker and a single cylinder, reciprocating-type vacuum pump were used as sound sources during the tests. The source impedance was measured using the direct method. A 0.114-m-diam and 0.3-m-long simple expansion chamber and a 0.006-m-diam and 0.025-m-long side-branch resonator were used as mufflers. Sound-pressure level measurements for the prediction scheme were made for several source–muffler and source–straight pipe combinations. The predicted and measured sound-pressure levels were compared for all cases considered. In all cases, correlation of the experimental results and those predicted by the developed expressions was good at low frequencies. Predicted and measured values of muffler insertion loss were also compared. The agreement between the two quantities was good.
New theoretical expressions for acoustic fluctuations due to temperature structure of the ocean
Authors: Thuraisingham R. A.
Published: October 2005

Existing models to obtain acoustic intensity and phase fluctuations due to thermal structure in the ocean, such as that developed by Chernov, are limited in their application. They are valid only for an isotropic medium and where the range is much greater than the correlation distance of the thermal structure. Extensions to short range and for an anisotropic medium are described here, both for the stochastic wave and ray models. Numerical estimates of acoustic fluctuations are easily evaluated from these theoretical expressions.
Acoustic diffraction from the junction of two joined parallel plates
Authors: Norris Andrew N.
Published: October 2005

Two parallel semi-infinite plates are joined together at their common end, with vacuum in the infinitesimal gap between them and acoustic fluid outside. The configuration is an idealization of a realistic structural member such as the bow or keel of a ship where the structural elements are joined at an acute angle. The exact solution for acoustic diffraction from the parallel double plate junction is obtained using thin plate theory and the Wiener–Hopf technique. The diffraction coefficient is strongly dependent upon frequency, unlike the analogous coefficients for edge diffraction from hard or soft screens. However, the relative simplicity of the general solution permits analytical comparisons with these idealized boundary conditions. At low frequencies the diffraction simulates the response from a soft or pressure release screen. At high frequencies, or more precisely under light fluid-loading conditions, the hard screen approximation is more appropriate. Numerical examples illustrate the transition from soft to hard diffraction, and an approximate but simple uniform diffraction coefficient is proposed which has the correct limiting behavior at low and high frequency.
Acoustic radiation from cylindrical shells due to internal forcing
Authors: Guo Y. P.
Published: October 2005

This paper studies sound radiation from cylindrical shells due to internal sources; the sources excite structural vibrations inside the shell, which are transmitted to the shell through structural coupling between the shell and its internals, and then partially radiated from the shell into the acoustic medium as sound. The internal structure is represented by an elastic plate attached to the shell along its axial direction, modeling decks in real underwater vehicles. A standard method for solving such coupled problems is used to derive solutions in terms of receptances of the shell and the plate, which relate the responses of the two to coupling forces and bending moments at the connections between them. The forces and moments are then determined by kinematic and dynamic balances between the shell and the internal plate. Far-field solutions are examined in detail to identify dominant features in the radiation process, such as those controlling the frequency characteristics and the directivity pattern of the radiated field.
Relationships between frequency-tuning and spatial-tuning curves in the mammalian cochlea
Authors: Geisler C. Daniel , Cai Yidao
Published: October 2005

The tuning curve of a single auditory-nerve fiber is a measure of the intensity levels producing that fiber’s threshold response at each of a number of frequencies. For many purposes it is desirable to know cochlear responses as a function of cochlear location (spatial distance from the stapes). Using assumptions of uniformity, the relationships between auditory-nerve-fiber frequency-tuning curves, basilar-membrane frequency-response curves, and basilar-membrane spatial-response curves are obtained. From the spatial-response characteristics which are then inferred from neural frequency-tuning curves, it appears that the tuning properties of the apical cochlea are fairly uniform and differ from the tuning properties of the basal cochlea.
Elastic wave scattering by shelled spherical scatterers in a focused field
Authors: Mittleman John , Thompson R. B. , Han Y. K.
Published: October 2005

Embrittlement of many important metal alloys has been related to the accumulation of undesirable materials at grain boundaries, a condition which may be detectable through measurement of ultrasonic scattering from the material’s microstructure. Grains with decorated grain boundaries are modeled as shelled microspheres embedded in an isotropic elastic host, and a practical means of predicting scattering from these particles is developed. The incident field often used for measuring backscattered grain noise is focused; both plane and focused incident fields are treated. Theoretical predictions of scattering from isolated scatterers are compared with experimental measurements on metal microspheres embedded in plastic to validate the computational procedure, then predictions of scattering from similar spherical structures embedded in a metal host are presented. In the former case theoretical predictions are found consistent with observations, although differences between shelled and nonshelled scatterers are obscured by the great contrast between host and scatterer. In the latter case, where host and core are quite similar, even thin shells can produce scattering readily distinguishable from the weak scattering in polycrystals that may be due to locally inhomogeneous properties. Results of this study can be used to calculate a backscattering coefficient for calculations of grain noise in metals containing, or composed of, numerous shelled scatterers.
Sound-power collection by the auditory periphery of the mongolian gerbil Meriones unguiculatus. II. External-ear radiation impedance and power collection
Authors: Ravicz Michael E. , Rosowski John J. , Voigt Herbert F.
Published: October 2005

Acoustic power flow into the external and middle ear of gerbil is computed from acoustic measurements and models of the external ear and used to predict the behavioral auditory threshold. The external-ear radiation impedance from the tympanic ring ZE measured in six gerbil ears with a calibrated acoustic source at frequencies from 10 Hz to 18 kHz is mass dominated below about 8 kHz, with a mean mass of 2720 kg/m4. ZE shows resonant behavior near 8 and 14 kHz. The frequency dependence of ZE is similar to that measured in cat, chinchilla, and models of the human external ear, but the mass and the resonant frequencies are higher. The power utilization ratio (PUR) computed from ZE and measurements of the middle-ear input impedance ZT presented previously [Ravicz et al., J. Acoust. Soc. Am. 92, 157–177 (1992)] suggests that appreciable power is transmitted to the middle ear only above 1.5 kHz. Mathematical external-ear models, consisting of tube segments and conical horns that include viscous and thermal losses, were developed from anatomical dimensions to match ZE over the entire frequency range of measurement. The radiation efficiency ηR computed from the models is near unity only above 12 kHz and falls to 10−5 as frequency decreases to 10 Hz. Predictions of the mean pressure gain from an external diffuse sound field to the tympanic membrane resemble measurements in another gerbilline species. The effective area of the ear in a diffuse sound field at the tympanic membrane EADFTM computed from PUR and ηR approaches the anatomical area of the pinna opening, 71 mm2, above 1.5 kHz and the geometric limit of λ2/4π determined by the wavelength λ above 12 kHz but decreases sharply below 1.5 kHz to 0.002 mm2 at 10 Hz. The diffuse-field sound pressure required to deliver 5×10−17 W to the middle ear between 10 Hz and 18 kHz resembles the behavioral auditory threshold [Ryan, J. Acoust. Soc. Am. 54, 1222–1226 (1976)]. This result supports the idea that the cochlea acts as a power detector at the auditory threshold.
Click- and tone-burst-evoked otoacoustic emissions in normal-hearing and hearing-impaired ears
Authors: Prieve Beth A. , Gorga Michael P. , Neely Stephen T.
Published: October 2005

Click-evoked otoacoustic emission (COAE) and tone-burst-evoked otoacoustic emission (TBOAE) input/output (I/O) functions and group latencies were measured in normal-hearing and hearing-impaired ears to determine the extent to which these two types of transient-evoked otoacoustic emissions (TEOAEs) were similar. When stimulus levels measured in 1/3 octave bands centered at 500, 1000, 2000, and 4000 Hz were similar, TBOAE and COAE I/O functions were essentially identical in regions of normal hearing. This held true in subjects who had normal hearing from 250 to 8000 Hz as well as for subjects who had normal hearing across some frequency ranges but hearing impairment across others. The high degree of correlation offers support to the view that both types of transient emissions share common generators. There were no significant differences in group delay between TBOAEs measured from normal-hearing and hearing-impaired subjects.
A model of articulator trajectory formation based on the motor tasks of vocal-tract shapes
Authors: Kaburagi Tokihiko , Honda Masaaki
Published: October 2005

This paper presents a modeling study of articulator movements for continuous speech utterances. The model determines the trajectories of the articulator movements that form the vocal tract into phoneme-specific shapes. Vowels, for example, are generated based on the specifications of the tract shape (motor tasks) related to the shape of the tongue and lips. Consonants, such as /p/ and /k/, on the other hand, can be generated by specifying a closure in the tract between the lips, or between the tongue and the palate. In the model, state variables represent the active movements of each articulatory organ as the displacement relative to the neutral position. In addition, tract variables are defined to specify the motor tasks of the lips and tongue as functions of the state variables of the jaw, lips, and tongue: The definition of the tract variables incorporates the representation of the coordinative structure of the articulatory system between the jaw and the lower lip and between the jaw and the tongue. This coordinative structure allows for an infinite number of trajectories that satisfy all of the given motor tasks. This redundancy is overcome by minimizing the cost function so that the movements of each articulatory organ are uniquely determined. Articulator movements were simulated for several utterances, and the simulated movements of the jaw, lips, and tongue agree well with measured data. The results show that it is valid to use the features of vocal-tract shapes to represent motor tasks when modeling articulator movements and that the model accurately represents the coordinated movements of the articulatory organs.
Analysis of the effects of electroglottographic baseline fluctuation on the F estimation in pathological voices
Authors: Vieira Maurílio N. , McInnes Fergus R. , Jack Mervyn A.
Published: October 2005

This paper reports an investigation of the influence of electroglottographic (EGG) baseline fluctuation on the precision of F0 estimation based on zero crossings. A passage read by 15 subjects suffering from various laryngeal pathologies was filtered with zero phase shift by several bandpass filters with a flat frequency response between 60 and 5000 Hz. A simple F0 extraction algorithm processed the filtered EGG signals providing good results even with data from severely affected larynxes. In general, all investigated errors, including a measure of jitter, reduced significantly when the attenuation in the rejection bands varied from 0 to 40 dB, with slight but consistent improvements thereafter. The best results, obtained with 80 dB of attenuation, indicated that unvoiced (or silent)-to-voiced errors and voiced-to-unvoiced (or silent) errors were under 1.17% and 2.26%, respectively, and at least 91.8% of the estimated F0 values had a precision better than 0.103%, considering an estimated error of 0.058% in the reference F0 contours; the incidence of gross errors due to F0 doubling or halving was under 0.44%. These results qualify the method as a very precise and robust F0 estimation algorithm for pathological voices.
Cross-language identification of consonants. Part 1. Korean perception of English
Authors: Schmidt Anna Marie
Published: October 2005

Twenty native Korean-speaking subjects heard 22 English word-initial consonants in three vowel contexts produced by three native English talkers. The subjects orthographically labeled each English consonant as the closest Korean consonant. They then judged how similar the English consonant was to the Korean consonant on a scale of 1 to 5. Some English consonants were labeled consistently as a single Korean consonant and judged to be very similar. Other English consonants were labeled consistently as a single Korean consonant but judged to be less similar. Still other English consonants were inconsistently labeled. Korean acoustic cues, vowel context, and token differences appeared to influence labeling choices.
The use of the method of moments with finite difference operator in acoustics
Authors: Shi Yucheng , Shirahatti U. S.
Published: October 2005

Weighted residual methods are frequently used for solving a variety of problems in electromagnetics, solid mechanics, weather prediction, and fluid mechanics. Amidst these weighted residual methods, the electromagnetics research community frequently uses a technique known as the method of moments (MM). MM can be used to systematically form the whole set of expansion functions needed to construct the approximate solution of the problem based on one given basis function. This property of the method of moments can be exploited to solve acoustic field equations in irregular domains. The method of moments with finite difference operator approximation is explored in this paper. As illustrations of the applications of this method, both one- and two-dimensional acoustic problems are solved in this paper. These applications help to highlight the potential of the method of moments.
Acoustic scattering from cylindrical shells with deck-type internal plate at oblique incidence
Authors: Guo Y. P.
Published: October 2005

This paper studies sound scattering from cylindrical shells with deck-type internal structures, represented by an elastic plate attached to the shell along its axial direction. A standard method for solving such coupled problems is used to derive solutions in terms of coupling forces and bending moments at the attachment locations, which themselves are determined by kinematic and dynamic balances between the shell and the internal plate, and hence, characterize the sound/shell/plate interactions. The scattered acoustic field is examined to identify dominant features in the scattering process and to reveal the effects of different attachment conditions on the far-field scattering. Discussed in detail are features in the scattering process associated with oblique incidence, which do not seem to have been previously studied.
An explicit time-domain solution for the reflection from a stratified acoustic half-space obtained by the boundary control method
Authors: He Sailing
Published: October 2005

An effective linear method for solving inverse problems, namely, the boundary control method, is used to determine analytically the density or velocity profile in a stratified acoustic half-space, which gives a specific class of transient reflection corresponding to a Dirichlet–Neumann mapping operator with a kernel of a sum of two sinusoidal functions. The parameter profile, which gives this prescribed reflection, is expressed in an exact and explicit form. Thus, this analytic solution can be used as a bench-mark for numerical approaches to this class of problems. The explicit reflection is checked against numerical results obtained by means of an independent direct method.
Torsional surface waves in nonhomogeneous and anisotropic medium
Authors: Dey S. , Gupta A. K. , Gupta S.
Published: October 2005

The paper discusses the possibility of propagation of torsional surface waves in (i) a nonhomogeneous elastic medium with polynomial variation of rigidity and density, (ii) exponential variation of rigidity with constant density, and (iii) exponential variation of both rigidity and density. It is also shown that homogeneous isotropic and anisotropic media will not allow torsional surface waves to propagate but some types of inhomogeneity in the rigidity and density in the medium allow such propagation. It is also observed that in certain types of nonhomogeneity there may be two torsional wavefronts.
Three-port parameters and equivalent circuit of radially polarized piezoelectric ceramic cylinders of finite length
Authors: Ebenezer D. D.
Published: October 2005

Three-port parameters of radially polarized piezoelectric ceramic cylinders of arbitrary length-to-radius ratio are presented. The three-port impedance matrix is first obtained by using two-dimensional electroelastic equations of state and the membrane approximation. It is then used to obtain an equivalent circuit. Admittance and A matrices are also derived. The matrices are then used to determine the input electrical admittance and the acceleration sensitivity for various boundary conditions to illustrate some of their uses.
Free vibration analysis of membranes using wave-type base functions
Authors: Kim Yoon Young , Kang Jeong Hoon
Published: October 2005

The free vibration analysis of general convex polygonal membranes is carried out. The selected based functions for the analysis are wave-type functions which propagate in one direction and vary sinusoidally in the other direction. The key feature of the present technique is to use the base functions that satisfy the governing differential equation exactly, so that only the boundary conditions need to be satisfied. If base functions are not chosen carefully, the dependence problem of the base functions may occur and a technique to select independent base functions is suggested.
Numerical simulation of the dynamics of acoustically levitated drops
Authors: Su Yu-Hsuan , Feng Z. C.
Published: October 2005

Numerical simulation of the dynamics of acoustically levitated drops is accomplished by solving the Helmholtz equation governing the acoustic scattering problem and the Laplace equation governing the motion of an inviscid and incompressible drop. The boundary element method with quadratic elements is used to solve the surface integral forms of both the Helmholtz equation and the Laplace equation simultaneously. Boundary conditions on the drop surface render a system of first-order differential equations which is integrated with respect to time by the use of fourth-order Runge-Kutta integration to study the drop translational frequency, shape oscillation frequency, and the static equilibrium shape. A spherical shape approximation method is used to obtain an analytic estimate of the minimum trapping pressure (MTP) and the translational frequency of the drop. In particular, the translational frequency is shown to agree with the analytic result obtained from the spherical shape approximation for a small acoustic number or a small wave number. The shape oscillation frequencies are found to increase initially with the increasing acoustic number, D [D=(a0Prms2)/(ρoc2σ), Prms is the root-mean-squared sound intensity, a0 is the equivalent radius of drop, ρo is the density of host medium, c is the sound speed in host medium, σ is the surface tension of the drop liquid] up to a critical value and then decreases with the increasing acoustic number due to the nonlinear nature of the acoustic radiation pressure. The equilibrium shape of the drop is computed by incorporating the normal viscous stress terms into the dynamical system intentionally to get rid of the transients. The equilibrium shapes are found to agree with the existing result for small acoustic numbers but differ for large acoustic numbers.
Acoustically enhanced bubble growth at low frequencies and its implications for human diver and marine mammal safety
Authors: Crum Lawrence A. , Mao Yi
Published: October 2005

Computations are made of the conditions necessary to obtain bubble growth by rectified diffusion under a variety of conditions associated with low-frequency sonar propagation in the ocean. The complex issue of microbubble nuclei stabilization is treated by assuming either a sufficient level of supersaturation to stabilize the initial bubble size, or by examining a microbubble nucleus with zero surface tension. The bubble growth rates and thresholds are obtained for a range of sound-pressure levels (re: 1 μPa) from 150–220 dB, for initial bubble radii from 1–10 μm, and for levels of the dissolved gas concentration from 100% to 223% of saturation. It was determined that for the range of conditions examined, it was necessary to utilize three different formulations of the equations for bubble growth. The results of these calculations (and assumptions concerning nuclei stabilization) indicate that for SPL’s in excess of 210 dB, significant bubble growth can be expected to occur, and divers and marine mammals exposed to these conditions could be at risk. For SPL’s below about 190 dB, however, except under relatively extreme conditions of supersaturation, significant bubble growth is unexpected.
Influence of fine structure and envelope variability on gap-duration discrimination thresholds
Authors: Münkner Stefan , Kohlrausch Armin , Püschel Dirk
Published: October 2005

The goal of the study was to investigate whether the temporal resolution of the auditory system is influenced by the variability of the stimulus envelope. To do so, the ability to detect an increment in the duration of a temporal gap (the test gap) was measured with an adaptive 3-IFC procedure. The stimulus consisted of a series of 10-ms broadband noise pulses. The pulses were separated by a 10-ms silent period, or temporal gap. In the main experiments, the test gap was either the first or the last gap in a series of 21 pulses. The variability in the stimulus’ envelope was controlled directly by applying a jitter to the onset of the individual pulses in the pulse trains. Additionally, the stimuli were presented with different fine structure variabilities which also induced differences in the variability of the envelope. The gap-discrimination thresholds for the jittered noise pulse trains showed strong dependence on the amount of jitter as long as the jitter was applied randomly leading to a different pattern for every stimulus. When the jitter was applied as a frozen jitter resulting in a constant pattern of pulses, the thresholds did not increase significantly. A similar result was obtained for the different fine structure variabilities. A frozen fine structure led to thresholds about 1 ms lower than those obtained with random noise stimuli. A measure for the envelope variability was provided by calculating the variances of the envelope spectrum of the gammatone-filtered stimuli. The results of the calculations show a qualitative correspondence to the experimental results.
Deformation models and correlation analysis in elastography
Authors: Bilgen Mehmet , Insana Michael F.
Published: October 2005

Cross-correlation functions are derived with the purpose of determining how strain inhomogeneities affect the displacement estimates used in ultrasound-based elastography. Variations in the strain profile occur in most imaging situations and are caused by fluctuations in the stress field or elastic modulus of the sample. An analytical framework for developing signal processing strategies in elastography is described, and the limitations of correlation-based methods for measuring displacements in tissuelike media caused by static compression are emphasized. This paper includes (1) an accurate approximation for an inverse coordinate transformation that relates pre- and postcompression reflectivity profiles of the media, (2) a derivation of the echo-signal cross-correlation function in media with deterministic or stochastic strain profiles; (3) mathematical and graphical descriptions of the consequences that nonuniformities in the strain profile impose upon the uncertainty of displacement estimation; and (4) a demonstration of the advantages of echo signal conditioning and ultrasonic-pulse shaping to reduce the nonstationary effects that attenuate the cross-correlation peak and reduce the signal-to-noise ratio for displacement estimation.