bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering of torsional waves by a circular crack in a transversely isotropic solid
Authors: Kundu T.
Published: October 2005

The scattering of torsional shear waves by a circular crack located at the interface of two transversely isotropic solids is studied here. The axis of the material symmetry and the axis of the crack coincide. The incident wave is taken as a torsional shear wave propagating perpendicular to the crack surface. Hankel transform representation of the scattered field is used. After some manipulations using the boundary conditions this leads to an integral equation over the crack for the displacement jump across the crack. This jump is expanded in a series of Legendre polynomials, which fulfill the correct edge condition, and the integral equation is projected on the same set of Legendre polynomials. The far field is computed by the stationary phase method. A few numerical computations are carried out for isotropic as well as anisotropic materials for both homogeneous and inhomogeneous solids. Results for the isotropic and homogeneous solid compare favorably with those available in the literature.
The prediction of the sound field due to an arbitrary vibrating body in a rectangular enclosure
Authors: Lam Y. W. , Hodgson D. C.
Published: October 2005

A numerical technique is presented for the prediction of the sound field due to an arbitrary vibrating body in a rectangular enclosure. The method, based on the Helmholtz integral equation, is claimed to have the potential for designing a realistic machine structure in enclosed surroundings. It is assumed that the vibration of the machine surface is known either from experiment or from a finite-element calculation. The accuracy of the technique is verified by using it to predict the sound field from a vibrating sphere in a rectangular enclosure for which the analytical solution is known. The potential of its application to realistic problems is shown by comparing its predictions of the radiation from a vibrating box in a commonly encountered rectangular room with experimental results.
Spectro-temporal integration in signal detection
Authors: van den Brink Willem A. C. , Houtgast Tammo
Published: October 2005

This paper is concerned with aspects of temporal integration and across-frequency integration in signal detection. Previous experiments on the detection of brief broadband signals (clicks) in continuous broadband noise revealed efficient spectral integration. The extent to which this effect is restricted to a critical time window was investigated by manipulating the temporal relations among the signal components in different frequency regions. In a typical experiment, the signal consists of nine brief Gaussian-shaped tone pulses, equally distributed at 1/3-oct intervals, each with a spectral width of about 1/3 oct, and each equally detectable in white noise. In the synchronized condition (i.e., coinciding peaks of the nine Gaussian envelopes), the detection threshold is reached when the levels of the nine individual tone pulses are about 8 dB below their individual threshold levels (efficient spectral integration). When the signal is progressively desynchronized (i.e., noncoinciding peaks of the Gaussian envelopes), detection threshold is found to increase. This suggests that efficient spectral integration in signal detection is confined to a narrow time window, with a typical value of 30 ms. Similar experiments were performed with respect to the efficiency of temporal integration. For constant-duration signals (100 ms), the detection threshold is found to increase when progressively widening signal bandwidth. The data indicate that the efficient temporal integration in signal detection is confined to a narrow frequency window, which, not surprisingly, corresponds to the critical bandwidth.
Active localization of virtual sounds
Authors: Loomis Jack M. , Hebert Chick , Cicinelli Joseph G.
Published: October 2005

A simple virtual sound display built around a microcomputer and analog hardware is described. The display implements most of the primary cues for sound localization in the ear-level plane. Judging both from informal observations by users and from objective data obtained in an experiment on homing to virtual and real sounds, it is concluded that simple displays like the one described are effective in creating the impression of external sounds to which observers can locomote with ease; in particular, this means that simulation of the direction-dependent spectral shaping effects of the pinnae is not a necessary requirement for extracranial sound localization.
Bending and in-plane wave transmission in thick connected plates using statistical energy analysis
Authors: McCollum M. D. , Cuschieri J. M.
Published: October 2005

In the analysis of the power transmission through junctions between thick plate structures, it is necessary to consider not only the transverse bending motion of the plates but also the in-plane wave motion. That is, for these types of structures both the shear and rotary inertia effects and the in-plane wave effects must be considered simultaneously in order to obtain a complete solution to the problem. In this paper, a statistical energy analysis approach is developed to evaluate the power transmission through the junction between two plates in an L-shaped configuration, where the solution includes the shear and rotary inertia effects (Mindlin bending) and the in-plane waves effects. Analytical results are presented for the absorption (or transmissibility) of the junction and the ratio between the incident bending wave power and the transmitted waves (bending and in-plane) power. Results for pure (classical) bending are also presented for comparison with the Mindlin bending results.
Optical and thermal parameter effects on laser-generated ultrasound
Authors: Telschow K. L. , Conant R. J.
Published: October 2005

The use of a pulsed laser source for the generation of elastic waves in materials is investigated, taking into account optical penetration into the material. Under appropriate conditions, a significant feature of the laser-generated elastic waveform is a precursor (sharp spike) signaling the arrival of the longitudinal wave. The shape of this precursor signal is strongly dependent on the optical and thermal properties of the material. This paper shows that the observed precursor can be understood through the use of models that account for optical penetration and thermal diffusion into the material.
Scattering of acoustic waves in an unbounded porous elastic medium
Authors: Shoumian Yu , Tian Yu
Published: October 2005

The scattering of acoustic waves in an unbounded elastic medium containing a great number of uniformly distributed fluid-filled closed spherical pores of the same size is studied in this paper. Relations between wave slowness and porosity are derived in the lowest long-wavelength approximation both for the compressional and shear waves. The results agree well with the experimental data. The Rayleigh’s fourth power law for the decay constants is also derived. The fluid inside the pore is assumed to be inviscid. The relations obtained are useful for geophysical exploration. As by-products, equivalent Lamé constants of the porous elastic medium are also obtained.
Correcting acoustic measurements of scatterer density for extinction
Authors: Foote Kenneth G.
Published: October 2005

Extinction is sometimes a major problem in acoustic surveys of fish stocks, as it often occurs when the fish are concentrated and easiest to survey. The same may be true of certain macrozooplankton, such as krill in swarms. This study aims to describe how to correct single-ping measurements of the vertical distribution of scatterer density for extinction. The general case is considered in which the aggregation density is variable and the mean backscattering and extinction cross sections vary with depth. By dividing the water column into a finite number of layers, with constant properties within each, a closed-form mean-field solution is derived. Methods of applying this to single-ping echo records and the quality of the solution are both examined. Extinction is discussed vis-à-vis multiple scattering. Application of the technique in other areas, e.g., in remote probing of the atmosphere by lidar, is mentioned.
A note on the pulse-echo-overlap method
Authors: Dominec Jiri
Published: October 2005

A second-order time difference approach is suggested to solve problems with the pulse-echo-overlap method of measuring the phase sound velocity.
Reply to ‘‘Comments on ‘The rheology of an anelastic medium studied by means of the observation of the splitting of its eigenfrequencies’ ’’ [J. Acoust. Soc. Am. 8
8, 1642 (1990)]
Authors: Caputo M.
Published: October 2005

In this letter, the author replies to comments written by R. L. Weaver [J. Acoust. Soc. Am. 88, 1642 (1990)] on an earlier article by Caputo [J. Acoust. Soc. Am. 86, 1984–1987 (1989)]. [AIP]
A field survey on annoyance caused by sounds from small firearms
Authors: Buchta Edmund
Published: October 2005

In this study, the results of a field survey on annoyance caused by sounds from small firearms are presented. Dose–response relationships were determined for about 400 randomly selected residents around two military and three civil shooting sites. After completion of personal interviews, extensive sound measurements with different time-weightings were carried out. Also, for the same respondents, the subjective effects of road-traffic sounds were determined enabling a comprehensive comparison of dose–response relations for impulse sounds and road-traffic sounds. The results show that A-weighted equivalent sound-pressure level, Leq , is a better acoustical measure for the prediction of annoyance caused by shooting sounds than the mean‘‘impulse’’ or ‘‘fast’’ time-weighted levels of individual impulses. The results of a principal components analysis showed that the subjective effects of the shooting sounds could be reduced to one overall psychological dimension with high negative loadings on object-centered and subject-centered annoyances, moderate positive loadings on perceived quality of the environment and high positive loadings on habituation to the impulse sounds. From the comparison of the dose–response relations for shooting and road-traffic sounds, it could be concluded that at least for relatively low and moderate levels, the A-weighted Leq of shooting sound is about 13 dB lower than that of equally annoying road-traffic sound.
Propagation of the difference frequency wave generated by a truncated parametric array through a water–sediment interface
Authors: Liu Wen-sen , Xu Zhen-xia
Published: October 2005

Muir et al. [T. G. Muir, C. W. Horton, Sr., and L. A. Thompson, J. Sound Vib. 64, 539–551 (1979)] observed that the propagation direction of the sound wave in the sediment insonified by a parametric array departed significantly from the prediction of Snell’s law. The wave fronts penetrated more steeply into the sediment and the attenuation at postcritical incidence was less than that predicted by the plane wave theory. It was found that mainly due to the variation of the length of the parametric array, the direction of the refracted sound wave occurs at or near the line-of-sight between the projector and the hydrophone. It has been proved, both theoretically and experimentally, that Snell’s law is still valid when the length of parametric array is kept constant. At postcritical incidence, the penetration of a parametric array can be deeper due to the contribution of the lateral wave and secondary sources close to the boundary.
Continuous wave phase detection for probing nonlinear elastic wave interactions in rocks
Authors: Johnson Paul A. , Migliori Albert , Shankland Thomas J.
Published: October 2005

A new method that uses nonlinear elastic wave generation to produce a continuous wave (cw) phase measurement from which dimensions or velocities of a body can be obtained is described. Like the technique of standing wave resonance for obtaining sound velocities, this method takes advantage of the high accuracy characteristic of frequency measurements. In the experiment, two intersecting, high-frequency primary signals f1 and f2 are mixed inside a sample, creating a directional beam at the difference frequency Δf=f1−f2. An externally generated, low-pass-filtered Δf signal is electronically mixed with the signal obtained from the sample. As either primary frequency is swept, the dc component from the mixer varies between relative maximum and minimum values at characteristic frequency intervals depending on the phase differences. The resulting interference signal can be used to calculate the distance from the mixing volume in the sample to the detector and to the two primary signal transmitters, providing that a single characteristic distance and wave velocities are known. The reverse experiment is determining velocities from known dimensions.
Simulations of rough interface scattering
Authors: Berman David H.
Published: October 2005

This paper describes numerical simulations of rough interface scattering. Both Dirichlet and fluid–solid boundary conditions are treated. The Rayleigh–Fourier method is used to compute exact plane-wave scattering amplitudes and results are compared to various approximations. The small-slope approximation of Voronovich performs remarkably well, while the tangent-plane approximation is shown to miss some essential physics of scattering. It is observed that at the Rayleigh angle there is a peak in the backscattering amplitude, even for plane-wave incidence. It is argued that the statistics of plane-wave scattering amplitudes are Gaussian.
The effect of ‘‘information value’’ and ‘‘accentuation’’ on the duration of Dutch words, syllables, and segments
Authors: Eefting Wieke
Published: October 2005

A production study was conducted to investigate the consequences of the features ‘‘information value’’ (‘‘new’’ versus ‘‘old’’ information) and ‘‘accentuation’’ (‘‘+accent’’ versus ‘‘−accent’’) on word durations. A professional speaker read aloud speech fragments in which both features were varied systematically. The results revealed that the factor information value by itself did not have an effect on word duration. Accentuation (which is closely related to information value) caused a difference in word duration of about 25%. Simultaneous variation of both factors in the conditions [new, +accent] versus [old, −accent] caused an average difference in duration of 21%. Measurements of the syllable and segment durations revealed that all segments and syllables in the words contributed to the durational changes that are caused by accentuation, which is in favor of our assumption that the word is a relevant unit of tempo.
Use of wave-number-domain windows in fast field programs
Authors: Wilson D. Keith
Published: October 2005

Fast field programs are known to produce spurious oscillations for sound level predictions deep within a shadow zone. These oscillations are actually a Gibbs phenomenon, and can be reduced by applying an appropriate window function prior to Fourier transformation of the radial wave-number spectrum. Errors caused by finite sampling of the wave-number spectrum are also discussed.
VCVs vs CVCs for stop/fricative distinctions by hearing-impaired and normal-hearing listeners
Authors: Revoile Sally G. , Kozma-Spytek Linda , Holden-Pitt Lisa , Pickett James M. , Droge Janet
Published: October 2005

Moderately to profoundly hearing-impaired (n=30) and normal-hearing (n=6) listeners identified [p, k, t, f, η, s] in [dvC], [Cvd], and [vCv] tokens extracted from spoken sentences. The [vCv]s were also identified in the sentences. The hearing-impaired group distinguished stop/fricative manner more poorly for [vCv] in sentences than when extracted. Further, the group’s performance for extracted [vCv] was poorer than for extracted [dvC] and [Cvd]. For the normal-hearing group, consonant identification was similar among the syllable and sentence contexts.
Plane-wave analysis of acoustic signals in a sandy sediment
Authors: Altenburg Robert A. , Chotiros Nicholas P. , Faulkner Carl M.
Published: October 2005

A weighted least-squares algorithm was developed to fit a plane wave to arrival time differences yielding wave front direction and speed estimates. The algorithm was applied to acoustic pulses entering a sandy sediment through the water–sediment interface. An acoustic projector in the water column was used to insonify an array of sensors embedded in the sediment. Pulsed carriers, from 5 to 80 kHz, were projected toward the sediment interface at grazing angles below, near, and above the critical value. The plane-wave fit was found to be good in all cases.
Acoustic scattering by two-dimensionally rough interfaces between dissipative acoustic media—Full wave, physical acoustics, and perturbation solutions
Authors: Bahar Ezekiel
Published: October 2005

Explicit expressions for the acoustic pressure and velocity scattered by two-dimensionally rough surfaces are derived using a full-wave approach. The conditions under which these solutions merge with the physical acoustic and small perturbation solutions in the high- and low-frequency limits are given. The acoustic media on both sides of the rough interface are characterized by their bulk modulus, equilibrium density, and relaxation time (to account for dissipation); the Dirichlet and Neumann boundary conditions are treated as special cases. The closed-form full-wave expressions for the surface element scattering coefficients are significantly different for these special cases. However, the corresponding physical optics solutions differ only in the sign of the acoustic reflection coefficient. The full-wave solution can be applied to composite surfaces with a broad range of roughness scales. Since it accounts for specular point and diffuse scattering in a unified self-consistent manner, there is no need to adopt a two-scale model of the rough surface. Thus the full-wave expressions for the rough surface scattered fields are also more suitable for application to broadband (transient) excitation problems and for the solution of inverse problems.
Updating a dosage–effect relationship for the prevalence of annoyance due to general transportation noise
Authors: Fidell Sanford , Barber David S. , Schultz Theodore J.
Published: October 2005

More than a decade has passed since a relationship between community noise exposure and the prevalence of annoyance was synthesized by Schultz [T. J. Schultz, J. Acoust. Soc. Am. 64, 377–405 (1978)] from the findings of a dozen social surveys. This quantitative dosage–effect relationship has been adopted as a standard means for predicting noise-induced annoyance in environmental assessment documents. The present effort updates the 1978 relationship with findings of social surveys conducted since its publication. Although the number of data points from which a new relationship was inferred more than tripled, the 1978 relationship still provides a reasonable fit to the data.
An adaptive modal-based active control system
Authors: Morgan Dennis R.
Published: October 2005

Active control for silencing sound and vibration has recently become the subject of much investigation, and is now being enhanced by the advent of adaptive filtering techniques. On another front, modal decomposition for active control problems has been shown to offer a number of practical advantages, as independent modal control can: minimize the number of actuators, sensors, and corresponding dimensionality of the controller, as well as minimize the control energy; provide robustness to system parameter uncertainty; and, minimize the adaptive convergence time by uncoupling the modal responses. In this paper, details are sketched for a narrow-band adaptive modal-based active control system that incorporates all of these features. The major topics addressed deal with modal filters, actuator prefilters, spatial sampling effects, and design methodology. Although this work pertains only to the narrow-band disturbance problem, these techniques can be readily generalized to the wideband case by using temporal filters to separate out different spectral bands for narrow-band modal-based processing. The analytical results are illustrated by numerical example for a vibrating cantilever beam, using a graphics display that was developed for real-time interactive design.
Dispersion of impulse sound above a curved surface
Authors: Daigle Gilles A. , Raspet Richard
Published: October 2005

Controlled experiments made indoors above a carefully constructed curved surface using pure tones have shown that the magnitude of the diffracted sound energy deep within the acoustic shadow can be accurately calculated from a residue series solution [Berry and Daigle, J. Acoust. Soc. Am 83, 2047 (1988)]. The theory also predicts dispersion, however, this aspect was not verified by the pure tone experiments. When the theory was used to predict impulse sound propagation in a refractive atmosphere the measured waveforms appeared to show considerably less dispersion than predicted [Don and Cramond, J. Acoust. Soc. Am. 80, 302 (1986)]. In this paper, impulse sound measurements made indoors above the same carefully constructed curved surface are described as well as outdoors measurements above a grass-covered curved surface. In particular, the measured pulse shapes are compared with the theoretical waveforms in order to verify the predicted dispersion. The outdoor experiments investigate the potential effects of atmospheric turbulence on the predicted dispersion. Satisfactory agreement between the measured and predicted pulse shapes is found in both the indoor and outdoor experiments.
Evaluations of the analytic solution for the acoustic field in an ideal wedge and the approximate solution in a penetrable wedge
Authors: Wang Lian Sheng , Pace Nicholas G.
Published: October 2005

Uniform asymptotic approximations to the analytic solution for the acoustic field of a cw point source in an ideal wedge [M. J. Buckingham, Proceedings of the NATO Advanced Research Workshop on Hybrid Formulation of Wave Propagation and Scattering (Nijhoff, Dordrecht, The Netherlands, 1984), pp. 77–105] and to the approximate solution in a penetrable wedge [M. J. Buckingham, J. Acoust. Soc. Am. 82, 198–210 (1987)] are obtained by a stationary phase method (SPM). Comparisons of the solutions are made. Very good agreements are found in the bright zones, the caustics, and the shadow zones of the sustained normal modes in small angle wedges, provided that the source is at a range that is not shorter than the range at which the lowest mode can be excited, or the source and the receiver are well separated. One of the major advantages of the present representations is that, in comparison with numerical integration, the results can be generated rapidly with a satisfactory accuracy.
An energy-conserving parabolic equation incorporating range refraction
Authors: Schurman I. W. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

A new parabolic equation (PE) is presented that is independent of k0 and capable of handling relatively large range variations in the index of refraction. This equation is similar to, and ostensibly simpler than, an earlier range refraction PE (RAREPE). The modified range refraction parabolic equation (MOREPE) is obtained by a transformation approach, and operator and multiscale formalisms are described to validate the equation. Principal properties of MOREPE are developed, including energy conservation and possession of the correct (Helmholtz) rays in the high-frequency, small-angle limit. Exact solutions with range variation in sound speed are presented to illustrate differences between standard PE (SPE) and MOREPE. Propagation examples in range-independent environments demonstrate close agreement between MOREPE and SPE, while examples with strong range dependence exhibit significant differences between the two equations in their predictions of acoustic intensity. Analytical and numerical comparisons of solutions to the one-way Helmholtz equation (HE1), MOREPE, and SPE demonstrate the increased accuracy of MOREPE over SPE in range-dependent environments.
A non-iterative time mapping algorithm for linear motion in 3-space
Authors: Ricker D. W.
Published: October 2005

The modeling of signal propagation or communication channels when the source-receiver or scatterer are moving at relativistic speeds is often complicated by time base distortion. In order to synthesize the received waveform, it is usually necessary to map time of signal reception to time of transmission recursively for each received time series sample. This laborious procedure which can severely limit the ability to carry out real time modeling may be considerably foreshortened if a piece-wise linear approximation is made to the motion in 3-space. Then, the recursive computation reduces to a 2-step closed-form algorithm.
In vivo measurement of basilar membrane stiffness
Authors: Olson Elizabeth S. , Mountain David C.
Published: October 2005

Basilar membrane stiffness measurements were made in the base of the gerbil cochlea. Basilar membrane stiffness was determined by contacting the basilar membrane with a stainless steel needle (tip diameter 25 μm) attached to a force transducer, putting the needle/transducer structure through a low-frequency sinusoidal excursion with amplitude 5 or 25 nm, and measuring the restoring force exerted on the needle by the basilar membrane at the applied frequency. Stiffness was calculated as the amplitude of the restoring force divided by the amplitude of the excursion. Stiffness was measured over a 24-μm range of static displacements of the basilar membrane and is presented as stiffness versus static displacement. In cochleas that were not damaged during surgery the stiffness versus displacement characteristic usually had the following features: (1) an initial stiffness plateau with average stiffness 0.6 N/m; (2) a second plateau or level off with average stiffness 9.1 N/m; and (3) an increase in stiffness beyond the second plateau that was consistent with the theoretical stiffness-vs-displacement function of a beam. These features were present both pre- and post-mortem.
Rotational waves in the elastic response of spherical and cylindrical acoustic targets in water
Authors: Hickling Robert , Burrows R. Kirk , Ball James F.
Published: October 2005

The elastic response of a solid sphere to a continuous train of plane waves is shown to consist principally of rotational waves, rather like smoke rings, where the rotational motion of a particular wave is centered at points on an annulus perpendicular to the axis of sound propagation. The rotational waves are most clearly evidenced in the standing modes of free vibration of the sphere, with the waves meshing together like a system of gears. Calculated plots of the displacement vector show how these modes are excited in the sphere by incident sound, and how, during a cycle of the excitation, a first harmonic briefly changes into the nearest fundamental as it changes direction during the oscillation. Other results are presented, including a demonstration that the rotational waves also occur in solid cylinders, with the rotation centered at points along lines parallel to the cylinder axis. It is speculated that the rotational waves occur in any closed body.
Acoustic tomography via matched field processing
Authors: Tolstoy A. , Diachok O. , Frazer L. N.
Published: October 2005

This paper suggests a new approach based on narrow-band, low-frequency data using air-deployed shots recorded on widely distributed large aperture vertical arrays. This approach uses fast, cheap, and high S/N data. Results to date with a simulated three-dimensional (3-D) eddy environment show that efficient characterization of the environment plus careful selection of the source/array geometry can lead to highly accurate estimates of the 3-D sound-speed profiles, e.g., maximum errors less than 0.2 m/s.
A symmetry suppresses the cochlear catastrophe
Authors: Shera Christopher A. , Zweig George
Published: October 2005

When the independent spatial variable is defined appropriately, the empirical finding that the phase of the cochlear input impedance is small [Lynch et al., J. Acoust. Soc. Am. 72, 108–130 (1982)] is shown to imply that the wavelength of the pressure wave in the cochlea changes slowly with position near the stapes. As a result, waves traveling in either direction through the basal turn undergo little reflection, and the transfer of energy between the middle and inner ears remains efficient at low frequencies. The slow variation of the wavelength implies that the series impedance Z̄ and shunt admittance Y of the cochlear transmission line are approximately proportional at low frequencies and thus requires that the width of the basilar membrane and the cross-sectional areas of the cochlear scalae taper in opposite directions. Maintenance of the symmetry between Z̄ and Y is both necessary and sufficient to ensure that the spatial derivative of the wavelength, and hence the phase of the cochlear input impedance, remains small. Although introduced in another context, the model of Zweig [“Finding the impedance of the organ of Corti,” J. Acoust. Soc. Am. 89, 1229–1254 (1991)] manifests the symmetry between Z̄ and Y. In other transmission-line models of cochlear mechanics, however, that symmetry is absent, and the spatial derivative of the wavelength diverges at low frequencies—the “cochlear catastrophe.” Those models therefore contradict the impedance measurements and predict little transfer of energy between the middle and inner ears.
Modeling synchronization and suppression of spontaneous otoacoustic emissions using Van der Pol oscillators: Effects of aspirin administration
Authors: Long Glenis R. , Tubis Arnold , Jones Kenneth L.
Published: October 2005

Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (suppression and synchronization) can be qualitatively simulated by the behavior of a single driven Van der Pol oscillator. Analytical and numerical investigations of a model of spontaneous otoacoustic emissions based on such an oscillator (with appropriate parametric changes in the nonlinear and negative damping components) lead to predictions of the nature of the changes in suppression and synchronization (frequency-locking) tuning curves when the levels of spontaneous otoacoustic emissions are modified. Observations of the suppression and synchronization of spontaneous otoacoustic emissions by external tones of different frequencies and levels were obtained while the levels of spontaneous emissions were altered by aspirin administration. Modeling an emission as a single Van der Pol oscillator qualitatively accounts for: (1) the reduction of the level of an external tone required to suppress the emission by a decibel amount equivalent to the level reduction induced by aspirin administration; (2) the broadening of the frequency-locking tuning curve of an emission whose level is reduced; and (3) the pulling of the emission frequency by an external tone. It does not account for: (1) the observed asymmetry in the slopes of the external-tone suppression curves (more gradual for frequencies of the suppressor tone higher, rather than lower, than that of the emission); and (2) the frequency pushing of the emission by an external tone.
A computational model of afferent neural activity from the cochlea to the dorsal acoustic stria
Authors: Pont M. J. , Damper R. I.
Published: October 2005

The first comprehensive computational modelof the precortical mammalian auditory system to include afferent neural processing up to the level of the dorsal acoustic stria (DAS) is described. The model consists of two scissile stages simulating (1) the cochlea and the auditory nerve (AN) and (2) the dorsal cochlear nucleus (DCN). The model derives its input from a 128-channel cochlear filterbank. Cochlear transduction, rectification, logarithmic compression, and two-tone suppression functions are performed at the first stage of the simulation. The 512 artificial neurons employed model the cell at the level of transmembrane potential and have interconnections that follow closely those reported in recent anatomical and physiological studies of the cat AN and DCN. The responses of the model to pure-tone stimuli (at various sound-pressure levels) and noise stimuli (at various levels and bandwidths) are reported in detail and compare well with published results. The model is being used to investigate the representation of initial English stop consonants (differing in voice-onset time) in the DAS; this work is briefly described.
Generalized function estimation of underwater transient signals
Authors: Le Hung T. , Wegman Edward J.
Published: October 2005

In this paper, a generalized approach to the transient signal characterization problems will be presented. Specifically, the class of transient signals as a subspace of an appropriate Hilbert space, namely the Sobolev space, which consists of time-limited and bandlimited signals will be characterized. It is shown that, under this setting, the optimal representation for the general case of transient signals both in the time and frequency domains is the class of generalized spline functions. In addition, to provide some motivational tool for studying the transient signal characterization problem, one specific class of transient signals, which is emitted from submarines, will be focused upon.
The articulatory kinematics of final lengthening
Authors: Edwards Jan , Beckman Mary E. , Fletcher Janet
Published: October 2005

In order to understand better the phonetic control of final lengthening, the articulation of phrase-final syllables was compared with that of two other contexts known to increase syllable duration: accent and slow tempo. The kinematics of jaw movements in [pap] sequences and of lower lip movements in [pE] sequences for four subjects were interpreted in terms of a task-dynamic model. There was evidence of two different control strategies: decreasing intragestural stiffness to slow down some part of the syllable, and changing intergestural phasing to decrease overlap of the vowel gesture by the consonant. The first was used in slowing down tempo, whereas the second was used to increase the duration of accented syllables over unaccented syllables. Both strategies were implicated in phrase-final lengthening. In accented syllables, final closing gestures generally were longer and slower, but not more displaced. The two slowest subjects, however, used the other strategy in their slow-tempo final syllables. Final lengthening in reduced syllables was more difficult to interpret. The relationship between peak velocity and displacement suggested that a lesser stiffness is obscured by an increased gestural amplitude. Thus, by comparison to lengthening for accent, final lengthening is like a localized change in speaking tempo, although it cannot be equated directly with the specification of stiffness.
Experimental evidence in the in vivo canine for the collapsible tube model of phonation
Authors: Berke Gerald S. , Green David C. , Smith Marshall E. , Arnstein David P. , Honrubia Vincent , Natividad Manuel , Conrad William A.
Published: October 2005

The in vivo canine model of the larynx was used to measure transglottic pressures and air flow during phonation. Conditions of supraglottal resistance were also simulated. Pressure drop-flow curves were compared with data on collapsible tubes. The in vivo in canine model of the larynx demonstrates a number of features similar to oscillation in collapsible tubes.
Characterizing pulses reflected from rough surfaces using ultrasound
Authors: Bozma Ömür , Kuc Roman
Published: October 2005

A model for the scattering of wideband signals from three-dimensional rough surfaces is presented. This development is an extension of the scattering based on the Kirchhoff approximation method for a monochromatic wave source. The usual plane-wave approximation is relaxed and the Kirchhoff method is extended to include spherically diverging waves from the scattering surface. The scattered signal is expressed in terms of the Fourier transform of the acoustic channel. The frequency correlation function of the channel is then derived for a rough surface having the Gaussian spectrum. The coherent and incoherent components of the scattered signal intensity are determined from the frequency correlation function. The theory is applied to the signals produced by the Polaroid transducer operating in air and mounted on a mobile vehicle capable of automatic translation and rotation. Theoretical results are compared with experimental observations from two different rough surfaces. The analytic results are verified over the observable range of incidence angles from 0° to 60°.
Reconstructing stratified fluid flow from reciprocal scattering measurements
Authors: Norton Stephen J.
Published: October 2005

This paper shows how an inversion formula can be derived for reconstructing the magnitude and direction of stratified fluid flow from two scattering measurements. The measurements are recorded by transmitting an acoustic pulse from a source below the region of stratified flow and then recording the scattered wave at another point horizontally displaced from the source. A second measurement is performed with the source and receiver interchanged and the result is subtracted from the first scattering measurement. This difference is, within the Born approximation, independent of scattering that arises from stationary inhomogeneities and thus solely sensitive to scattering due to flow. As a by-product, the sum of the two scattering measurements with source and receiver interchanged yields a quantity sensitive only to scattering from stationary inhomogeneities. This allows the stationary inhomogeneities to be recovered independently of flow.
Effects of anisotropy upon the normal modes in a borehole
Authors: Ellefsen K. J. , Cheng C. H. , Toksöz M. N.
Published: October 2005

Elastic anisotropy affects the modes generated during acoustic logging. To study these effects, the wave equation was solved using a variational method for a model consisting of a fluid-filled borehole through a solid whose anisotropy is defined in the Cartesian coordinate system. The solution for each normal mode includes its phase velocity, group velocity, pressures in the fluid, and displacements in the solid. The most significant findings are: (1) two quasiflexural waves exist and have different phase and group velocities; (2) for the slow quasiflexural wave, the particle displacements in the plane perpendicular to the borehole, when viewed together, are aligned with the polarization of the slow, planar qS wave whose wave-number vector is parallel to the borehole; and (3) for the fast quasiflexural wave, the particle displacements in the plane perpendicular to the borehole, when viewed together, are aligned with the polarization of the fast, planar qS wave whose wave-number vector is parallel to the borehole.
A narrow-band approximation to the acoustic pressure field
Authors: McCann Kevin J. , Lee-McCann Freda
Published: October 2005

Broadband theoretical calculations of the acoustic pressure field generally suffer from the need to perform a large number of calculations at each of several frequencies across the frequency band and to, subsequently, construct the required time series through a Fourier synthesis. The computational load for such a series of calculations can be prohibitive especially for high frequencies. This paper presents a theoretical approach within the framework of normal-mode theory that significantly reduces the computational requirements for broadband calculations. The limits of the applicability of this method have been examined, and the technique has been used in comparisons with experimental data. The method is easily extended to accommodate range dependence in the environment.
Stimulated ultrasound absorption in liquids
Authors: Lewis T. J. , Barnes C. , van der Sluijs M. J.
Published: October 2005

It is shown that if two ultrasonic absorption processes, each with a relaxation frequency, exist in a liquid, then under certain conditions a nonlinear quasiresonance equation of state may be derived. If further absorption processes are associated with clusters in the liquid, a cluster being a local aggregation of molecules, then stimulated three-wave combination-frequency interaction is possible when a primary and a secondary pressure wave of different frequencies exist in the liquid. These conditions can occur in resonator and pulse-echo experiments. When the clusters have a significant second-order compressibility, the absorption can be either enhanced or reduced, according to circumstances, with maxima or minima at frequencies much lower than the relaxation frequencies. The theory is used to explain the anomalous resonance-like absorptions that have been reported for toluene, acetic acid, alcohols, and certain biomolecules.
Lamb wave interaction with lap-shear adhesive joints: Theory and experiment
Authors: Rokhlin S. I.
Published: October 2005

Lap-shear joints are made from two plates that overlap in the joint area. In this paper a theoretical and experimental analysis of Lamb wave interaction with such joints is given. In this joint evaluation technique Lamb waves are excited and received outside the joint area and a conclusion about joint quality is drawn based on the phase delay and transmission losses of the ultrasonic signals in the joint. The mode transformation at the joint edges is very important for such tests. This phenomenon is studied in this paper by considering mode conversion on the boundary between the region exterior to the joint area and the two adhesively joined plates inside the joint. The problem is addressed theoretically by the Wiener–Hopf technique for a perfect joint that is represented by a double thickness plate and for a weak joint that is approximately by slip boundary conditions between the two plates in the joint area. This work shows, both theoretically and experimentally, how to select the mode type and frequency of the Lamb modes excited outside the joint to obtain the appropriate mode in the joint area for successful discrimination of bond quality.
Active control of the acoustic radiation of a vibrating structure using a superposition formulation
Authors: Song Limin , Koopmann Gary H. , Fahnline John B.
Published: October 2005

In this paper, optimal control theory is applied to the problem of reducing the acoustic power radiated from a complex, three-dimensional, vibrating structure. Using the principle of wave superposition, a vibrating structure’s acoustic field can be shown to be approximately equivalent to the sum of the fields due to a finite number of acoustic sources located in the interior of the radiating body. Based on this transformation, the total time-averaged, acoustic power output from the vibrating structure can be expressed in terms of the strengths of the interior point sources. Two methods are then used to optimally reduce the acoustic power output from the vibrating body. The first method consists of placing a secondary source outside the structure and, by optimizing its source strength, minimizing the total, time-averaged acoustic power output of the entire system. The second method assumes that the vibrating structure’s normal surface velocity can be altered such that the total power radiated from the vibrating structure is minimized. The optimum surface velocity distribution produced by this method is shown to be dependent on the number and location of the surface nodes defining the geometry of the structure.
On the interpretability of speech/nonspeech comparisons: A reply to Fowler
Authors: Diehl Randy L. , Walsh Margaret A. , Kluender Keith R.
Published: October 2005

Fowler [J. Acoust. Soc. Am. 88, 1236–1249 (1990)] makes a set of claims on the basis of which she denies the general interpretability of experiments that compare the perception of speech sounds to the perception of acoustically analogous nonspeech sounds. She also challenges a specific auditory hypothesis offered by Diehl and Walsh [J. Acoust. Soc. Am. 85, 2154–2164 (1989)] to explain the stimulus-length effect in the perception of stops and glides. It will be argued that her conclusions are unwarranted.
Dynamic spectral shape features as acoustic correlates for initial stop consonants
Authors: Nossair Zaki B. , Zahorian Stephen A.
Published: October 2005

A comprehensive investigation of two acoustic feature sets for English stop consonants spoken in syllable initial position was conducted to determine the relative invariance of the features that cue place and voicing. The features evaluated were overall spectral shape, encoded as the cosine transform coefficients of the nonlinearly scaled amplitude spectrum, and formants. In addition, features were computed both for the static case, i.e., from one 25-ms frame starting at the burst, and for the dynamic case, i.e., as parameter trajectories over several frames of speech data. All features were evaluated with speaker-independent automatic classification experiments using the data from 15 speakers to train the classifier and the data from 15 different speakers for testing. The primary conclusions from these experiments, as measured via automatic recognition rates, are as follows: (1) spectral shape features are superior to both formants, and formants plus amplitudes; (2) features extracted from the dynamic spectrum are superior to features extracted from the static spectrum; and (3) features extracted from the speech signal beginning with the burst onset are superior to features extracted from the speech signal beginning with the vowel transition. Dynamic features extracted from the smoothed spectra over a 60-ms interval timed to begin with the burst onset appear to account for the primary vowel context effects. Automatic recognition results for the 6 stops (93.7%) based on 20 features was better than the rates obtained with human listeners for a 50-ms segment (89.9%) and only slightly worse than the rates obtained by human listeners for a 100-ms interval (96.6%). Thus the basic conclusion from our work is that dynamic spectral shape features are acoustically invariant cues for both place and voicing in initial stop consonants.
Approximate expressions for the lowest dipole resonance frequency of an elastic sphere in an elastic solid
Authors: Scharnhorst Kurt P.
Published: October 2005

The lowest dipole resonance frequency of rigid spherical inclusions in low shear media is known to be ω=3(cs/a)/(1+2ρ̄)1/2. A generalization of this formula to relatively large matrix shear rigidities is considered.
A review of otoacoustic emissions
Authors: Probst Rudolf , Lonsbury-Martin Brenda L. , Martin Glen K.
Published: October 2005

Otoacoustic emissions measured in the external ear canal describe responses that the cochlea generates in the form of acoustic energy. For the convenience of discussing their principal features, emitted responses can be classified into several categories according to the type of stimulation used to evoke them. On this basis, four distinct but interrelated classes can be distinguished including spontaneous, transiently evoked, stimulus-frequency, and distortion-product otoacoustic emissions. The present review details the findings that have been described for each emission type according to this classification schema. Additionally, the known features of emitted responses are discussed for both normally hearing and hearing-impaired humans and experimental animals, and with respect to their potential clinical applications. The findings reviewed here clearly indicate that future studies of otoacoustic emissions will significantly increase our understanding of the basic mechanisms of cochlear function while, at the same time, provide a new and important clinical tool.
Cross sections of generalized Rayleigh scatterers
Authors: Junger Miguel C.
Published: October 2005

This paper highlights the radically different wavelength dependences of the ratio of scattering to geometric cross section for stiffness-, resistance-, and mass-controlled scatterers characterized by their bulk modulus and structural damping. The relation between solutions formulated by various authors, notably between Rayleigh’s and Lamb’s mutually exclusive results, is explored. Finally, the generalized Rayleigh scattering solution is illustrated for a cavity in a viscoelastic matrix.