bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of postlingual deafness on speech production: Implications for the role of auditory feedback
Authors: Waldstein Robin S.
Published: October 2005

This study investigated some effects of postlingual deafness on speech by exploring selected properties of consonants, vowels, and suprasegmentals in the speech of seven totally, postlingually deafened individuals. The observed speech properties included parameters that function as phonological contrasts in English, as well as parameters that constitute primarily phonetic distinctions. The results demonstrated that postlingual deafness affects the production of all classes of speech sounds, suggesting that auditory feedback is implicated in regulating the phonetic precision of consonants, vowels, and suprasegmentals over the long term. In addition, the results are discussed in relation to factors that may influence the degree of impairment, such as age at onset of deafness.
Frequency discrimination in the monkey
Authors: Prosen C. A. , Moody D. B. , Sommers M. S. , Stebbins W. C.
Published: October 2005

This study evaluated frequency discrimination ability in 11 monkeys over an extended period of time using a repeating-standard procedure and the method of constant stimuli. The intersubject variability of the difference limens for frequency (ΔF) was large, as reported by other investigators, but similar in magnitude to the variability of the difference limens for intensity (ΔI) from three of the same subjects in an intensity discrimination experiment. Continued training generally resulted in a rapid decrease in ΔF’s, followed by a longer-term, slower decrease. For one subject ΔF’s slowly decreased throughout a 190-week time period. This long-term training effect was specific to frequency discrimination; a similar effect was not observed for the same subject tested in an intensity discrimination experiment. Finally, ΔF’s from the well-trained monkeys of this study were larger than monkey ΔF’s from this laboratory reported in an earlier study, and than human ΔF’s. An anatomical explanation for the human/monkey ΔF magnitude difference is explored.
Revision of estimates of acoustic energy reflectance at the human eardrum
Authors: Stinson Michael R.
Published: October 2005

An improved analysis procedure has been applied to standing wave patterns measured previously [B. W. Lawton and M. R. Stinson, J. Acoust. Soc. Am. 79, 1003–1009 (1986)] in human ear canals. Revised acoustic energy reflection coefficients, at the eardrum, are obtained for 20 ears for frequencies between 3 and 13 kHz. The new analysis addresses anomalous features of the standing wave patterns, apparent at frequencies above 8 kHz, due primarily to the curvature of the ear canal. Much better agreement is now found, at these higher frequencies, between the theoretical form assumed for the standing wave patterns and the experimental data. The revised values of eardrum reflectance are somewhat smaller, especially for frequencies above 11 kHz. The reflectance rises from about 0.25 at 4 kHz up to 0.7 at 8 kHz, falls to a minimum of 0.5 at 11 kHz, then rises to 0.6 at 13 kHz. Considerable intersubject variability in the results is noted.
Radiation and vibrational properties of submerged stiffened cylindrical shells
Authors: Harari A. , Sandman B. E.
Published: October 2005

The vibratory response of submerged cylindrical shells is investigated. The shell response is presented in terms of the spatial wave-number spectrum of the normal surface displacement. The power output of the vibrating shell into the fluid and the far-field radiation from the shell are presented as a function of the wave number of the exciting force. The effects of structural damping and stiffeners are also studied.
Environmentally tolerant beamforming for high-resolution matched field processing: Deterministic mismatch
Authors: Schmidt Henrik , Baggeroer A. B. , Kuperman W. A. , Scheer E. K.
Published: October 2005

Standard adaptive beamforming or matched field processing requires accurate replica fields finely gridded over the search parameter space for localization with sidelobe control. Multiple constraints to the maximum likelihood method (MLM) technique are introduced in order to construct a beamformer (MCM) more tolerant to environmental mismatch of a deterministic nature. The result is a plane-wave or matched field beamformer that accommodates some mismatch in the environment while still suppressing sidelobes. This beamformer maintains its localization and sidelobe control over a coarser grid of the search parameter space than the standard MLM beamformer which requires an extremely fine grid for localization and sidelobe control. Examples simulating the performance of the MCM beamformer for plane-wave and matched field processing for an Arctic environment are given.
Nonlinear wave propagation through rigid porous materials. I: Nonlinear parametrization and numerical solutions
Authors: McIntosh Jason D. , Lambert Robert F.
Published: October 2005

It is well known that the flow resistance, as defined by Darcy’s law, becomes a function of the fluid velocity when the fluid velocity becomes sufficiently large. For porous materials in air, there appears to be two separate nonlinear flow regimes: For low velocities, the resistance coefficient increases with the square of the fluid velocity; and, for high velocities, the resistance coefficient increases linearly with the magnitude of the fluid velocity. Similar regimes also exist for the mass coefficient; however, the mass coefficient is observed to decrease with increasing fluid velocity. (For pure-tone excitation, it is shown that these relationships then hold for the complex magnitude of the particle velocity.) In this paper, the two nonlinear flow regimes are parametrized for several porous materials. Nonlinear corrections are made to linear wave theory, and numerical solutions for pure tones are obtained that are then used to predict surface admittance and internal pressures of finite length sample. A simple surface pressure criterion is put fourth based upon the materials nonlinear parameters that gives an approximate maximum surface pressure that a porous material could be exposed to before nonlinear phenomena become important in describing the material’s characteristics.
Nonlinear wave propagation through rigid porous materials. II: Approximate analytical solutions
Authors: Lambert Robert F. , McIntosh Jason D.
Published: October 2005

A wave perturbation method of analyzing the internal propagation and surface admittance characteristic of highly porous acoustic materials with rigid frames at high particle velocities is presented. It is an iterative method whose implementation is based on experimental observations. Numerical results for an open-cell foam material are compared with both experiments and exact numerical solutions of the fundamental equations of nonlinear motion. Most of the salient features of the surface admittance of a bulk material are predicted analytically with the accuracy increasing as the frequency of excitation is increased. The method is restricted to pure-tone excitation.
Analysis of acoustic radiation and scattering from a submerged spherical shell by energy streamlines
Authors: Zhang Jingdong , Zhang Guangrong
Published: October 2005

The energy streamlines of acoustic radiation and scattering from a submerged spherical shell are studied by numerical simulation, where the shell is excited by either an internal force subtending a polar angle α or a point sound source located near the surface of shell. Patterns of energy flow give a clear sense to the propagation channel of sound energy and are beneficial to provide information for the control of vibration and acoustic radiation of the submerged shell. Besides, the method for computing the stream function [J. Acoust. Soc. Am. 80, 681–684 (1986)] is improved on by a high accurate form of numerical integration. For a given accuracy, fewer intensity data at grid points are needed. This will decrease the cost and labor in an experimental measurement.
Dispersion and attenuation of surface waves due to distributed surface-breaking cracks
Authors: Zhang Ch. , Achenbach J. D.
Published: October 2005

Dispersion and attenuation of surface waves propagating over the free surface of a half-space containing distributed surface-breaking cracks are investigated. The 3-D problem of scattering of surface waves by a single surface-breaking crack is first formulated and the characteristic amplitude factor of the scattered surface wave is expressed in terms of the crack opening displacements. A relation between this amplitude factor and the scattered power flow is then derived. The scattering cross section is introduced as a measure of energy removal from the incident surface wave. By using energy considerations, the coefficient of attenuation is subsequently expressed in terms of the scattering cross section. Use of the Kramers–Krönig relation then yields an expression for the phase velocity. Numerical results are given for both the coefficient of attenuation and the phase velocity, as functions of the crack density, a characteristic length dimension of the crack and the frequency. The theoretical framework provided in this paper may lead to a novel application of surface waves for the detection and characterization of fatigue damage of metals under cyclic loading.
Thick plate bending wave transmission using a mobility power flow approach
Authors: McCollum M. D. , Cuschieri J. M.
Published: October 2005

The mobility power flow (MPF) approach is used in this paper to describe the flexural behavior of an L-shaped plate structure consisting of thick plates with rotary inertia and shear deformation effects included in the analysis. The introduction of the thick plate effects significantly increases the complexity of the structural mobility functions used in the definitions of the power flow terms; however, because of the substructuring that is used in the MPF approach, the complexity of the problem is significantly reduced as compared to solving for the global structure. Additionally, with the MPF approach the modal behavior is described. The MPF analysis of the L-shaped plate is performed for the case of point force excitation on one plate, with the two plates being identical in both size and thickness. The results of this analysis are compared to results from the finite-element analysis (FEA) and the statistical energy analysis (SEA) and show very good agreement in the low- and high-frequency regimes, respectively.
Sleep disturbances caused by vibrations from heavy road traffic
Authors: Arnberg Peter W. , Bennerhult Ove , Eberhardt Jacob L.
Published: October 2005

The influence of whole-body vibrations, noise, and a combination of the two, caused by heavy road traffic (150 events/night) on sleep, subjectively experienced sleep quality, and performance was investigated under controlled laboratory conditions for male and female subjects 20–35 years of age. A room was built above a vibrator table, with the legs of the bed mounted directly on the table through holes in the floor. Vertical vibrations were found to be attenuated by the mattress with 20–40 dB for frequencies >10 Hz, whereas horizontal vibrations were slightly amplified. It could be concluded that when traffic noise [50-dB(A) peak level] is accompanied by vibrations with peak levels of 0.24 m/s2 vertically and 0.17 m/s2 horizontally as measured on the frame of the bed (stimulus duration approximately 2 s, dominant frequency approximately 12 Hz), sleep is more disturbed than is the case when noise alone occurs. The amount of REM sleep, which was significantly reduced for the vibration level mentioned above, was even more disturbed when a higher exposure level, 0.34 m/s2 vertically and 0.24 m/s2 horizontally, was applied. The subjectively rated sleep quality was lower for the higher than for the lower vibration level. Performance in the morning was only influenced for the higher vibration level. It could be concluded that vibration exposure levels near the recommendation made in ISO-standard 2631 for the awake state disturb sleep in man.
A variational principle for underwater acoustic propagation in a three-dimensional ocean environment
Authors: Taroudakis M. I. , Athanassoulis G. A. , Ioannidis J. P.
Published: October 2005

The problem of determining the sound field due to a point harmonic source in an ocean environment with an arbitrary three-dimensional local variation of field parameters (including irregular interfaces) is studied with the help of a variational principle. The variational principle is established by proving that the Euler–Lagrange equations of a suitable functional coincide with the field equation and the exact boundary and interface conditions of the complete elliptic boundary value problem. The method presented in the paper is a hybrid one, in the sense that the pressure field is represented by modal series expansions in the range-independent region, and a suitable localized expansion in the range-dependent region of the environment. These representations retain full mode coupling and, in conjunction with the variational principle, reduce the problem to a linear system of equations free of any a priori restrictions. It is expected that this system would be efficiently used for the numerical solution of the problem, especially in a shallow water environment and in the low-to-moderate frequency range.
Seafloor reverberation fluctuations
Authors: McDaniel Suzanne T.
Published: October 2005

Reverberation intensity fluctuations are not only important because they impact the performance of active sonar systems, but also because they may provide insight into the major scattering processes. In this article, a model for the fluctuations of signals backscattered from rough surfaces is developed, and its predictions are compared with high-resolution bottom backscatter data. For reverberation due to Bragg scattering, the model predicts a unique dependence on beamwidth, which is supported by the data. A dependence on waveform, i.e., a frequency diversity effect is also predicted. This effect is, however, not unique to the Bragg scattering process.
Temperature elevation in tissues generated by finite-amplitude tone bursts of ultrasound
Authors: Wu Junru , Du Gonghuan
Published: October 2005

The temperature elevation in tissues generated by an ultrasonic beam of plane sawtooth wave tone bursts along its axis is calculated based on a solution of an extended Burgers’ equation for a medium with loss due to various relaxation processes. The absorption coefficient of the medium is assumed to be proportional to frequency to the bth power (1≤b≤1.4). The results show that when the power generated by a transducer is kept constant, an enhancement of temperature rise in the medium due to narrow- and high-amplitude bursts of ultrasound is evident. For example, if spatial-peak temporal-average intensity, ISPTA=0.1 W/cm2=const, the temperature rise generated by sawtooth wave tone bursts with a duty factor of 10−4 (ISPPA=1000 W/cm2 at the low-loss fluid and tissue interface where the sawtooth wave just forms) is about twice that generated by its corresponding linear continuous wave counterpart.
An equation for acoustic propagation in inhomogeneous media with relaxation losses
Authors: Nachman Adrian I. , Smith James F. , Waag Robert C.
Published: October 2005

An equation for acoustic propagation in an inhomogeneous liquid medium with relaxation loss is systematically derived from the classical dynamic equations together with the appropriate thermodynamic and constitutive relations. The derivation assumes small acoustic perturbations, but accommodates arbitrary spatial inhomogeneities in material compressibility, density, and parameters of relaxation. The linearized wave equation obtained for N relaxation mechanisms has order N+2, is causal, and yields the expected dependency of attenuation and phase velocity on frequency. A similar equation is also obtained for gases. The corresponding reduced wave equation simplifies to the classical form with a complex frequency-dependent compressibility for which the Kramer–Kronig conditions are verified and for which an explicit expression is obtained in terms of medium properties. Exact analytic expressions valid at all frequencies are given for the spatially varying attenuation coefficient as well as phase velocity. A Green’s function is found for the constant coefficient part of the equation. The results are used to illustrate the effect of relaxation on scattering and also may be employed to model scattering in applications such as image reconstruction.
Sound scattering by spherical and elongated shelled bodies
Authors: Stanton T. K.
Published: October 2005

Describing the scattering of sound by elongated objects with high aspect ratios (ratio of length to diameter) usually involves great numerical difficulties. The recently developed deformed cylinder solution was shown to be increasingly accurate in the limit of very high aspect ratios (≳5:1) while requiring relatively low computation times and was applied to objects of constant composition [T. K. Stanton, ‘‘Sound scattering by cylinders of finite length. III. Deformed cylinders,’’ J. Acoust. Soc. Am. 86, 691–705 (1989)]. In this article, the approximate formulation is used to describe scattering by prolate spheroids, straight finite cylinders, and uniformly bent cylinders where the objects are composed of an elastic shell surrounded by fluid and filled with either a fluid or gas. The calculations are compared with those involving spherical shells based on the formulation derived in Goodman and Stern [J. Acoust. Soc. Am. 34, 338–344 (1962)]. The calculations are made over a wide range of frequencies and shell thicknesses (ranging from solid elastic objects to thin-shelled objects). Since the deformed cylinder formulation is most accurate for angles of incidence normal or near normal to the lengthwise axis, the calculations are limited to broadside incidence. The simulations show significant variations in the modal interference structure as the shell thickness and shape are varied. Comparisons are also made between predictions and laboratory data involving straight and bent finite-length cylindrical shells (stainless steel) with 3:1 aspect ratios and 52% shell thicknesses. The study not only shows reasonable agreement between the predictions and data, but also illustrates the dramatic change in scattering cross section due to the bend of the object (12 dB in this case).
Critical ratio and critical bandwidth for the Atlantic bottlenose dolphin
Authors: Au Whitlow W. L. , Moore Patrick W. B.
Published: October 2005

Masked underwater pure-tone thresholds were obtained for an Atlantic bottlenose dolphin using an up–down staircase method of stimulus presentation and a go/no-go response paradigm. Two types of masking noise were used: a broadband noise and variable bandwidth noise with sharp low- and high-frequency cutoffs. The animal’s critical ratio was measured at frequencies of 30, 60, 90, 100, 110, 120, and 140 kHz. For frequencies of 100 kHz and below, the critical ratios were similar to those measured by Johnson [J. Acoust. Soc. Am. 44, 965–967 (1968)]. The dolphin’s critical bandwidth at frequencies of 30, 60, and 120 kHz was measured with the variable bandwidth noise. The critical bandwidth was 10.4 dB (11 times) wider than the critical ratio at 30 kHz, 8.2 dB (6.6 times) wider at 60 kHz, and 3.5 dB (2.2 times) wider at 120 kHz.
Singing in shallow-water ambient noise
Authors: Weston David E.
Published: October 2005

The spectrum of the ambient noise has been observed for two sites about 40 m deep in the Bristol Channel. For winds above 5 kn (2.6 m/s), there is a series of characteristic peaks, e.g., at 10, 28, 47 Hz, etc. Up to six peaks have been seen, the frequency of each varying inversely with the water depth as the latter changes through the tidal cycle. The peaks are due to a combination of resonance effects, associated with angles near the vertical and angles near the steep critical angle for the underlying rock. It is shown how information may be deduced on sediment depth and on the presence or otherwise of seabed gas. A similar effect has been seen for water 595 m deep in the Norwegian Sea, with a peak at 1.7 Hz. The significance is discussed for theories of ambient noise and acoustic transmission. An account of the depth dependence of shallow-water ambient noise at higher frequencies is appended.
Adaptive control of a two-stage vibration isolation mount
Authors: Sommerfeldt Scott D. , Tichy Jiri
Published: October 2005

An adaptive control system has been developed that may be used for active noise and vibration control problems involving one-dimensional propagation. Based on the least-mean-squares (LMS) algorithm, the adaptive controller performs both system identification and control in real time, without the need for a priori measurements of the system. Since the controller is adaptive in nature, it is possible to track changes in the system while maintaining optimal control. In the present application, the adaptive control system was applied to the problem of minimizing the force transmitted through a two-stage vibration isolation mount. The control system was implemented in real time using a Motorola DSP56000ADS signal-processing board and applied on a physical vibration isolation mount. For periodic excitations, the adaptive controller was capable of providing 30- to 40-dB attenuation of the transmitted vibration. For broadband excitation, some limitations exist, but the controller was still capable of providing about 20-dB attenuation over the lower frequency range. The controller also demonstrated the ability to track changing system parameters to maintain optimal control of the system.
The propagation of axisymmetric waves on a fluid-loaded cylindrical shell
Authors: Photiadis Douglas M.
Published: October 2005

A ring drive applied to an infinite cylindrical shell immersed in a fluid will generate a bulk acoustic wave emanating from the drive and evanescent surface waves propagating along the cylinder. In this paper, the response on and near the surface of the cylinder is examined for frequencies below the ring frequency of the shell. Approximate analytic results covering almost the entire cylinder are given for the induced surface velocity field. Expressions for both the nearfield, including the drive admittance, and the farfield are given and compared with numerical results. Simple approximate formulas for the velocities and the excitation strengths of the surface waves are presented, and explicit expressions are derived for the acoustic field. Various aspects of the phenomena, the nature of the surface waves, the rate of falloff of the acoustic field, and the buildup of the evanescent fields are examined.
Source field modeling by self-consistent Gaussian beam superposition (two-dimensional)
Authors: Felsen L. B. , Klosner J. M. , Lu I. T. , Grossfeld Z.
Published: October 2005

Gaussians are useful models for high-frequency source field inputs into complex environments because they approximate the outputs of certain transducers, have favorable spectral and filtering properties, and can be propagated similar to ray fields. By recent analytic developments, any source field can be expressed exactly as a self-consistent superposition of Gaussians on a discretized (configuration)–(wave number) phase space lattice. This extends the use of Gaussians systematically to realistic transducer outputs. The method is already being applied to electromagnetic and acoustic propagation. It is here extended to modeling the radiation from transducers into an elastic solid. Restricting to the two-dimensional case, a distribution of forces over a finite, one-dimensional planar aperture is expanded self-consistently into Gaussian basis elements, which are then propagated into the unbounded medium. Numerical results reveal how successive addition of Gaussians for the compressional and shear potentials, as well as the displacements, homes in systematically on the assumed aperture profile, and on an independently generated numerical reference solution for the radiated near and far fields. Moreover, it is demonstrated how different self-consistent choices of beams affect the convergence. Furthermore, the validity of complex-source-point modeling of the Gaussians is explored for later applications where the input will be required to propagate across interfaces, as in a layered medium.
A small volume thermodynamic system for B/A measurement
Authors: Zhang Jian , Dunn Floyd
Published: October 2005

A thermodynamic method capable of determining the B/A value of 4-ml sample volumes is described. The method involves a procedure in which the static pressure of the sample is altered in a short period of time, to approximate an adiabatic process, during which the ultrasonic velocity is measured. The velocity change so determined is used to calculate the B/A value. The B/A measurement error is less than 0.7%.
An acoustical investigation method for a bar with nonlinear inclusions
Authors: Lokshin A. A. , Itskovits M. A. , Rok V. E
Published: October 2005

In this paper an acoustical investigation method based on the nonlinear interaction of waves is proposed. It is assumed that only the ends of the bar are accessible for investigation.
Analysis of boundary conditions for elastic wave interaction with an interface between two solids
Authors: Rokhlin S. I. , Wang Y. J.
Published: October 2005

The boundary conditions for an interface between two solids are analyzed to model a thin viscoelastic interface layer. Boundary conditions that relate stresses and displacements on both sides of the interface are obtained as an asymptotic representation of three-dimensional solutions for an interface layer in the limit of small wavelength to thickness ratio. The interface boundary conditions obtained include interface stiffnesses and inertia and terms involving coupling between normal and tangential stresses and displacements. The applicability of such boundary conditions is analyzed by comparison with exact solutions for ultrasonic wave reflection. Fundamental boundary conditions are introduced where only one transverse or normal mass or stiffness is included. It is shown that the solution for more exact interface boundary conditions which include two inertia elements and two stiffness elements can be decomposed into a sum of fundamental solutions. The transition between welded and slip boundary conditions on an interface with a thin viscous layer is also analyzed as a function of interface thickness, viscous skin depth, and frequency.
Influence of voids in interface zones on Lamb wave propagation in composite plates
Authors: Vasudeva R. Y. , Govinda Rao P.
Published: October 2005

An attempt is made to develop a simple analytical model to study the influence of voids in the interface zones—leading to a weak adhesion—between the constituent laminas of a composite plate treating the thin adhesive layer as a linear elastic material with voids (LEMV) [S. C. Cowin and J. W. Nunziato, J. Elasticity 13, 125–147 (1983)]. The frequency equation for free harmonic wave motion in a sandwich plate with an LEMV adhesive layer at the core is derived and the dispersion curves for Al/adhesive/Al sandwich are compared for a thin adhesive layer core with those obtained from other available imperfect bond model studies.
A generalized diffraction tomography algorithm
Authors: Gelius L.-J. , Johansen I. , Sponheim N. , Stamnes J. J.
Published: October 2005

Available diffraction tomography algorithms are based on Fourier transform techniques and require either plane-wave illumination in a uniform background medium or far-field illumination combined with paraxial approximations. In this paper a generalized diffraction tomography algorithm is introduced that can handle both irregularly spaced measurement data, nonuniform background models, and general aquisition geometries. Using data from water tank experiments, the method’s ability to yield high-quality reconstructions of geometry and velocity, as long as the weak-scattering assumption is satisfied, is demonstrated.
Elastic wave propagation in fluid-loaded multiaxial anisotropic media
Authors: Nayfeh Adnan H. , Chimenti D. E.
Published: October 2005

Theoretical investigations supported by extensive experimental comparisons are carried out on the interaction of ultrasonic waves with multilayered media. It is assumed that each constituent of the plate can possess up to as low as monoclinic symmetry. The plate is assumed to be immersed in a fluid and subjected to incident acoustic waves at arbitrary angles from the normal as well as at arbitrary azimuthal angles. Reflection and transmission coefficients are derived from which all characteristic behavior of the system is identified. Solutions are obtained for the individual layers that relate the field variables at the upper and lower layer surfaces. The response of the total plate proceeds by satisfying appropriate interfacial conditions across the layers.
An eigenvector method to determine the transient response of cylindrical shells in a fluid with uniform axial flow
Authors: Stepanishen Peter R. , Ebenezer D. D.
Published: October 2005

A general time domain approach is presented to evaluate the vibratory response of cylindrical shells in time-invariant axial flows to broadband time-dependent excitations. The approach is based on the use of an in vacuo eigenvector expansion with time-dependent coefficients for the velocity field of the shell. A set of convolution integral equations are developed for the eigenvelocities that are coupled due to the fluid loading. These equations are similiar to those developed for planar vibrators and are readily solved by marching forward in time. The known terms in the equations are the ρc fluid-loaded admittances of each eigenvector and the radition impulse responses. Since these are easily obtained, a large number of eigenvectors can be included in the analysis. Numerical results illustrating the responses of a simply supported cylindrical shell to an impulsive ring excitation are presented.
Ray tracing for reconstructive tomography in the presence of object discontinuity boundaries: A comparative analysis of recursive schemes
Authors: Andersen Anders H.
Published: October 2005

A comparative analysis of recursive ray tracing strategies for tomographic reconstruction from projections with diffracting sources is presented. One algorithm employs ray tracing in reprojection toward a correction of the true projection values for subsequent straight-ray reconstruction. The other algorithm performs curved-ray reconstruction along the retraced rays by algebraic methods for each recursive step. The performance for reconstruction of objects exhibiting discontinuity boundaries is studied. Within the geometrical optics approximation, the forward process is also shown to lead to multiple linking refracted rays. In an object of low velocity, there may be ranges of receive positions over which no linking refracted rays exist. Geometrically diffracted rays are introduced to describe the signal actually received over the ‘‘forbidden’’ range.
Noncollinear interaction of a tone with noise
Authors: Lind Stephen J. , Hamilton Mark F.
Published: October 2005

An experiment was performed to investigate the noncollinear interaction of a high-frequency tone with low-frequency noise. The nonlinear interaction took place in an air-filled rectangular duct. A low-frequency band of noise was transmitted in the (0,0) mode together with a high-frequency tone in the (1,0) mode. The angle between the two interacting waves was 55°. Measurements of the frequency spectra were made at locations that were well within the shock formation distance of either primary wave. The spectral shapes of the sum and difference frequency sidebands of noise are scalloped in appearance, and the number of nulls in each sideband increases with range from the source. Theoretical predictions for the nonlinearly generated sidebands are in good overall agreement with experiment. The predictions are based on a quasilinear analysis developed previously to describe the noncollinear interaction of two tones in a rectangular duct [M. F. Hamilton and J. A. TenCate, J. Acoust. Soc. Am. 81, 1703–1712 (1987)]. Comparisons are made with the corresponding case of collinear interaction, in which both primary waves propagate in the (0,0) mode.
Coherent propagation of sound in correlated distributions of resonant spherical scatterers
Authors: Berger N. E. , Twersky V.
Published: October 2005

Expressions for underwater propagation in bubble regions based on the index of refraction (η) in uncorrelated random distributions of monopole resonators are restricted to sparse bubble packing (very small volume fraction w). As w increases, correlations arise, and coupling with higher-order multipoles is not necessarily negligible. To provide prototypes for data inversion, integral equations are analyzed for η in correlated distributions of spheres (including up to quadrupole coefficients) in terms of shell and moment expansions of the Percus–Yevick correlation function. Graphical results for w up to 20% indicate the decrease in magnitudes at resonance, the increase in resonance frequency, and the broadening of the resonance region relative to the uncorrelated case. A simple explicit three-moment approximation is derived for distributions of monopoles plus dipoles that provides good accord with machine computations (based on ten-moment or on eight-shell expansions) to about w=7.5%, and also holds at least qualitatively for larger w. The explicit form may also be used with the first three moments of other correlation functions.
Discriminating between coherent and incoherent frequency modulation of complex tones
Authors: Carlyon Robert P.
Published: October 2005

A series of experiments measured the discrimination by human listeners of frequency-modulated complex tones which differed only in the coherence of frequency modulation (FM). For the coherently modulated tones all components were modulated by the same 5-Hz sinusoid, and by the same percentage of their starting frequencies, whereas for the incoherently modulated tones the modulation of one (target) component differed from that of the rest. When the 400-ms complex was composed of consecutive harmonics of a common fundamental, performance improved monotonically with increases in modulator delay, and was nearly perfect at the longest delays. When the complex was inharmonic, performance was near chance at all modulator delays, both for component frequencies between 1500 and 2500 Hz, and for component frequencies between 400 and 800 Hz. It is argued that listeners detected incoherence in harmonic complexes by detecting the resulting mistuning of the target component. This conclusion was supported by the finding that listeners were usually at least as good at detecting a fixed mistuning of the center component of a harmonic complex as they were at detecting a modulator phase delay imposed on it. A final experiment, with a stimulus duration of 1 s and slower modulation rates, showed that listeners could detect incoherence for some inharmonic complexes. However, detection was worse than for harmonic complexes and was, it is argued, based on weak harmonicity cues. The results of all experiments point to the absence of an across-frequency mechanism specific to the detection of FM incoherence.
Age of learning affects the authenticity of voice-onset time (VOT) in stop consonants produced in a second language
Authors: Flege James Emil
Published: October 2005

This study examined whether Spanish–English bilinguals are able to fully differentiate Spanish and English /t/ according to voice-onset time (VOT) if they learn English as a second language (L2) in early childhood. In experiment 1, VOT was measured in Spanish words spoken by Spanish monolinguals, in English words spoken by English monolinguals, and in Spanish and English words spoken by bilinguals who learned English either as young children or as adults. As expected, the Spanish monolinguals produced /t/ with considerably shorter VOT values than the English monolinguals. Also as expected, the late L2 learners produced English /t/ with ‘‘compromise’’ VOT values that were intermediate to the short-lag values observed for Spanish monolinguals and the long-lag values observed for English monolinguals. The early learners’ VOT values for English /t/, on the other hand, did not differ from English monolinguals’ VOT. The same pattern of results was obtained for stops in utterance-medial position and in absolute utterance-initial position. The results of experiment 1 were replicated in experiment 2, where bilingual subjects were required to produce Spanish and English utterances (sentences, phrases, words) in alternation. The results are interpreted to mean that individuals who learn an L2 in early childhood, but not those who learn an L2 later in life, are able to establish phonetic categories for sounds in the L2 that differ acoustically from corresponding sounds in the native language. It is hypothesized that the late L2 learners produced/t/ with slightly longer VOT values in English than Spanish by applying different realization rules to a single phonetic category.
A wave-vector–time-domain technique to determine the transient acoustic radiation loading on cylindrical vibrators in an inviscid fluid with axial flow
Authors: Ebenezer D. D. , Stepanishen Peter R.
Published: October 2005

A wave-vector–time-domain method that was used to obtain the transient acoustic radiation loading on vibrating finite cylinders is extended to include the effects of the presence of inviscid axial flow. The method is based on the use of the in vacuo modes of vibration of the shell which have infinite rigid extensions. The solution to the boundary value problem for the pressure is first obtained in wave-vector–time space. The time-dependent modal forces are then expressed as a sum of the modal radiation impulse responses of the finite cylinder convolved with the time-dependent modal velocities. The modal radiation impulse responses are obtained by using the impulse responses of an infinite cylinder and the modes in wave-vector space. The approach can thus be easily used to obtain the radiation impulse responses for various boundary conditions, length to radius ratios, and arbitrary space- and time-dependent surface velocities. Numerical results are presented for a wide range of Mach numbers and for length to radius ratios of simply supported cylindrical shells.
Fiber-optic air-backed hydrophone transduction mechanisms
Authors: Bucaro J. A. , Houston Brian H. , Williams Earl G.
Published: October 2005

It is predicted that, under certain conditions, the acoustic response of a thin-walled, tubular, air-backed fiber-optic hydrophone will exceed that predicted by the usual quasistatic approximations. Measurements of the acoustically induced optical phase shift for a fiber wound, thin-walled tube are presented to confirm the reasonableness of this prediction.
Models for the generation of the binaural difference response
Authors: Gaumond Roger P. , Psaltikidou Maria
Published: October 2005

Two simple models are examined in order to explain the observation that a portion of the binaural-evoked response is less than the sum of monaural-evoked responses in human and animal subjects. The sum of monaural responses minus the binaural response is called the binaural difference (BD). Each model acts on binaural input signals and applies a single memoryless nonlinearity. One model (IE) applies a rectifying nonlinearity to the difference of input signals, while the other (EE) applies a compressive nonlinearity to the sum of input signals. These models are suggested by properties of inhibitory–excitatory (IE) and excitatory–excitatory (EE) neurons of the auditory brainstem. Parameters can be found that enable each model to produce a ratio of BD to summed monaural response which is invariant with input stimulus level. The IE model, but not the EE model, has a BD whose level is linearly related to input stimulus level.
Phase conjugation in underwater acoustics
Authors: Jackson Darrell R. , Dowling David R.
Published: October 2005

Phase-conjugate mirrors are used in optics to compensate for aberrations caused by inhomogeneities in the propagation medium and by imperfections in optical components. In acoustics, analogous behavior can be achieved by a time-reversed retransmission of signals received by an array. Compensation for multipath propagation and array imperfections is automatic and does not require knowledge of the detailed properties of either the medium or the array. The behavior of acoustic phase-conjugate arrays is illustrated in several examples, some highly idealized and some more realistic. The effects of aperture size and inhomogeneities in the propagation medium are treated for both the near-field and far-field regions. It is concluded that phase-conjugate arrays offer an attractive approach to some long-standing problems in underwater acoustics.
A study of a vehicle ground speed sensor using the ultrasonic wave doppler effect
Authors: Kobayashi Hiroshi , Kimura Toshiya , Negishi Masami
Published: October 2005

The Doppler effect is composed of two phenomena, the propagation in the air and the reflection from the road surface of the ultrasonic wave signal. A detailed investigation was made of the relation between these two phenomena and the S/N and frequency bandwidth of the Doppler signal. It was clarified that the best transmission conditions were achieved with a wavelength of 3 mm and a directivity angle of 5 deg. The best reception condition was attained with a new method for sensing the Doppler signal. This method involves setting the reception frequency at a level determined by the optimum transmission conditions.
Active control of total vibratory power flow in a beam. I: Physical system analysis
Authors: Pan Jie , Hansen Colin H.
Published: October 2005

Excitation of a beam may produce a combination of longitudinal, flexural, and torsional waves. The active control of one kind of wave by an actuator may create waves of the other kinds which may not be excited under the uncontrolled conditions. The generation and propagation of each wave in the beam depend upon the distribution of the forces, the geometrical shape and prestress condition of the beam, and the discontinuity and boundary conditions. This paper concentrates on the effect of the excitation and control forces on these waves and the control of the total power flow along a beam of infinite length and rectangular cross section. An expression for the power flow for an arbitrary distributed point excitation force and an arbitrary distributed point control force is obtained. This expression allows a study of the nature of the power flow for each wave under an excitation force and the effect of the control forces on these waves when the total power flow is minimized.
An assessment of the effect of residential acoustic insulation on prevalence of annoyance in an airport community
Authors: Fidell Sanford , Silvati Laura
Published: October 2005

A social survey was undertaken to compare the prevalence of noise-induced annoyance in two residential populations with similar aircraft noise exposure in the vicinity of Hartsfield International Airport (ATL) in Atlanta, Georgia. One population was composed of residents of homes that had been treated to increase their acoustic transmission loss. The other population was composed of residents of homes that had not been so treated. No clear benefit of home noise insulation was observed in terms of lowered prevalence of annoyance to aircraft noise exposure.
Propagation, generation, and detection of SAW in a multiperiodic system of metal strips on a piezoelectric substrate
Authors: Danicki Eugeniusz , Gafka Dariusz
Published: October 2005

An infinite periodic system of groups of equidistant metal strips deposited on a piezoelectric half-space is considered. Such a system may be useful for analyzing a single group of strips if the period of the groups is sufficiently large. A dispersion relation for generally slanted surface acoustic wave (SAW) propagation with respect to electrodes is derived and analyzed. Numerical examples are given for a wave propagating along, and perpendicular to the electrodes. A functional relationship for strip currents dependent on strip potentials has been derived. This can be applied for analyzing interdigital transducers (IDT) having a finite number of periodic fingers. Bragg’s reflection of SAW from metal strips is also analyzed.
The relationship between upward refraction above a complex impedance plane and the spherical wave evaluation for a homogeneous atmosphere
Authors: Raspet Richard , Baird Gordon E. , Wu Wenliang
Published: October 2005

An investigation has been carried out on the relationship between the residue series method for the prediction of sound propagation in an upward refracting atmosphere and the spherical wave analysis of sound propagation in a homogeneous atmosphere. It is shown that, in the limit of small sound velocity gradients, the Airy function solution developed by Pierce for sound propagation over the earth’s surface does approach the Sommerfeld integral for spherical wave reflection in a homogeneous atmosphere for a limited range of values of wave number. For complex impedance with phases greater than π/3, it is found that the surface wave pole identified for sound propagation in a homogeneous atmosphere is present in the upward refracting atmosphere. This pole arises from the residue series. Methods suggested in the literature for searching for the poles will fail for impedances with phase angles greater than π/3.
Rapid computation of acoustic fields in three-dimensional ocean environments
Authors: Kuperman W. A. , Porter Michael B. , Perkins John S. , Evans Richard B.
Published: October 2005

Adiabatic and coupled-mode theory is amenable to precalculations that can subsequently be used in a nonredundant manner to perform rapid three-dimensional acoustic field computations for a complex ocean environment. Algorithms have been developed to take advantage of both horizontal and vertical precalculated quantities. Complex three-dimensional field computations are then reduced to ‘‘spreadsheet’’ type manipulations of partial solutions to the wave equation. The method is illustrated by applying it to a Gulf Stream environment near the continental shelf. Results from adiabatic, coupled-mode, and parabolic-equation computations are compared.
The duct leakage relation for the surface sound channel
Authors: Weston D. E. , Esmond C. G. , Ferris A.
Published: October 2005

The leakage attenuation from a duct is simply related to the field level outside the duct, and the relation can be applied to the surface sound channel. High-frequency measurements over the Biscay Abyssal Plain support the predicted relation and indicate that the loss is mainly due to scattering at very shallow angles, presumably from the surface waves. Similarly low-frequency measurements in the same area show a diffraction loss occurring with effective angles that are again very shallow. Measurements by Reynolds and Pryce at 7.5 kHz are also shown to correspond very closely to low-angle scattering, ruling out any large contribution from entrained bubbles. In addition, it is possible to estimate the residual bulk absorption. But their results at 3.25 kHz show marked additional effects that are interpreted as wide-angle scattering and absorption due to small fish, and the existence of such deep-water fish attenuation is thought to be both novel and important. Use of our leakage relation has helped to identify and to disentangle five separate loss mechanisms.