bluuebunny/crossref_metadata_2025 huggingface dataset:
The temporal evolution of masking and frequency selectivity in the goldfish (C
a
r
a
s
s
i
u
s a
u
r
a
t
u
s)
Authors: Coombs Sheryl , Fay Richard R.
Published: October 2005

The temporal evolution of masking and frequency selectivity was studied in the goldfish using classical respiratory conditioning and a tracking psychophysical procedure. The temporal position of a brief tonal signal within a longer duration, tonal masker has little or no effect on signal detectability when the frequency of the masker is less than or equal to that of the signal. For masker frequencies above that of the signal, signal detectability improves as the signal onset is delayed relative to that of the masker. These patterns of tone-on-tone masking are quite similar to those observed for humans. These temporal masking patterns are qualitatively similar in shape to the peristimulus-time histogram profiles of the low-frequency saccular fibers thought to be used in this task. Frequency- and time-dependent changes in signal detectability result in specific changes in the sharpness of psychophysical tuning curves (PTC). In general, PTCs determined for signals occurring at masker onset are the most broadly tuned, and PTCs determined in forward masking are the most sharply tuned. The PTCs for signals temporally centered in the masker are intermediate. These results suggest that temporal tone-on-tone masking patterns and the temporal evolution of psychophysical tuning curves result from the response properties of peripheral auditory-nerve fibers.
Signal uncertainty and psychometric functions in profile analysis
Authors: Raney Jill J. , Richards Virginia M. , Onsan Zekiye A. , Green David M.
Published: October 2005

Experiment 1 was conducted to compare the effects of signal frequency uncertainty on the detection of a change in spectral shape and on the detection of a tone in wideband noise. Results indicate that for both tasks the uncertainty effect was small, being on average about 3 dB. In a second experiment, psychometric functions were measured for the detection of changes in the spectral shape of multicomponent complexes. Psychometric functions for profile tasks have a 25-dB range and are similar to those measured for the detection of an increment in the level of a single sinusoid. These psychometric functions are different from those found when detecting a signal in noise, which typically have a 10-dB range. Three equations for the shape of the psychometric functions were compared. The difference in the resulting fits was small, thus preventing an unambiguous choice of functional form.
An experimental study of acoustoelectric transducers with nonuniform distribution of the piezoelectric coefficient
Authors: Chapeau-Blondeau François , Greenleaf James F. , Harrison William B. , Hanson M. R. B.
Published: October 2005

In this paper, an experimental test of a theoretical model published previously is presented that describes the behavior of an acoustoelectric transducer with a nonuniform distribution of the piezoelectric coefficient within its bulk. Results of this theoretical model are first reviewed. Uniform and nonuniform piezoelectric transducers were fabricated, following a procedure described herein. The receive transfer functions of the transducers were recorded experimentally, and a comparison is made with the theoretical transfer functions predicted by the model, which shows good agreement. The transmit transfer functions of the uniform and nonuniform transducers were also measured and are reported. Numerical calculations of the different transfer functions given by the theoretical model for a uniform transducer associated with different backing materials are also presented, and the results are shown to be equivalent to the results following from the Mason equivalent circuit. Comparisons with experimental results and with Mason’s equivalent circuit verified the new theoretical model.
Roving-level tone-in-noise detection
Authors: Kidd Gerald , Mason Christine R. , Brantley Merry A. , Owen Grace A.
Published: October 2005

The detectability of tones, or of intensity increments to tones, in bands of random noise was measured for conditions in which the overall level was fixed or was randomly roved from interval to interval of every experimental trial. The purpose of the within-trial rove was to limit the usefulness of a detection strategy based on overall level or level within a single ‘‘critical band.’’ At ‘‘supracritical’’ bandwidths, the functions relating masked threshold to noise bandwidth for the roved conditions were similar to those obtained when no rove was employed. At ‘‘subcritical’’ bandwidths, thresholds were higher in some roved conditions, but, for the largest rove, were still lower than would be predicted from arguments based purely on level detection—with one exception. A comparison of observer performance relative to the statistical limits imposed by the roving-level procedure indicated that the traditional critical-band energy-detector model could not account for the results, which are attributed to discrimination based on spectral shape or on waveshape.
Infants’ monaural localization of sounds: Effects of unilateral ear infection
Authors: Morrongiello Barbara A.
Published: October 2005

The aim in this study was to examine the impact of unilateral ear infection (i.e., otitis media with effusion) on infants’ localization of sounds in the horizontal plane. Twenty eight infants 6 to 18 months of age were tested at the time of an ear infection, as well as 2 weeks later. Sound localization was measured using a two-alternative forced-choice procedure to examine infants’ abilities to discriminate a sound shift of 8°, 12°, 16°, and 20° off midline and along the horizontal axis, either ipsilateral or contralateral to the infected ear. A head and/or eye movement in the direction of the sound was designated as a correct response and was visually reinforced. Results revealed significant negative effects of unilateral ear infection on sound localization performance. All infants showed more correct localization responses for sounds shifted ipsilateral to the problem ear 2 weeks following their ear infection than at the time of the infection. Localization of sounds shifted contralateral to the infected ear did not vary with test date, and significantly exceeded ipsilateral performance when tested at the time of an ear infection. Results are consistent with adult data which indicates that, with unilateral hearing loss, a sound ipsilateral to the problem ear is displaced in location along the horizontal axis toward the well-functioning ear. These findings indicate the importance of balanced binaural functioning for horizontal localization and highlight the plasticity of the developing human auditory system.
An exact solution for finite-amplitude plane sound waves in a dissipative fluid
Authors: Mitome Hideto
Published: October 2005

The propagation of finite-amplitude plane sound waves in a dissipative fluid can be described by Burgers’ equation, and its exact solution obtained. In this paper, an exact solution for the sound pressure, which is suitable for direct numerical computation of the waveform in the time domain, is derived. Numerical results illustrate that this solution describes the entire propagation process, including shock formation and decay. Computation limits are determined in connection with the computational system. It is found that computation is possible for D0>0.0114 and any value of X with the present system, where D0 indicates the importance of dissipation relative to nonlinearity and X is distance normalized by the lossless shock formation distance. It is also found that the solution for the limiting value of D0 connects smoothly with the Fubini solution for X<1 and with the Fay solution for X>3.5. Since the present solution is exact and yields the waveform at any distance without introducing the Fourier series expansion of finite terms, it can serve as a standard solution for various approximate methods. As examples, changes in the energy density and the saturation phenomena are shown.
A Galerkin scheme for the time domain integral equation of acoustic scattering from a hard surface
Authors: Ding Y. , Forestier A. , Duong T. Ha
Published: October 2005

The transient acoustic scattered wave from a hard surface is computed using a space-time integral equation. A variational formulation of this integral equation is obtained from an energy identity, leading to a Galerkin-type numerical procedure. By choosing an appropriate basis for the discretized functional space, this scheme is of the marching-in-time type with matrix coefficients. This technique is applied to a sphere, a box, and dihedron targets.
A comparison of intrasubject variation across sessions of three vocal frequency perturbation indices
Authors: Higgins Maureen B. , Saxman John H.
Published: October 2005

Within-subject variation of three vocal frequency perturbation indices was compared across multiple sessions. The magnitude of jitter factor (JF), pitch perturbation quotient (PPQ), and directional perturbation quotient (DPF) was measured every other day for 33 consecutive days for ten female and five male normal young adult speakers. Perturbation measures were calculated using a zero-crossing analysis of taped [i] and [u] productions. Pearson product-moment correlations among the three perturbation indices were calculated to examine their relation over time. Coefficients of variation for JF, PPQ, and DPF were considered indicative of the temporal stability of the three measures. JF and PPQ provided redundant information about laryngeal behaviors in steady-state productions. DPF, however, appeared to measure different laryngeal behaviors. Also, JF and PPQ varied considerably within individuals across sessions while DPF was the more temporally stable measure. Multiple sampling sessions and measurement of both the magnitude and direction of period differences are advised for future investigations of vocal frequency perturbation.
A three-dimensional parabolic equation model that includes the effects of rough boundaries
Authors: Collins Michael D. , Chin-Bing Stanley A.
Published: October 2005

A three-dimensional parabolic equation (3DPE) model that handles wide propagation angles in depth, narrow propagation angles in azimuth, and rough boundaries is derived and solved numerically with the method of alternating directions. A homogeneous boundary condition, which is easily incorporated into the numerical solution of the 3DPE, is applied at the ocean surface to approximate the effects of rough boundaries in terms of a reflection coefficient that depends on grazing angle. Calculations are presented to demonstrate the accuracy of the 3DPE and to demonstrate that horizontal coupling, the effects due to the term involving azimuth derivatives, can be important in shallow water (previous work has focused on deep-water applications). The model is applied to problems involving rough boundaries and range dependence.
A boundary integral equation method for acoustic scattering in a waveguide with nonplanar surfaces
Authors: Dawson Trevor W. , Fawcett John A.
Published: October 2005

A boundary integral equation method (BIEM) is formulated to compute the scattering of underwater sound from compact deformations of an oceanic waveguide’s surfaces. The method involves only integrations over the finite area of the waveguide surface deformations. Numerical computations are given for specific deformations of the ocean floor.
A sediment time-angle spreading model
Authors: McCammon D. F.
Published: October 2005

To model time-angle spreading from rough sediment layers, a large-scale forward-scattering approximation is applied to the correlation of the characteristic function in the expected value of the intensity. A composite distribution is derived for the transmitted and reflected portions of the acoustic wave through multiple closely spaced layers. Time spread data comparisons are used to set these composite variances at 20° on the consolidated layers and 2°–4° on unconsolidated surficial layers. These values are tested against some independent measurements of angle spreading and found to give good agreement. The model validation at low grazing angles implies that only a small number of layers are apparently participating in the scattering process at the surface of many sediments.
A generalized approach to random noise synthesis: Theory and computer simulation
Authors: Hsueh Keng D. , Hamernik Roger P.
Published: October 2005

A generalized approach to the synthesis of Gaussian and non-Gaussian random noises as well as purely impulsive waveforms having a preselected amplitude spectrum has been developed. The basic idea behind the synthesis is to construct the amplitude-time waveform from the frequency domain, i.e., from the amplitude and phase spectra. By maintaining a predetermined (reference) amplitude spectrum and performing certain specific manipulations of the phase spectrum within any selected band of frequencies and then applying the inverse discrete Fourier transform (IDFT), peaks in the non-Gaussian random waveform can be constructed from the selected band of frequencies that have been phase manipulated. Entire families of signals can thus be produced having the same energy spectrum, but statistical characteristics that vary along the continuum from Gaussian (skewness=0 and kurtosis=3) through non-Gaussian (variable skewness, kurtosis, and crest factor) to purely impulsive (shock/transient) signals. The theoretical background and the results of a series of numerical simulations will be presented which demonstrate the functional relation between various phase spectrum manipulations and the descriptors of the synthesized random noise. The results show that the approach is viable and that the synthesized random waveforms can be easily tailored to simulate a variety of real-world acoustic/vibration signals, e.g., high kurtosis (impulsive) industrial noises, helicopter noises, missile vibrational signals, etc.
An alternative structure for adaptive broadband beamforming with imperfect arrays
Authors: Huang Kuang-Chih , Chang Shun-Hsyung , Chen Yuan-Hwang
Published: October 2005

A linearly constrained adaptive beamformer, under certain strategies, is hypersensitive to array imperfections when the input SNR exceeds a certain threshold. Due to array imperfections, the desired signal does not fall exactly in the constrained look direction, and then it is canceled out as an interference. To tackle this problem, this paper proposes an alternative structure for the adaptive broadband beamforming system that may obtain a broader beamwidth in the look direction without imposing any derivative constraint on the adaptive processor. The simulation results illustrate that the proposed adaptive beamformer performs with a better response to array imperfections than the conventional Frost beamformer, because the former may broaden the beamwidth in the look direction to concede greater perturbations without the corresponding array rejection of the desired signal.
A large-scale acoustic pulse holography reconstruction
Authors: Brown J. B. , Halse M. R. , Hudson W. J. , Robinson P. N. , Rogers S. J.
Published: October 2005

A backprojected reconstruction method is presented that has been developed by imaging buildings in an area 91.4×91.4 m using the echoes from a revolver fired into an exponential horn. The signals were received with a nondirectional microphone. Frequencies above 1 kHz were used to emphasize diffuse scattering rather than specular reflection. Consideration was given to the variation in echo amplitudes and arrival times arising from air turbulence. Acceptable images were produced when an iterative cleanup algorithm and an amplitude-limited point-spread deconvolution were used.
Optical analysis of finite-amplitude ultrasonic pulses
Authors: Wolf J. W. , Neighbors T. H. , Mayer W. G.
Published: October 2005

Finite-amplitude pulses are examined acousto-optically using a newly developed light-diffraction apparatus. Based on an optical analysis of ultrasonic transducer response to continuous-wave excitation at and near the fundamental frequency, pulse Fourier spectra are derived for input to a light-diffraction model, providing quantitative agreement between experiment and theory. The diffraction theory predicts that a light-diffraction pattern produced by a harmonically distorted acoustic pulse train will exhibit asymmetry in the intensity distribution with respect to the zero order. To simulate harmonic distortion, pulse frequency spectra are used for input to a computational model that is based on the Burgers’ equation for propagation of finite-amplitude acoustic waves in a nonlinear medium. The spectrum, propagation, and light-diffraction models give a complete description of light diffraction by finite-amplitude pulses and provide good agreement with experimentally obtained diffraction patterns.
Comparison of ray and wave approaches to acoustic impulse propagation prior to a shadow boundary
Authors: Don C. G. , Cramond A. J.
Published: October 2005

The presence of wind and temperature gradients causes sound to follow curved ray paths, changing the relative delay between direct and reflected components. The way this changes the excess attenuation of propagating acoustic impulses and their waveforms is considered by using ray-bending theory, including intensities, for an atmosphere supporting either a linear or a nonlinear sound-speed gradient. These predictions are contrasted with those from creeping-wave theory, assuming a linear gradient, and both are compared with experimental results for impulses propagating close to the ground. Although the measured gradients are nonlinear, impulse behavior is found to be best predicted by assuming an effective linear gradient. A technique involving impulse rise times is used to determine shadow-boundary distances and hence the profile of the boundary.
Line and plane arrays of resonant monopole scatterers
Authors: Tolstoy Ivan , Tolstoy Alexandra
Published: October 2005

Arrays of n identical resonators (bubbles, gas-filled balloons, and thin shells) in periodic arrays of spacing l and insonified by a plane wave at frequencies near the monopole resonance (bubble) frequency ω0 display strong resonances due to multiple scatter interaction. One-dimensional systems (linear arrays) in full spaces exhibit pronounced partial resonances (quasiresonances or QRs), for both finite and infinite n, with absolute magnification of the free-field amplitude (i.e., in the absence of the system) of up to 7×102 inside or on the surface of each resonator. These QR effects have strong directionality: The amplitude response of each scatterer may vary by a factor of about 200, depending upon the direction of arrival of the insonifying plane wave. Of some general interest are the infinite line and plane arrays of the kind discussed by Weston [D. E. Weston, J. Acoust. Soc. Am. 39, 316–322 (1967)], for which we provide an improved treatment using exact estimates of multiple scatter interaction, as a result of which strong new resonances (QRs) are predicted under some conditions.
Effect of the compliance on the scattering of an elastic object immersed in fluid: A general formulation
Authors: Borgiotti Giorgio V.
Published: October 2005

The scattering of a linear elastic object can be represented by the product of three linear operators. The first and the third of them represent the coupling of the source of the incident field to the scatterer and the scatterer to the observation point, respectively, and depend only on the boundary geometry and on the fluid acoustic properties. The object physical properties are summarized by the middle operator, expressing the deviation of the relevant elastodynamic properties of the actual object from those of a perfectly transparent object, having the same size and shape. This formalism leads also to a natural rigorous decomposition of the scattering into the sum of a rigid and an elastic component, the latter being possibly substantially higher than the first, as shown by some numerical examples.
A parametric analysis of attenuation mechanisms in composites designed for echo reduction
Authors: Lim Raymond , Hackman Roger H.
Published: October 2005

The fundamental attenuation mechanisms operating in a particular class of composites are investigated for their viability as underwater anechoic materials. The type of composites of interest consists of dense (visco-) elastic inclusions in rigid, low-density, water impedance-matched, elastic hosts. Composites similar to this have been studied by Kinra2 and shown to attenuate transmitted elastic waves in a resonant regime of the imbedded inclusions. Our calculations indicate that the processes giving rise to the attenuation would also be appropriate for echo reduction. As a reference material, a composite of lead-loaded silicone rubber spheres in a rigid epoxy is studied. The processes operating at both the water–epoxy and epoxy–rubber interfaces are studied theoretically. Using the spherical elastic T matrix, effects due to resonant scattering are analyzed by reference to the scattered and absorption cross sections calculated for both a single rubber sphere and two rubber spheres imbedded in an infinite epoxy matrix. The dynamics at the water–epoxy interface is analyzed via classical elastic theory at a plane interface. The results of our analysis indicate that resonant compressional to shear mode conversion at the inclusions could be an effective way of producing the desired effects. Consequences of the mode conversion leading to attenuation include the trapping of backscattered shear waves and the enhancement of dissipation processes within the inclusions.
Inner hair cell responses to the 2f1-f2 intermodulation distortion product
Authors: Nuttall Alfred L. , Dolan David F.
Published: October 2005

Recordings of dc and ac receptor potentials from pigmented guinea pig inner hair cells indicate strong responses to the 2f1-f2 intermodulation tone when f1 and f2 are greater than the hair cell characteristic frequency and do not cause a response when given individually. The effective magnitude of this cubic distortion product (CDP) was about 25–30 dB below equal sound level primaries over a 20–30-dB range of their sound levels. The relative strength of the CDP declined at a rate greater than 180-dB/oct separation of the primaries. When magnitude of f1 or f2 was held constant, the growth of CDP was nonmonotonic, exhibiting a distinct maximum. With a constant level of f1 or f2, optimal CDP was produced when the level of f2 was 10–15 dB greater than f1. Strong two-tone suppression from the primaries has a role in shaping the CDP growth. The ac receptor potentials of the CDP show a 150°–200° phase shift when the primaries are increased over a 50-dB range. These results support the hypothesis of a propagated CDP in the cochlea and are consistent with the major features of related studies of human psychoacoustic experiments, afferent nerve neural rate functions, and ear canal distortion products.
Physiological mechanisms of psychophysical masking: Observations from auditory-nerve fibers
Authors: Delgutte Bertrand
Published: October 2005

Masking might be due either to the spread of the excitation produced by the masker to the place of the tone signal along the cochlea or to the suppression of the response to the signal by the masker. In order to identify the contributions of these two mechanisms to tone-on-tone masking, masked thresholds of auditory-nerve fibers were measured in anesthetized cats using the same stimulus paradigms and detection criteria as in psychophysics. Suppressive masking was identified by comparing thresholds for simultaneous masking with those for a nonsimultaneous masking technique resembling pulsation thresholds. These nonsimultaneous thresholds do not include the contribution of suppression to masking because suppression only occurs for stimuli that overlap in time. For each masker and signal frequency, the fibers with the lowest (or ‘‘best’’) masked thresholds had characteristic frequencies (CF) slightly on the opposite side of the masker frequency with respect to the signal frequency, consistent with the psychophysical phenomenon of off-frequency listening. Patterns of best masked thresholds against signal frequency resembled psychophysical masking patterns in that they showed a maximum for signal frequencies close to the masker, and a skew toward high frequencies. Masking was found to be both excitatory and suppressive, with the relative contribution of the two mechanisms depending on the frequency separation between signal and masker. Suppressive masking was large for signal frequencies well above the masker. For these conditions, simultaneous thresholds grew more rapidly with masker level than did nonsimultaneous thresholds, suggesting that the upward spread of masking is largely due to the growth of suppression rather than to that of excitation.
The transient field of a planar ultrasonic transducer coupled to a lens: Experiments and simulations
Authors: Djelouah H. , Baboux J. C. , Perdrix M.
Published: October 2005

In this paper a study of the transient ultrasonic field radiated, in a fluid, by a planar transducer coupled to a lens is proposed. The transient pressure is measured using two small probes of different radii. Experimental waveforms are compared to waveforms that have been calculated using the impulse response method, extended in order to take account of the finite size of the receivers. The transient pressure field is interpreted by the concept of geometrical wave and edge waves. The averaging effect due to the finite size of the receivers, which acts differently on the ultrasonic field components, is put in evidence.
Oscillational instabilities in single-mode acoustic levitators
Authors: Rudnick Joseph , Barmatz M.
Published: October 2005

An extension of standard results for the acoustic force on an object in a single-mode resonant chamber yields predictions for the onset of oscillational instabilities when objects are levitated or positioned in these chambers. The results are consistent with experimental investigations. The present approach accounts for the effect of time delays on the response of a cavity to the motion of an object inside it. Quantitative features of the instabilities are investigated. The experimental conditions required for sample stability, saturation of sample oscillations, hysteretic effects, and the loss of the ability to levitate are discussed.
A fast exact numerical solution for the acoustic response of concentric cylinders with penetrable interfaces
Authors: Schuster Gerard T.
Published: October 2005

A fast exact numerical algorithm is presented that computes the line source acoustic response of concentric cylinders filled with acoustic material of contrasting impedances. The fast exact numerical method solves a cylinder scattering problem by a boundary integral equation method. By azimuthal symmetry, the discrete approximation of these integral equations are discrete periodic convolutions with respect to the angular variable. Application of a discrete Fourier transform reduces the boundary integral equations to a system of linear algebraic equations. The response is economically computed by algebraic division and an inverse fast Fourier transform. The dominant cost per temporal frequency is O(N log2 N) algebraic operations, where N is the maximum number of discretization points along the circumference of the cylinder.
Shear horizontal surface waves on an isotropic elastic cylinder
Authors: Kielczyński P. , Pajewski W. , Szalewski M.
Published: October 2005

This paper comprises theoretical and practical results concerning the problem of propagation of surface shear horizontal (SH) waves on monolithic, elastic cylinders. It was proved that SH surface waves have a multimode structure and their pulses propagate with a velocity that tends asymptotically to the velocity v0 of the shear bulk waves for increasing frequency. On the other hand, the phase velocity vp of surface SH waves decreases asymptotically to the velocity v0, as a function of frequency. For the obtained theoretical formulas, numerical calculations were performed and are valid for homogeneous elastic cylinders. The experiment was carried out for glass cylinders. Satisfactory agreement between theoretical and experimental results was stated.
A boundary integral formulation for thin-walled shapes of revolution
Authors: Martinez R.
Published: October 2005

Much of the recent literature on boundary elements has addressed the practical limitations of the method. One issue under current scrutiny appears to be the inapplicability of formulations based on the Helmholtz integral to free-flooded shapes characterized by kh≪1, where k and h are the acoustic wavenumber and the object’s cross-sectional thickness dimension. The present article develops and applies a modal boundary integral technique especially tailored to thin geometries of revolution. The problems chosen for its demonstration are cases of acoustic diffraction by an open-ended cylindrical duct containing a sound source, where the scattering wall’s outer and inner surfaces are an infinitesimal distance apart, and are respectively rigid and either rigid or compliant. The study concludes that general shapes with kh≪1 or kh=0 should be treatable by at least one established numerical approach, after some analytical reinterpretation.
One-way wave equations for seismoacoustic propagation in elastic waveguides
Authors: Wetton Brian T. R. , Brooke Gary H.
Published: October 2005

One-way or parabolic wave equations for time-harmonic propagation in two-dimensional elastic waveguides are considered. It is shown that the direct application of a rational linear approximation with real coefficients to the elastic wave propagation case results in exponential growth in the numerical solutions. Elementary analysis demonstrates that this kind of approximation does not treat properly the modes with complex wavenumber which can exist in elastic waveguides. A new bilinear square-root approximation with complex coefficients is introduced that accommodates all mode types and leads to stable numerical solutions. In the case of thick elastic layers (such as sea-bottom sediments), this new approximation gives accurate total field prediction. When thin elastic layers (such as ice on the sea surface) are present, however, the method introduces excessive damping to modes with wavenumbers significantly different from a reference wavenumber.
The effect of fluid–structural coupling on acoustical decays in a reverberation room in the high-frequency range
Authors: Pan Jie , Bies David Alan
Published: October 2005

The effect of the fluid–structural coupling between the modes of a sound field and the modes of test panels placed in the sound field upon their decay behavior is investigated in the high-frequency range. Quasitransient solutions of the average energies in the room and the panels are used to estimate the reverberation times in the room and to calculate the decay curves of a test panel. Experiments are conducted that verify these solutions. The estimated and measured results are in good agreement, which indicates that the average decay behavior of the room and panels can be analyzed in terms of the average modal parameters. The average modal parameters of the test panels and the reverberation room can be related to the Sabine absorption coefficient αSab of the panels. This result suggests an interpretation for the Sabine absorption coefficient of a modally reactive surface and provides a way to estimate this quantity using the statistical energy analysis (SEA) method. The dependence of the αSab upon the room properties, in which the panel is measured, is demonstrated both experimentally and analytically.
A planar array for the generation of evanescent waves
Authors: Trivett D. H. , Luker L. D. , Petrie S. , Van Buren A. L. , Blue Joseph E.
Published: October 2005

Wavenumber-frequency calibration of underwater, planar, receiving arrays requires the ability to generate single-wavenumber pressure fields over the surface of the array. When the wavenumber-frequency region of interest is evanescent, transmitting arrays previously constructed have been found to generate fields contaminated with harmonics, acoustic wavenumbers, and nonacoustic wavenumbers from the excitation of antisymmetric Lamb waves. An array that greatly reduces contamination has recently been constructed using a sheet of polyvinylidene fluoride (PVDF) with independent rectangular electrode stripes. The array operates in the frequency range of 500 Hz to 2 kHz and generates evanescent waves with phase speeds between 30 and 150 m/s. Contamination due to the excitation of antisymmetric Lamb waves is eliminated by shifting the phase speed of the Lamb wave out of the region of interest. This is accomplished by bonding the thin sheet of PVDF directly to a thick plate of LEXAN. Contamination from harmonics and acoustic wavenumbers is eliminated by driving the electrode stripes with suitably chosen shading coefficients generated by a simple-source numerical algorithm. Measured pressure fields and phase velocities compare favorably with numerical calculations.
The attenuation of ultrasound in aqueous suspensions of casein micelles from bovine milk
Authors: Griffin William G. , Griffin Mary C. A.
Published: October 2005

The ultrasonic attenuation of skimmed milk, of the serum containing the soluble whey proteins and small casein aggregates and of ultrafiltered serum was measured in the frequency range 15–96 MHz. From these measurements the attenuation due to the colloidal casein micelles in serum was obtained. For the serum, α∝f1.86±0.02; for the soluble proteins, Δα∝f1.16±0.04; and for the casein micelles, Δα∝f1.06±0.05. The ultrasonic attenuation of the soluble proteins is similar to that of other protein solutions; however, ultrasonic attenuation of the casein micelles differed from that of the soluble proteins. Using the theory of Allegra and Hawley [J. Acoust. Soc. Am. 36, 1545–1564 (1972)] for the ultrasonic attenuation of suspensions of elastic spheres, the expected attenuation for a model of the casein micelle suspension was computed. The frequency-dependent attenuation, α′(f ), of the spheres is taken as an unknown for this model and, by varying α′(f ), a fit between the experimental data and the predictions of the theory was obtained. This fit requires the attenuation of the micelles to vary as f1.40±0.10 and the micellar attenuation to be higher than for a typical protein solution of the same concentration. This suggests that relaxation processes of the casein polypeptide chains in the casein micelles differ from those of most soluble proteins studied so far by ultrasonic attenuation measurements. This conclusion is consistent with results from nuclear magnetic resonance spectroscopy.
A hierarchy of examples illustrating the acoustic coupling of the eardrum
Authors: Rabbitt R. D.
Published: October 2005

Basic principles underlying the acoustic coupling of the eardrum are illustrated in the form of a hierarchy of examples ranging from a simple piston coupled to a semi-infinite acoustic duct, to a flexible partition coupled to a variable cross-section duct, and to a closed cavity. The hierarchy illuminates some of the limitations of various simplified elements commonly used to model the middle ear and demonstrates the necessity of treating the acoustics and the eardrum as an integrated subsystem. Results show that the tympanic cavity and the secondary middle-ear air chambers contribute fundamental features to the acoustic coupling of the ear. The nature of the acoustic coupling limits the passive energy absorption and transmission properties of the eardrum. The magnitude and frequency dependence of the energy dissipation within the ultrastructure of the partition, due to bending and transverse deflection, is discussed in analogy to possible dissipation mechanisms within the eardrum itself. Examples are provided for several simple systems reproducing some of the gross anatomical characteristics of the cat eardrum.
Stimulus selection in adaptive psychophysical procedures
Authors: Green David M.
Published: October 2005

In adaptive psychophysical procedures, the stimulus should be presented at a relatively high level rather than near the middle of the psychometric function, which is often defined as the ‘‘threshold’’ value. For some psychometric functions, the optimal stimulus placement level produces 84% to 94% correct responses in a two-alternative forced-choice task. This result is disquieting because the popular two-down one-up rule tracks a relatively low percentage of correct responses, 70.7%. Computer simulations and a variety of psychometric functions were used to confirm the validity of this analysis. These simulations also demonstrate that the precise form of the psychometric function is not critical in achieving the high efficiencies. Finally, data from human listeners indicate that the standard deviation of threshold estimates is indeed larger when the stimulus presented on each trial is at a stimulus level corresponding to 70.7% rather than 94% correct responses.
The influence of spectral prominence on perceived vowel quality
Authors: Beddor Patrice Speeter , Hawkins Sarah
Published: October 2005

Research indicates that, when the first and second formants of a vowel are separated by less than about 3.5 Bark, perception of its height and some other aspects of its quality is determined by some weighted average of the low-frequency spectrum, rather than by particular harmonic or hypothetical formant frequencies (as is the case with more widely spaced formants). This spectral averaging has been called the center of gravity (COG) effect. Although the existence of the effect is generally accepted, the factors that govern it are poorly understood. One possibility is that the influence of the spectral envelope on perceived vowel quality increases as low-frequency spectral prominences become less well defined. A series of three experiments examined this possibility in: (1) nasal vowels, where the lowest spectral prominence is broader and flatter than that of oral vowels; (2) one- versus two-formant vowels with bandwidths appropriate for oral vowels; and (3) two-formant vowels with very narrow or very wide bandwidths. The results of these experiments show that, when two or more spectral peaks lie within 3.5 Bark of one another, F1 and the centroid (an amplitude-weighted average frequency that estimates the COG in the low-frequency spectrum) roughly determine the boundaries within which the perceptual COG lies; the frequencies of spectral peaks dominate responses when formant bandwidths are narrow, whereas overall spectral shape exerts more influence when spectral prominences are wide. Assuming that all vowels undergo the same processing, it is suggested that vowel quality, particularly height, is determined both by the frequency of the most prominent harmonics in the low-frequency region and by the slopes of the skirts in the vicinity of these harmonics. These two effects are most clearly separable in vowels with poorly defined spectral prominences whose shape cannot be adequately described by specifying the frequencies and degree of prominence of just one or two harmonics, or hypothetical formant peaks.
The time course of acoustic/phonemic cue integration in the sensorineurally hearing-impaired listener
Authors: Schum Donald J. , Collins M. Jane
Published: October 2005

There is limited documentation available on how sensorineurally hearing-impaired listeners use the various sources of phonemic information that are known to be distributed across time in the speech waveform. In this investigation, a group of normally hearing listeners and a group of sensorineurally hearing-impaired listeners (with and without the benefit of amplification) identified various consonant and vowel productions that had been systematically varied in duration. The consonants (presented in a /haCa/ environment) and the vowels (presented in a /bVd/ environment) were truncated in steps to eliminate various segments from the end of the stimulus. The results indicated that normally hearing listeners could extract more phonemic information, especially cues to consonant place, from the earlier occurring portions of the stimulus waveforms than could the hearing-impaired listeners. The use of amplification partially decreased the performance differences between the normally hearing listeners and the unaided hearing-impaired listeners. The results are relevant to current models of normal speech perception that emphasize the need for the listener to make phonemic identifications as quickly as possible.
Stationarity of acoustic intensity measurements on steel plates
Authors: Guigné Jacques Y. , Williams Paul G. , Adams John G.
Published: October 2005

The problem of identifying reproducible frequency bands useful for the nondestructive evaluation of steel plates using the dynamic acoustical intensity scanning concept (DAIS) is addressed. Reproducible frequency bands are essential so that subsequent changes in sound intensity patterns can confidently be attributed to structural changes rather than to random fluctuations. A number of evaluation methods are tried. Stationary frequency bands are identified by all methods in the range of 100–4000 Hz. The most sensitive and practical evaluation method is deemed to be the comparison of intensity versus time data collected separate from the plate scans. This method is accurate, convenient, and can be automated to exclude all unwanted frequency bands during testing. The remanent intensity factor technique, while useful in identifying stationarity, is less sensitive and more difficult to implement.
Temporal integration in zebra finches (P
o
e
p
h
i
l
a g
u
t
t
a
t
a)
Authors: Okanoya Kazuo , Dooling Robert J.
Published: October 2005

Three zebra finches were trained with operant techniques to respond to pure tones. Absolute thresholds were obtained for nine durations of a 3-kHz tone and five durations of a 1-kHz tone. The temporal integration functions finches were described using the negative exponential function proposed by Plomp and Bouman [J. Acoust. Soc. Am. 31, 749–758 (1959)]. The time constants obtained for zebra finches are about 250 ms, which are similar to those reported for a number of species, including humans and other bird species.
Three-dimensional Green’s function for wave propagation in a linearly inhomogeneous medium—the exact analytic solution
Authors: Li Y. L. , Liu C. H. , Franke S. J.
Published: October 2005

A new exact solution of the Helmholtz equation is obtained in closed form for the case of a point source in a layered medium with refractive index variation of the form n=(1+Az)1/2. The solution is obtained by starting with a onefold integral representation for the solution that was derived by Holford [J. Acoust. Soc. Am. 70, 1427–1436 (1981)] and Jeng and Liu [J. Acoust. Soc. Am. 81, 1732–1740 (1987)]. The solution is particularly interesting because the classical ray picture for the medium exhibits a caustic and therefore a shadow zone is formed in the unbounded medium. The power flux due to a point source in such a medium is computed and the flow of energy into the region beyond the caustic surface is illustrated. The effects of scattering by turbulence are studied and it is shown that scattering can drastically affect the field levels in the shadow zone. Also, the field patterns of a simple array are studied in such a medium and are compared to patterns in a homogeneous medium.
Matrix methods in reflection and transmission of compressional waves by stratified media
Authors: Lekner John
Published: October 2005

The techniques used in optics and microwave and radio physics for the easy and efficient calculation of reflection and transmission by stratified media are adapted to acoustic compressional waves. The method involves taking the product of N 2×2 matrices when the stratification is approximated by N layers. These layers can be chosen to have linear variation in the acoustic parameters to best represent the actual stratification without undue complexity in the resulting matrix elements. It is possible to guarantee unimodularity of the matrices, thus making sure that energy conservation and a reciprocity law are automatically satisfied. Accuracy is tested against an exactly solvable model stratification, in which the density and speed of sound both vary exponentially with depth.
Reflection and transmission of elastic waves from a fluid-saturated porous solid boundary
Authors: Wu Kunyu , Xue Qiang , Adler Laszlo
Published: October 2005

Based on the classical work of Biot [J. Acoust. Soc. Am. 28, 168 (1956)] which predicts that three different kinds of bulk waves may propagate in the fluid-saturated porous solid, the wave equation is solved to determine the energy reflection and transmission coefficients of plane elastic waves at oblique incidence on an interface between a fluid and a fluid-saturated porous solid. For this purpose, the necessary formalism of the energy equation, the Poynting energy flux vector, and the sound intensity of elastic waves in fluid-saturated porous media are presented. Two general cases of mode conversion have been investigated: (1) The initial wave is incident from the fluid to the interface and generates three transmitted bulk waves in the fluid-saturated porous solid, and (2) the initial wave is incident from the fluid-saturated porous solid to the interface and generates three reflected bulk waves in the same medium. Furthermore, the transmission of sound through a fluid-saturated porous solid plate immersed in fluid is calculated. Measurement of sound transmission through a porous plate was carried out using experimental techniques suggested by Plona [Appl. Phys. Lett. 36, 259 (1980)]. Good correlation between measured and calculated values of the angular behavior of the transmission coefficients for fast, shear, and slow waves was obtained after adjusting the theory for experimentally obtained attenuation.
The bichromatic intensity correlation of radiation reflected off a randomly irregular surface
Authors: Frankenthal Shimshon
Published: October 2005

When phase information is absent (incoherent detection), the basic statistical entity relevant to data processing is the bichromatic four-point coherence. Using the strength and size parameters Φ 2 and Λ, an integral expression for this quantity is formulated and evaluated for a high-frequency signal scattered by a phase screen that represents the randomly reflecting ocean cover (or, alternatively, a randomly refracting thin layer). The evaluation is illustrated by a treatment of the monochromatic mean-square intensity 〈I 2〉, then applied to the bichromatic intensity correlation 〈I1I2〉. Viewed as a function of the frequency-independent parameter ΛΦ, 〈I2〉 rises from 1 to 2, passing through a maximum which scales as log k (the wavenumber) at some intermediate value of ΛΦ that depends only on the form of the screen statistics. By constrast, 〈I1I2〉 saturates at 1. Moreover, even when ΛΦ is large, the second and fourth coherence moments are found to be consistent with the assumption that the bichromatic signal possesses joint normal statistics only within a narrow range of frequency separations (∼O(1/Φ)), which nonetheless encompasses the coherent bandwidth (∼O(1/ΛΦ 2)).
Acoustic scattering from a non-Gaussian ocean surface
Authors: Henyey Frank S. , Wurmser Daniel
Published: October 2005

The effect of hydrodynamic nonlinearities on ocean surface scattering is considered. A recently developed expression for the bispectrum of the surface elevation is used to calculate the lowest-order correction due to this effect. The result is comparable in magnitude to the tilt correction, which has been recently calculated.