bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption of ultrasound in binary solutions of polyacrylamide with water
Authors: Haque M. F. , Fast S. J. , Yun S. S. , Stumpf F. B.
Published: October 2005

The absorption coefficient of ultrasound and shear viscosity in binary solutions of polyacrylamide with water were studied as a function of concentration and temperature. In addition, the absorption coefficient was measured as a function of frequency. The value of α/f2 increased by twofold, at 3% concentration and 20 °C, from the water value while the shear viscosity increased by four orders of magnitude. The temperature dependence of α/f2 for the polymer solutions is similar to that of pure water.
A high-angle one-way wave equation for seismic wave propagation along rough and sloping interfaces
Authors: Greene Robert R.
Published: October 2005

A model of acoustic propagation in solid media has been derived. It is a one-way wave equation based on a high-order approximation, called a Padé approximation, to the square-root function. The physical properties of the environment are modeled as stratified, thin, homogenous layers. The model can be applied to obtain an approximate solution in range-dependent environments by allowing the properties of the layers to vary in range. Furthermore, the effects of rough or sloping reflecting interfaces can be approximated using an equivalent reflector, consisting of two thin layers whose properties vary in range.
Scattering by a partially illuminated, doubly periodic, doubly infinite surface
Authors: Lakhtakia Akhlesh , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

Using the plane-wave decomposition of the incident field and the T-matrix method, scattering by a partially illuminated, doubly periodic, doubly infinite surface is investigated. The general expressions thus derived are simplified for the case when the illuminated area is large. Numerical examples illustrating the applicability of the procedure are also given.
The inverse source problem for an oblique force on an elastic plate
Authors: Michaels Jennifer E. , Pao Yih-Hsing
Published: October 2005

A time-dependent concentrated force applied obliquely on the surface of a plate generates elastic waves in the plate. The determination of the location, orientation, and time history of the force from the transient wave records is referred to as the inverse source problem of elastic waves. This paper presents an iterative method of deconvolution which determines the orientation and time-dependent amplitude of the force from the transient response of the plate surface at a minimum of two locations, the source location being given. Numerical results are presented for forces with various orientations and time histories, and for synthetic data both with and without noise.
Radiation from a point source and scattering theory in a fluid-saturated porous solid
Authors: Norris Andrew N.
Published: October 2005

The time harmonic Green function for a point load in an unbounded fluid-saturated porous solid is derived in the context of Biot’s theory. The solution contains the two compressional waves and one transverse wave that are predicted by the theory and have been observed in experiments. At low frequency, the slow compressional wave is diffusive and only the fast compressional and transverse waves radiate energy. At high frequency, the slow wave radiates, but with a decay radius which is on the order of cm in rocks. The general problem of scattering by an obstacle is considered. The point load solution may be used to obtain scattered fields in terms of the fields on the obstacle. Explicit expressions are presented for the scattering amplitudes of the three waves. Simple reciprocity relations between the scattering amplitudes for plane-wave incidence are also given. These hold under the interchange of incident and observation directions and are completely general results. Finally, the point source solution is Fourier transformed to get the solution for a load which is a delta function in time as well as space. We obtain a closed form expression when there is no damping. The three waves radiate from the source as distinct delta function pulses. With damping present, asymptotic approximations show the slow wave to be purely diffusive. The fast and transverse waves propagate as pulses. The pulses are Gaussian-shaped, which broaden with increasing time or radial distance.
Acoustical characteristics of annealed French horn bell flares
Authors: Lawson Bruce , Lawson Walter
Published: October 2005

One-third octave airborne sound level measurements were recorded for four yellow brass and three nickel–silver French horn bell flares of varying hardness. The sound level associated with the unannealed brass flares was higher in the 1–3 kHz range than with the annealed brass bell flares, whereas the opposite relationship was observed for nickel–silver bell flares. The measured acoustical differences support musicians’ claims that the material of a French horn affects its tone quality.
A 5- to 50-kHz synthetic cylindrical nearfield calibration array
Authors: Van Buren A. L. , Jevnager M. D. , Tims A. C.
Published: October 2005

The direct measurement of farfield acoustic radiation from underwater transducers in a shore-based facility is often impossible because of the limited size of measurement tanks. The Trott nearfield calibration array (NFCA) concept solves this problem by allowing the farfield radiation to be determined from measurements made close to the transducer. We describe here the development of a 5- to 50-kHz synthetic cylindrical NFCA that is suitable for measurement tanks as small as about 2.5 m in each dimension and that can be operated at hydrostatic pressures up to 6.8 MPa. The NFCA is synthesized using a single line of 48 piezoelectric ceramic hydrophone elements spaced 2.54-cm apart center-to-center and amplitude shaded in a special way. The transducer to be calibrated is driven electrically and rotated near the line about an axis parallel to the line. The response of the line is measured at equally spaced angular positions, thereby creating a virtual cylindrical array surrounding the transducer. We then obtain the azimuthal farfield pattern of the transducer by computer processing the angular responses together with a set of complex shading coefficients. We evaluated the line experimentally by calibrating a large piston transducer in a cylindrical measurement tank less than 2.5 m in diameter. The resulting computed farfield patterns are in excellent agreement with corresponding patterns obtained from direct farfield measurements made in a lake.
Rayleigh angle backscattering of ultrasonic beam from single crystal nickel in 111 and 110 planes
Authors: Adler Laszlo , Wang Shaio-Wen , Bolland Ken , de Billy Michel , Quentin Gerard
Published: October 2005

In previous papers [M. de Billy, L. Adler, and G. Quentin, J. Acoust. Soc. Am. 72, 1018–1020 (1982); J. Appl. Phys. 53, 8756–8758 (1982)], we have reported that maximum amplitude of backscattered ultrasonic waves observed at the Rayleigh angle from a liquid–isotropic solid interface. It was also established that the angle at which this maximum takes place can be used to measure accurately the velocity of the Rayleigh wave on liquid–solid interface. In this paper we present results of the Rayleigh angles backscattering phenomenon from liquid–single crystal nickel interface. It has been shown that due to the anisotropy of the crystal the angle at which the maximum of backscattering amplitude takes place vary with the crystal orientation. This method is used to measure Rayleigh velocity distribution on the anisotropic interface. The surface wave velocity distribution measured from backscattering agrees very well with theoretical calculations using an algorithm to calculate surface velocity distribution on anisotropic surfaces.
Sound field fluctuations in a shallow water waveguide
Authors: Clay C. S. , Wang Y-Y. , Shang E. C.
Published: October 2005

Experimental measurements of sound transmissions in a laboratory waveguide are analyzed. The transmissions were from a single source to a vertical array of receivers that operated as a mode filter. Water waves on the surface caused the sound fields to fluctuate at the receiver. We used theories of coherent mode transmission to describe the experiments. Within a mode, sound field fluctuations have three components: (1) phase fluctuations due to fluctuations of the horizontal component of the wave number, (2) fluctuations of depth-dependent eigenfunctions at source and receiver positions, and (3) mismatch of the mode filter to the local eigenfunction. Analysis showed that most of the fluctuations of the mode filtered signals were due to components (2) and (3).
Applicability of the Biot theory. II. Suspensions
Authors: Ogushwitz P. R.
Published: October 2005

The Biot theory is used to compute compressional wave speeds and attenuation in fluid–solid suspensions. The frame moduli are estimated from the self-consistent theory of composites, assuming needle-shaped pores and spherical or ellipsoidal grains of uniform size. The permeability is computed from the Kozeny–Carman equation. The attenuation data are matched by assuming that all losses are caused by viscous absorption in the fluid.For suspensions of kaolinite, polystyrene beads, and glass beads in various fluids, the Biot model agrees with experimental sound speed data at least as well as do other models. For aqueous suspensions of kaolinite, of attapulgite, and of hydrous aluminum silicate pigments, the Biot model generally is in better agreement with attenuation data than are other models.
Theory of ultrasonic resonances in a viscoelastic layer
Authors: Fiorito R. , Madigosky W. , Überall H.
Published: October 2005

We present a resonance theory for the acoustic transmission and reflection coefficients of an elastic plate imbedded in a fluid medium, which includes the effects of plate viscosity. This formulation provides a direct means for determining the material parameters of the plate from the measured acoustic resonances of the Rayleigh and Lamb waves in the plate (i.e., their positions in frequency or angle, their widths, and their heights) which are given in our formalism by explicit analytic expressions that depend on the material parameters. Viscosity is seen to manifest itself in a decrease of the resonance peaks and in a broadening and frequency dependence of the resonance widths, which may be used to determine the frequency-dependent loss factor of the plate.
Control of rate and duration of speech movements
Authors: Ostry David J. , Munhall Kevin G.
Published: October 2005

A computerized pulsed-ultrasound system was used to monitor tongue dorsum movements during the production of consonant-vowel sequences in which speech rate, vowel, and consonant were varied. The kinematics of tongue movement were analyzed by measuring the lowering gesture of the tongue to give estimates of movement amplitude, duration, and maximum velocity. All three subjects in the study showed reliable correlations between the amplitude of the tongue dorsum movement and its maximum velocity. Further, the ratio of the maximum velocity to the extent of the gesture, a kinematic indicator of articulator stiffness, was found to vary inversely with the duration of the movement. This relationship held both within individual conditions and across all conditions in the study such that a single function was able to accommodate a large proportion of the variance due to changes in movement duration. As similar findings have been obtained both for abduction and adduction gestures of the vocal folds and for rapid voluntary limb movements, the data suggest that a wide range of changes in the duration of individual movements might all have a similar origin. The control of movement rate and duration through the specification of biomechanical characteristics of speech articulators is discussed.
Measures of the sentence intonation of read and spontaneous speech in American English
Authors: Lieberman Philip , Katz William , Jongman Allard , Zimmerman Roger , Miller Mark
Published: October 2005

The visual abstraction procedure used in previous studies of declination was tested using 12 subjects who each fit the F0 contours of 19 spoken short simple sentences with baselines. These baselines were found to be poorly replicated by the fitters. An objective all-points least-squares best-fit procedure was tested on this corpus and on a set of sentences that had been produced in both spontaneous and read speech by six speakers. The all-points linear regression line was a better descriptor of the F0 contours than either baselines or toplines. Declination did not always occur in these simple declarative sentences; there was more variation present in the F0 contours of sentences that had been uttered during spontaneous speech; 35% of the spontaneous sentences did not show declination; 45% of these sentences better fit the breath-group model. Their F0 contours could be described by a level all-points linear regression line followed by a falling terminal segment.
Phonetic identification by elderly normal and hearing-impaired listeners
Authors: Dorman M. F. , Marton K. , Hannley M. T. , Lindholm J. M.
Published: October 2005

Young normal-hearing listeners, elderly normal-hearing listeners, and elderly hearing-impaired listeners were tested on a variety of phonetic identification tasks. Where identity was cued by stimulus duration, the elderly hearing-impaired listeners evidenced normal identification functions. On a task in which there were multiple cues to vowel identity, performance was also normal. On a /b d g/ identification task in which the starting frequency of the second formant was varied, performance was abnormal for both the elderly hearing-impaired listeners and the elderly normal-hearing listeners. We conclude that errors in phonetic identification among elderly hearing-impaired listeners with mild to moderate, sloping hearing impairment do not stem from abnormalities in processing stimulus duration. The results with the /b d g/ continuum suggest that one factor underlying errors may be an inability to base identification on dynamic spectral information when relatively static information, which is normally characteristic of a phonetic segment, is unavailable.
Nonlinear resonant oscillations in closed tubes—An application of the averaging method
Authors: Ochmann Martin
Published: October 2005

The application of the averaging method to the one-dimensional inhomogeneous, nonlinear acoustic wave equation with dissipative term makes it possible to give asymptotic solutions for any kind of external resonance excitation. It shows that the lowest-order solution consists of the superposition of two modulated counterpropagating waves, where the amplitude of each is a solution of Burgers equation. The method is extended to the treatment of oscillating boundaries; in that case it also leads to Burgers equations. Explicit stationary solutions are given for the particularly important forms of the external excitation, harmonic distributed forces, and harmonic oscillating boundaries. The application of several other computational methods to this problem leads to the same results.
Propagation of sound above a finite layer of snow
Authors: Nicolas J. , Berry J.-L. , Daigle G. A.
Published: October 2005

Measurements of the sound field from a point source above a relatively soft surface layer backed by an acoustically hard material are reported. These were made outdoors over layers of snow from 5 to 50 cm thick and to propagation distances of up to 15 m. The conditions of the snow layer varied from newly fallen to aged and windblown snow. Experiments were also conducted indoors at shorter distances above reticulated foam of similar thicknesses. The theory of Pyett [Acustica 3, 375–382 (1953)] for the acoustic impedance of a porous layer is used to extend the solution for reflection of spherical waves from a porous half-plane to reflection from a porous layer. This simple theory shows good agreement with the indoor measurements at all frequencies. Similarly good agreement between this theory and experiments over snow layers outdoors is obtained above about 200 to 500 Hz depending on the geometrical configuration. However below these frequencies the measurements suggest that the layer of snow behaves as semi-infinite porous ground.
A Markov process model of ocean sediments
Authors: Sockell Michael , Besieris Ioannis , Kohler Werner , Freese Herbert
Published: October 2005

Monochromatic plane-wave illumination of a randomly stratified, laterally homogeneous sediment layer is considered. The deposition process creating the stochastic layering is assumed to be a continuous parameter, finite state Markov chain. A Riccati equation for the plane-wave reflection coefficient is formulated and first-order partial differential equations for relevant probability density functions are subsequently obtained. These equations are solved numerically for a two-material turbidite model similar to the one considered by Gilbert [J. Acoust. Soc. Am. 68, 1454–1458 (1980)]. Statistical moments of the reflection coefficient are computed at 25 and 250 Hz as a function of overall sediment thickness. These equations are also used to derive the nonrandom or ‘‘smooth’’ geoacoustic model that is appropriate in the low-frequency limit.
Ocean acoustic tomography: Travel time biases
Authors: Spiesberger John L.
Published: October 2005

The travel times of acoustic rays traced through a climatological sound-speed profile are compared with travel times computed through the same profile containing an eddy field. The exact travel time difference is compared with its constituent terms, one of which is linearly related to the deviation of the sound speed (referenced to the climatological profile) and the others which are nonlinearly related to the deviation. At ranges that are much greater than the eddy scale and for eddy fields whose range-averaged temperature anomaly is small, the numerical results are: (1) the values of the nonlinear terms are insensitive to changes in the positions of the eddies and (2) the nonlinear terms are approximately proportional to the range between the source and receiver and to the square of the eddy anomaly. At a 1084-km range in the east Atlantic at 24 °N (36 °N) the nonlinear terms can account for 17% (90%) of the exact travel time change where the temperature anomalies associated with the eddies are typically ±0.5 °C (±1 °C). Linearized inversions (based on the linear estimator of the travel time difference) which use the exact travel time differences for data should yield biased results since the average values of the nonlinear terms are not zero. If an a priori knowledge of the eddy spectrum is known, the nonlinear terms could be computed for each ray and subtracted from the exact travel time change. It may then be beneficial to use the corrected set of travel time differences in a linear inversion which would require no iteration.
A fast-field program for sound propagation in a layered atmosphere above an impedance ground
Authors: Raspet R. , Lee S. W. , Kuester E. , Chang D. C. , Richards W. F. , Gilbert R. , Bong N.
Published: October 2005

This paper studies sound propagation in a layered atmosphere bounded by a ground, whose impedance is described by the Delany–Bazley–Chessell’s empirical model. The problem is formulated in terms of a Green’s function integral in the spectral domain, and is numerically evaluated by a Fast Field Program (FFP). Numerical results are included to show that (i) in simple test cases, the FFP solution is in excellent agreement with existing asymptotic solutions; (ii) numerical overflow arises when the number of layers is large and/or the frequency is high, and a method to circumvent this difficulty is described; and (iii) the FFP is a most powerful tool in solving propagation problems in layered media bounded by complex impedances.
Calculation of the acoustic material signature of a layered solid
Authors: Kundu T. , Mal A. K. , Weglein R. D.
Published: October 2005

A theory is presented for the calculation of the acoustic material signature of a multilayered elastic half-space overlain by a fluid. The solid layers are composed of homogeneous isotropic linearly elastic materials and are firmly bonded at the interfaces. The calculation procedure is valid at an arbitrarily high frequency of excitation. Results are presented for a uniform, a single layered and a four layered model of the half-space at two frequencies of excitation; one moderate (35 MHz) and the other relatively high (370 MHz). Several new features of the material signatures and their possible use in the material characterization of layered specimen are indicated.
An advanced computational method for radiation and scattering of acoustic waves in three dimensions
Authors: Seybert A. F. , Soenarko B. , Rizzo F. J. , Shippy D. J.
Published: October 2005

The method proposed in this paper provides a computational method for implementing the Helmholtz integral formula for acoustic radiation and scattering problems associated with arbitrary shaped three-dimensional bodies. In particular an isoparametric element formulation is used in which both the surface geometry and the acoustic variables on the surface of the body are represented by second-order shape functions within the local coordinate system. A general formula for the surface velocity potential and the exterior field is derived. This result is applicable to nonsmooth bodies, i.e., it includes the case where the surface may have a nonunique normal (e.g., at the edge of a cube). Test cases are shown involving spherical, cylindrical, and cubical geometry.
Contributions to the theory of sound propagation in ducts with bulk-reacting lining lining
Authors: Rienstra S. W.
Published: October 2005

A theoretical analysis of sound propagation in cylindrical ducts lined with porous material (bulk absorbers) is presented. Three configurations are discussed. (1) The porous material is homogeneous; then the sound field is built up of modes. (2) The properties of the liner vary slowly in an axial direction. A pure modal solution is, in general, not possible, but the field can be described by modes of the homogeneous liner, of which the amplitudes and wavenumbers vary in an axial direction slowly with the liner (multiple scale solution). (3) The porous material is embedded in an annular structure of partitions. For structural reasons this is a common situation. If the pitch of the partitions is small, the sound field in the liner is, per circumferential mode, decoupled from the duct field, and its effect can be described acoustically by an impedance (per circumferential mode). This ‘‘quasi-point-reacting’’ boundary condition may be easily incorporated in calculation procedures for ducts with locally reacting lining.
Study of nonlinear oscillations of bubbles in Powell–Eyring fluids
Authors: Shima Akira , Rajvanshi Satish C. , Tsujino Tomoji
Published: October 2005

To study cavitation phenomena in non-Newtonian fluids, problems about nonlinear oscillations of bubbles are theoretically examined by using a Powell–Eyring model as a rheological model. The equation of oscillation of bubbles in Powell–Eyring fluids subject to pulsating pressures and the equation of natural frequency of a bubble are derived. According to numerical calculations for the bubbles in polymer solutions, the effects of polymer concentration and pressure amplitude on frequency response curves are clarified. The relation between the impulse pressure occurring during the bubble oscillation and the ratio of the frequencies are also examined.
Variation of the speed of sound in air with humidity and temperature
Authors: Wong George S. K. , Embleton Tony F. W.
Published: October 2005

This paper describes the influence of humidity on the speed of sound in standard atmospheric air at various temperatures. The prediction is based on theoretical and experimental data obtained for the variation of the ratio of specific heats, γ, in humid air. Over a temperature range from 0°–30° Celsius, the maximum uncertainty in the sound speed ratio ch/c0, is estimated to be about 400 ppm. Comparison is made with known experimental measurements and theoretical data.
The MATE acoustic frequency cross correlations of intensity
Authors: Ewart T. E. , Macaskill C. , Uscinski B. J.
Published: October 2005

In the Mid-Ocean Acoustic Transmission Experiment (MATE), measurements were made of the fluctuating phase and amplitude of signals propagated 18.1 km at four frequencies (2,4,8, and 12.5 kHz) over a wholly refracted Fermat path. Extensive oceanographic instrumentation of that transmission path permits evaluation of the space–time correlations of the index of refraction. The scattering regimes span the important region from well before the medium focus to beyond it, but do not extend to the very far field. In the past two years, solutions for the propagation of the fourth moment of the complex amplitude of a wave propagating in a random field have become available; these solutions are applicable at all ranges. Ewart and Reynolds discuss MATE and compare the acoustic results with theory for the intensity autospectra [J. Acoust. Soc. Am. 75, 785–802 (1984)]. The theoretical solutions have recently been extended to include acoustic frequency dependence. In this paper predictions from the new theory, based on space–time medium correlations where both internal waves and low wavenumber finestructure have been considered, are compared with the measured acoustic results from MATE. These comparisons include the cross correlations and cross spectra of intensity as a function of acoustic frequency separation. The agreement between theory and experiment is shown to be somewhat poorer for the cross spectra than for the autospectra. It is postulated that the lack of agreement arises either from the sensitivity of the cross spectral predictions to the precise form of the medium correlation function or from the fact that the first order correction to the evaluation of the fundamental solution (which has not been evaluated for the two frequency case) is more significant for the cross spectra of intensity than for the autospectra.
Computer modeling of resonant sound scattering from a periodic assemblage of wedges: Comparison with theories of diffraction gratings
Authors: Novarini Jorge C. , Medwin Herman
Published: October 2005

Starting with an exact point source impulse solution for diffraction and reflection from an infinite wedge, the acoustic field is calculated for plane waves scattered by a periodic assemblage of pressure release or rigid wedges. The calculated angles and fractional strengths of the diffracted orders compare very well with predictions of exact theories for scattering from diffraction gratings. Under otherwise identical conditions, the change in the wedge impedance to describe rigid or pressure release boundary conditions can cause dramatic changes in the energy distribution. This work validates the use of the wedge assemblage technique of numerical calculation for cases in which the wedge separations are as little as one-half wavelength. It is shown that in this realm only diffractions are important, and that facet reflections do not contribute to the scattered energy.
Caustics in range-averaged ocean sound channels
Authors: Weston David E. , Focke Karl C.
Published: October 2005

The caustics present after range averaging are illustrated by depth plots of range-averaged ray calculations and also of energy flux calculations. Although well understood, these infinities prevent the range-averaging method from giving a well-behaved summary of the propagation, and so three approaches to the true level are presented here. One solution is to assume some source directivity; in particular, a variation with the square of the grazing angle not only corresponds to the physically meaningful dipole radiation from a near-surface source with its image, but removes all trace of the caustics. Second, a local wave approach patches together a solution, replacing the infinity by a peak shape calculated from an Airy function convolution. This predicts a broad pedestal shape at both source and conjugate depth, with a small sharp peak riding on it, although usually for the source depth only. Third, a full wave approach for the whole water column is represented by range averaging of parabolic equation field calculations, the results agreeing with those from the other approaches.
Using ultrasonic S
H waves to estimate the quality of adhesive bonds in plate structures
Authors: Yew C. H. , Weng X. W.
Published: October 2005

A method using SH waves to estimate the quality of an adhesive layer in a bonded plate is presented in this paper. A mathematical analysis of SH-wave motions in a bonded plate consistent with the experimental arrangement was carried out in full. We have found that the cutoff frequency of the second mode waves in the plate is dependent upon the thickness and the mechanical properties of the adhesive layer, and the waves in the plate resonate at this frequency. This wave resonating phenomenon was used in the experimental determination of the property of the adhesive layer. An experimental verification of the method was carried out using adhesives of several different properties. We have demonstrated that the resonant frequency of the second mode wave in the plate is dependent upon the moduli and thickness ratio between the adhesive layer and plate as predicted by the analysis.
Thresholds for the detection of inharmonicity in complex tones
Authors: Moore Brian C. J. , Peters Robert W. , Glasberg Brian R.
Published: October 2005

Thresholds were measured for the detection of inharmonicity in complex tones. Subjects were required to distinguish a complex tone whose partials were all at exact harmonic frequencies from a similar complex tone with one of the partials slightly mistuned. The mistuning which allowed 71% correct identification in a two-alternative forced-choice task was estimated for each partial in turn. In experiment I the fundamental frequency was either 100, 200, or 400 Hz, and the complex tones contained the first 12 harmonics at equal levels of 60 dB SPL per component. The stimulus duration was 410 ms. For each fundamental the thresholds were roughly constant when expressed in Hz, having a mean value of about 4 Hz (range 2.4–7.3 Hz). In experiment II the fundamental frequency was fixed at 200 Hz, and thresholds for inharmonicity were measured for stimulus durations of 50, 110, 410, and 1610 ms. For harmonics above the fifth the thresholds increased from less than 1 Hz to about 40 Hz as duration was decreased from 1610–50 ms. For the lower harmonics (up to the fourth) threshold changed much less with duration, and for the three shorter durations thresholds for each duration were roughly a constant proportion of the harmonic frequency. The results suggest that inharmonicity is detected in different ways for high and low harmonics. For low harmonics the inharmonic partial appears to ‘‘stand out’’ from the complex tone as a whole. For high harmonics the mistuning is detected as a kind of ‘‘beat’’ or ‘‘roughness,’’ presumably reflecting a sensitivity to the changing relative phase of the mistuned harmonic relative to the other harmonics. The results are discussed in relation to theories of pitch perception.
Variability in production of the vowels /i/ and /a/
Authors: Perkell Joseph S. , Nelson Winston L.
Published: October 2005

A hypothesis on the nature of articulatory targets for the vowels /i/ and /a/ is proposed, based on acoustic considerations and vowel articulations. The conjecture is that positioning of points on the tongue surface in a repetition experiment should be most accurate in the direction perpendicular to the vocal-tract midline, at the acoustically critical point of maximal constriction for each vowel. The hypothesis was tested by: examining x-ray microbeam data for three speakers, conducting a partial acoustical analysis, and performing a modeling study. Distributions were plotted of the midsagittal locations of three tongue points at the time of maximal excursion toward the vowel target for numbers of examples of the vowels, embedded in a variety of phonetic contexts. More variation was found along a direction parallel to the vocal tract midline than perpendicular to the midline, supporting the hypothesis. Statistics on formant values for one subject have been calculated, and pairwise regressions of displacement and formant data have been run. An articulatory synthesizer [Rubin et al., J. Acoust. Soc. Am. 70, 321–328 (1981)] has been manipulated through displacements similar to the subject’s articulatory variation. Although articulatory synthesis showed systematic relationships between articulatory relationships and formant frequencies, there were no significant correlations between the subject’s measured articulatory displacements and his formant data. These additional results raise questions about the methodology and point to the need for additional work for an adequate test of the hypothesis.
First-principle approach to the calculation of elastic moduli for arbitrary periodic composites
Authors: Tao Ruibao , Sheng Ping
Published: October 2005

We present a first-principle approach to the calculation of effective elastic moduli for arbitrary periodic composites. The method is based on the iterative solution of the inhomogeneous elastic wave equation in wave-vector space. By using Fourier coefficients of the periodic system as structural inputs, the present approach offers the advantage of circumventing the need for explicit boundary-conditions matching across interfaces. As a result, it can handle complex unit-cell geometries just as easily as simple cell geometries. We illustrate the application of this method by calculating the effective moduli of (1) a three-dimensional porous frame composed of a simple cubic array of fused solid spheres, and (2) a periodic two-component composite.
Dependence of acoustoelastic birefringence on plastic strains in a beam
Authors: Hirao Masahiko , Pao Yih-Hsing
Published: October 2005

Acoustoelastic birefringence is measured by transmitting ultrasonic shear waves at two perpendicular polarizations through the thickness of an aluminum beam. From the data obtained before bending, after bending, and after the beam has been sectioned to relieve the residual stresses, the acoustoelastic birefringence induced by residual stress is separated from that induced by texture change. Supplemented with strain-gauge data at all these states, the texture-induced anisotropy is shown to be related to plastic (permanent) strains in the beam. A nearly linear relationship is observed in compressional deformation of 6061-T6 aluminum up to −0.6% plastic strain in the beam, whereas the birefringence is almost independent of tensile plastic strain.
Acoustic and perceptual correlates of the non-nasal–nasal distinction for vowels
Authors: Hawkins Sarah , Stevens Kenneth N.
Published: October 2005

For each of five vowels [i e a o u] following [t], a continuum from non-nasal to nasal was synthesized. Nasalization was introduced by inserting a pole-zero pair in the vicinity of the first formant in an all-pole transfer function. The frequencies and spacing of the pole and zero were systematically varied to change the degree of nasalization. The selection of stimulus parameters was determined from acoustic theory and the results of pilot experiments. The stimuli were presented for identification and discrimination to listeners whose language included a non-nasal–nasal vowel opposition (Gujarati, Hindi, and Bengali) and to American listeners. There were no significant differences between language groups in the 50% crossover points of the identification functions. Some vowels were more influenced by range and context effects than were others. The language groups showed some differences in the shape of the discrimination functions for some vowels. On the basis of the results, it is postulated that (1) there is a basic acoustic property of nasality, independent of the vowel, to which the auditory system responds in a distinctive way regardless of language background; and (2) there are one or more additional acoustic properties that may be used to various degrees in different languages to enhance the contrast between a nasal vowel and its non-nasal congener. A proposed candidate for the basic acoustic property is a measure of the degree of prominence of the spectral peak in the vicinity of the first formant. Additional secondary properties include shifts in the center of gravity of the low-frequency spectral prominence, leading to a change in perceived vowel height, and changes in overall spectral balance.
Acquisition of a 250-word vocabulary through a tactile vocoder
Authors: Brooks P. L. , Frost B. J. , Mason J. L. , Chung K.
Published: October 2005

In a previous experiment [P. L. Scilley, ‘‘Evaluation of a vibrotactile auditory prosthetic device for the profoundly deaf,’’ unpublished Masters thesis, Queen’s University, Kingston, Canada (1980)] two normal subjects learned to identify 70 and 150 words, respectively, using the Queen’s Tactile Vocoder. In the present experiment, the most advanced subject continued word learning until a tactile vocabulary of 250 words was acquired. At this point randomized tests were given to obtain an indication of final performance level. From these data conditional probabilities of correct response for each stimulus word and significant confusions were obtained, which provides insight into the advantages and present limitations of the tactile vocoder.
Soil impedance measurements by an acoustic pulse technique
Authors: Don C. G. , Cramond A. J.
Published: October 2005

Impulses generated by the discharge of a rifle cartridge have been used to determine the complex acoustic impedance of grassland, cultivated earth, a layered forest floor, and highly reflecting stone impregnated ground. The length of the grass coverage is found to have a marginal effect on the impedance while measurements over broken soil indicate that only the first centimeter of earth influences the reflected pulse. Alterations to the impedance of the base material of a forest floor are clearly demonstrated as layers of pine needles or leaves are applied, while a limitation of the pulse technique is demonstrated by measurements over stony ground. Calculated impedance values are not consistent with predictions based on measured flow resistivity.
The sound field in a finite cylindrical shell
Authors: Junger M. C.
Published: October 2005

The sound field excited by vibrating boundaries in a finite cylindrical space, e.g., in a cylindrical shell, differs from the pressure distribution in an infinite cylindrical shell of comparable structural wavelength by the pressure diffracted by the end caps. The latter pressure component is comparable in magnitude to the pressure generated by the vibrating cylindrical boundary, but does not introduce additional resonances or antiresonances. Finally, a third pressure component associated with end cap vibrations is formulated.
Volume scattering: Echo peak PDF
Authors: Stanton T. K.
Published: October 2005

The statistical properties of the backscattered acoustic echo from clouds of scatterers are examined. These clouds could be plankton, nekton, bubbles, etc., or a combination. The clouds of interest are sufficiently dense so that echoes from the individual scatterers overlap. The scatterers are assumed to be randomly distributed in space so that, at high enough acoustic frequencies, the individual echoes are not correlated (random phase). The probability density function (PDF) of the maximum echo value achieved in a depth gate has been analytically derived, computer simulated, and measured in the field. It is shown to be quite different than the Rayleigh PDF of the envelope, even for gate durations smaller than one transmission ping duration. An approximate analytical expression for the echo peak PDF is derived by first modeling the echo as a discrete ‘‘stepped’’ waveform where the ‘‘steps’’ are statistically independent of each other. The problem is then solved by straightforward extremal statistics. There is excellent agreement between the theoretical PDF, computer simulations, and field data. While we are concerned with gate durations several times one ping duration, the analytical expression for the PDF is shown to accurately describe the PDF over ranges of the gate duration less than the ping duration to much greater than the ping duration. From the echo peak PDF one can (1) estimate the abundance of occasional large scatterers that are within the clouds (for example large fish feeding on plankton) since their occurrence is differentiable from the rest of the cloud in the PDF, and (2) clearly differentiate between conditions where the echoes overlap and do not overlap. Once it is determined whether or not they overlap, lower or upper bounds in scatterer density (number per unit volume) may be calculated. Both of these applications can be performed in situ.
Measurement of sound absorption in low salinity water of the Baltic Sea
Authors: Schneider Hans G. , Thiele Rolf , Wille Peter C.
Published: October 2005

Shallow water propagation measurements in the thermocline–halocline refractive sound channel of the Baltic Sea are utilized to estimate the absorption coefficient in low salinity water of 8 ppt (8.0 pH, 4 °C) for 0.5–10 kHz. The lower margin of the present data which are derived from transmission loss by subtraction of cylindrical spreading can be represented by the Francois and Garrison formula of 1982. However, measurements of the boron relaxation frequency indicate that this agreement does not necessarily support the assumed salinity dependence of the relaxation frequency but might be produced by appropriate scattering loss of the refractive channel.
Measurement of number and size distributions of reflecting objects by pulsed ultrasound
Authors: Stravs Andrej A. , Stockar Urs von
Published: October 2005

The echoes of different types of reflectors, which appear alternately but in a random way in certain positions in the sound beam of an ultrasonic probe, may be registered and classified according to their amplitude heights. If the response profiles (echoes versus position) are known and differ from each other, the number distribution of the reflectors can be deduced based on geometrical considerations and by using the acquired histogram of echo amplitudes. The principle has been demonstrated with steel balls of different sizes rolling on a central axis perpendicular to a round piezo, yielding the distribution of relative sizes.
Relations among different frequency rating procedures for traffic noise
Authors: Flynn Daniel R. , Yaniv Simone L.
Published: October 2005

A series of calculations was performed to ascertain how well one frequency-weighted rating, such as weighted sound level, loudness level, or perceived noise level, may be predicted from another such rating. A total of 103 average sound level spectra, measured at several distances from different types of highways, was used in these calculations. It was found that knowing a single noise rating, such as the A-weighted sound level, enables one to predict other outdoor ratings in this set of 103 spectra with a standard deviation of the order of 1–2 dB. If, in addition, traffic speed and mix and the distance to the highway are taken into account, these standard deviations can be reduced to 0.5–1 dB, depending upon the particular noise rating of interest. Equations are given for predicting one rating from another; the associated standard deviations are presented as a measure of how well any given rating can be predicted from a single measured, or otherwise known, noise rating. It is concluded that it is not critical which frequency-weighting procedure is used in conjunction with highway noise criteria since one descriptor can be predicted from another with small statistical uncertainty. Thus, if human response criteria, or stimulus-response relationships, have been developed in terms of one frequency-weighting procedure, these may be translated into equivalent criteria expressed in terms of a metric that is easier to measure or predict.
Algorithms for removing recovery-related distortion from auditory-nerve discharge patterns
Authors: Miller Michael I.
Published: October 2005

The probability that a cochlear nerve fiber discharges during some specified time interval depends on both the acoustic stimulus and on refractory effects due to earlier spike discharges. With the objective of separating the stimulus-related effects from refractory-related effects seen in poststimulus-time histograms, various maximum-likelihood estimation schemes have been developed. By modeling auditory-nerve fiber discharges as a self-exciting point process in which the intensity depends on both the time during stimulation and the history of discharge, we have been able to independently verify the likelihood estimates of Gaumond et al. [J. Acoust. Soc. Am. 74, 1392–1398 (1983)] under conditions when the recovery function is known. Secondly by maximizing the likelihood function of the neural event process subject to periodic stimulus constraints we have derived estimates which as the number of stimulus presentations and or stimulus periods increase are free from the effects of both absolute and relative recovery-related distortion. Under conditions when the recovery function is unknown, a recursive algorithm is proposed that yields the joint maximum-likelihood estimates of both the stimulus-and recovery-related components in the response histograms. We state the conditions under which unique maximum-likelihood estimates exist and prove that the recursive algorithm converges to those unique estimates.
A comparison among four direct boundary integral methods
Authors: Schuster Gerard T. , Smith Lance C.
Published: October 2005

Four distinct direct boundary integral equation (BIE) schemes, two of which are new, are derived and are used to solve multibody scattering problems. These schemes are similar in that each is a composite of integral operators that are completely continuous and are dissimilar in that they are either a mixture of equations of the first and second kind or are strictly of the second kind. Their relative usefulness is determined by analysis and numerical experiments, suggesting that the optimal scheme is governed by the tradeoff between stability and computational efficiency. To partially verify these BIE methods each was used to compute the scattering from a cylindrical obstacle and results of each method were compared to the analytic solution. In addition, one of these schemes was used to calculate the line source responses to half-space and two-layer models. The numerical and analytic solutions are in favorable agreement.
Boundary effects on transient radiation fields from vibrating surfaces
Authors: Guyomar Daniel , Powers John
Published: October 2005

The transient radiation or diffraction from a planar source imbedded in an infinite baffle is analyzed for three different baffle conditions (rigid, free-space, and soft). For an excitation separable in time and space, it is shown that the field is related to the normal derivative of the input field only. A method is also given for computing the transient fields based on a wave decomposition in the spatial frequency domain. This method is a time generalization of the angular spectrum theory that presents transient wave propagation as a time-varying spatial filter, allowing a linear systems interpretation of the diffraction. The formalism is shown to easily include the effects of a finite receiving aperture. The method is amenable to computing the field from an arbitrary time excitation and an arbitrary spatial distribution. The method is valid for arbitrary distances to the observation point and uses computationally efficient FFT calculations.