bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of acceleration on the resonance frequencies of crystal plates
Authors: Lee P. C. Y. , Wu Kuang-Ming , Wang Y. S.
Published: October 2005

The changes in the thickness-shear resonance frequencies of circular crystal plates subjected to steady in-plane acceleration of arbitrary direction are studied. A closed-form solution for a circular plate under acceleration with three or more points of mounting is obtained. From this solution, initial stress and strain fields are computed at each and every point of the plate as a function of plate orientation, direction of acceleration, and positions of supports. These fields are then taken into account in the coupled equations of the incremental thickness-shear and flexural vibrations through the second- and third-order elastic stiffness coefficients of the crystal. Due to the space dependence or nonuniformity of the initial fields and the smallness of the frequency changes, (Δf/fo in order of 10−9) a perturbation method is used to calculate the changes in the thickness-shear resonances. The frequency changes as function of the acceleration direction for several configurations of the supports for AT cut of quartz are computed. These are then compared with experimental values of A. W. Werner [Interim Reps. 10−11, Bell Telephone Labs. (1959)] and W. L. Smith [Interim Reps. 12−13, Bell Telephone Labs. (1960)].
Laboratory study of jet-noise suppressors
Authors: Arndt R. E. A. , Fuchs H. V. , Michel U.
Published: October 2005

Experiments on four different types of subsonic jet-noise suppressors are reported. The suppressors were compared to a clean circular jet on an equal-thrust per unit-exit-area basis. On this basis the noise production of the different jets varied only slightly, in contrast to some results reported previously.
Backward masking: Detection versus recognition
Authors: Bland David E. , Perrott David R.
Published: October 2005

The backward detection masking of 10-ms tonal targets by a 150-ms tonal mask was contrasted with the backward recognition masking of the same tones by the same mask. The target-mask interval required for 75% correct performance was about eight times as great in the recognition condition as in the detection condition. Furthermore, a generalized improvement in performance occurred over the initial course of training in both the detection and recognition conditions. In a second experiment it was found that a remote mask produced greater backward recognition masking but less backward detection masking. That these differences were observed with the same subjects, at the same level of training, and with identical stimuli, indicates that procedural differences alone cannot account for the differences between backward detection and recognition masking.
Group delay distortions in electroacoustical systems
Authors: Blauert J. , Laws P.
Published: October 2005

We report on measurements of group delay distortions introduced into electroacoustical transmission by the fact that earphones and loudspeakers are not necessarily minimum phase systems. Psychoacoustical tests show further that the measured distortions can approach the magnitude of the threshold of perceptibility, but in most cases will be well below this value.
Perceptual effects of spectral modifications on musical timbres
Authors: Grey John M. , Gordon John W.
Published: October 2005

An experiment was performed to evaluate the effects of spectral modifications on the similarity structure for a set of musical timbres. The stimuli were 16 music instrument tones, 8 of which were modified in pairs. This modification consisted of exchanging the shape of the spectral energy distribution between the two tones within each pair. The three-dimensional spatial representation of similarities among the 16 tones was obtained by multidimensional scaling techniques and compared to a previous scaling of the original 16 unmodified tones [J. M. Grey, J. Acoust. Soc. Am. 61, 1270–1277 (1977)]. The pairs of tones which had exchanged spectral shapes in fact exchanged orders on the spatial axis which had been previously interpreted as relating to spectral shape, thereby supporting the earlier interpretation. The two remaining axes of the spatial solution also retained their original interpretations, relating to various temporal details of the tones. A set of formal quantitative models for the spectral dimension was constructed and tested, and the results further supported the interpretation of this perceptual axis.
Simultaneous pure-tone masking: The dependence of masking asymmetries on intensity
Authors: Vogten L. L. M.
Published: October 2005

Phase locking between probe and masker was used in a series of pure-tone masking experiments. The masker was a stationary sine wave of variable frequency; the probe a fixed-frequency tone burst. We have observed that for small frequency separation the masking behaves asymmetrically around the probe frequency. This asymmetry depends on intensity. For a 1-kHz probe at low stimulus levels there is a maximum masking effect at about 60 Hz above the probe frequency, whereas at high levels maximum masking is produced at a frequency definitely below the probe frequency. These results are discussed in relation to current neurophysiological and psychophysical data. For the high-level asymmetry possible interpretations are suggested in terms of two changes in the excitation pattern of the basilar membrane, (a) a shift of the top and/or (b) a slope asymmetry, both increasing with level. The low-level asymmetry will be treated in a second paper [Vogten, J. Acoust. Soc. Am. 63, 1521–1528 (1978)].
Acoustical properties of the human skull
Authors: Fry F. J. , Barger J. E.
Published: October 2005

The acoustical properties insertion loss, reflection loss, and sound speed were measured on a series of fresh and subsequently formalin immersed human skulls. Measurements were made in the frequency range from 0.25 to 6 MHz. Most studies were restricted to an upper frequency limit of 2.2 MHz. An axisymmetric focused beam configuration was used as the sound source for the measurements and the receivers were small disk-type (3-mm-diam) piezoelectric ceramics. The geometric and temporal character of the focused beam was studied as a consequence of passage through the skull sections. Some skulls were sectioned so that their individual layer components could be studied. A simple three-layer analytical model seems to explain the major aspects of insertion and reflection loss. The dominant feature in determining human adult skull losses is the middle layer (diploe) of cancellous bone. This study corroborates previous work on insertion loss as a function of frequency for composite skull. The study provides new quantitative information on the acoustic scattering properties of diploe, scound velocity, and dispersion in composite skull and its components, attenuation coefficients in skull components and sound-beam distortion and shifts after transmission through composite skull. We conclude that with selection of appropriate frequencies (0.5–1.0 MHz) and beam configuration it will be possible to perform clinically significant transkull diagnostic imaging and interrogation in the adult human brain.
Log-periodic acoustic lens–acoustic filter plate study
Authors: Sternberg Robert L. , Anderson Warren A. , Stevens Gerald T.
Published: October 2005

Graphical comparative experimental data is presented showing the variation of the useful aperture diameter, directivity index, and beamwidth as a function of frequency for an acoustic lens alone and for an acoustic lens–acoustic filter plate combination. For the lens alone the aperture diameter is, of course, constant while the directivity index and beamwidth vary with frequency, but for the combined lens–filter plate device the effective aperture diameter varies with frequency while the directional parameters are effectively constant.
Comment on the contribution of cross-modal terms to the local response of structures to random pressure fields
Authors: Garrelick J. M. , Chayes L.
Published: October 2005

The conditions under which cross-modal terms may be neglected in the calculation of the local response of structures to random pressure fields are presented for a particular class of problems.
Fast straight-line-train fitting algorithm for application with Olive’s speech-coding method
Authors: Strube H. W.
Published: October 2005

According to Olive, the log–area vocoder parameter curves may be replaced by straight-line trains. Here a fast algorithm is presented for fitting a straight-line train to a sampled function in the least-squares sense. The segment boundaries are given, their ordinate values are calculated. When the boundaries are the same for several functions, the first part of the algorithm need be applied only once. The number of operations increases linearly with the number of samples.
Formant extraction from linear-prediction phase spectra
Authors: Yegnanarayana B.
Published: October 2005

Extraction of formant information from linear-prediction phase spectra is proposed. It is shown that the derivative of phase spectrum gives reliable formant information. Since the phase spectra for several resonators in cascade are additive, the resonance peaks are additive in the derivative of the phase spectrum unlike in the magnitude spectrum and hence the problem of identifying merged peaks is very easily solved by this method. Application of the method is illustrated through examples of linear-prediction spectra obtained for simulated models and for actural speech segments.
Range dependence of underwater echoes from randomly rough surfaces
Authors: Mikeska E. Eugene , McKinney Chester M.
Published: October 2005

Experimental underwater measurements of the echo reflected or backscattered from randomly rough model pressure relief surfaces in a laboratory tank are presented as a function of range and relative roughness. Measurements of peak echo pressure amplitude were made at a frequency of 100 kHz at normal incidence; Rayleigh parameters of the surfaces were 0, 1.95, 3.90, and 7.82. The results illustrate the transition from mirror image reflection from a plane surface to spherically spreading backscattering from a surface having irregularities larger than the wavelength, with intermediate range dependence for surfaces having moderate relative roughness.
Piezoelectric polymer flexural disk hydrophone
Authors: Sullivan T. D. , Powers J. M.
Published: October 2005

Piezoelectric polyvinylidene fluoride (PVF2) film has been successfully used as the transduction material in the construction of a practical hydrophone, thus demonstrating the feasibility of using this material in underwater acoustics. The PVF2 film is mounted on a flexing circular plate (disk) for strength under hydrostatic pressure; strains developed on the disk surface by incident acoustic pressure are exploited to excite the PVF2. An analytic expression has been developed to find the free-field voltage sensitivity of the hydrophone when the disk boundary is simply supported, and the sensitivity of a carefully constructed prototype was measured for experimental verification. Additional hydrophones were constructed to produce better sensitivity and were tested under a wider range of temperatures and pressures. Hydrophones constructed to withstand pressures up to 4 MPa typically exhibited sensitivities of −200 dB//1 V/μPa and were neutrally buoyant in water.
Free oscillations of submerged spherical shells
Authors: Lou Y. K. , Su T. C.
Published: October 2005

Free vibrations of a spherical shell submerged in a fluid medium are investigated. It is found that no undamped natural frequency of the submerged shell can exist even if the surrounding fluid is assumed inviscid. In this case the damping is solely due to the compressibility of the fluid. However, for the intermediate modes, the damping components of the complex frequencies are extremely small; thus, an almost steady-state, undamped free oscillation is possible for these modes and a pronounced resonance may be observed for the forced vibrations. When the shell is submerged in an ideal fluid, it is shown that there exist two real natural frequencies for each mode. These frequencies are lower than the corresponding in vacuo natural frequencies. The effect of fluid viscosity on the complex natural frequencies has also been examined. It is found that for small viscosities, the viscosity has essentially no effect on the real component of the natural frequencies.
Analysis of the vibratory excitation of gear systems: Basic theory
Authors: Mark William D.
Published: October 2005

Formulation of the equations of motion of a generic gear system in the frequency domain is shown to require the Fourier-series coefficients of the components of vibration excitation; these components are the static transmission errors of the individual pairs of meshing gears in the system. A general expression for the static transmission error is derived and decomposed into components attributable to elastic tooth deformations and to deviations of tooth faces from perfect involute surfaces with uniform lead and spacing. The component due to tooth-face deviations is further decomposed into appropriately defined mean and random components. The harmonic components of the static transmission error that occur at integral multiples of the tooth-meshing frequency are shown to be caused by tooth deformations and mean deviations of the tooth faces from perfect involute surfaces. Harmonic components that occur at the remaining multiples of gear-rotation frequencies are shown to be caused by the random components of the tooth-face deviations. Expressions for the Fourier-series coefficients of all components of the static transmission error are derived in terms of two-dimensional Fourier transforms of local tooth-pair stiffnesses and stiffness-weighted weighted deviations of tooth faces from perfect involute surfaces. Results are valid for arbitrary, specified tooth-face contact regions and include spur gears as the special case of helical gears with zero helix angle.
Statistics of amplitude and spectrum of blasts propagated in the atmosphere
Authors: Schomer P. D. , Goff R. J. , Little L. M.
Published: October 2005

This paper describes the measurement and analysis of over 11 000 blast recordings. These data are used to develop a statistical base for blast propagation and to establish one-third octave spectra for these blasts. These results can then be used to predict community blast noise levels. The blasts are divided into rather broad amplitude groupings and it is shown that received blast spectra are dependent only on grouping and not on absolute peak amplitude or distance (2–15 miles). One interesting result is that early in the morning and at far distances (normally over 5 miles) amplitudes are greatest upwind.
Reflection of acoustic waves at the interface of two highly stressed elastic half-spaces
Authors: Nowinski J. L.
Published: October 2005

Using the method of incremental deformations formulated by Biot [Mechanics of Incremental Deformation (Wiley, New York, l965)], the amount of prestressing in a half-space of an incompressible material is determined by analyzing the value of the reflection coefficient of the acoustic equivoluminal waves impinging upon the deformed boundary of the half-space. An illustrative example, solved in detail, shows that the results may serve as a basis for a nondestrictive evaluation of the level of prestressing.
Reflection of Rayleigh waves by strips, grooves, and periodic arrays of strips or grooves
Authors: Simons Donald A.
Published: October 2005

The plane-strain version of the title problem is solved by a perturbation scheme. The fields are represented as convolutions of Green’s functions with unknown surface-traction distributions. Integral equations governing these tractions are obtained by applying boundary conditions which represent the effect of the surface layers. The equations are solved by singular perturbation techniques, asymptotically as the ratio of layer thickness to incident wavelength or strip width tends to zero. The cases of a fixed number of strips and a number of strips which become infinite in the asymptotic limit, are treated separately. Closed-form expressions for the reflection coefficient are obtained.
Matrix theory of elastic wave scattering. II. A new conservation law
Authors: Waterman P. C.
Published: October 2005

Upon resolving the surface traction into spatial derivatives and surface derivatives of the displacement, a new conserved elastodynamic field quantity is found, having dimensions of energy density. For periodic time dependence, the flux associated with this new quantity differs from the true energy-flux vector by only a solenoidal term, and is far simpler to compute. The conservation requirement is shown to be the basis of one form of Huygens’ principle, and in addition leads directly to the T-matrix equations without the necessity of introducing the Green’s dyadic.
Parametric acoustic sources of rectangular aperture
Authors: Moffett Mark B. , Mellen Robert H. , Konrad William L.
Published: October 2005

A model is presented for predicting source levels and beam patterns generated by parametric acoustic sources of rectangular aperture. This model is a generalization of a previous model for square and circular apertures [J. Acoust. Soc. Am. 61, 325–337 (1977)]. Because the nonlinear absorption of the primary beams is less for a rectangular projector than for a square projector of equal area and primary source level, it is possible to obtain larger difference-frequency source levels from rectangular projectors than from their square (or circular) couterparts. The conditions required for such enhanced source levels are discussed, and the results of an experimental test of the model are presented.
Bottom reverberation-derived scattering strengths in shallow water off the Argentinian coast
Authors: Blanc S. , Novarini J. C. , Núñez A. L.
Published: October 2005

Measurements were carried out in shallow water 23 m deep off the Argentinian coast in quasi-isovelocity conditions. The data were analyzed for grazing angles in the interval 1°50′–8°. A method to make an indirect determination of bottom-scattering strengths in shallow water has been worked out. It consists of separating the surface, volume, and bottom contributions according to their time decays in recordings of signals from distant explosions. For this purpose, a simplified model based on the equivalence of both bistatic and monostatic experimental geometries was used. The results show a slight increase in bottom-scattering strength with grazing angle and with frequency according to the 1.0 power 3 dB/octave). An attempt to correlate scattering strength with type and roughness of the sea bed was also carried out. The coincidence between our results and direct measurements made under similar conditions by others suggests the validity of the present method.
Modeling of the cat eardrum as a thin shell using the finite-element method
Authors: Funnell W. Robert J. , Laszlo Charles A.
Published: October 2005

A finite-element model of the cat eardrum is presented which includes the effects of the three-dimensional curved conical shape of the drum. The model is valid at low frequencies (below 1–2 kHz) and within the range of linear vibration amplitudes. The material properties used are based on a review of the literature. The critical material parameters are the stiffness (2×108 dyn cm−2) and thickness (40 μm) of the pars tensa. The model exhibits a vibration pattern and amplitude very similar to those observed experimentally using laser holography. A number of parameters are varied in order to study their relative importance in the model.
Unconventional reciprocity calibration of transducers
Authors: Rudnick Isadore
Published: October 2005

The procedure for the reciprocity calibration of transducers in unconventional acoustic geometries is described.
Masking-level differences for repeated filtered transients
Authors: Yost William A. , Dolan David
Published: October 2005

Masking-level differences (MLDs) for repeated high-pass (2000-Hz) and low-pass (2000-Hz) 100-μs pulses were obtained as a function of the number of transient repetitions and the repetition rate. MLDs compared to the NoSo condition were obtained for the NoSπ and NoSd binaural configurations (Sd refers to the conditions in which there was a 1.1-ms interaural delay for the transient signals). MLDs of 11–14 dB were obtained for the low-pass transients independent of the number of transients, repetition rate, or type of binaural configuration. MLDs of 2–4 dB were obtained for the high-pass transients only if the transients were repeated 12 or more times. These results for the high-pass transients did not depend on the repetition rate or type of binaural configuration. The results suggest that high-frequency binaural auditory channels can process noisy low-frequency binaural auditory channels can process noisy low-frequency temporal envelopes, but not as well as low-frequency channels can process low-frequency temporal and spectral information.
Intensity of guitar playing as a function of auditory feedback
Authors: Johnson Cynthia , Pick Herbert L. , Garber Sharon , Siegel Gerald M.
Published: October 2005

Subjects played an electric guitar while auditory feedback was attenuated or amplified at seven sidetone levels varying in 10-dB steps around a comfortable listening level. The sidetone signal was presented in quiet (experiment I) and several levels of white noise (experiment II). Subjects compensated for feedback changes, demonstrating a sidetone amplification as well as a Lombard effect. The similarity of these results to those found previously for speech suggests that guitar playing can be a useful analogue for the function of auditory feedback in speech production. Unlike previous findings for speech, the sidetone-amplification effect was not potentiated by masking, consistent with a hypothesis that potentiation in speech is attributable to interference with bone conduction caused by the masking noise.
A simple ultrasonic transducer for measuring shear-wave velocities
Authors: Ferris C. D. , Ambardar A.
Published: October 2005

A fabrication technique for constructing a simple shear-wave mode ultrasonic transducer is discussed. These transducers have been used successfully in determining the elastic moduli of compact bone.
The influence of middle-ear muscle contraction on auditory threshold for selected pure tones
Authors: Morgan Donald E. , Dirks Donald D. , Kamm Candace
Published: October 2005

The influence of middle-ear muscle (MEM) contraction on auditory threshold has been measured for pure tones of 0.25, 0.5, and 1.5 kHz. The reflex-activating signal was a 3-kHz pure tone. Signal paradigms were chosen to reduce or eliminate the effects of binaural loudness summation, contralateral direct masking, and contralateral remote and backward masking effects, and to maximize the influence of MEM contraction. Results indicate that under no condition was behavioral threshold affected by the MEM contraction induced using a pure-tone stimulus of 3 kHz, 105 dB SPL.
Diffraction by a screen above an impedance boundary
Authors: Thomasson Sven-Ingvar
Published: October 2005

This paper is aimed at solving the problem of diffraction by a screen above a locally reacting, infinitely large plane. A general solution is given in terms of an integral equation on the diffracting object. An explicit solution is obtained in the sense of physical optics. Comparisons are made with other solutions by Lindblad and Jonasson. The main disadvantage of these solutions is that their validity is unknown; for sufficiently low screens they are not applicable. The present solution avoids these problems and also extends the knowledge to screens of finite length. To improve the solution numerically, a new method of evaluating integrals of two-dimensional Fourier transforms is discussed and applied. This technique may also be used to evaluate the radiated field from a vibrating surface in a plane infinite baffle. In an experimental section, a close agreement is found between theory and experiments in model scale, indoors as well as outdoors, which also indicates that the method of measuring the ground impedance is useful. The influence of various parameters on the insertion loss is discussed in connection with the model experiments.
Contribution of ultrasonic measurements to the study of liquid crystals. II. Smectics, cholesterics, and mixtures
Authors: Natale G. G.
Published: October 2005

The study of ultrasonic propagation in liquid crystals, greatly intensified in recent years, has provided a useful contribution to the knowledge we currently have about these systems. A previous paper (Part I of a two-part series) contains a review and analysis of the ultrasonic work done on the nematic mesophase. In the present paper, most ultrasonic experimental investigations performed to date in smectic and cholesteric compounds, and some liquid-crystalline mixtures, are presented in a systematic manner; the results are discussed and compared, whenever possible, to the predictions of several theories (outlined in the paper) for the various mesophases and the many possible phase transitions. In the course of this analysis, several areas which need further ultrasonic studies are identified; these areas are summarized in the concluding section of the paper.
Acoustic scattering from silicone rubber cylinders and spheres
Authors: Davis C. M. , Dragonette L. R. , Flax L.
Published: October 2005

Scattering of acoustic waves from silicone rubber cylinders and spheres is considered. The effect of shear is found to be negligible. Special consideration is given to cases where the specific impedance of the rubber equals that of water.
Transient scattering by arbitrary axisymmetric surfaces
Authors: Neilson H. C. , Lu Y. P. , Wang Y. F.
Published: October 2005

A numerical method using Kirchhoff’s retarded potential integral equation to determine the time-dependent pressure distribution on the surface of an arbitrary smooth, convex, and axisymmetric rigid scattering body due to the impact of a plane acoustic wave having discontinuous wave front incident from any direction is developed and presented. This numerical technique is developed for general purposes, and it is applicable not only to single structures of same shape but also to composite structures of different shapes such as circular cylindrical, spherical, conical, and toroidal segments as well as flat plate. Typical numerical solutions for a hemisphere-capped cylinder impinged upon by a unit-step-pressure pulse from three different directions, i.e., axial incidence, side-on incidence, or oblique incidence of 30° off the longitudinal axis of the cylindrical section are presented. Numerical solutions of transient scattering of acoustic waves of normal incidence by a sphere are also given, and results agree very well with the analytical solutions obtained by other investigators.
Distortion of the sonic-boom pressure signature by high-speed jets
Authors: Hall Sydney-Lynne V.
Published: October 2005

Mach-2.5 (0.30 caliber) projectiles were used to simulate supersonic aircraft; the acoustic impedance mismatch was provided by either of two rectangular nozzles having exit Mach numbers of 1.00 and 1.82 when delivering correctly expanded helium jets. These nozzles were operated from 40%–150% expansion at a fixed position relative to the presure transducer when the projectile miss distance was 36 or 108 body diameters from the transducer. Schlieren optical photographs demonstrated that the bow shock was always folded or ’’wrinkled’’ after passing through either of the jets. As exit Mach number decreased, the size of the shock-front folds, as well as the divergent jet spread angle, increase and the bow shock becomes increasingly bent forward by the jet. Pressure signatures measured with a jet operating started 40–80 μs earlier than those measured without a jet. All pressure signatures obtained with a jet operating exhibited similar varieties of waveforms as F-104, B-58, XB-70, SR-71, and Concorde 002 flight test results. The wide variations in overpressure, rise time, duration, and wave shape are attributed to the velocity and density fluctuations of the turbulent jets.
Use of the complex exponential expansion as a signal representation for underwater acoustic calibration
Authors: Beatty Louis G. , George James D. , Robinson A. Zed
Published: October 2005

A modified Prony method is developed to provide a complex exponential signal representation for use with underwater acoustic calibration waveforms. The approach is tested using simulated waveforms, and the simulation results are validated with limited experiments. Results show the complex exponential is an ideal signal representation for underwater acoustic calibration because of its remarkable ability to extrapolate calibration waveforms beyond the actural observation period. Results are shown of real reciprocity calibration experiments that are valid down to 25 Hz where the calibration waveforms are generated from a 5-ms current ramp and where a 5-ms observation period is used. The period of the low-frequency limit is eight times the observation period used in the calibration.
Observations of the phase and amplitude of individual Fermat paths in a multipath environment
Authors: Ewart Terry E. , Ehrenberg John E. , Reynolds Stephen A.
Published: October 2005

FM slide and pulsed-tone signals at 2, 4, 8, and 16 kHz were transmitted from a source to a receiver at the same depth 1100 m distant. Three wholly refracted paths were observed in the return signals, and a discussion of the six-hour time series of the arrival times and amplitudes for each path is presented. Evidence is given of acoustic frequency-dependent scattering, and scattering from oceanic fine structure is suggested as the most likely physical mechanism to explain the observations.
Joint volume reverberation and biological measurements in the tropical Western Atlantic
Authors: Gold Barry A. , Renshaw Wayne E.
Published: October 2005

Volume reverberation and biological data were gathered during January in the western tropical Atlantic Ocean. Day and night scattering strengths in 1/3-octave bands from 1.0 to 20.0 kHz are presented which are compared to other data collected in the same area by a different agency. Identification of fishes captured, their lengths and computed swimbladder volumes, as well as resonance frequencies are given.
Surface-wave rays in elastodynamic diffraction by cracks
Authors: Gautesen A. K. , Achenbach J. D. , McMaken H.
Published: October 2005

A geometrical diffraction theory has been worked out to analyze the fields generated by diffraction of high-frequency waves by cracks. The theory accounts for curvature of incident wavefronts, curvature of crack edges, and finite dimensions of the crack by providing first-order corrections to the results for a semi-infinite crack. The diffracted fields include direct diffractions from the crack edges as well as well as diffractions of signals which travel via the crack faces. On the faces of the crack the main contributions to the diffracted fields come from rays of surface waves. The directions of these surface-wave rays, and the amplitudes, wavelengths, and phases of the associated surface-wave motions have been related to the corresponding quantities of the incident body-wave rays. Reflection and diffraction of surface-wave rays by the edge of a crack have also been analyzed. As an example, diffraction by a penny-shaped crack of a plane longitudinal wave under normal incidence has been considered in some detail. Explicit expressions are given for the diffracted fields. In these expressions a correction was introduced to extend the validity of the results to the normal axis through the center of the crack, which is a caustic axis. A simple expression for the scattering cross section is presented.
Vibration of circular double-plate systems
Authors: Swamidas A. S. J. , Kunukkasseril V. X.
Published: October 2005

Vibrational characteristics of circular double-plate systems connected together by concentric, intermediate, elastic ring supports have been considered in this work. The analysis is based on the assumption that both of the plates are thin, elastic, and isotropic. Also, the plates are subjected to initial in-plane loads. The solutions are shown to be in terms of Bessel functions for the case of complete and annular (with equal in-plane loads) circular isotropic plate systems. The vibrational characteristics of the systems are illustrated by presenting numerical results for isotropic plate systems with one intermediate connection. When both the plates are identical with identical edge forces and boundary conditions, in-phase and out-of-phase vibration modes are observed.
Normal-mode theory of enclosures with thermoviscous dissipation at the walls
Authors: Burns Stephen H.
Published: October 2005

This paper treats a limiting case of normal-mode theory for which all of the dissipation occurs in the thermoviscous boundary layer in the fluid near the walls. This case differs from that of finite-impedance walls primarily in its more complicated dependence of the viscous dissipation on the mode numbers. The normal-mode theory with infinite-impedance walls is shown on a term-by-term basis to be equivalent to the Kirchhoff tube theory. An example of how one might exploit this equivalence is given. Calculated absorption coefficients for infinite-impedance walls are compared with the experimental coefficients in the literature.
Amplitude shading of irregular acoustic arrays
Authors: Sullivan Edmund J.
Published: October 2005

A method of generating amplitude shading coefficients for iregular arrays is demonstrated. By applying a scale transformation to the element coordinates and making the assumption that the cross section of the main lobe is elliptical, an existing technique can be applied. The method allows for steering within certain constraints. Although this approach strictly applies only to planar arrays, an example is given of an array which conforms to a conic surface in order to demonstrate the utility of the technique even when the required planar condition is not met. For this example, beam patterns are generated for the broadside case and the 45° steered case.
Calculated frequency spectra of axially symmetric extensional vibration in disks with Poisson’s ratio of 1/3
Authors: Ikegami Seiji
Published: October 2005

Frequency spectra of axially symmetric extensional vibration of an isotropic disk plate have been calculated for the critical value, 1/3, of Poisson’s ratio σ of the disk material, and the spectra have been compared with the earlier works on spectra for σ<1/3 (0.18) and those for σ≳1/3 (0.37). In spite of absence of the imaginary loop in the present dispersion curve, there appears to be no drastic change in spectral pattern. The frequency of the present spectra increases rather rapidly with decreasing r (diameter/thickness ratio), showing no thickness dependence even near the normalized cutoff frequency k. It is suggested from the present spectra that disk material with σ of 1/3 is not suitable for application of disk in the thickness extensional mode.
Multidimensional classification of normal voice qualities
Authors: Singh Sadanand , Murry Thomas
Published: October 2005

This study investigates and acoustically defines some of the perceptual parameters used to distinguish among normal male and female voices. Twenty normal speaking subjects, ten male and ten female, produced speech segments which were paired, randomized, and presented to ten listener judges. The judges rated the similarity of all combinations of voices on a seven-point scale, and these similarities were analyzed by a multidimensional analysis technique, INDSCAL. For each speaker, eight acoustical measures were obtained, and psychophysical ratings of four commonly used descriptive terms were made by ten speech pathologists. These measurements and ratings provided the interpretation of the INDSCAL solution and were also submitted to correlational analyses. The results indicate that, when distinguishing among the voices, the judges gave the greatest weight to the male versus female dimension and its acoustical correlates. The results of both the INDSCAL analysis and the correlational analyses suggest that listeners may use different perceptual strategies to classify male voices than they use to classify female ones.
Occurrence of glottal stops in fluent speech
Authors: Umeda Noriko
Published: October 2005

The use of glottal stops in continuous speech in American English has not been well studied, in spite of the common belief that they may serve as boundary markers. This paper reports the result from measurements of five speakers’ readings of four stories, each arranged in both list and story form. Data were analyzed according to the difference in speakers, materials, versions, phonological situations (phoneme sequence and stress situations), grammatical conditions, and frequency of occurrence of words. Results show that higher-level factors such as speaker’s reading style and difficulty of material have a stronger influence than phonological and grammatical factors.
Theory of binaural interaction based on auditory-nerve data. III. Joint dependence on interaural time and amplitude differences in discrimination and detection
Authors: Colburn H. S. , Latimer J. S.
Published: October 2005

This paper is primarily concerned with issues of symmetry–asymmetry in the joint dependence of binaural performance on interaural time delay and interaural amplitude ratio. The predictions of our model based on auditory-nerve data are shown to be inadequate for available data showing asymmetries in interaural time discrimination. Measured detection thresholds for a 500-Hz tone burst masked by wide-band noise are reported for nonunity amplitude ratios and both polarities of delays in order to test for asymmetries analogous to those observed in the time discrimination case. The detection results show only small asymmetries and are not inconsistent with the model. A general discussion of our model and the implications of available empirical results leads to a suggested modification of the model. We show by an example that modifications of the type we are suggesting are capable of describing the detection data and at least the gross trends of the discrimination data.
Phase insensitive acoustoelectric transducer
Authors: Heyman Joseph S.
Published: October 2005

Conventional ultrasonic transducers transform acoustic waves into electrical signals preserving phase and amplitude information. When the acoustic wavelength is significantly smaller than the transducer diameter, severe phase modulation of the electrical signal can occur. This results in anomalous attenuation measurements, background noise in Non-Destructive Evaluation (NDE), and in general complicates data interpretation. In this article, we describe and evaluate a phase insensitive transducer based on the acoustoelectric effect. Theory of operation of the Acousto-Electric Transducer (AET) is discussed and some optimization procedures outlined for its use. Directivity data for for the AET is contrated with a conventional piezoelectric transducer. In addition, transmission scanning data of phantom flaws in metal plates is presented for both transducers and demonstrates a significant improvement in resolution with the AET.
Diffraction, reflection, and interference during near-grazing and near-normal ocean surface backscattering
Authors: Novarini Jorge C. , Medwin Herman
Published: October 2005

Theory for the impulse response of a spherical wave backscattered from a plane strip has been used with a computer model of a randomly rough long-crested ocean surface to reveal the relative contributions of diffraction, facet reflection, and interference at near-grazing and near-normal incidence and to incorporate acoustical shadowing in a natural way. The major findings for near-grazing incidence are that backscatter is due to diffraction at troughs and crests; the backscattering strength is −54 dB at 5 m/s and only 2 dB more at 20 m/s, both flat for grazing angles 1° to 10°; and it decreases about 3 dB for an octave increase in frequency, independent of wind speed. At normal incidence the decreasing value of the backscattered coherent intensity with increasing roughness is due to interference. It is related to the transform of the probability density function of the surface height until the roughness parameter g (=4k2σ2) reaches approximately 5, where there is a deep minimum due primarily to interference of the highly coherent diffracted contributions. At normal incidence the backscatter is dominated either by diffraction or reflection, depending on the sphericity of the wave front.
Statistics of low-frequency multipath fluctuations in the ocean
Authors: Porter Robert P. , Spindel Robert C.
Published: October 2005

Statistics of fluctuations of low-frequency sound in the ocean are analyzed for an arbitrary number of paths. Covariances are derived for the intensity, phase rate (time derivative of the phase), and related parameters. Power spectra are derived from the covariances. The multipath results are based on weakly fluctuating single paths whose phase is perturbed by the internal-wave field. The theory is illustrated by deriving some results for a single internal wave. We specialize to a large number of equal energy paths by appealing to the central-limit theorem which states that the Cartesian components for the multipath field are Gaussian distributed. Some results available in the literature are shown to be valid for the special case of a large number of paths. Power spectra for data obtained in a recent experiment are shown to follow the predictions of this analysis.
Acoustic resonant frequencies in an eccentric spherical cavity
Authors: Kanellopoulos John D. , Fikioris John G.
Published: October 2005

The interior boundary-value scalar (acoustic) problem in the region between two spheres of radii R1, R2 and distance d between their centers is considered for both Dirichlet and Neumann boundary conditions. Surface singular integral equations are used to formulate the problem. Their solution is obtained in terms of spherical wave functions in combination with related addition theorems. It is then specialized to the case of small values for kd=2πd/λ to yield exact, closed-form expressions for the coefficients gns in the resulting relations ωns(kd) =ωns(0) [1+gns(kd)2+⋅⋅⋅] for the resonant (natural) frequencies of the cavity. Numerical results, comparisons, and possible generalizations are also included.
Frequency discrimination in the chinchilla
Authors: Nelson David A. , Kiester Thomas E.
Published: October 2005

Chinchillas were trained with shock-avoidance procedures to discriminate or detect pure-tone frequency differences. Initial attempts at determining frequency-difference thresholds utilized a complex discrimination paradigm and a go–no-go response. Although discriminations of large frequency differences were obtained from chinchillas after considerable training, discriminations of small frequency differences could not be trained. Therefore, determinations of frequency-difference thresholds could not be made with the complex discrimination paradigm and the go–no-go response task. A simple detection paradigm, involving the detection of frequency alternation in an ongoing train of tone bursts proved to be a more successful technique. Frequency-alternation detection was quickly learned by six chinchillas, and frequency-difference thresholds were obtained with an adaptive sequential procedure. Psychometric functions were reconstructed from the threshold tracking data of chinchillas, and comparisons were made with differential frequency thresholds from cats and humans obtained by previous investigators. Differential frequency thresholds from chinchillas paralleled those from cats and were about twice as large. Differential frequency thresholds from humans were considerably smaller than from chinchillas, especially for low-frequency tones. When a constant detectability index was used to specify differential frequency sensitivity in chinchillas, chinchilla and human differential sensitivity functions paralleled one another. Human differential sensitivity was about ten times better than that of the chinchilla.
Some observations on cochlear mechanics
Authors: Rhode William S.
Published: October 2005

A set of experiments was conducted using the Mössbauer effect to determine the vibratory characteristics of the basilar membrane, Reissner’s membrane, the malleus, incus, and oval window in squirrel monkey. A few measurements were also made in guinea pig in the basal cochlear region. The nonlinear vibration properties of the basilar membrane are described in detail for the midfrequency region in the squirrel monkey. Only in this region have nonlinear effects been observed. A comparison of mechanical and neural data indicates good qualitative agreement.
Scattering in the depth direction from a quadratic sound channel
Authors: Beran Mark J. , Whitman Alan M.
Published: October 2005

We present here a calculation of first-order scattering resulting from temperature fluctuations in a sound channel. We consider the channel profile to be quadratic and the fluctuation spectrum to be anisotropic and caused by internal waves. The source is taken to be a finite beam. We discuss the nature of the results and indicate how calculations may be made when the channel is not quadratic.
Diffraction of arbitrarily oriented directional sources by rigid planar screens
Authors: Johnston G. W.
Published: October 2005

An analysis has been carried out to determine the diffracted fields due to directional sources located near rigid planar screens with application to the suppression of noise by acoustic barriers, especially highway barriers. Firstly, the diffracted field due to an arbitrarily oriented point dipole source is obtained by source position differentiation using the classical exact results due to McDonald. The dipole results are then combined with the monopole results to obtain the diffracted fields due to a series of combined sources having arbitrary directivity and orientation with respect to the plane of the screen. It is noted that while the diffraction problem with simple sources and planar screens exhibits reciprocity, diffraction results obtained in the present problem do not exhibit reciprocity with respect to source and observer locations. Typical computed insertion loss results are shown indicating the trends associated with source directionality, source orientation, and source location. Barrier insertion loss reductions, relative to those obtained with simple sources, are noted for vertically oriented directional sources located close to, and below, the diffracting edge.
Resonance scattering of acoustic waves from cylindrical shells
Authors: Murphy J. Diarmuid , Breitenbach Edward D. , Überall Herbert
Published: October 2005

The theory of resonance scattering, recently developed for acoustic-wave scattering from elastic objects and elastic-wave scattering from cavities, is applied here to the problem of sound scattering from fluid-filled elastic cylindrical shells in a fluid, in particular air-filled aluminum shells in water. The eigenvibrations of the shell appear as resonances in the scattering amplitude of each normal mode; these are superimposed on a smooth background which if the shell is made thinner, converts from the amplitude of a rigid to that of a soft cylinder. The resonances themselves are exhibited by subtracting the background from the total amplitude and are seen to become less numerous as the shell gets thinner.
A new approach to the guinea pig auditory nerve
Authors: Alder V. A. , Johnstone B. M.
Published: October 2005

A new approach to the guinea pig auditory nerve is presented. This approach, which has several advantages over previous methods, enables stable recordings from primary nerve fibers to be made. Entry to the auditory nerve is through the modiolus via scala tympani of the basal turn of the cochlea.