bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Analysis of Power Injection and Response in Structures and Rooms
Authors: Lyon R. H.
Published: September 2005

The calculation of input power and response of simple models of rooms and structures is described. The approach is essentially statistical. Random variations in time are not considered; these fluctuations are averaged out. Randomness is introduced into the system models by considering basic parameters such as resonance frequencies and observation position to be selected statistically. Simplifying assumptions on the damping and mode shapes are made. The average and variance of power injected by point sources are calculated. The statistics of response near and away from the driving point are also found. It has not been possible to calculate the exact forms for the response distributions. Accordingly, in order to find confidence coefficients for estimation intervals, a distribution is chosen ad hoc. The selected one, the gamma distribution, has several desirable features. It is, in fact, exact for some important cases. Two kinds of estimation intervals are derived and applied to some simple examples. Finally, an interesting alteration of the frequency-spacing statistics, inspired by nuclear spectroscopy, is explored. It is found that a “level-repulsion” phenomenon causes small separations in resonance frequency to be less probable. This can smooth the multimodal response of systems in some important, practical instances.
Ultrasonic Technique for Determining Sound-Velocity Changes in High-Loss Materials
Authors: Asay James R. , Lamberson Donald L. , Guenther Arthur H.
Published: September 2005

A pulse-transmission technique is described that allows the determination of small changes of the acoustic velocities in high-loss materials. The technique employs phase comparison between a transmitted acoustic pulse and the input rf signal to establish a null pattern in the superimposed output. The method has useful applications in situations where it is necessary to detect changes as small as one part in 104 in the velocities. It has been used in ultrasonic investigations employing propagation frequencies higher than 10 MHz and for total attenuation losses as high as 50 dB. Data are presented illustrating the shear velocity as a function of one-dimensional stress in polymethylmethacrylate.
Finite Transform Solution of the Vibrating Beam with Ends Elastically Restrained
Authors: Sharp George R. , Cobble M. H.
Published: September 2005

The beam equation for a uniform-cross-section damped beam elastically restrained against rotation at either end, is solved for the displacement under very general conditions of arbitrary initial and distributed load conditions. The solution is based on the properties of an Hermitian operator.
Envelope Periodicity Detection
Authors: Filip Miroslav
Published: September 2005

A simple nonlinear method for detecting the (fundamental) period of a complex signal is presented being based on the time-envelope shape rather than on the fundamental spectral component; the described detector produces pulses coinciding approximately with the major peaks, or envelope maxima, of the input waveform. Though primarily developed for musicological purposes, the method is not limited specifically to that application. Fundamentals of the theory are given for an arbitrary periodic input function, and some characteristic quantities are derived, such as maximum level difference between second harmonic and fundamental permitted in a two component signal, and minimum level difference needed for a signal of interest superimposed on, or modulated by, an interfering inharmonically related sinusoid. The method is also briefly compared with the zero-crossing detection, and a combination of linear filtering with subsequent envelope periodicity detection is suggested. There are some common points between the operation of the described detector and auditory periodicity-pitch detection.
Noise, You Can Get Used to It
Authors: Webster J. C. , Lepor M.
Published: September 2005

On the basis of several Laboratory studies, a three-band preferred-frequency speech interference level (PSIL.) of 64 dB (based on the octaves centered at 500, 1000, and 2000 Hz), or an A-weighted level (LA) of 71 dB, were proposed as the criteria levels for acceptable voice communications. Two validation surveys were undertaken where ambient noise levels were measured and subjective questionnaires were completed in various ship's spaces. When asked to rate a space along a five-point scale of noisiness (very quiet, quiet, moderately noisy, very noisy, and intolerably noisy), responses tended to center on moderately noisy regardless of objective noise level (PSIL, LA, PNL, LL), confirming the remark, “You get used to it.” When asked to give binary judgment on whether (1) normal speech was affected, (2) work was affected, (3) the space was acceptable, or (4) the environment was loud (and/or noisy, and/or annoying), vice very loud (and/or very noisy, and/or very annoying), the following results were obtained: 80% thought that neither speech nor work was affected (and the space was acceptable) at PSIL of 67 dB (68 dB) or 73 dBA (74 dBA); 20% would accept higher noise levels, but 20% also said levels this high did affect speech and work and made the space “uncomfortable” and the noise “loud.”
Multidimensional Analyses of Circuit Quality Judgments
Authors: McDermott Barbara J.
Published: September 2005

Listeners judged paired comparisons of speech samples transmitted through 22 circuits, each of which introduced a different type of distortion. One group of listeners made preference judgments and another group made similarity judgments. A different multidimensional scaling procedure was applied to each set of data. Both of these procedures represent the stimuli as points in a multidimensional subjective space whose coordinates correspond to the subjective attributes underlying the judgments. The procedure applied to the preference judgments also represents the listeners as vectors in the same subjective space. A listener's vector is located according to the relative weight he assigns to each attribute. The results of these analyses revealed a high degree of correspondence between the three-dimensional solutions representing each type of judgment. The underlying attributes common to the two spaces are interpreted as over-all clarity, a distinction between signal distortion and background distortion, and subjective loudness. Listeners generally agree in their preferences for signals according to over-all clarity. Individual differences in preference for either signal or background distortion account for most of the variability between listeners. Some additional variability is introduced by individual differences in preferred loudness.
Auditory Fatigue during Articulation: Preliminary Observations
Authors: Karlovich Raymond S. , Luterman Barry F.
Published: September 2005

Four subjects were exposed to a high-SL pure-tone fatigue stimulus for 3 min. During exposure, the subjects read a passage aloud during one session and they read the same passage silently during another session. The reading-aloud condition produced consistently greater TTS than the reading-silently condition for the entire 3 min of recovery measured. The data are interpreted in terms of impedance changes in the ear caused by vocal articulation. The results also may be germane to the contradictory literature concerned with the idea of a central factor in auditory fatigue.
Alteration of Afferent, Tone-Evoked Activity of Neurons of the Cochlear Nucleus following Acoustic Stimulation of the Contralateral Ear
Authors: Klinke R. , Boerger G. , Gruber J.
Published: September 2005

Recordings were made by means of stereotaxically, introduced microelectrodes from single neurons of the cochlear nucleus of cats in light barbiturate anesthesia. The ipsilateral ear was acoustically stimulated with aa earphone, and the resulting neuronal activity recorded. Following this, the contralateral ear was simultaneously stimulated, and the activity resulting from this binaural stimulation was measured. The sound pressure in both ears was low enough to preclude suprathreshold acoustic crosstalk. It was shown that the evoked activity of afferent neurons of the cochlear nucleus was reduced by contralateral acoustic stimulation. This inhibition was dependent on the frequency of the contralaterally applied tone.
Cochlear Responses to Bitonal Stimuli and Function of Efferents
Authors: Nieder P. , Nieder I.
Published: September 2005

Differential cochlear electrodes were used to record neural and microphonic responses to bitonal stimuli with low-frequency components. Modulation effects were observed for both types of response. The nature of the effects are interpreted as indicating a peripheral reflex activation of the endings of the crossed olivocochlear bundle. Hybrid electrical chemical mechanisms are proposed for afferent and efferent synapses with hair cells that could form a basis for explanation for these and other results.
On Estimating Aural Harmonics
Authors: Schubert Earl D.
Published: September 2005

Clack's rather ingenious method of estimating the strength of the aurally generated second harmonic, even when it is below audible levels, appears, at first, to offer a procedure for estimating distortion in the auditory system. On closer inspection, however, it appears the method may face the, the same certainties as the method of “best beats”, particularly at frequencies below 1 kHz.
Critical-Angle Reflectivity
Authors: Becker F. L. , Richardson R. L.
Published: September 2005

A method that predicts the observed critical-angle reflection minimum for a liquid-solid interface is presented. Confirmation between calculated and observed values is shown. Shear-wave attenuation was found to be the most significant parameter in determining the depth of the minimum.
Effect of Masking Noise and Pulse Level upon Jitter Detection
Authors: Pollack Irwin
Published: September 2005

Jitter-detection thresholds were determined over a wide range of pulse levels and in the presence of band-limited masking noise. Pulse level modifies jitter thresholds of high pulse frequencies substantially more than that of low and intermediate pulse frequencies. This result is apparently at variance to that predicted by a simple temporal coding underlying auditory jitter. Noise masking is substantially more effective upon relatively low-frequency pulse trains (average interpulse intervals between 2 and 15 msec) than upon higher-frequency pulse trains. Noise masking by low or high noise frequencies is substantially less effective than intermediate noise frequencies, in the vicinity of 1 kHz. This frequency region has also been implicated by other investigators as critical for pulse-frequency discrimination.
Applicability of Amplitude Detection for Measuring the Acoustic Velocity of Confined Gases
Authors: Lewis J. L. , Nierode D. E. , Gaggioli R. A. , Romer I. C.
Published: September 2005

A constant-geometry amplitude-detection method for establishing the acoustic velocity of gases confined in tube, which was suggested earlier, has been employed successfully. This method is also compared with two other suggested amplitude-detection schemes and with the phase-detection scheme of El-Hakeem.
Bistatic Measurements of Acoustic Waves Scattered from a Statistically Rough Known Surface
Authors: Boles W. D. , Fung A. K. , Moore R. K.
Published: September 2005

The complete bistatic scattering pattern of a rough surface with known statistical properties has been obtained for angles of incidence 10° apart from the vertical down to 30° from grazing using 1-MHz acoustic waves in water. Bistatic patterns corresponding to other incident angles within this range can easily be interpolated, thus giving rise to what is believed to be the first such complete set of scattering patterns. The surface was formed from a sheet of mild steel, after which the roughness was sampled along profiles and the surface statistics computed. The roughness was such that the standard deviation was approximately 12 of the incident wavelength and the correlation distance was about 18 wavelengths. The availability of these complete scattering patterns is important to the understanding of the basic scattering process. They allow, for the first time, comparison of the various scattering theories to experimental measurements for other than the plane of incidence. Also pointed out is the transition of the shape of the patterns as the incident angle is changed.
Operational Method for Evaluating the Farfield Radiation from Plane Boundaries
Authors: Maidanik G.
Published: September 2005

An operational method is proposed for evaluating integral equations that are often encountered in the solutions for the farfield radiation from plane boundaries. This method leads to results that are similar to those obtained by the method of steepest descent.
Frequencies of a Hanging Chain
Authors: Huang Tseng , Dareing D. W.
Published: September 2005

The three lowest natural frequencies of transverse vibration are derived for a long hanging chain, the upper end of which is fixed and the lower portion is confined. The method by which the natural frequencies are obtained, is described and mode shapes are given.
Damping of a Rectangular Stress Pulse in a Thin Elastic Rod by External Coulomb Friction
Authors: Wilms E. V.
Published: September 2005

A thin elastic rod is clamped between two rigid plates. The governing partial differential equation is nonlinear owing to the presence of Coulomb friction, which acts at the surfaces of contact. The displacement, velocity, and strain may be solved for when a stress pulse is applied for particular time periods. The stress wave penetrates the rod to a depth which depends on the applied stress and the friction force. When the motion of the rod is entirely damped out by the friction, a residual stress distribution remains.
Spatial Correlation of Ocean Movements and Sound-Velocity Fluctuations
Authors: Beckerle J. C.
Published: September 2005

Long period variations of sound speed at 560 m depth in the Sargasso Sea show correlations with to-and-fro movements of a ship 39 miles away that was keeping station during acoustical measurements. The results suggested that long-crested internal gravity waves may be responsible.
Surface-Coupled Losses in Surface Sound Channel Propagation. II
Authors: Schulkin M.
Published: September 2005

In a previous Letter [M. Schulkin, J. Acoust. Soc. Amer. 44, 1152(L), (1968)], an empirical relation was presented for wind-speed controlled losses in ocean-surface duct propagation. which holds over a wide range of frequencies (1.5 to 25 kHz) and waveheights. This relation is as = 1.64 (fh)1/2 dB limiting ray cycle, where f is the acoustic frequency in kilohertz and h is the mean crest-to-trough waveheight in feet. In this Letter, evidence is presented that this behavior can result front the combined effect of (1) bubble-density distribution with a tail that falls off approximately as R−7.2, where R is the bubble radius; (2) bubble-volume concentration decaying with depth z approximately as a ɜ−1.2 modified by a small dependence on layer depth and hydrostatic pressure; and (3) bubbles that mostly originate from breaking wind waves.
Comment on “On the Detection of a Known Signal in a Non-Gaussian Noise Process” [R. L. Spooner, J. Acoust. Soc. Amer. 44, 141–147 (1968)]
Authors: Helstrom Carl W.
Published: September 2005

Detection of a signal of known shape in white Gaussian noise of unknown spectral density can be accomplished with the same error probabilities as when the spectral density of the noise is known.
Reply to “Comments on ‘On the Detection of a Known Signal in a Non-Gaussian Noise Process’” [C. W. Helstrom, J. Acoust. Soc. Amer. 45, 1055(L) (1969)]
Authors: Spooner Ronald L.
Published: September 2005

Some points in the original paper are reiterated and emphasized.
Nonlinear Design Technique for High-Power Magnetostrictors
Authors: Whymark Roy R.
Published: September 2005

A nonlinear design technique is described for predicting the high power sound output and efficiency of a magnetostrictor. The method is based upon the assumption that the magnetic permeability of the active material is strain invariant. An experimental perturbation technique, and an alternative method involving the measured strain field, are used to determine the complex transformation ratio of a Ni-Co ferrite at various values of the field, induction and strain. The results are plotted as sets of nonlinear design characteristics. The transformation ratio is used in conjunction with the Van Dyke equivalent circuit to predict the nonlinear sound output and efficiency of a magnetostrictor formed from the ferrite. The magnetostrictor is a slotted bar transducer resonating at 24.8 kHZ in the fundamental-length mode. A novel feature of the experiments is the use of a piezoelectric transducer (dummy load) to backdrive the magnetostrictor to vary the strain independently. The magnetostrictor sound output is predicted to an accuracy greater than 15% at induction swings as large as one-third of saturation. The shape of a skewed resonance curve is successfully predicted indicating that nonlinearity is a cause of the resonance curve distortion.
Vowel Amplitude Modulations in Patients with Laryngeal Diseases
Authors: Koike Yasuo
Published: September 2005

The amplitudes of sustained vowels were measured at the dominant amplitude peak of each fundamental period of the acoustic signal picked up by a microphone coupled to the pretracheal skin. Serial correlation coefficients were computed and correlograms were made for each sample to investigate the periodicity in the modulation of the amplitude. Three groups of subjects were studied: 15 cases with laryngeal neoplasms, six cases with unilateral laryngeal paralysis, and 20 normal subjects as a control group. In each group of subjects, a high correlation was often found between the consecutive dominant amplitude peaks. The correlograms for patients with laryngeal neoplasms often displayed strong periodicities with periods of three to 12 fundamental periods, while for the paralysis cases no evidence of periodic modulations in the same range was found. The results seem to indicate that amplitude information may be useful for the development of an objective measure to evaluate laryngeal dysfunction and to detect some pathologies in the larynx.
Measurement of Ultrasonic Attenuation and Phase Shift in the Presence of Noise
Authors: McSkimin H. J. , Pateman T. B.
Published: September 2005

For measuring attenuation by the ultrasonic pulse-echo method, a selected echo—obtained by pulse modulating a very stable CW carrier—is directly heterodyned to produce a video signal with a beat frequency of a few hertz. This signal is then sampled at the repetition rate and filtered to give a low-frequency CW output with a signal-to-noise ratio some 30 dB greater than for the selected echo. Phase shift at the wave frequency produces an equal phase shift at the beat frequency, and can be measured with a phase meter. The detection system is sensitive for weak signals and is linear. Readout of amplitude and phase can be made on standard recorders. In a second arrangement, the selected echo is added algebraically to a reference signal having a slightly different frequency. with the CW beat frequency resulting processed as before. Because of the good phase stability, this method can be used at frequencies in the high megahertz range.
Nearly Spherical Acoustic Lenses
Authors: Feldman Henry R.
Published: September 2005

A method of realizing an underwater acoustic lens that forms an image with no aberration of an object lying at infinity in a given direction is described. The lens is nearly spherically symmetric so that the aberrations for objects off this axis are small. It makes use of two existing materials of uniform acoustic velocity as the lens media. The equations governing the structure of such a lens and some results of their solution are given.
Acoustic Pulses Scattered by a Rigid Sphere Immersed in a Fluid
Authors: Rudgers Anthony J.
Published: September 2005

The scattered field, produced when a plane-wave pressure pulse is incident upon an ideally rigid sphere, is expressed in the terms of classical scattering theory. Using an incident pulse of known spectral content, the resultant scattered pulse is determined, at a number of field points, with a computer. The time-varying forms of the scattered pulses, thus obtained using the completely rigorous classical theory, display characteristics that may be interpreted in terms of circumferential or creeping waves propagating along the periphery of the sphere. The scattered pulse may be conceived as the superposition of a specularly reflected pulse, with a form similar to the incident pulse, and attenuating pulses that travel along the periphery of the sphere from the boundary of the geometrical shadow to the observation point.
Continuous and Discrete Inverse-Scattering Problems in a Stratified Elastic Medium. I. Plane Waves at Normal Incidence
Authors: Ware Jerry A. , Aki Kehti
Published: September 2005

This paper investigates the problem of obtaining an analytic solution and practical computational procedures for recovering the properties of an unknown elastic medium from waves that have been reflected by or transmitted through the medium. The medium consists of two homogeneous half-spaces in contact with a heterogeneous region. The analytic solution is obtained by transforming the equation of motion for the propagation of plane waves at normal incidence in a stratified elastic medium into a one-dimensional Schrödinger equation for which the inverse-scattering problem has already been solved. The practical computational procedures are obtained by solving the corresponding discrete inverse-scattering problem resulting from approximating the heterogeneous region with a sequence of homogeneous layers such that the travel time through each layer is the same. In both the continuous and discrete inverse scattering problems, the impedance of the medium as a function of travel time is recovered from the impulse response of the medium. A discrete analogy of the continuous solution is also developed. Similar results are obtained for a stratified elastic half space bounded by a free surface.
Vibrational and Stability Characteristics of Circular Membranes Subjected to Gyroscopically Induced Inertia Loads
Authors: Kessel P. G. , Schlack A. L.
Published: September 2005

An analytical study is presented for the response of circular membranes subjected to a simultaneous state of constant spin and precessional motions at a fixed angle of nutation. The equations of motion are formulated for a random orientation of the membrane relative to the spin axis, from which a Hill equation may be obtained for the amplitude coefficients of the motion. A considerable reduction in mathematical difficulties occurs for two special, but frequently occurring, orientations of the membranes: (a) membranes perpendicular to the spin axis and (b) membranes parallel to the spin axis. These equations of motion contain distributed harmonic inertial forces that excite certain modes and whose amplitude and frequency depend on the spin and precessional motions. For Case (a), the natural frequencies of the membrane are reduced by the precessional angular velocity and angle of nutation, while for Case (b), it is necessary to solve a Mathieu equation with the associated stability characteristics for the amplitude coefficients of the motion.
The Evolution of Human Hearing
Authors: Masterton Bruce , Heffner Henry , Ravizza Richard
Published: September 2005

Five descriptive parameters of hearing—high-frequency and low-frequency sensitivity, lowest threshold. best frequency, and area of the audible field—are compared statistically, first, among mammals in general, and then, among seven animals selected to approximate a phylogenetic sequence of man's ancestors. Three potentially explanatory parameters body size, maximum binaural time disparity, and recency of common ancestry with man—are also explicitly included in the analysis. The results show that: high-frequency hearing (above 32 kHz) is a characteristic unique to mammals, and, among members of this class, one which is commonplace and primitive. Being highly correlated with functionally close-set ears, it is probably the result of selective pressure for accurate sound localization. Low-frequency hearing improved markedly in mankind's line of descent, but the kind and degree of improvement are not unique among mammalian lineages. High sensitivity developed in the earliest stages of man's lineage and has remained relatively unchanged since the simian level. The frequency of the lowest threshold has declined in Man's lineage—the greatest drop probably occurring during the Eocene. The total area of the audible field increased until the Eocene and has decreased since then.
Comments on the Differential-Electrode Technique
Authors: Dallos Petter
Published: September 2005

The theory of differential electrode technique is briefly reviewed, especially as it pertains to the recording of remote CM. Median isopotential curves for the first- and third-turn electrode placements are given for 18 guinea pigs. The differences and similarities between differential and single intracochlear as well as round-window electrodes are discussed. Special attention is paid to the CM that is recordable from the third turn at high frequencies with differential electrodes. On the basis of dc polarization experiments, it is concluded that this high-frequency CM is not a local response. Some performance criteria for the evaluation of the adequacy of differential electrodes are developed.
Computers in Acoustics: Symbiosis of an Old Science and a New Tool
Authors: Schroeder M. R.
Published: September 2005

This paper reviews the impact of digital computers on acoustics research since their introduction about a decade ago. The influential rôle that computers have attained in acoustics has resulted from their imaginative use as research tools for analysis, control of experiments, modeling, and simulation—rather than from straightforward calculating applications. Illustrative examples discussed in this paper include modeling of the human speech-production process and the mechanical and neural aspects of hearing, speech analysis and synthesis, automatic speech and speaker recognition, generation of musical sounds and psychoacoustic test stimuli, study of the perceptual correlates of acoustic stimuli, multidimensional scaling, simulation of ray propagation in the deep ocean and in reverberant enclosures, acoustic measurements in concert halls, digital modeling of auditorium designs. Monte Carlo simulation of wave propagation in multimode transmission media, and acoustic image reconstruction of unknown objects by “inverse diffraction” on the computer.
Response of Uniform Beams to Homogeneous, Random Pressure Fields
Authors: Crocker Malcolm J. , White Robert W.
Published: September 2005

A study of the expression for the response power spectral density of linear systems to random pressures shows that the response problem essentially reduces to evaluating the joint acceptance of the system with the pressure field. A novel method using a coordinate transformation is presented. This method enables one to determine very simply the joint acceptance of a beam that has arbitrary end constraints with a pressure field that has a spatial-pressure correlation function that is easily described mathematically. The joint acceptance of a simply supported beam with a reverberant acoustic field as a function of mode number and nondimensionalized frequency parameter (beam length/acoustic wavelength) has been computed for the first 16 modes. An engineering approximation for the joint acceptance of a simply supported flat plate with a reverberant acoustic field is obtained from the beam results. The method is also used to determine very simply beam and flat-plate joint acceptance with a turbulent-boundary-layer pressure field and with an acoustic plane wave.
Analysis of an Integral Equation Arising from the Investigation of Vertical Directivity of Sea Noise
Authors: Anderson M. W. , Tittle R. L.
Published: September 2005

An integral equation relates the single frequency vertical distribution of ambient ocean noise to the measured array output when the noise power at the array arises from the superposition of uncorrelated plane waves. This integral equation has an infinite number of solutions. However, from the physical viewpoint, there is one solution, referred to as the “principal solution,” which is the most plausible representation of the true noise field. The “principal solution,” is precisely defined, and then classical Hilbert space theory is used to determine this solution from a finite number of array measurements. The number of measurements required depends only on the interelement spacings of the array. In selecting this finite number of steering angles to make the array measurements, any choice that yields independent samples for a certain finite sequence of trigometric functions is sufficient. Not surprisingly, these measurements contain all the information available in the observed distribution, the array output, and an explicit expression is given for the observed distribution. Special array configurations are exhibited for which the “principal solution” is a partial sum in the Fourier expansion of the true noise field.
Acoustic Propagation in a Channel with Range-Dependent Sound Speed
Authors: Warfield J. T. , Jacobson M. J.
Published: September 2005

Ray geometry, travel time, and spreading loss are studied in a horizontal channel in which sound speed depends on range. Formulas valid for a general sound-speed function are developed, and then specialized to the class of linear functions. Rays reaching a fixed receiving point are then isolated and studied. Properties of corresponding arrivals at a fixed receiving point are compared for the cases of a range gradient channel and a constant sound speed channel. Differences in initial inclination angle, travel time, and spreading loss are found and bounds on these differences are obtained. For a CW source, the total field at a receiving point is then determined. It is demonstrated that the introduction of even a weak range gradient causes major changes in the amplitude and phase, including the occurrence of interference nulls accompanied by a sharp offset in phase. Finally, approximate formulas are developed for the phase shift of the total field, caused by a constant range gradient, relative to the phase in isospeed channels.
Stability of a Plane Shock Wave in Free Space and in the Presence of Rigid or Interfacial Boundaries
Authors: Kovitz A. A. , Briscoe M. G.
Published: September 2005

The attenuation of small perturbations in the shape of a plane shock wave is studied for three distinct cases — (A): when a rigid boundary (wall) parallel to the plane of the unperturbed shock is present; (B): when a perturbed interface between two different media exists in the wake of the shock; (C): when there is no boundary (free space). The solution is obtained by extension of a method due to Zaidel. It is shown that for weak shock waves the attenuation becomes very weakly dependent on the nature of the boundary. Numerical results are obtained for shock waves with initially sinusoidal perturbations and initially Gaussian perturbations. For initially sinusoidal perturbations, Case (A) shows the slowest damping (highest peak-to-peak ampli-after some time) whereas Case (B) exhibits the most rapid damping. On the other hand, an initially Gaussian perturbation shows the slowest damping (magnitude of maximum disturbance) for Case (B) and the fastest damping for Case (A). Furthermore, the Gaussian perturbation damps monatonically with time whereas the sinusoidal perturbation damps approximately in the manner of a zero-order Bessel function — i.e., in an oscillating fashion.
On the Utilization of Ferrofluids for Transducer Applications
Authors: Cary Boyd B. , Fenlon Francis H.
Published: September 2005

An assessment of the suitability of ferrofluids for acoustic transducer and receiver applications has led to the following conclusions: First, the magnetostrictive mode of operation is not efficient enough to offer an alternative to conventional solid materials in use. Second, the piston motion of the ferrofluid induced by an applied field gradient does provide a real alternative to conventional magnetostrictive transducers. For an applied static field of 4000 Oe and a field gradient of 1000 Oe/cm, it is possible to achieve an overall efficiency that is greater than that for the ferromagnetic solids. Third, ferrofluids appear to provide a desirable alternative for pressure-sensing applications in severe environments (e.g., detonations) where piezoelectric and pyroelectric materials suffer fatigue and failure. Fourth, ferrofluids offer the prospect of obtaining broadband frequency response when radiating or receiving in liquid media.
On the Motor Control of Coarticulation in CVC Monosyllables
Authors: MacNeilage Peter F. , DeClerk Joseph L.
Published: September 2005

This study was an attempt to account for the motor control of speech production by a model in which discrete phoneme commands are modified according to phonological context by three motor system mechanisms. The model was evaluated by consideration of high-speed cinelluorograms, and electromyograms from nine articulatory locations, recorded while one subject produced 36 consonant-vowel consonant monosyllables. The syllables were formed by every possible combination of initial and final consonants /b/, /d/, and /g/, and the syllable nuclei /i/, /u/, /æ/, and /ɔ/. In every possible case, some aspect of the motor control of a later syllable component was influenced by the identity of the previous one. Except in a few cases, some aspect of the motor control of an earlier syllable component was influenced by the identity of the following one. These latter influences were of greater magnitude and complexity, and more reflected in movement, in the initial consonant than in the vowel. Some of the context effects on phonemes could be accounted for by the three motor system mechanisms but a number could not. The results suggested that syllabic factors are influential in the “premotor” command structure of speech, and, in particular, that the CV form is a relatively cohesive component of CVC syllables.
Acoustic Pulse Distortion in Thermally Relaxing Liquids
Authors: Barakat Richard , Baumann Elizabeth
Published: September 2005

Pulse propagation in a thermally relaxing liquid is studied theoretically. First, Whitham's theory of wave propagation in systems governed by more than one velocity is utilized to obtain qualitative information. Second, Laplace transform solutions are obtained for particle velocity and pressure for rectangular and Gaussian pulses as well as semi-infinite sine wave. Detailed numerical calculations are included.
Stress Waves in Nonhomogeneous Elastic Rods
Authors: Reddy Damoder P.
Published: September 2005

Longitudinal wave propagation in a nonhomogeneous semi-infinite elastic rod is considered. The non-homogeneity may be due to the axial variation of Young's modulus or of density or of both. An arbitrary time-dependent stress is applied at the end, x = 0, of the rod. The normal stress as a function of position and time is obtained using the theory of the propagating surfaces of discontinuity by expanding the stress as a Taylor series about the time of arrival of the wavefront. The coefficients of the Taylor expansion are obtained as solutions of linear ordinary differential equations with variable coefficients. For the case where the Young's modulus E(x) varies as (1 + ax)2a, it is shown that the stress at the wavefront varies as (1 + ax)α, where a and α are constants.
Masking of Tones Before, During, and After Brief Silent Periods in Noise
Authors: Elliott Lois L.
Published: September 2005

Masking of a short tone (located inside or on the skirts of a narrow noise band or masked by wide-band noise) demonstrates interactions between sets of onset and offset effects and their relation to temporal development of auditory frequency contours.
From Gap to Jitter Discrimination
Authors: Pollack Irwin
Published: September 2005

Jitter and asynchrony discrimination are considered as special cases of the discrimination of temporal irregularities within auditory pulse trains. Variation in the number of nonjittered intervals permits spanning the range between the discrimination of a single temporal discontinuity (the asynchrony or gap test) and the discrimination of temporal modification to each interval (the jitter test). At high pulse frequencies, the discrimination of temporal irregularities is determined primarily by the number of jittered intervals. Jitter thresholds are approximately inversely proportional with the fourth root of the number of jittered intervals.
Comments on “Natural Frequencies and Modes of Skew Membranes” [S. Durvasula, J. Acoust. Soc. Amer. 44, 1636–1646 (1968)]
Authors: Laura P. A.
Published: September 2005

Additional pertinent references are pointed out in this Letter. Some of the results obtained by Durvasula are compared with values recently published in the open literature.
Remarks on “Absolute Sound Speed Measurements in Water” [A. Carnevale et al., J. Acoust. Soc. Amer. 44, 1098–1102 (1968)]
Authors: Del Grosso Vincent A.
Published: September 2005

Recently published pure-water round-speed data are compared to earlier Naval Research Laboratory data with a caveat to their application to existing sea-water sound-speed tables.
Supersonic Flow through Statistically Roughened Wall Ducts
Authors: Ortloff C. R. , Jones J. P.
Published: September 2005

The mean-square static-pressure distribution induced by statistically roughened duct walls on a supersonic stream passing through its interior is analyzed in this Letter. It is found that the maximum value of the mean-square static pressure occurs on the duct walls and that this value is inversely proportional to (M∞2 − 1)12.
Definition of a Linear Medium for One-Dimensional Longitudinal Motion
Authors: Thurston R. N.
Published: September 2005

If the longitudinal stress is linear in the extension, then the exact equation of one-dimensional motion, in a material (“Lagrangian”) description, is the linear wave equation. This result provides a rational basis for defining a hypothetical linear solid or fluid medium. Such a medium has nonzero higher-order elastic constants. The expected consequences of linearity of the equation of motion are noted. These include distortionless propagation of finite-amplitude waves, the absence of interaction of waves with each other, stress independence of the travel time or resonance frequency, and the absence of acoustic radiation pressure. The idea of distortionless propagation of traveling waves is treated in detail in both the material and spatial descriptions, and it is emphasized that distortion of longitudinal mechanical waves is not a necessary consequence of kinematics. In a spatial (“Eulerian”) description, the linear medium has a nonlinear equation of motion, but this nonlinear equation has distortionless traveling wave solutions of the form f(t±x/V). Some examples are given of three dimensional constitutive equations that yield the described linear behavior in one dimension. The equation of state of the hypothetical linear medium is highly unrealistic, but is of interest because nonlinear phenomena can be ascribed to departures from it. [An appendix discusses the momentum in a plane progressive wave. Consistent with the absence of radiation pressure, the instantaneous momentum in a plane progressive wave in a semi-infinite linear medium that was initially at rest is simply proportional to the displacement of the face. The still persistent idea that every wave train of intensity J propagated with speed W has momentum J/W2 per unit volume is shown to be an unwarranted generalization. Such a wave train can be set up in the semi-infinite linear medium if the prescribed velocity at the face is the sum of a sinusoidal part and a properly chosen constant term. A special equation of state is found for which power and momentum are related as above in the initially formed simple (purely progressive) wave resulting from a sinusoidal velocity of the face that starts at time zero.]
High-Sensitivity Logarithmic Recorder of Ultrasonic Attenuation
Authors: Anderson George P. , Chick Bruce B.
Published: September 2005

A sensitive instrument for measuring and recording the amplitude ratio of two video pulses from an ultrasonic echo train is described. The instrument has been designed primarily for ultrasonic attenuation studies using pulse-echo techniques but may also be used for through transmission, and/or single echo measurements. The unit selects two pulses from the echo train, peak detects them, and measures their amplitude difference in a differential logarithmic voltmeter calibrated in decibels. The resultant output may also be applied to an external recorder. Provisions for zero suppression are included to permit the use of the most sensitive meter range (0.01-dB resolution) when small changes in attenuation are to be measured against a large background attenuation. Automatic gain control, operating from the first selected echo, has been incorporated in order to maintain operation in the linear portion of the receiver dynamic range.
Ultrasonic Attenuation in ZnO
Authors: Claiborne L. T. , Hemphill R. B. , Einspruch N. G.
Published: September 2005

Results are presented for the temperature and frequency dependence of the attenuation of two piezoelectrically active ultrasonic waves in ZnO: (1) compressional waves propagated along the c axis, and (2) shear waves propagated normal to the c axis and polarized along the c axis. Measurements of the phonon phonon attenuation were made over the frequency range 60 MHz to 3.97 GHz and the temperature range 4.2° to 300°K. The frequency dependence at 40°K is of the 1.0 and 0.7 power for the shear and compressional modes, respectively; at 300°K. the frequency dependence is ∼1.6 for both modes. The temperature dependence ranges from at least T4 at low temperatures to essentially T0; at 300°K for the shear mode; the temperature dependence for compressional waves at frequencies below 2.0 GHz does not appear to reach a T4 dependence for temperatures down to ∼20°K.
Viscous Drag on Dislocations in LiF and NaCl
Authors: Fanti F. , Holder J. , Granato A. V.
Published: September 2005

The damping constant B for the viscous drag on dislocations was measured for NaCl and LiF. A novel technique was employed to improve the accuracy of the measurements, and many specimens were used to check the reproducibility of the results. Measurements of both the attenuation and velocity changes resulting from dislocation pinning by cobalt-60 gamma irradiation were made. The values obtained are B=2.4 and 1.6×10−4 in cgs units for LiF and NaCl, respectively. These values compare favorably both with theoretical estimates and with values determined from direct measurements at higher stresses by etch-pit techniques. From the ultrasonic measurements, it is deduced that the viscous drag force is linear in the velocity and that relativistic velocities cannot be achieved in LiF and NaCl at room temperature at the yield stress of soft crystals. The results found demonstrate that relatively precise values for the dislocation drag can be obtained ultrasonically, that values for the dislocation densities in specimens can be determined from nondestructive ultrasonic measurements, and that the ultrasonically determined dislocation velocities are directly related to those determined by etch-pit measurements at higher stresses.
Ultrasonic Attenuation at Microwave Frequencies in Aluminum Oxide and Ruby
Authors: McBride S. L. , Maris H. J. , Truell R.
Published: September 2005

The temperature dependence of the attenuation of longitudinal waves propagating along the c axis of aluminum oxide and ruby has been measured at frequencies of 0.4 GHz, 1.23 GHz, 2.32 GHz, and 2.94 GHz in the temperature range 20° to 100°K. The ruby samples contained 0.025, 0.08, 0.2, and 0.9% chromium by weight. respectively. In undoped aluminum oxide, in the temperature range 40° to 50°K, the attenuation is frequency independent and varies as T9. At higher temperatures, the attenuation is frequency dependent and varies less rapidly with temperature. The effect of chromium impurities is to increase the attenuation at low temperatures and to decrease it at high temperatures. The measurements are interpreted in terms of collisions between the low-energy phonons, constituting the sound wave, and the thermal phonons. Evidence is presented that the main contribution to the attenuation is from collisions of the sound-wave phonons with transverse thermal phonons. The dependence of the attenuation on temperature, frequency, and chromium concentration found experimentally is in good agreement with that theoretically predicted for this type of collision mechanism.
Reaction Paths and Activation Energies for Dislocation Unpinning
Authors: Teutonico L. J. , Lücke K. , Heuser F. W. , Granato A. V.
Published: September 2005

For the purpose of developing a theory of thermally assisted amplitude dependent damping, the equilibrium configurations and activation energies of pinned dislocations are calculated. The model is of a dislocation pinned by an arbitrary number of equidistant pinning points of equal strength. New features not found for a simple double loop are obtained, but most of the important physical processes for the general case are already obtained for a triple loop. The more important of these features are: (i) There are intermediate energy minima between the pinned state and the broken-away state; (ii) for a given stress more than one reaction path between the pinned state and the broken-away state may exist; (iii) multiple-pin breakaway can occur by a single activation; (iv) thermal breakaway can occur at smaller loop lengths or at smaller stresses than is the case for a single pin. A discussion is given of the possible reaction paths of the dislocation in the general (N-loop) problem. It is shown which equilibrium configurations lie along the lowest reaction path. For the case of long loops, expressions are obtained for the activation energies for both breakaway and repinning along this reaction path.
Frequency Modulation and the Difference Limen for Frequency
Authors: Feth Lawrence L. , Wolf Richard V. , Bilger Robert C.
Published: September 2005

A system for tracking difference limen for frequency (ΔF) is described. The system uses a function generator to frequency modulate a BFO. The amplitude of the modulating voltage is controlled by a recording attenuator. Intuitive spectral analysis of the modulated tone proves to be insufficient and correction factors are given to allow determination of ΔF from de calibration data. When real rather than intuitive spectrum is used for calibration of the system, ΔF does not increase with modulation rate from 1 to 16 Hz. Consideration of the spectra produced by various waveforms indicates that the discrepancy between de calibration and spectral width is minimal for a trapezoidal modulating waveform.
Frequency Selectivity During Amplitude Discrimination of Signals in Noise
Authors: Greenberg Gordon Z.
Published: September 2005

A signal was presented in each observation interval of two-alternative, temporal-forced-choice trials, and 12 observers each selected the louder of the two signals. The observers were informed that the signals of each trial would be of 1000 Hz and either 2 or 4 dB different in amplitude. Some 70% of the trials did in fact present such pairs of 1000-Hz signals. Surreptitiously, on infrequent and randomly determined trials, one of the signals presented, a probe signal, was of a frequency other than 1000 Hz. The probe-signal method thus applied to the nominal amplitude discrimination task produced results clearly demonstrating differential performance as a function of the signal frequency, for 10 of the 12 observers. For those 10 observers, the relation between performance and signal frequency appears asymmetrical about 1000 Hz.