bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Per- and Poststimulatory Fatigue in Pitch Perception
Authors: Skinner Paul H. , Antinoro Frank
Published: September 2005

While changes and recovery in loudness sensitivity have been studied over time by many investigators, changes in the perception of pitch have been observed only at discrete time intervals; and changes during these measurement intervals can only be attributed to normal variation or error. No graphic display of an observer's pitch judgments over time has been available for inspection under the usual psychophysical procedures. The method used in this study permitted the continuous recording of the subject's perception of pitch over time under perstimulatory and poststimulatory conditions. In Expt. 1, pitch perception was studied under per and poststimulatory fatigue with 60- and 90-dB sensation-level signals at 250, 500, 1500, 2500, and 4500 Hz. In Expt. 2, pitch perception was examined after stimulation of 100 dB SL for 10 min at the above frequencies. In Expt. 3, a fatiguing stimulus at 750 Hz was presented for 2 min at 120 dB SPL. Pitch perception was then studied at adjacent frequencies: 550, 650, 850, 950 Hz. No systematic change in pitch perception was observed under any of the experimental conditions. Since these findings conflict with similar studies, special attention was given to procedural and theoretical reasons for the discrepancies.
Stochastic Approach to the Noise in Magnetic Tape
Authors: Yu F. T. S.
Published: September 2005

The noise in magnetic tape is approached by viewing it as a stochastic process. A conditional probability distribution of the unmagnetized particles (as well as the magnetized particles), defined under the effective recording gapwidth, is derived. The corresponding mean and variance are also calculated. The general application to a typical magnetic tape is given. The signal-to-noise ratio and the dynamic range of the tape are defined. A procedure for determining the information capacity of a given magnetic tape is also discussed. It is found that the information capacity of a multichannel tape should increase compared with that of a single channel; however, this advantage is somewhat reduced by the physical separation of the channels. Finally, a conclusion is drawn, that the noise in the magnetic tape is a discrete, nonadditive, nonstationary random process, which is in contrast with the usual assumption that it is an additive stationary Gaussian process.
Calibration of Standard Condenser Microphones: Coupler versus Electrostatic Actuator
Authors: Koidan Walter
Published: September 2005

The response frequency characteristics of a “1-in.” condenser microphone measured by an electrostatic actuator is likely to be significantly different from that measured by reciprocity in an acoustic coupler because of the radiation impedance of the microphone diaphragm with the actuator in place. It cannot be assumed, except at low frequencies, that the radiation impedance is negligible and that the actuator calibration yields the pressure response. Such an assumption also is apt to lead to errors in the determination of the free field response when calculated with the aid of the free-field correction.
Quadrature Sampling of High-Frequency Waveforms
Authors: Grace O. D. , Piti S. P.
Published: September 2005

The quadrature sampling technique, which obtains samples of the quadrature components of a high-frequency band-limited waveform by direct sampling of the waveform, is shown to lead to an exact interpolation formula. In this formula, the quadrature components of the signal are represented explicitly by low-pass interpolation formulas that greatly facilitate digital processing of the signal when compared to commonly used sampling formulas. For example, the amplitude modulation (envelope) and phase modulation of a signal can be computed directly from these quadrature components.
Fast Beam-Forming Algorithm
Authors: Williams Jack R.
Published: September 2005

Digital beam forming in the frequency domain is suggested based on phase shifting by complex multipliers of Fourier series sinusoids. An analogy is then shown between the formation of sequential beams in a line array and the fast Fourier transform, which allows a substantial reduction in the number of multiplications required to form the sweeping beam.
Impulse Duration and Temporary Threshold Shift
Authors: Loeb Michel , Fletcher John L.
Published: September 2005

Subjects were exposed, on different test days, to 166-dB (peak normal-incidence) impulses 34, 58, 72, or 96 μsec in duration spaced 1 sec apart. For each pulse duration, the subjects were first exposed to one pulse, then the number of pulses was doubled on successive days until the temporary threshold shift (TTS) following exposure exceeded 30 dB. Intercorrelations of numbers of impulses required to reach criterion TTS at each duration were obtained; they were highest when durations were similar. At the largest pulse duration, a median of only four impulses was required to achieve criterion, some individuals exceeded criterion at one impulse, while others required hundreds. No evidence was seen of a 4-kHz notch; maximum shift was at high frequencies (10–15 kHz) and relatively independent of impulse duration. There is reason to believe that if one exceeds allowable TTS in the speech-range frequencies with this kind of impulse noise, there is a chance of producing permanent high-frequency loss.
Primate Vocalizations and Human Linguistic Ability
Authors: Lieberman Philip
Published: September 2005

Some representative vocalizations of captive rhesus monkey, chimpanzee, and gorilla were recorded and analyzed by means of sound spectrograms and oscillograms. It was found that these animals' vocal mechanisms do not appear capable of producing human speech. The laryngeal output was breathy and irregular. A uniform cross section, schwalike configuration appeared to underlie all the vocalizations. These animals did not modify the shape of their supralaryngeal vocal tracts by means of tongue maneuvers during a vocalization. Formant transitions occurred in some vocalizations, but they appeared to have been generated by means of laryngeal and possibly velar or lip movements. The nonhuman primates lack a pharyngeal region like man's, where the cross-sectional area continually changes during speech. The data suggest that speech cannot be viewed as an overlaid function that makes use of a vocal tract that has evolved solely for respiratory and deglutitious purposes; the skeletal evidence of human evolution shows a series of changes from the primate vocal tract that may have been, in part, for the purpose of generating speech. Articulate speech may not have been fully developed in some of man's ancestors. The study of the peripheral speech-production apparatus of a fossil thus may be useful in the assessment of its phylogenetic grade.
Critical Angles Associated with the Reflection-Refraction of Elastic Waves at an Interface
Authors: McNiven H. D. , Mengi Y.
Published: September 2005

Goodier and Bishop established that there is a “critical” incident angle that a train of Sv waves makes with the traction-free surface of an elastic half-space and that as the incident angle passes through this critical value from above, the reflected P wave passes through grazing incidence and emerges as a surface wave. In this paper, study is made of the fate of a train of Sv waves on striking the plane interface between two elastic materials. It is found that there are five critical angles associated with such a wave and the emerging wave which passes through grazing incidence corresponding to each angle is transformed into a surface wave. The wave is like a Rayleigh wave in that the magnitude of motions accompanying it decay exponentially away from the interface, particle motions have an elliptical orbit, and the wave travels with a constant phase velocity. The wave is unlike a Rayleigh wave in that its velocity is not the velocity of Rayleigh waves and, in fact, depends on the incident angle. The method which is used to establish the nature of the waves that emerge probably is as important as the results. The method, which is graphical, is based on the notion of slowness surfaces developed by Synge using the solution of the field equations of elasticity. The method itself is the result of a systematic exploitation of an idea introduced by Musgrave.
Normal-Mode Solutions for the Dynamic Response of Structural Members with Time-Dependent In-Span Conditions
Authors: Pilkey W. D.
Published: September 2005

This paper deals with the inclusion of in span conditions, such as time-dependent displacements, in normal-mode solutions for the dynamic response of structural members. Both displacement and acceleration normal-mode approaches are discussed.
Stochastic Born Series for Sound Propagation in Random Media. I. The Expectation of the Field
Authors: Bugnolo Dimitri S.
Published: September 2005

The propagation of acoustic waves in stochastic media is a problem of fundamental importance in the study of the stability of such media. This paper represents a first attempt to construct a full Born series for the expectation of the potential function. Keller's second-order results are obtained as a special case. An example, with no particular application in mind other than to establish a bound on the region of absolute convergence, is used to illustrate the theory. Higher-order moments of the solution, as well as other examples, are best left as the subjects of other papers.
Calculation of Horizontal Ranges and Sound Intensities by Use of Numerical Integration Techniques
Authors: Miller Max K.
Published: September 2005

The purpose of this paper is to point out some advantages in the calculation of horizontal ranges, travel times, and sound intensities by means of numerical techniques that seem to have been overlooked in the past. The integrals for horizontal range, travel time, and sound intensity are evaluated directly for reflected rays, while appropriate modifications are made for refracted rays. This approach to the problem of calculating sound intensities is discussed, and two numerical examples are given that point out the accuracy and advantages of the method.
Bottom Backscattering near Grazing Incidence in Shallow Water
Authors: Wong How-Kin , Chesterman W. D.
Published: September 2005

Data obtained from measurements of the backscattering of 48-kc sound from the sea bottom at 12 locations in the inshore waters of Hong Kong show that the bottom backscattering strength increases by some 25 dB as the textural grade changes from clay through silt and sand to rock. For the range of grazing angles from 0.5° to 6° the backscattering strength is constant. The experimental results also show that a knowledge of the percentage of sand and the effective bottom roughness is particularly useful for the estimation of bottom reverberation levels. The attenuation coefficient of 48-kc/sec sound at 20°C in the subtropical waters of Hong Kong is found to range from 9.4 to 12.8 dB/kyd, depending upon local conditions. The average value obtained is 11.2 dB/kyd.
Acoustic Imaging in a Turbid Underwater Environment
Authors: Green P. S. , Bellin J. L. S. , Knollman G. C.
Published: September 2005

Theoretical and experimental studies are presented concerning underwater acoustic imaging in general with particular emphasis on acoustic visualization in highly turbid water. A derivation is made of the relationship between image-plane and object plane pressure distributions in an acoustic imaging system embodying a single spherical lens, and the theory is applied to both diffusely and specularly reflecting objects. The attenuation and scattering coefficients of sea water containing various ocean-bottom sediment suspensions are determined; it is found that for an acoustic frequency of 2.5 MHz (employed in the experimental work), several hundred parts per million suspended sediment concentration effects an acoustic attenuation twice that of sea water alone. A method for underwater acoustic image conversion is described which involves a sampled matrix of piezoelectric elements. Two novel switching techniques are discussed for sequentially connecting with high selectivity the various sensor elements to the output terminal. Typical shadow, focused shadow, and backscatter acoustic images are displayed that were obtained with a 100-element collinear version of the image-conversion system. The collinear array has a sensitivity threshold of better than 10−10 W/cm2 and a resolution on the order of 1.5 mm. Some of the images which are presented were taken at a range of approximately 4 m in water containing several hundred parts per million of suspended diatomaceous earth of micron particle size.
Visualization of Standing Acoustic Waves Using Time-Averaged Optical Holographic Interferometry
Authors: Salant R. F. , Alwang W. G. , Cavanaugh L. A. , Sammartino E.
Published: September 2005

Time-averaged optical holographic interferograms of standing acoustic waves (longitudinal modes), in a duct of square cross section, have been obtained. The three-dimensional fringe patterns clearly indicate the locations of the antinodal planes.
Transverse Vibrations of Tapered Cantilever Beams with End Support
Authors: Mabie H. H. , Rogers C. B.
Published: September 2005

Free vibrations of nonuniform cantilever beams with an end support have been investigated, using the equations of Bernoulli-Euler. Two configurations of interest are treated: (a) constant width and linearly variable thickness, and (b) constant thickness and linearly variable width. Charts have been plotted for each case from which the fundamental frequency, the second harmonic, and the third harmonic can be easily determined for various taper ratios. The Tables from which these charts were plotted are also included.
Measurements of the Particle Velocity and Pressure of the Ambient Noise in a Shallow Bay
Authors: Banner Arnold
Published: September 2005

Sound perception by marine animals may be affected by the particle velocity on the pressure of ambient noise. Levels of ambient noise measured with a velocity hydrophone in very shallow water were found to be considerably above the associated pressure levels, particularly at low frequencies. This difference is probably due to nearfield components of ambient particle motion and may be important in acoustic signal detection by mechanoreceptor organs.
Reply to “Comments on ‘Focusing Properties of Cylindrical Liquid-Filled Acoustic Lenses with Large Diameter-to-Wavelength Rations’” [Edward S. Eby, Maier O. Fein, and Peter J. Burt, J. Acoust. Soc. Amer. 44, 1744–1745(L) (1968)]
Authors: Folds D. L. , Brown D. H.
Published: September 2005

E. S. Eby, M. O. Fein, and P. J. Burt point out an incorrect equation used in the determination of optimum fluid indices and maximum d λ ratios. Corrected equations are presented with comments on their effects on the remainder of the paper.
Effect of Rain on Underwater Noise Level
Authors: Bom Nicolaas
Published: September 2005

The underwater noise due to precipitation has been measured in a small, shallow lake. The local wind speed, rain rate, atmospheric pressure, and noise level were recorded. If was found that the noise due to wind and the contribution from bottom and boundary reflections over the period during which the data were recorded had a negligible effect. The data in the interval 300–9600 Hz have been analyzed in octave bands, and an estimate of the average noise level versus rain rate has been obtained. In comparison with the laboratory work done by Franz on splashes as a source of sound, our results show significantly higher noise levels and a difference in the shape of the noise level versus frequency curve. However, the average rate of change in noise level with change in rain rate is in agreement.
Breakage of Tobacco Mosaic Virus by Acoustic Transients: A Hydrodynamical Model
Authors: Hamrick Philip E. , Cleary Stephen F.
Published: September 2005

Tobacco Mosaic Virus (TMV) particles have been exposed to single pulse acoustic transients of 10−7 sec duration produced by the rapid thermal expansion following the absorption of an intense pulse of light from a Q-switched ruby laser in an optically dense media. A hydrodynamical model is proposed, which relates the observed breakage at the center of the TMV particles, as seen in electron micrographs of exposed particles, to the structure of the TMV particles and to the amplitude and form of the acoustic transient. A velocity gradient of 4 × 107 per sec, which produces a force at the center of the TMV particle of the order of the force necessary to break a carbon-carbon bond, has been found to be sufficient to break the TMV particle.
Intensity Equations in Ray Acoustics. II
Authors: Uginčius Peter
Published: September 2005

A new expression for the intensity in ray acoustics is derived, which is valid for a general stationary medium in which the index of refraction may be a continuous function of all three space variables. This expression is derived with the WKB approximation on the wave equation, which results in a line integral along the sound ray. The integrand ∇ ⋅ r′, where r′ = dr/ds is the direction of the ray, is given explicitly in such a way that the integral can be evaluated in closed form for the general case. The result is in terms of functions that can be calculated by integrating simultaneously the vector eikonal equations for the ray paths, together with two other associated vector differential equations.
Propagating and Standing Sawtooth Waves
Authors: Temkin Samuel
Published: September 2005

The well-known theory for energy dissipation in weak shock waves is applied to the case of propagating and standing acoustic waves of finite amplitude. The known results for the decay of plane, cylindrical, and spherical waves propagating in a fluid are obtained by means of a simple technique previously used by Rudnick [J. Acoust. Soc. Amer. 25, 1012 (L) (1953)] and based on the assumption that the waves are of the sawtooth type with a weak discontinuity each wavelength. The same technique is then applied to large-amplitude resonant oscillations in tubes, assuming that the acoustic field can be represented by two sawtooths traveling in opposite directions inside the tube. These calculations are of a very simple nature and yield solutions that compare favorably with results obtained by more rigorous techniques.
Note on “Comments on ‘The Use of Noise Bands to Establish Noise Pitch’” [D. D. Greenwood, J. Acoust. Soc. Amer. 44, 634–635(L) (1968)]
Authors: Schubert E. D.
Published: September 2005

Two points are made regarding Professor Greenwood's comments.
Acoustic Ray Tracing in a Layered Atmosphere: An Analog Approach
Authors: Davis R. S. , Austin M. E.
Published: September 2005

Ray tracing in a layered atmosphere is accomplished by using a general-purpose analog computer. Diode function generators are used to simulate the functions V and dV/dy, which are continuous functions defined for all values of range and altitude. It is shows that these diode function generators approximate quite well the speed of sound profiles.
Distribution Pattern of Cochlear Combination Tones
Authors: Sweetman Richard H. , Dallos Peter
Published: September 2005

This study is designed to determine whether or not traveling waves accompany combination tone components generated in the cochlea, and also to describe the amplitude distribution of these nonlinear products. Cochlear microphonics were monitored with the differential electrode technique from the first and third turns of guinea pig cochleas. Cancellation of the distortion components was attempted by introducing bone-conducted pure tones at the frequency of the combination tone and of controllable amplitude and phase. It was demonstrated that combination tone components can never be canceled simultaneously throughout the cochlea. It was shown that the reason for this inability to cancel is that combination tones are not distributed as their own frequency would indicate, but instead, they seem to have a distribution peculiar to these nonlinear components.
Binaural Masking with Sine-Wave Maskers
Authors: Wightman Frederic L.
Published: September 2005

The detectability of one binaural tone, masked by another of the same frequency, was measured as a function of the phase difference between them. In one condition, the tone to be detected, the signal, was the same in both ears. In another condition, the signal was inverted at one ear causing a 180° interaural phase difference in the signal. The masking tone was always the same in both ears. It was presented continuously in one experiment, and was gated on and off with the signal in another experiment. In contrast with similar work in which a noise masker was used, binaural signals inverted at one ear are less detectable in some conditions than binaural signals that are the same in both ears: a negative MLD. The negative MLD was largest (about 10 dB) in gated masking conditions and was found to be dependent on signal-masker duration, growing smaller with longer duration. The detectability of interaurally in-phase signals as a function of the phase difference between signal and masker can be accounted for by a simple energy-detection model. However, no existing theory can adequately explain the results obtained with out of-phase signals, although the results suggest the operation of a system with some of the properties of Durlach's equalization-cancellation mechanism.
Evaluation of the Acoustic Response of an Air-Water Siren
Authors: Mitchell W. S. , Muster D.
Published: September 2005

The characteristics of air-operated sirens are described in the literature. Them are also papers devoted to sirens using liquids. This paper is concerned with the characteristics of a siren that can function with either water or air. The siren was built and operated with air at a maximum pressure differential of 4 psig (psi at ground level) and at 7 psig with water over a frequency range of from 50 Hz to 1 kHz. Comparison of the acoustic output of the device for both fluid media showed that, in general, there is little physical change in the siren response; the output pressure fluctuation had a sawtooth waveform. Fluid viscosity produces a damping effect on the response of the liquid-operated siren so that a more nearly sinusoidal pressure waveform occurs. In addition, it is found that the flow coefficient is dependent on frequency. The experimental results indicate that liquid-operated sirens should be further developed for use as underwater sound sources.
Speech Analysis-Synthesis System Based on Homomorphic Filtering
Authors: Oppenheim Alan V.
Published: September 2005

A digital speech analysis-synthesis system based on a recently proposed approach to the deconvolution of speech is presented. The analyzer is based on a computation of the cepstrum considered as the inverse Fourier transform of the log magnitude of the Fourier transform. The transmitted parameters represent pitch and voiced unvoiced information and the low-time portion of the cepstrum representing an approximation to the cepstrum of the vocal-tract impulse response. In the synthesis, the low-time cepstral information is transformed to an impulse response function, which is then convolved with a train of impulses during voiced portions or a noise waveform during unvoiced portions to reconstruct the speech. Since no phase information is retained in the analysis, phase must be regenerated during synthesis. Either a zero-phase or minimum-phase characteristic can be obtained by simple weighting of the cepstrum before transformation.
Acoustically Induced Optical Anisotropy in Liquids
Authors: Riley Ward A. , Klein W. Richard
Published: September 2005

A systematic study of acoustically induced birefrigence in castor oil is described. Particular emphasis is placed upon the evaluation of a measuring technique based upon a polarization analysis of the Fraunhofer optical diffraction spectrum. Results obtained using this measuring technique are compared with results of measurements made in the optical nearfield.
Direct Experimental Verification of Creeping Waves
Authors: Harbold M. L. , Steinberg B. N.
Published: September 2005

The Watson transformation has been developed for diffraction problems in the frequency region where the numerical values can be obtained more easily than by the use of the exact normal-mode series. A physical interpretation of this mathematical technique was given by Franz as creeping waves that travel around the surface at a velocity less than that in free space and that are attenuated by radiation. Thus far, only indirect measurements have been made experimentally. Herein is presented the report of a series of experiments that give direct verification of these waves for scattering by rigid spheres and cylinders in air. Radiation of creeping waves circumnavigating the obstacle was verified by interference measurements in the backscattered field with continuous waves. To detect the “isolated” creeping wave as it circumnavigated the scatterers, incident wave pulses in conjunction with high-speed digital logic techniques were used. Coincidence techniques were used for precise measurement of velocity, and amplitude decay was determined by sampling and comparing CW pulses at two points in space and time by Lissajous pattern techniques.
Instrumentation for 80-Hz Seismic Communications
Authors: Ikrath K. , Schneider W. A. , Johnson R. F. , Murphy K. J.
Published: September 2005

A continuous-wave single-frequency seismic carrier for transmitting information by amplitude, phase, and frequency modulation has proven useful and practical in situations where electromagnetic means of communication are not feasible. An 80-Hz, 20-kg seismic transducer using 10 W maximum power was utilized for transmission through low-velocity media; an 80-Hz, 300-kg transducer using 200 W maximum power was utilized for transmission through high-velocity media. For reception, an 80-Hz resonant seismic transducer equipped with a frequency trimmer was used. Efficient signal insertion into soil was achieved by employing an artificial mechanical-elastic transmission line as an impedance transformer. A mathematical model for a slotted steel tube, which operates as an impedance transformer, is presented with a mathematical description of the impedance transformation process. Seismic-coupling efficiency was derived by comparing an actual system with a theoretically ideal transducer-medium system. Experimental and theoretical results based on data recorded during tests on various seismic media are analyzed in terms of the mathematical model employed. Results verify the validity and soundness of design and operation of a seismic communications system.
High-Frequency Response of Point-Excited Submerged, Spherical Shells
Authors: Junger M. C. , Feit D.
Published: September 2005

The classical, modal formulation of the harmonic vibrations and radiation loading of submerged elastic shells requires extensive calculations for high-frequency excitations. An alternative formulation in terms of attenuated traveling waves similar to the “creeping-wave” formulation commonly used in high-frequency diffraction analyses, is adapted to thin spherical shells excited by a radial point force. Applying Watson's transformation to the normal-mode series for the radial velocity and to the associated wave-harmonic series for the surface pressure, the shell response is expressed as the sum of (1) a primarily structure-borne field consisting of three modes, two of them rapidly attenuated, characterized by the wavenumbers of point-excited effectively infinite, submerged plane plates; and (2) a diffracted field, resembling “creeping waves” on “pressure-release” spheres. A single structure-borne mode suitably represents shell response and surface pressures except in the vicinity of the drive point (within 5° for the parameters used here).
Free Vibrations of an Infinite Plate Based on the Linear Coupled Theory of Thermoelasticity
Authors: Mowbray D. F. , Anderson G. L.
Published: September 2005

This paper considers the free vibration modes of an infinite plate of uniform, arbitrary thickness, based on the linear coupled theory of thermoelasticity. Transcendental equations relating frequency of vibration, wavenumber, elastic properties, and thermal properties are derived for traction free bounding surfaces and several surface heat-transfer conditions. As a numerical example, the roots of the equations for adiabatic plate surface conditions are evaluated. These roots allow the significance of the coupling of the elastic and thermal deformation fields to be evaluated with respect to the vibration amplitude attenuation and phase velocity, and permit calculation of the thermoelastic energy dissipation.
Modern-Day Rock-and-Roll Music and Damage-Risk Criteria
Authors: Flugrath James M.
Published: September 2005

Ten rock-and-roll dance bands were recorded in one dance hall catering to teenagers. One hundred level measurements for each linear, A-weighted, C-weighted, and octave bands 500, 1000, 2000, and 4000 Hz were computed for analysis of variance, average level, and standard deviation for the 12-h recording of each dance band. The spectrum of rock-and-roll music was found to peak at 2000 Hz, and C-weighted minus A-weighted (C — A) values were found to be approximately 1. The standard deviations of sound-level measurements and octave-band measurements were found to be quite small, indicating that amplified rock-and-roll music can be considered as a form of “steady-state” sound if many measurements over time are averaged. It was found that the average levels of several of the dance bands exceeded both “equal-energy” and “average-level” damage-risk criteria.
Testing and Performance of a Wide-Band Underwater Liquid Communicator
Authors: Mitchell W. S. , Muster D.
Published: September 2005

The majority of devices employed in underwater communication use electromagnetic or electrodynamic processes. This paper reports on the experimental development of an underwater communicator that operates by the process of liquid modulation. The device generates acoustic energy in a flowing fluid through mechanical displacements of a modulating valve. Acoustic response of the modulator contains frequencies up to 3 kHz. Thus, it is a potential source for generating audible underwater sound. The modulator has been used with water to produce underwater speech communication that possesses excellent intelligibility. Present research has been accomplished while using low system pressure differentials. Sufficient increase of the system pressure is expected to produce satisfactory underwater communication by means of liquid modulation.
Spectrum Broadening Due to Ocean-Wave Interference
Authors: McNicholas J. V.
Published: September 2005

Spectrum broadening, caused by ocean-wave interface, is explained in terms of an equivalent fluctuating dipole arm.
Ultrasonic Imaging Systems for Nondestructive Testing
Authors: Berger Harold
Published: September 2005

Methods for detecting ultrasonic images are briefly reviewed, and discussed in light of their potential application to nondestructive test problems. In a typical nondestructive test system involving a water immersion tank, the ultrasonic image detector should respond to an ultrasonic intensity of 10−2 W/cm2 or less. This requirement eliminates from consideration number of detection methods involving photographic, chemical, or thermal mechanisms. Of the remaining image detection systems, only a few have been applied to nondestructive test problems. These include the surface relief technique, the Pohlman cell, and scanning methods involving piezoelectric transducers. The latter method has been most used for image applications, with mechanical movement of the transducer(s) in a C scan method. Electron scan of a single piezoelectric detector to provide a television presentation is coming into wider use. A description of one such system is given. For a thin, flat inspection object, the system offers good inspection speed, resolution, and sensitivity to inhomogeneities. Thick, irregularly shaped inspection objects present problems because lens systems are involved. Lenses for imaging are not well developed. Also, the use of a lens tends to slow the inspection of a thick object because one must examine the object by focusing at different depths. Pulsed television systems and holographic techniques offer some promise in that area. A new phase-sensitive color television ultrasonic image system offers hope for improved detection of subtle discontinuities.
Utilization of the Liquid Surface Levitation Effect as a Means of Ultrasonic Image Conversion for Materials Inspection
Authors: Gericke Otto R. , Grubinskas Robert C.
Published: September 2005

An ultrasonic image conversion cell utilizing the liquid-surface-levitation effect has been developed. This effect is based upon the principle that the surface of a free liquid will be deformed in accordance with the cross-sectional intensity distribution of an impinging ultrasonic beam. The image-conversion cell has been successfully applied for nondestructive-testing purposes. It can be coupled directly to an ultrasonically excited test specimen to obtain characteristic liquid-surface relief patterns depicting internal discontinuities. A significant advantage of the conversion cell is the fact that it does not require the test specimen itself to be immersed in a liquid. Also, because the conversion cell produces a “real-time” image, pulsed, frequency-modulated, and continuous-wave modes of ultrasonic excitation can be used, and thus, various types of ultrasonic images can be obtained.
Wave Analysis of a Luneberg-Gutman Fluid Acoustic Lens
Authors: Lord Gary
Published: September 2005

A wave solution has been obtained for the acoustic fields inside a class of perfectly focusing spherical lenses that have been previously described by Luneberg and Gutman. Plane-incident radiation on a lens having a continuous radially varying refractive index, prescribed by Gutman, is assumed. The radial functions for the eigenfunction expansion are defined by an integral solution of the radial portion of the separated scalar Helmholtz equation for the interior of the lens. This defining integral leads immediately to recurrence relations that are useful in the computations. The integral may also be evaluated asymptotically for large wavenumber-aperture products, for functions of low order, in order to normalize suitably the sequences of functions generated recursively. Axial and polar patterns were obtained for various lenses for wavenumber-aperture products up to 240.
Image Scanner Using Diode Switching
Authors: Suckling E. E. , Hendrickson J. R.
Published: September 2005

A system is described for ultrasonic viewing of objects by flooding them with coherent CW ultrasound, focusing the scattered or reflected energy through a single sonic lens, and projecting this onto a rotating sonic mirror, which sweeps a sonic image across a linear transducer placed at the appropriate focal distance. The transducer is a single narrow crystal bearing on its rear face a vertical row of 64 small, closely-spaced electrodes, which are sampled in sequence for the piezoelectric voltage they are detecting. Conventional electronic circuitry is described for converting the electrode voltages into a video signal by way of diode switching. Horizontal spot motion on an oscilloscope is controlled by voltage derived from the scanning mirror position and vertical spot position relates to the particular electrode being sampled. A sonic mirror sweeping the image across the crystal in 15 sec and an electrode sampling rate of 20 000 samplings/sec is able to give 4000 picture elements or a picture of 64 lines where the horizontal and vertical resolutions are about equal. Mechanical and circuit diagrams of the system are shown and static video signals of two simple image conditions are illustrated. Critical comparisons are made between this and other systems for ultrasonic viewing, possible advantages and disadvantages of this system are mentioned, and practical and theoretical design problems are discussed.
Analytical and Experimental Studies of Multiple-Unit Impact Dampers
Authors: Masri S. F.
Published: September 2005

The exact solution for the symmetric two impacts/particle/cycle motion of an n-unit impact damper attached to a sinusoidally excited primary system is derived analytically, and its asymptotically stable regions are determined. Simulated motion on a digital computer and experimental studies with a mechanical model are presented, and they show good agreement with theoretical results. It is found that properly designed multiple-unit impact dampers are more efficient than equivalent single-unit impact dampers in regard to vibration reduction and noise level of operating units.
Cross Correlation in Structural Systems: Dispersion and Nondispersion Waves
Authors: White P. H.
Published: September 2005

The use of cross correlation as a tool for analyzing propagation of energy in structural systems is investigated. Each energy-transmission path will have a characteristic delay time, and examination of the cross-correlation function of input and response can guide in the determination of the most significant path or paths. Difficulties occur in distributed systems or when the propagation is by a dispersive mechanism. The principles of correlation analysis are examined for both dispersive and nondispersive systems. Experimental evidence is presented that supports the theory and concepts developed. On the basis of these preliminary results, it appears that the technique holds promise and bears further investigation.
Perception of Pitch in a White-Noise Mask
Authors: Richards Alan M.
Published: September 2005

Three mel scales, derived from fractionation data, and representing three differential noise conditions are obtained. It is found upon comparison that the presently found no-noise function differs in no essential manner from the generally accepted mel scale advanced by Stevens (1940). However, upon the introduction of a wide-band masker, the shape of the mel function becomes more positively accelerated. In general, when holding the intensity of the masker constant, this acceleration is inversely related to the sensation level of the experimental tones above masked threshold, and is not frequency dependent. Although this relationship is not dependent upon frequency per se, the magnitude of pitch shift increases with frequency.
Effects of Pure-Tone Masking on Low-Pass- and High-Pass-Filtered Noise
Authors: Young I. M.
Published: September 2005

Threshold measurements were obtained for low-pass- and high-pass-filtered noises in the presence of pure tones in normal subjects. High-pass-filtered noise with cutoff frequencies at 2400 Hz and above yielded masking peaks near the cutoff frequencies. When noise was filtered with cutoff frequencies at 1200 Hz and below, pure tones of 800 and 1000 Hz had the greatest masking effect. For low-pass-filtered noise, as the bandwidth increased, masking peaks moved from low frequency to high. The masking effect was indistinguishable from that of white noise when filtered noise was cutoff at frequencies of 2400 Hz and above. These results suggest that there is a definite mechanical resonant frequency effect on noise when the width of filtered noise exceeds a critical value. Masking effects are discussed in relationship to mechanical resonant frequency and the interaction of difference and summation tones.
Generation of Speechlike Signals by Excitation of the Vocal Tract at the Lips
Authors: Mermelstein P.
Published: September 2005

In speech studies where articulatory activity is of prime interest and where no excitation through vocal-cord vibration is available or desirable, one wants to examine the response of the vocal tract to an external excitation source. This note describes a method to generate such a speechlike signal from the incident and reflected waves caused by excitation of the vocal tract at the lips. The result approximates the signal that would have been generated by periodically exciting the same tract configuration at the glottis, provided that the tract is not completely constructed within its interior.
Velocity Dispersion of Isotropic Rods of Square Cross Section Vibrating in the Lowest-Order Longitudinal Mode
Authors: Booker R. E.
Published: September 2005

The velocity dispersion of the first-order longitudinal mode of two isotropic 24ST aluminum rods of square and circular cross sections has been investigated and the results compared with the experimental results of Morse and the theory of Nigro. It is shown that the theory of Nigro does not adequately account for the lowest-order velocity dispersion in a square rod. Morse observed that the velocity dispersion curves of a square and of a circular rod coincide as a function of diameter-to-wavelength ratio, provided the equivalent diameter of the square rod is assumed to be 1.13 times the thickness of the rod. An equivalent diameter of 1.155 times the thickness of the square rod is shown to be superior for the present experimental results, as it ensures almost full coincidence of the two dispersion curves over the full range of diameter-to-wavelength ratio.
Light-Wave/Elastic-Wave Analogies in Crystals
Authors: Henneke Edmund G. , Green Robert E.
Published: September 2005

General consideration is given to the analogies that exist between the propagation of light waves and the propagation of ultrasonic waves in anisotropic media. A historical survey is given of prior work in this area, followed by a comparison of present views of the analogies with those of other investigators. The inability to obtain a direct one-to-one analogy for all phenomena is discussed.
Ultrasonic Determination of the Diffusion Coefficient of Carbon in α-Iron at 408° and 430°C
Authors: Lord A. E.
Published: September 2005

The ultrasonic attenuation at 31 MHz and 60 MHz has been measured in an iron single crystal from room temperature to 625°C, using zinc sulfide vacuum-evaporated, thin-film transducers. Longitudinal waves propagating along the [110] direction were used, and the attenuation was measured in both the “carbon-free” condition (wet-hydrogen-treated) and the carburized condition. We have apparently observed the carbon Snoek peaks in the carburized specimen. Assuming that the Snoek peak occurs only via octahedral site to octahedral site jumps, we obtain a diffusion coefficient of carbon in a α iron, at 408 ±5°C, of Dc = 4.52 × 10−9 cm2/sec, and at 430°±5°C, of Dc = 8.85 × 10−9 cm2/sec. These values fall in a region previously devoid of diffusion data. The new values connect, in a relatively smooth manner, the low temperature Snoek-effect-determined diffusion coefficients with the high temperature mass-flow-determined coefficients. It must be mentioned, however, that in the case of the diffusion of carbon in α-iron, the extraction of the diffusion coefficient from the Snoek damping data is by no means obvious. This point is discussed.
Properties of the Summating Potential of the Guinea Pig's Cochlea
Authors: Honrubia Vicente , Ward Paul H.
Published: September 2005

In the guinea pig, the cochlear-microphonic potentials and the summating potential (SP) have been simultaneously recorded by means of micropipettes located inside the scala media of each turn of the cochlea. The polarity of the SP recorded in the first turn is negative for the high frequencies (i.e., 6000 Hz) at low levels of sound pressure. For the lower frequencies (i.e., 900 Hz), the SP is recorded positive before it becomes negative. The lower the frequency, the greater the SPL (sound-pressure level) required to produce a negative SP in the first turn. The SPL at which the SP for low frequencies becomes negative is lower the greater the distance from the oval window. The SP magnitude is linearly dependent upon the logarithm of the duration of sound within the range of values investigated from 40 msec to 2 sec. The amplitude of the negative SP rose monotonically as the intensity of the stimulus was increased, and the neighboring areas of the basilar membrane contributed to the production of the SP. Increase in duration of stimulation increased the amplitude of the SP without bringing into activity new areas of basilar membrane.
Pitch of Frequency-Modulated Sinusoids
Authors: McClelland Keener D. , Brandt John F.
Published: September 2005

The pitch elicited by 300-, 1000-, and 3000-Hz sinusoids frequency modulated by 20, 200-, and 2000-Hz sinusoids (the latter for the 3000-Hz carrier frequency only) was investigated at 20 and 50 dB SL. The frequency deviation of the carrier frequency was ± 100 Hz for all stimulus conditions. Five normal-hearing listeners matched unmodulated sinusoids in a free-response task to any and all “pitches” perceived in the FM signals. Pitch matches occurred to individual spectral components when the component frequency spacing exceeded critical bandwidth. When component spacing was less than critical bandwidth, pitch matches occurred randomly within the energy band, at the center of the energy band, or at the ends of the energy band. No pitch matches were made in response to anything but spectral-energy information.
Lateralization and Detection of a Tonal Signal in Noise
Authors: McFadden Dennis
Published: September 2005

The ability to lateralize a tonal signal against a white-noise background was investigated by presenting that signal at different intensities to the two ears and asking the listener to indicate which ear received the more intense signal. The signal (500 cps, 250 msec) was gated on every trial during the single observation interval, and the more intense signal was equally likely to be presented to the leaf ear as to the right. Both the interaural phase relation of the signal and the magnitude of the interaural intensive difference were variables of interest. For signals both in phase (S0) and 180° out of phase (Sπ), six-point psychometric functions were determined with interaural intensive differences of 3. 6. and 12 dB In addition, detection functions were obtained for each of these interaural conditions using a single-interval forced-choice technique. Particularly for the smaller interaural intensive differences. S0 and Sπ signals led to lateralization functions of quite different forms. Noise: in phase interaurally (N0), continuous 44 dB SPL/cycle.
Effect of Multimode Guided-Wave Propagation on Ultrasonic Phase Velocity Measurements: Problem and Remedy
Authors: Papadakis Emmanuel P.
Published: September 2005

Multimode guided-wave patterns in bounded ultrasonic specimens have been shown to interfere with phase delay measurements made by the pulse superposition method and the pulse-echo-overlap method. The phase shifts associated with the nodes in the multimode guided wave patterns invalidate the McSkimin ΔT criterion for the choice of the proper cyclic matching between echoes when the nodes are near the echoes used. The adverse effect of nodes upon the McSkimin criterion has been documented by extensive measurements employing shear waves in square barsand thick plates. In free-wave propagation without nodes, the ΔT criterion remains valid. A method employing video pulses to establish the proper cyclic match for rf measurements has been developed to supplement or replace the McSkimin ΔT criterion in all cases including those of adverse specimen geometry. Advantages and limitations of the video overlap criterion are discussed.
Effect of Cloth Covers on Sound Absorption of Glass Fiber
Authors: Ando Y.
Published: September 2005

Sound reflection coefficients from cloth covers on glass fiber were measured by the “Interference Pattern Method.” A suitable combination of cloth and glass fiber was found to make the reflection coefficient smaller than that of the case of only glass fiber, at frequencies over 5 kHz.
Elastic Constants of Filamentary Composites with Hexagonal Symmetry
Authors: Behrens Ernst
Published: September 2005

The calculation of elastic constants of filamentary composites by the “method of long waves” is extended from square to hexagonal symmetry.