bluuebunny/crossref_metadata_2025 huggingface dataset:
First-Occurrence Time of High-Level Crossings in a Continuous Random Process
Authors: Rice James R. , Beer Ferdinand P.
Published: September 2005

This paper deals with the statistical distribution of the first-occurrence and first-recurrence times of the crossing of a given level in a continuous random process. Approximate forms of the first-occurrence and first-recurrence time densities are found by considering the successive crossings to form a renewal process. A relatively simple exponential distribution is found to give an appropriate representation of the limiting case when the crossings of the level under consideration are statistically rare events. Numerical examples are worked out for some stationary Gaussian processes. The method is of use in evaluating survival probabilities for randomly excited mechanical systems subject to failure upon occurrence of a sufficiently high load.
Finite-Difference Method for the Investigation of the Vibrations of Solids and the Evaluation of the Equivalent-Circuit Characteristics of Piezoelectric Resonators. II
Authors: Lloyd P. , Redwood M.
Published: September 2005

This part of the paper describes the results obtained by use of a finite-difference method to determine the characteristics of several types of contour mode of vibration of rectangular and square plates of piezoelectric ceramic. Four extensional modes (of “length,” “edge,” and “radial” types) are discussed in some detail, together with two types of flexural or shear mode. Predicted resonant frequencies are within 2% of experimental values, over a wide variation in the relative lengths of the two sides of the rectangle. Typical vibration patterns of displacement are presented, with positions of nodes. For the four extensional modes, the piezoelectric strength (as expressed by the motional capacitance of the equivalent circuit) is calculated for rectangles of various proportions.
Intelligibility of Speech Presented to the Right or Left Ear in Binaural Noise
Authors: Dirks Donald D. , Carterette Edward C.
Published: September 2005

As part of a systematic study of ear dominance, for a continuum of sounds from speech to nonspeech, intelligibility scores for PB words were obtained from 7 listeners. White noise was presented in phase at each ear while speech was delivered to either the right or left ear. No significant differences were found between right- and left-ear presentations under these conditions, This result is contrary to the findings of an earlier study, but is essentially identical to a more recent investigation.
Critical Bands and the Residue
Authors: Henning G. Bruce
Published: September 2005

The existence region of the tonal residue provides an estimate of the width of critical bands.
Effect of End Constraints on the Damping of Laminated Beams
Authors: DiTaranto R. A. , Blasingame W.
Published: September 2005

The use of laminated elastic-viscoelastic beams as a means for obtaining vibration damping, together with reasonable structural stiffness, has been the object of extensive theoretical and experimental investigations. The particular theoretical and experimental work considered herein is the effect of end constraints on the composite loss factor of vibrating laminated beams. According to theoretical findings rise where, the damping of laminated beams is independent of boundary conditions and depends solely on the geometry of the beam's cross section and properties of the damping material. Results of tests conducted on 3-, 5-, and 9-layered beams having various end conditions showed good correlation with the theory.
Masking of Surface Reverberation by Volume Reverberation
Authors: Shaffer Robert L.
Published: September 2005

Measurements of the backscattering of 4-kcps sound from the surface of the sea at a grazing angle of 5° and a wind speed ranging from less than 5 ft (knots) to greater than 35 kt were made off Bermuda. It was assumed that surface backscattering is wind-speed-dependent; volume backscattering, on the other hand, was assumed not to be wind-speed-dependent in order to distinguish between surface reverberation and volume reverberation. It was observed that volume reverberation prevails at the lower wind speeds (smooth sea surface), whereas surface reverberation prevails at the higher wind speeds (moderate to rough sea surface). The surface scattering strength data compared favorably with results previously reported in the literature.
Convergence of the Keck-Beyer Perturbation Solution for Plane Waves of Finite Amplitude in a Viscous Fluid
Authors: Blackstock David T.
Published: September 2005

Keck and Beyer have given a perturbation solution of the equation for plane sound waves of finite amplitude in a viscous fluid. The solution may be represented as a power series in the parameter N, which characterizes the importance of nonlinearity relative to dissipation. Convergence properties with respect to N have not heretofore been established. In this Letter, a global definition of the function represented by the Keck-Beyer solution is obtained by showing that certain approximations used by Keck and Beyer are equivalent to reducing the differential equation to Burgers' equation, which has an exact solution. The exact solution is then expanded to obtain the Keck-Beyer results. Since the expansion is valid for all values of N, it is concluded that the Keck-Beyer series converges for all values of N.
Use of a Power-Sensitive Detector in Pulse-Attenuation Measurements
Authors: Southgate P. D.
Published: September 2005

The use of the acoustoelectric effect in measurements of the decay of multiply reflected acoustic pulses in a specimen is described. The detector is a wafer of piezoelectric semiconductor arranged to absorb a small proportion of each successive pulse. Since the voltage generated is proportional to pulse power and is not sensitive to phase, many types of pulse decay form distortion, which may be associated with such measurements, are eliminated. The efficiency of detection is discussed, and it is shown to be comparable with that of a piezoelectric transducer.
Ultrasonic Internal Conical Refraction in Potassium Chloride
Authors: Artman Robert A.
Published: September 2005

Analysis of discrepancies among current reports on ultrasonic internal conical refraction arc serious enough to cast doubt on the existence of the effect. Data have been taken on ultrasonic shear waves propagating in the [111] direction in a cubic single crystal (potassium chloride), which is large enough to show the essential details of the effect. Measurements of the distribution of energy and polarization direction around the perimeter of the base of the cone, the dependence of the amplitude on the polarization direction of the input transducer, and the angle of refraction are presented. The measurements appear to support a proposal that the results observed are, as in optics, a direct consequence of beam spread in the input radiation.
Visible Cavitation in Liquid Helium
Authors: Finch R. D. , Wang Taylor G. J.
Published: September 2005

Visible cavitation has been obtained readily in liquid helium using a barium titanate cylinder resonant at about 46 kc/sec. The nature of the cavitation changes in various temperature régimes, and these changes are reflected by changes in the threshold, as measured by the driving voltage of the transducer. Below about 2.13°K, the threshold for visible cavitation is an order of magnitude higher than the threshold for noise; but between 2.13°K and the λ point the visibility threshold drops and becomes comparable to the noise threshold. Static pressure has a much greater effect on the visibility threshold than on the noise threshold. The results are discussed and the conclusion is reached that the information obtained is more pertinent to the dynamics of the cavities than their nucleation.
Measurement of Viscoelastic Properties of Liquids at 3000 Mc sec
Authors: Lamb J. , Seguin H.
Published: September 2005

A description is given of an experimental system that enables the shear mechanical impedance of liquids to be measured at 3000 Mc/sec. Traveling waves are excited in a BC-cut quartz disk that is located in a resonant cavity and both surfaces of the disk are loaded acoustically by the test liquid. Results obtained are in reasonable agreement with predictions from measurements made at lower temperatures and at frequencies up to 78 Mc/sec, using the principle of reduced variables based upon frequency-temperature superposition.
Continuous Distribution of Dislocations and Energy Dissipation in Metals
Authors: Mura T. , Lyons W. C.
Published: September 2005

A theoretical study of the energy dissipation in metals is presented. Zener's coupled thermoelasticity is joined with the theory of continuous distribution of oscillating dislocations to yield theoretical results that are an improvement on the existing theoretical results of Eshelby. In general, the results obtained in this paper predict a peak in the internal energy loss and not a monotonic increase in internal energy predicted by Eshelby [J. D. Eshelby, Proc. Roy. Soc. (London) A197, 396–416 (1949)].
Radiative Absorption of Sound by Water Vapor in the Atmosphere
Authors: Calvert James B. , Coffman J. W. , Querfeld C. W.
Published: September 2005

The absorption of sound at infrasonic frequencies in the atmosphere is dominated by vibrational relaxation absorption and radiative absorption. These processes are of comparable importance. The strength of the total radiative absorption depends sensitively on the concentrations of minor atmospheric constituents and the temperature. Aline-by-line calculation of the radiative absorption arising from the infrared rotation spectrum of water vapor under typical conditions at sea level and at 7.5 and 15 km altitude is presented.
Thermoelastic Vibrations of a Beam
Authors: Jones John P.
Published: September 2005

The equations of motion of a beam with the lateral surface thermally insulated are derived, including the effects of shear deformation and rotatory inertia. Thermoelastic coupling in the heat-conduction equation and in the elastic-constitutive relations is also included. Axial deformations of the beam are taken into account. Two examples are presented and discussed.
Three-Dimensional and Shell-Theory Analysis for Axisymmetric Vibrations of Orthotropic Shells
Authors: Mirsky I.
Published: September 2005

Exact solutions of orthotropic elasticity obtained previously by the author are applied to the problem of wave propagation in an infinite cylindrical shell. In addition, asymptotic solutions are developed for the high-frequency range. Numerical results of frequency versus wavelength, based on the exact and asymptotic theories, are compared with an approximate shell theory.
Reflection of a Plane Acoustic Step Wave from an Elastic Spherical Membrane
Authors: Milenkovic Veljko , Raynor S.
Published: September 2005

The problem of interaction of an acoustic pressure step wave with an elastic spherical membrane is considered. An operational method is introduced that transforms the solution expanded in spherical modes into a series converging rapidly in the neighborhood of the discontinuous leading wavefront. A solution is obtained for the reflected pressure field, valid for a short time after wave arrival. Pressure is computed on the frontal surface of the membrane and in the far field up to 60° from the symmetry axis. The effect of membrane material and thickness on the pressure profile of the reflected wave is shown.
Table of Intensity Increments
Authors: Tobias Jerry V.
Published: September 2005

Small intensity increments can be produced by adding larger intensity increments. A table is presented covering the range of small-intensity increments from 0.008682 through 6.0206 dB in 60 large-intensity increments of 1 dB.
Capacitor Microphone with Ceramic Diaphragm
Authors: Winter T. G. , Bass H. E.
Published: September 2005

A capacitor microphone using the ceramic boron nitride as the diaphragm has been built and tested at room temperature. This material was chosen because it offers promise of maintaining suitable strength and flexibility to 1000°C. Design and the frequency response at room temperature are given. Development was halted before testing at elevated temperatures.
Some Physical Effects of Acoustically Induced Cavitation in Liquid Helium and in Liquid Nitrogen
Authors: Jarman Peter D. , Taylor Kenneth J.
Published: September 2005

The onset of acoustically induced cavitation in liquid helium is stated to be similar to that in unfiltered air-saturated water. Relative desinient and incipient sound-pressure thresholds for stable- and transient-type cavitation are given. Sonoluminescence from liquid helium was never detected, although check experiments with ethyl alcohol indicated that the light-detection system was very sensitive. The intensity of sonoluminescence from liquid nitrogen is reported to be 10−3−10−2 times that from water.
Laboratory Calibrator for Gradient Hydrophones
Authors: Bauer B. B.
Published: September 2005

A calibrator has been developed for gradient hydrophones consisting essentially of a water-filled drum driven axially by two transducer motors. To the first approximation, the sound pressure and velocity functions within the drum are those that one encounters at the pressure node and velocity loop in a standing wave.
The Story of Acoustics
Authors: Lindsay R. Bruce
Published: September 2005

The historical progress, of the science of acoustics is surveyed from the earliest recorded phenomena and theories to the present status of the subject. Considerable attention is paid to the development of both mathematical and experimental tools for studying the production, propagation, and reception of sound, particularly in the 18th and 19th centuries. The impact of Rayleigh's work on modern acoustics is estimated. Contemporary developments are treated only briefly. The endeavor has been made to refer in almost all cases to original sources.
Correlation Detection in Local-Noise Fields
Authors: Jacobson M. J.
Published: September 2005

This paper is concerned with the effect of local noise on the ability of a correlation system to detect a distant, localized signal source. Each of two receiving points is surrounded by a local, circular noise field. Additional noise is assumed to arise from a circular field of infinite radius. The mean and variance of the detector output are computed and the output signal-to-noise ratio is determined. The degradations in signal-to-noise ratio resulting from local noise and also from finite receiving-point spacing are examined in detail when the local noise crosscorrelation is taken to be negligible. Finally, the local-noise crosscorrelation is investigated. Upper bounds are found, the maximum correlation over steering delay is examined, and the delay locations of maximum correlation are determined.
Effect of Prolonged Exposure to a Binaural Intensity Mismatch on the Locus of a Dichotically Produced Tonal Image
Authors: Elfner Lloyd , Perrott David R.
Published: September 2005

An experiment is reported on the effect of six consecutive 21-min periods of exposure to frequencies of 700, 1000, or 3000 cps, dichotically presented with a 50-dB interaural intensity imbalance, on the subsequent locus of the dichotically produced auditory image of the same frequencies. Significant differences in the locus of the auditory image were found among the test frequencies. There was a differential effect on the locus of the image of the test frequencies as a function of the frequency of the saturation tone. No significant changes were noted in the sensitivity of the auditory system to the frequencies employed. No changes in pitch were reported, although preexperimental instructions did not direct attention to this phenomenon. The results are discussed in terms of several theoretical models for localization.
Interaural Phase Effects in the Masking of Signals of Different Durations
Authors: Green David M.
Published: September 2005

The detectability of a pulsed, 250-cps sinusoid in noise was measured under three interaural phase conditions and at three durations. The conditions were (1) signal and noise in one ear only, SmNm, (2) signal in one ear and the same in-phase noise in both ears, SmN0, (3) signal in both ears, but with a 180° phase difference, and the same in-phase noise in both ears, SπN0. The detectability of the signal was about 9 dB better in Condition 2 than in Condition 1, and about 7 dB better in Condition 3 than in Condition 2. The difference in detectability is slightly dependent on signal duration, the largest difference appearing at the shortest duration. The psychometric functions were essentially the same in all conditions, except for an attenuation constant. The results are contrasted with two theories used to account for the binaural effects; some discrepancy between both theories and the results are noted.
Use of Sensation Level in Measurements of Loudness and of Temporary Threshold Shifts
Authors: Ward W. Dixon
Published: September 2005

The hypothesis that equal sensation levels (SL) of stimulation give rise to equivalent loudnesses in normal observers is disproven by showing that recruitment often occurs near threshold even in normal ears. Since neither constant sound pressure levels (SPL) nor constant SL's including 0 dB SL (threshold itself), can be assumed to produce equal loudness, it is suggested that observers be equated at the most comfortable listening level (MCL).
Numerical Results for Scattering by a Hemisphere on a Plane
Authors: Barakat Richard , Cohen Edward
Published: September 2005

We present numerical results for Twersky's solution of the scattering of a plane wave by a hemispherical boss on a plane.
Reply to “Comment on ‘Vibrational-Energy Transmission in a Three-Element Structure’” [D. E. Newland, J. Acoust. Soc. Am. 39, 755 (L) (1966)]
Authors: Lyon Richard H. , Scharton Terry D.
Published: September 2005

The choice of a definition of coupling-loss factor is discussed. Its calculation is designed to give a proper “average” value. Its form is chosen to be consistent with the internal-loss factor.
Large-Amplitude Linear Vibrations of Tensioned Strings
Authors: Dimeff John , Lane James W. , Gardner Murray S.
Published: September 2005

The transverse motion of a tensioned string driven parametrically by a moving end support is examined both analytically and experimentally. The conditions required to linearize the equations of motion for vibrations over a large-amplitude range at constant frequency are developed and shown to be physically realizable.
Vibration of Cantilever Beams to which Dynamic Absorbers are Attached
Authors: Snowdon J. C.
Published: September 2005

The simultaneous application of two dynamic absorbers to an undamped cantilever beam is discussed theoretically. The dynamic absorbers possess viscous damping. They are tuned and damped in the so-called optimum manner for which it is possible to suppress the resonances of the beam in a uniform and symmetrical fashion. The beam is exalted by a sinusoidally varying force situated either at its free end or at its midpoint. It is to these locations that the dynamic absorbers are attached. The absorbers are tuned to suppress the first and second beam resonances, the optimum values of absorber tuning and damping depending upon the location of the absorbers and upon the beam resonance that is of concern. In addition to the rôle of the absorbers in suppressing the first and second beam resonances, excitation of the third resonance is essentially avoided when the driving force is situated at the midpoint of the beam because a nodal point of the third mode occurs very near to the beam center.
Surface-Wave Propagation in a Continuously Stratified Medium
Authors: DiNapoli F. R. , Middleton F. H.
Published: September 2005

The problem of long range propagation in a continuously stratified medium is considered for those cases where the stratification is such that a region of slow sound velocity is found to be embedded in a region of relatively faster sound velocity. It is then possible to explain the guiding mechanism of the medium in terms of surface-wave theory. The technique employed utilizes an equivalent integral-equation representation for the differential equations describing the boundary-valve problem, and yields information concerning the dispersive character of the medium. As a means of illustrating the mechanics of this technique and demonstrating its application, dispersion curves are obtained for the particular case of propagation in the sofar sound channel.
Reduction of Aircraft Noise Measured in Several School, Motel, and Residential Rooms
Authors: Bishop Dwight E.
Published: September 2005

Field noise reduction measurements in 21 school, motel, and residential rooms during flyovers of jet and propeller aircraft are described. The measured noise reduction for most rooms was found to lie within or near the range of moderate noise-reduction values observed in previous measurements of houses and wood-frame air-base buildings. Sizeable differences in room noise reduction values were observed during successive aircraft flyovers. For jet-aircraft flyovers, the root-mean-square value of the standard deviations for noise-reduction measurements in school and motel rooms was 2.7 PNdB. For the four residential rooms studied, a root mean-square value for the standard deviations of 3.4 PNdB was observed.
Amplitude of Békésy Tracings with Different Attenuation Rates
Authors: Harbert F. , Young I. M.
Published: September 2005

Amplitude measurements of threshold fixed-frequency Békésy tracings were made for interrupted and continuous tones on normal and pathological ears. Comparison of four attenuation rates (1, 2, 4, and 8 dB/sec) on the same subjects indicates that bottoms of spikes were at similar sound-pressure levels (SPL) foe different attenuation rates both for interrupted and continuous tones, while the tops and midpoint of spikes were at significantly different levels as attenuation rate varied. Standard audiometry thresholds related best with the SPL of bottoms of spikes of pulsed-tone tracings in both normal and pathological ears. Doubling the attenuation rate changes amplitude in the ratio of about 1 to 1.62 and increases pen reversals per unit time in the ratio of approximately 1 to 1.23. This is true for both interrupted- and continuous-tone tracings for all frequencies in both normal and pathological ears. Separation between interrupted- and continuous-tone tracings in pathological ears is not significantly different for various attenuation rates when measured between bottoms of spikes for different attenuation rates.
Pitch Discrimination of Jittered Pulse Trains
Authors: Rosenberg Aaron E.
Published: September 2005

Listeners are presented with pulse-train stimulus pairs and asked to judge whether they can hear a difference between them. The interval between pulses is a random variable, identically and independently distributed for each stimulus of a pair. Two distributions are observed: one, nominally Gaussian, and the other, nominally the distribution of the amplitude of a sinusoidal wave whose phase is uniformly distributed. The principal experimental parameters are the mean interval between pulses and root-mean-square deviation or jitter about this interval. The stimuli of each pair are identical in other respects—pulse shape (50-μsec pulse width), loudness (30 or 35 dB sensation level)—but differ in polarity pattern. Two pattern combinations are observed. For the range of mean pulse intervals investigated, 5–15 msec, the stimuli of each pair are generally discriminable when unjittered. However, the results indicate that, when jittered in amounts greater than 1 or 1.5 msec, the stimuli may be rendered nondiscriminable. This critical amount of jitter coincides with a flattening of the power-density spectra of the stimuli for frequencies greater than 250 or 200 cps. On the basis of this result and the results of other investigations, it is hypothesized that the correlates of discrimination for unjittered or lightly jittered stimuli are distinct neural volley patterns associated with basilar-membrane activity in the 300- to 1000-cps region.
Choice of Reference Conditions for Speech Preference Tests
Authors: Hecker Michael H. L. , Williams Carl E.
Published: September 2005

Preference tests used in the evaluation of speech-communication systems typically employ as reference conditions different levels of one type of distortion, produced by a single reference system. A new preference test has been developed to explore the possible advantages of using several reference systems that represent fundamentally different types of distortions. The new test was experimentally compared with the more conventional test, and it was found that the preference judgments obtained with the new test exhibited a significantly smaller variance among the listeners. This finding suggests that, by using several reference systems that represent an appropriate variety of distortions, preference tests can be constructed that are more efficient than those developed to date.
Statistics of F2 Adjacent to Consonants and Prediction of F2 Onsets
Authors: Pickett J. M. , Coulter D. C.
Published: September 2005

The purpose was to evaluate ways of predicting the onset frequency of the second vowel formant (F2) following consonant constrictions. Spectrograms of 604 constrictions were measured to obtain the frequency and slope of F2 offset just prior to each constriction, the duration of the constriction, and the frequency of F2 onset after the constriction. Three types of F2 onset prediction were applied to each constriction: (1) holding the F2 offset frequency, (2) linear extrapolation of F2 offset slope, and (3) exponential extrapolation of the offset slope. Statistical analyses of these data indicated that linear extrapolation gave poor results, that holding predictions were superior to predicting merely the modal onset, and that exponential extrapolations were better than holding offsets under certain conditions of offset slope and frequency region. Articulatory place and complexity of consonant constriction were found to be related to prediction error.
Effect of Acoustoelectric Interactions on the Electrical Impedance of a CdS Bar
Authors: Adler E. L. , Farnell G. W.
Published: September 2005

The effect of acoustoelectric interactions on the electrical impedance of a piezoelectric semiconductor (CdS) bar is analyzed. With the assumption that the acoustic damping is dominated by the electronic effects, the impedance undergoes substantial changes whenever the bar dimensions approach odd multiples of a half-wavelength of sound. In the presence of a biasing drift field, the impedance behavior is drastically modified and, under conditions of acoustic amplification, the real part of the impedance becomes negative for some frequencies in the neighborhood of the mechanical resonances. A linear theory for this effect is presented and the magnitude of the impedance changes are illustrated by calculations for a (1-cm) bar of CdS.
Changes in an Electrode Process Brought About by Small-Scale Acoustic Streaming
Authors: Rowe W. E. , Nyborg Wesley L.
Published: September 2005

Ultrasound in the absence of cavitation was applied in a special manner to a process in which the sonic effect on surface layers and mass transport of reactants could be studied. The process selected involved cyclic anodic and cathodic polarization of a platinum electrode in dilute acid. The test electrode was a small platinum sphere mounted on the tip of an 85-kc/sec Mason horn. Sound applied during selected parts of the cycle caused pronounced changes in recordings of the electrode potential versus time. These changes probably result from the transport of dissolved gases, via small-scale acoustic streaming, to and from the electrode surface. An order-of-magnitude approach is given to the theory for mass transport associated with the acoustic streaming.
Low-Temperature Speed of Sound in Single-Crystal Ice
Authors: Proctor Thomas M.
Published: September 2005

Only one of the previous measurements of the elastic constants and speed of sound in single-crystal ice I had been extended below −30°C. All of the five independent elastic constants have now been measured down to 65°K. Elastic-constant data have been fitted to second-degree polynomials. From these polynomials, a 0°K value for the cij's is extracted and a Debye characteristic temperature of 224°K is calculated. This Debye temperature compares favorably with that previously computed from heat-capacity data. No sudden changes in the pseudoelastic anisotropic factor c33/c11 are found to take place at 190°K, as had been previously reported.
Why Strike Out the Mighty kc?
Authors: Ward W. Dixon
Published: September 2005

Mandatory use of “kc, sec” in place of “kc” is protested.
Effects of Slow Steady Flow on a Pure-Tone Sound Field
Authors: Smith P. W.
Published: September 2005

The effect of a slow steady flow of ideal fluid upon a superimposed pure-tone sound field is examined, especially for effects upon the acoustic admittance vector. It is assumed that the total field is derivable from a scalar potential and that terms of second order in Mach number are negligible. Blokhintsev's transformation [NACA Tech. Mem. No. 1399(1956)] to a flowfree acoustic problem is shown to be awkward, except for rigid, nonporous boundaries, because of complications in the transformed boundary conditions. For one dimensional fields, it is shown that the steady flow has no direct effect on the acoustic admittance or the magnitudes of acoustic pressure and particle velocity. However the steady flow may affect the terminating admittance of a one dimensional field, and thereby become evident within that field. If the correct value of terminating admittance is used in the analysis, then a flowfree acoustic solution will yield correct values for the magnitudes of the true pressure and particle velocity and for both magnitude and phase of the true admittance at every point.
Computerized Investigation of Threshold-Decision Phenomenon
Authors: Campbell Richard A. , Hutton C. L. , Stuckey C. W.
Published: September 2005

Threshold determination within the framework of the block up-and-down, two-interval, forced-choice (BUDTIF) method has been investigated using a computerized Monte Carlo technique. Two aspects of the results are presented in preliminary fashion. (1) In a block up-and-down threshold-estimating method, modifications that yield minimal variance within individual runs may not automatically be assumed to yield minimal variance between successive threshold estimates. (2) The optimal number of trials per block was the smallest that yields a valid solution depending on the target performance level; use of a memory of more than one block for level change decisions is not indicated.
Feedback and Psychophysical Variables in Signal Detection
Authors: Carterette Edward C. , Friedman Morton P. , Wyman Melvin J.
Published: September 2005

144 observers, divided into eight groups of 18 each, were run in a two-alternative, temporal, forced-choice auditory-signal-detection task. At each of two signal intensities, four levels of information feedback were used. No feedback (NF); correct feedback on every trial (F100), on three-fourths (F75), or half (F50) of the trials, with incorrect feedback on remaining trials. The results were that (a) NF and F100 led to higher probability of correct responding P(C) than either F75 or F50 for both signal intensities; (b) P(C) for NF was higher under the higher intensity but lower under the lower intensity than for F100; (c) on trials immediately following trials on which observer's response and feedback agreed, detection rates were higher and false-alarm rates were lower than following disagreement trials, whereas these differences were close to zero for F50. It is argued that feedback leads the observer to change his criterion following disagreements. The effect of this variability is to depress the mean detectability index d′ of signal-detectability theory.
Physiological Correlate of Tonal Masking
Authors: Finck Alfred
Published: September 2005

A gross, slow potential that is differentially sensitive to the frequency of a tone burst was recorded from the region of the auditory nerve in the hamster. An experimental paradigm similar to that employed in psychological studies of tonal masking was used to measure neural-response amplitude change in the presence of a second tone. The influence of one tone upon the other, as evidenced by the neural response, yielded functions similar to the masking curves generated by human listeners. Increases in the level of the signal required increases in the level of the masker in order to maintain the masking criterion. High-tone maskers were seen to be less effective than low-tone maskers. Masking was viewed as a preempting of neural activity by the secondary tone.
Experiment in Ferroelectric-Tape Recording
Authors: Yu Tiong Suy , Dunn Hugh K.
Published: September 2005

Longitudinal recording has been achieved on plastic tape coated with ferroelectric material. Reproduced levels were constant with frequency at the low end, but in the system used there was an upper frequency limit at about 1800 cps with a tape speed of 147 ips. On one of the media tested, the recordings decayed about 9 dB in 150 sec, at a humidity of 20%. Improvement of the high-frequency limitation probably depends on better design of the reproducing head. More-permanent recordings might be obtained with stronger recording fields, resulting in deeper penetration of the recording medium, or perhaps with the use of a material with more-suitable characteristics.
Optical-Fiber Ultrasonic Delay Lines
Authors: Gelles I. L.
Published: September 2005

The ultrasonic pulse-propagation characteristics of nonmetallic optical fibers were investigated the 10-Mc/sec region. It was found that the lowest-order longitudinal L(0,1) mode and the lowest torsional or T(0) mode could be propagated, using piezoelectric transducers. The L(0,1) mode was propagated through single fibers as well as flexible bundles of fibers. The T(0) mode was propagated through single fibers. The attenuation was of the order of 0.1 dB/μsec in fused silica fibers of 75 μ diam, and about three times greater in clad glass fibers of the same diameter. In very-short-fiber lines, many echoes were observed and the end-face geometry was not critical. In flexible-fiber bundles with epoxy fused ends, no echoes were seen owing to the high attenuation of the epoxy, which was greater than 10 dB/mm of coated length. Dispersion was negligible in the single-fiber lines and flexible fiber bundles, but severe in rigid, fully fused fiber-optic bundles that behaved essentially as solid rods. There was no significant difference in the ultrasonic behavior of optically coherent and noncoherent flexible-fiber bundles of short length. Flexible fiber-optic bundles with fused ends appear to retain the simple acoustic-mode structure of the single fiber. Various multiple-fiber arrays are considered in parallel and series grouping and with different input-output configurations. A multiple-delay generator using a combination of glass and fused silica fibers of different lengths is described. Further applications are discussed.
New Method for the Measurement of Ultrasonic Attenuation in Solids at High Temperatures
Authors: Gobran N. K. , Youssef H.
Published: September 2005

The specimen under test is in the form of a rod with plane parallel ends. A thin annular groove is worked in the rod at about one-third of its length. A transmitting-receiving quartz crystal delivers ultrasonic pulses to the rod at its remote end. The pulse heights of the reflections from the constriction and the other end are measured on a cathode-ray oscillograph. Assuming a plane-wave propagation, a formula is derived to calculate the attenuation constant of the short portion of the rod in terms of the mentioned pulse heights. The obtained formula is independent of the length or attenuation of the long portion of the rod. This enables one to heat the short portion while the long portion is cooled, thus overcoming the difficulties of matching usually met with in high-temperature measurements between a quartz transducer and specimen. The method is applied to measure the attenuation of longitudinal waves in pure aluminum at temperatures up to 700°K for frequencies of 3 and 5 Mc/sec, respectively. The results indicate a thermally activated internal friction whose value agrees with that previously obtained by Kâ at a frequency of 1 cps.
Parametric Solution of the Dispersion Relation for Guided Sound Propagation in Shallow Water
Authors: Pierce Allan D.
Published: September 2005

The normal-mode dispersion relation for guided propagation in a liquid layer lying above an infinitely deep liquid bottom appears as a transcendental equation relating the angular frequency ω and the horizontal wavenumber k in Perkeris' classic solution. It is shown in this paper that this transcendental equation may be solved exactly in a parametric form for any given normal mode. Equations are derived and discussed. They give frequency, phase velocity, and group velocity in terms of a single parameter μ and mode number n.
Plastic Deformation in Random Vibration
Authors: Karnopp Dean , Scharton Terry D.
Published: September 2005

A randomly excited single-degree-of-freedom oscillator in which an idealized form of plastic deformation can take place is studied. Through the use of an artificial process, statistics of this nonlinear, hysteretic system are deduced from linear system-response statistics in two régimes of operation. The expected accumulated plastic deformation is found as a function of time and some other statistics derivable from the artificial process are indicated. A numerical example is given that illustrates the use of the method with low-cycle fatigue data.
Underwater-Sound Reflection from a Pressure-Release Sinusoidal Surface
Authors: Barnard G. R. , Horton C. W. , Miller M. K. , Spitznogle F. R.
Published: September 2005

Numerical predictions for the reflection of plane sound waves from a pressure-release sinusoidal surface of large slope are compared with experimental data. The approach introduced recently by Uretsky [J. Acoust. Soc. Am. 35, 1293–1294 (1963)] for the calculation of reflection coefficients was adopted with some modification owing to the geometrical parameters of the surface and the frequency of the incident sound. The geometry of the surface and the experiment were such that theory could be tested with three orders of the grating spectra.
Normal Hearing Threshold Determined by Manual and Self-Recording Techniques
Authors: Knight J. J.
Published: September 2005

Data are presented relating to the thresholds of three different samples of normally hearing subjects, which indicate that the British standard and recommended ISO reference zero for audiometers is insufficiently stringent by approximately 3 dB over the frequency range 0.5 to 6 kcps. Determinations of threshold, made with the same audiometer and the same earphone placement, by a conventional manual method and by a self-recording method showed the latter to give an average threshold more sensitive than the manual usage gave by less than 1 dB. The inaccurate nature of current procedures for audiometer calibration employing a single subjective correction for all receivers of a particular pattern is stressed.
Normal Threshold of Hearing for Pure Tones by Earphone Listening with a Self-Recording Audiometric Technique
Authors: Rice C. G. , Coles R. R. A.
Published: September 2005

Two independent series of measurements of normal auditory threshold have been carried out with fixed-frequency self-recording audiometers. The results are in close-agreement with each other, but yield threshold levels that are distinctly more acute than the International Stanford reference levels (ISO-R,389; 1964), the exact difference varying somewhat according to different methods of application of the standard to TDH-39; MX-41-AR earphones. Possible reasons for the more-acute thresholds are discussed.
Equivalent Threshold Sound-Pressure Levels for the TDH39/MX41-AR Earphone
Authors: Whittle L. S. , Delany M. E.
Published: September 2005

Recent subjective threshold calibrations of a range of audiometric earphones permit direct comparison of their equivalent threshold sound-pressure levels on various artificial ears and couplers. Values of equivalent normal threshold sound-pressure level, compatible with ISO Recommendation R389, are given for the TDH39 MX41-AR earphones on an NBS type 9A coupler.
Effects of Bandpass-Filtered Noise upon the Intelligibility of Filtered Speech
Authors: Singh Sadanand , Brokaw Sonia P. , Fricke James E.
Published: September 2005

Intelligibility scores were obtained from 240 listeners for monosyllabic words. In Expt. 1, noise was introduced at the lowest end of the spectrum and, in Expt. 2, at the highest. Throughout the listening task, speech was presented through one of four “equally contributing intelligibility bands” (quarter-bands) of the speech spectrum: 300–760, 760–1450, 1450–2550, and 2550–7000 cps. Intelligibility in the channels (quarter-bands) at the opposite ends from the noise was superior in the experimental condition to that in the control, the control being characterized by no introduction of noise. Thus, effects similar to previously reported studies of release from masking were evident.
Backscattering Strengths of Sea Ice
Authors: Chapman R. P. , Scott H. D.
Published: September 2005

Reverberation was measured from smooth young ice and from heavily rafted winter ice in the Canadian East Coast waters. “Point” charges were used as sound sources and an omnidirectional hydrophone as the receiver. Backscattering strengths were measured in octave bands from 0.4 to 25.6 kc/sec over a range of grazing angles from 15° to 60°. The scattering strengths for the rough ice are approximately equal to the smallest that have been reported for Arctic ice and are substantially greater than those measured for the smooth ice. Values previously reported for young broken and refrozen ice in the Gulf of St Lawrence generally fall between those measured for the rough and smooth ice. There is little variation of scattering strength with frequency for either rough or smooth ice.
SONIC SIGNAL SPLITTING PRODUCED BY AN ORIFICE
Authors: Michael Paul L. , Hogan Donn P.
Published: September 2005

A ring-shaped directivity pattern has been observed when an acoustical signal is transmitted from an orifice in the wall of a buried pipe when the gaseous medium in the pipe is under high pressure. This effect appears to result from a combination of conditions that are similar to those that produce jet noise patterns and acoustical streaming around an orifice. The experimental work in which these effects were measured was sponsored by the American Gas Association as part of a sonic leak-pinpointing project.
Measurement of Vibration Amplitudes, Using Laser Beams
Authors: Deferrari Harry A. , Andrews Frank A.
Published: September 2005

The technique of using CW laser beams for the measurement of small vibration amplitudes is discussed. Limitations of the method and its possible applications are considered.
Shifts in Auditory Thresholds Produced by Ipsilateral and Contralateral Maskers at Low-Intensity Levels
Authors: Dirks Donald D. , Norris Jane Chandler
Published: September 2005

The present investigations were conducted to determine and describe some of the acoustic parameters of central masking. Shifts in threshold were observed during the following monotic and dichotic conditions: (1) pulsed pulsed, in which both test signal and masker were pulsed simultaneously; (2) pulsed continuous, in which the test tone was pulsed but the masker was continuous; and (3) continuous-continuous, in which both test tone and masker were steady. Test signals of 250, 1000, and 4000 cps were used. It was found that the degree of threshold shift resulting from central masking factors was dependent on the temporal presentation of the test signal and masker (whether pulsed or steady). Threshold shifts due to central masking increased with frequency and were related to the spectrum level of the masker. The largest shifts in threshold were found for a 4000 cps test signal when the masker was a pure tone close in frequency. In these instances, lateralization of the test signal toward the midline was observed as the threshold shift increased and, at times, subjects were unable to distinguish between the test tone and pure-tone masker. Although the results can be explained on the basis of central masking factors, the manner in which the subjects traced their thresholds during the condition where both test signal and masker tone were continuous suggested that all observed shifts in threshold may not be clue to masking alone.
Axisymmetric Vibrations of Prolate Spheroidal Shells
Authors: DiMaggio F. , Rand R.
Published: September 2005

Nontorsional extensional axisymmetric modes and frequencies of elastic prolate spheroidal shells as a function of eccentricity are obtained by a numerical technique. The mode spectra have two distinct branches, analogous to those of spherical and cylindrical shells. Extensive results are presented for the lower branches.
Composite Loss Factors of Selected Laminated Beams
Authors: Di Taranto R. A. , Blasingame W.
Published: September 2005

Theoretical damping values have been determined for three- and five-layer beams having representative cross sections. Trends are obtained that show damping effects produced by changes in cross-sectional geometry of the beam and properties of the damping material. The results are a series of characteristic curves displaying an increase in damping with increased frequency for the low frequency range, a peaking of the curves in the midfrequency range and a decrease in damping for the high frequencies. In addition, they show that increased viscoelastic material thickness and increased shear storage modulus shift the damping curve toward the low frequencies, while an increased thickness of the elastic layers, considered herein, appear to have no appreciable effect on composite damping behavior. For equal over-all beam thickness and equal viscoelastic-material thicknesses, the three-layer beam provided higher damping at the low frequencies whereas the five-layer beam yielded better damping at the peak, and at higher frequencies. Approximate analytical expressions are derived that verify the low- and high-frequency characteristics and predict the peak damping frequency and composite loss factor.
Generalized Matrix Method for the Design and Analysis of Vibration-Isolation Systems
Authors: Smollen Leonard E.
Published: September 2005

Matrix equations of rigid-body motion for a general isolation system are presented and conditions for decoupling translational and rotational motions are discussed. The effective rotational and translational stiffnesses of a set of isolators arbitrarily oriented with respect to the center of mass of an isolated rigid body are developed by matrix techniques. Influence coefficients for determining loadings on the isolator's elastic axes owing to arbitrary g loads at the system center of mass are also presented in matrix form. The application of the matrix techniques presented to the design of vibration isolation systems is illustrated through an example.
Direct-Energy Density in Transmission-Loss Measurements
Authors: Donato R. J.
Published: September 2005

Attention is drawn to the errors that might arise in allowing for the direct energy in a receiving enclosure. Formulas are developed for the mean direct-energy density throughout the room and also for its dependence on the distance from the radiating wall. Comparisons with the reverberant levels in the room are made for various assumed distributions of wall absorption.