bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Plane-Symmetric Mass Loading on the Response of Ring-Stiffened Cylindrical Shells
Authors: Michalopoulos C. D. , Muster D.
Published: November 2005

An analytical study of the in vacuo vibrations of a simply supported, mass-loaded thin cylindrical shell that is reinforced by equally spaced ring stiffeners is presented. Four masses are attached to each stiffening ring in a plane-symmetric fashion. The rotatory inertia of the masses is taken into account, but similar effects for the shell and ring stiffeners are neglected. Lagrange's equations are used to derive the dynamic equations of the shell structure and the Jacobi iteration method is employed to find the natural frequencies and corresponding mode shapes. Results are given for various values and angular position of the masses. When the value of the masses is allowed to become zero, the results for the ring-stiffened shell are in close agreement with those of previous investigators. Modal analysis is used to obtain the response of the structure to two different types of excitation: (1) a band of uniform internal pressure applied as a pulse in time, (2) a pressure wave that strikes the shell transversely. Numerical results are not presented for these two cases. [The investigation was supported by the U. S. Office of Naval Research.]
Non-Gaussian Response Statistics and Reliability Prediction
Authors: Smits Talivaldis I.
Published: November 2005

The concept of a wear-dependent failure rate h(t|Δ) is used to find the (average) failure rate for a dynamical system threatened by both wearout and overload failure, on the basis of its response statistics. Analytical expressions for h(t|Δ) are conservatively fitted in terms of N+(Yc(Δ), the average frequency of crossings of the overload level, and νF̄(Δ*-Δ), the exceedance probabilitiy of partial damages per cycle (computed from “peak” statistics) times the peak occurrence probability. A Weibull fit, exp{−Δ(η/θ)β}, is produced as a conservative bound on typical crest and “peak” exceedance probabilities. Values of β for impulsive and Gaussian noise generally lie between 1 and 2 (between the exponential and the Rayleigh distributions). This makes β⩽0.5 for partial wear. Using the orthodox failure theories, the h(t|Δ) are found to be bounded above by h(t|Δ*). (The case of a variable wearout level Δ* is also considered.) The probability density of wear in an operational system is approximated via renewal theory; a truncated normal distribution is useful. [Work supported by Research Technology Division, Air Force Systems Command, U. S. Air Force.]
Peak Statistics of Linear Systems Excited by Impulsive Noise
Authors: Hedin George L.
Published: November 2005

Various response “peak” statistics of linear systems excited by Poisson impulsive noise having a normal impulse-strength distribution are examined analytically as well as experimentally. Considerations of such statistics are significant in damage and reliability predictions, particularly in the more non-Gaussian case of low average impulse density. By employing two independent methods, analytic expressions for the output crest (level crossing), positive maximum, and rise (minimum to maximum excursion) distributions for rather general linear systems are derived. The first method is based on either analytical or empirical knowledge of the maxima and minima of the system's impulse response function. The second, an approximate method, is based largely on considerations of total transmitted energy. Empirical results for these statistics, measured on an analog simulation of a bimodal system, are presented and compared to results obtained from the aforementioned theories. [Work supported by Research Technology Division, Air Force Systems Command, U. S. Air Force.]
Linear Filter Theory for Circular Array Processing
Authors: Vettori G.
Published: November 2005

A transparent circular array in monochromatic plane waves can be regarded as a “linear spatial filter” in which the contour phase function f(φ−θ), due to a plane wave from direction θ, is the filter impulse response when the plane wave is represented by a delta function δ(φ−θ). The spatial frequency spectrum F(s) [the Fourier transform of f(φ)] is saddleshaped and limited to a bandwidth 2R/lgr;. The angle-spatial bandwidth product is then 4πR/λ, analogously to time-frequency bandwidth product. A spatial processing filter, of impulse response h(φ), can be put in “series” to synthesize a desired directly function g(φ) at the output, whose spectrum G(s) satisfied the above bandwidth limitation. Function h(φ) is then obtainable as the inverse transform of H(s)=G(s)/F(s). Optimization of H(s) for maximum signal-to-background ratio for a signal source in isotropic monochromatic reverberation [describable at the array input as white (in s) noise] leads to a matched filter with H(s)=F(s)*/|F(s)|2 that whitens the spectrum measured at the contour and gives a processing gain of 4πR/λ. Then g(φ) is a sin x/x function.
Digital Recording and Reading Equipment for Underwater Sound Studies
Authors: Laval R. , Castanet A.
Published: November 2005

Digital computers are of considerable interest for the analysis of signals in the field of underwater acoustics. The defects of analog recording (limited dynamic range, instability of the time base) may be eliminated by recording the signals directly in digital form during the experiments. A special equipment has been constructed at the SACLANT ASW Research Centre that permits the simultaneous recording in digital form of 5 channels, 8-kHz bandwidth each, with a dynamic range of 84 dB. The recorded signals can be replayed into a digital computer for detailed processing. A 14-channel analog tape recorder of a standard type is used. Two channels are left available for analog recording if desired. A counter track associated with an “editing device” permits fast and precise location of the samples of signals to be selected for analysis.
Circumferential Waves in Structurally Reinforced Metallic Cylindrical Shells in Water
Authors: Grace O. D. , Goldsberry T. G.
Published: November 2005

Formation of the back-scattered farfield circumferential-wave pattern for disk-reinforced (compartmentalized) air-filled, metallic cylindrical shells in water is traced through the scattered nearfield to the cylindrical surface. Patterns for single- and multicompartmented shells are displayed. The nondimensionalized frequency, d/λ(=dν/c, where d is the shell thickness, and c is the compressional group velocity in the shell material at the driving frequency ν) is 0.55. Isovelocity and isodecay profiles of the circumferential-wave nearfields of the single- and three-compartmented shells are presented. [Work under contract with the U. S. Office of Naval Research, Code 463.]
Spectral Character of Ice Vibrations in the Central Arctic Ocean from 0.1 to 100 cps
Authors: Prentiss David , Davis Edward , Kutschale Henry
Published: November 2005

During April and May 1962, the vertical component of ice vibrations from 0.1 to 100 cps was recorded abroad drifting ice island ARLIS II in the Central Arctic Ocean. The displacement spectra are characterized by smoothly decreasing amplitudes proportional to f−2 from amplitudes of 2.4×104 mμ at 0.1 cps to 1.0 mμ at 6 cps, with a small-amplitude plateau around 2 cps of 1 mμ. At higher frequencies, the characteristics are (1) an amplitude minimum between 6–10 cps of 0.1 mμ; (2) an amplitude maximum between 30–70 cps of 2 mμ. There is some correlation between local wind velocity and the ambient ice amplitudes. Under the quietest conditions of minimum local wind, the ice surface from 1 to 10 cps is quieter than most quiet land sites. Under the most unfavorable conditions, the ambient noise from 30 to 80 cps approaches that of many noisy land sites. Fracturing produces local ice tremors that enhance the ambient level between 0.7 and 10 cps. In general, the shape of the amplitude spectra of both local and distant explosions are strikingly similar to the ambient spectra. In the 10–20-cps band, the reverberation spectra following distant explosions rise smoothly 6–10 dB relative to the ambient level. The time decay of reverberation amplitudes from a local shot appear to follow a power law with an average loss of −2.11±0.03 dB/sec from 1 to 100 cps and a maximum loss of −2.76±0.12 dB/sec at 20 cps.
Transient Response Spectra of Coupled Acoustical Resonators
Authors: Reddy N. N. , Lowery Richard L.
Published: November 2005

The maximum absolute pressure magnification of a Helmholtz resonator for an excitation of one cycle of a sine wave is 3.14, occurring when the natural period of the system is equal to the excitation period. When two resonators are coupled together, the response is a function of two uncoupled natural frequencies and a coupling frequency of the system. The maximum pressure magnification can be much higher than that of a single acoustic resonator. The objective of this paper is to explore the pressure response of two coupled Helmholtz resonators to an excitation of a single sine pulse. Theoretical results are compared with experimental values. The experimental procedures used to produce the transient pressures and to obtain the response measurements are illustrated. The pressure magnification factors are presented as a function of the various frequencies of the system. The absolute maximum pressure magnification for representative systems has been investigated by utilizing numerical techniques on a high speed digital computer. All results are presented in the frequency domain.
Reduction of Sound Generated from a Plate Boundary Layer by a Vibrating Wall
Authors: Wehrmann O. H.
Published: November 2005

The influence of an active flexible wall on the stability of the boundary layer on a flat plate was investigated experimentally. An unstable Tollmien-Schlichting wave in the boundary layer was generated by a vibrating ribbon. The active flexible wall simulated a matching propagating wave by a number of small elements vibrating with a stepwise increasing phase relation in the flow direction. The pressure fluctuations in the boundary layer on the flexible wall could be increased or reduced, depending on the phase relation between the wall and the velocity fluctuations. In the case where the velocity fluctuations and the wall vibrations are in phase, a significant reduction of the pressure fluctuations and sound radiation could be obtained
Effects of Low-Pass Filtering on Perception of Consonant Clusters
Authors: Grubb Patti
Published: November 2005

Twenty-four consonant clusters that occur prevocalically in English were spoken with the vowel /a/. Four clusters were fricative+stop+/l/ or /r/; 15 were stop or fricative+/l/ or /r/; three were fricative+stop; and two were fricative+nasal. Three male speakers recorded three samples of each syllable. Sound-pressure levels and durations of the syllables were measured from graphic-level recordings. The syllables were subjected to low-pass filtering at 750, 1000, 1250, 1500, 1750, or 3000 cps. Syllables were presented binaurally via earphones at a comfortable listening level to seven adults with normal hearing. Responses of the listeners were analyzed by plotting confusion matrices. Identifications of the syllables were compared on the basis of voicing, manner, and place of production of the first and second elements of the clusters. Five different “families” of clusters based on identifiability at various cutoff frequencies were discerned. The relationship of clusters within a family is not readily explained on the basis of manner or place of production or voicing.
Finite-Element Modeling of a Cantilever Beam
Authors: Kuzanek Jerry F.
Published: November 2005

Several different finite-element models of a uniform isotropic cantilever beam were designed and the frequencies and mode shapes of these models were obtained through the use of a structural analysis computer program. Results were compared against both the Bernoulli-Euler and Timoshenko theories of transverse vibrations of uniform beams. All of the first 14 frequencies of some of the models that attempted to simulate the effects of rotary inertia and shear flexibility differed from the corresponding frequencies according to the Timoshenko theory by less than 1.6%. The first 14 mode shapes of these models differed slightly from the corresponding mode shapes according to the Timoshenko theory. These differences, as well as decisions made concerning the design of the models, are the topics for discussion.
Focusing Properties of Liquid-Filled Cylindrical Lenses with D/λ>15
Authors: Folds D. L. , Brown D. H.
Published: November 2005

A mathematical model that includes the effects of the lens shell has been developed and used to predict theoretical directivity patterns. With the aid of this model, a cylindrical lens 40 cm in diameter was constructed and tested at frequencies ranging from 25 to 900 kHz. Experimental directivity patterns compared favorably with those predicted theoretically. The results of this investigation indicate that cylindrical lenses are useful at D/λ values up to 150, which is a factor of 10 greater than previously reported.
Formation of Ultrasonic Images by Holographic Techniques
Authors: Mueller R. K. , Sheridon N. K.
Published: November 2005

Experiments demonstrating the formation of optical images of objects immersed in sound-propagating media (water, in our case) and illuminated by ultrasonic waves are described. The image formation is achieved via a sound-diffraction pattern that is used as an optical hologram. A visible diffraction pattern due to sound waves diffracted off an acoustically illuminated object and an acoustic reference beam is produced at the surface of the water by the balance of the radiation pressure of the sound waves with the surface tension of the water. Since the radiation pressure is proportional to the sound intensity, the surface deformation produced in this manner has all the characteristics of a hologram. Coherent light reflected off this surface, therefore, forms a conjugate pair of optical images of the acoustically illuminated object. The optical reconstruction is reduced in size in the ratio of acoustic to optical wavelength and has to be viewed with magnifying optics. Objects transparent to sound waves appear transparent in the optical reconstruction, and, thus, internal features of the objects can be viewed or recorded.
Changes of Middle-Ear Acoustic Impedance Resulting from Contralateral Noise, Female and Male Subjects
Authors: Shallop Jon K.
Published: November 2005

One might hypothesize that various subjects differ in the magnitude of changes in middle-ear acoustic impedance resulting from noise stimulation. If these impedance changes are apparently different, this may indicate differential middle-ear musculature strength among various subjects. Twenty young adults (10 females and 10 males) with normal hearing sensitivity served as subjects for the following experiment. Measures of acoustic impedance were obtained with the Zwislocki Acoustic Bridge (Grason-Stadler, model 3) at 500 Hz under two conditions—no noise and 105 dB SPL of white noise in the contralateral ear. As might be expected, the noise resulted in easily detectable impedance changes, however, these changes were not significantly different between the subject groups. Acoustic reactance increased for both groups (females 330 Ω and males 350 Ω), while acoustic resistance decreased for both groups (females 88 Ω and males 90 Ω). Several subjects with the smallest and greatest impedance changes were later exposed to intense noise stimulation and auditory threshold shift was measured. The results of the findings regarding impedance change and temporary threshold shift will be discussed in the paper.
Recording of the Movement of the Human Basilar Membrane
Authors: Jako Geza J. , Hickman Kenneth E. , Maroti Lewis A. , Holly Sandor
Published: November 2005

The vibrations of the human basilar membrane have been thoroughly studied by von Békésy. He used visual observation of moving silver particles on the membrane. In our preliminary experiments, we used fresh human temporal bones. The basilar membrane was exposed in the apical turn using microsurgical instruments with illumination provided by fiber optics. The cochlear fluid was moved through the round window, similar to the Békésy experiments. The movement of the basilar membrane was recorded electro-optically, using special cochlear probes described in a paper by Jako, Hickman, and Adkins at the 72nd Meeting of the Acoustical Society. Recent developments in photosensor technology, and accurate alignment of the fiber optics with the photosensors, have permitted continuing improvements in probe resolution. This technique allows instrument recording of time, phase, and frequency relations of motions at various places along the membrane while it is stimulated by sine waves, pulses, and speech. [Supported by a grant from the American Otological Society and the volunteer efforts of the participants.]
A Model of the Nonlinear Behavior of Cochlear Microphonic and Summating Potential
Authors: Engebretson A. Maynard , Eldredge Donald H.
Published: November 2005

Whitfield and Ross have proposed a nonlinear model that seems to explain summating potential that is observed in the cochlear voltage. One would not expect their model to explain the interference effect reported by Wever. However, we find that, by choosing an appropriate nonlinearity, in addition to summating potential almost all of the cochlear microphonic phenomena can be explained in terms of one nonlinear mechanism. These phenomena include distorted waveshapes observed in the cochlea; harmonic frequencies produced by distortion; combination tones, which are produced when two signals are present; and the linearization of the operating characteristic of one signal when a second signal is introduced (interference effect). A simple nonlinear analog model is discussed and the striking similarities between the behavior of the model and biological data is shown. [Work supported by National Institutes of Health, Public Health Service, U. S. Department of Health, Education and Welfare.]
Scattering of Plane Wave by Infinite Hemicylindrical Bosses with Random Radii on a Plane Surface
Authors: Hayre H. S. , Klos W. A.
Published: November 2005

This paper extends previous work on the subject of scattering of a plane wave incident on infinite hemicylindrical bosses of a given radius with periodic spacing to those with random radii; the surface described above may be considered as one possible representation of certain surfaces encountered in practice. The probability-density function of the radius is assumed to be uniform, and the spacing between the centers of adjacent bosses is maintained constant. The spacing is assumed to be so selected that the shadow effects are negligible for the angles of incidence considered in this study. The scalar form of Helmholtz integral formulation was used to solve this problem. Obviously, some of the inherent assumptions in this technique are invalid at the intersection of the hemicylinders and the plane background surface. This work shows that the presence of such discontinuities in the surface does not reduce the usefulness of this simple theoretical approach in calculating the scattered field in a closed form. Some numerical calculations were made using the IBM 1401 computer, and a comparison between the theoretical and experimental results for the scattered acoustic fields from various models of such surfaces supports the above results. [This work is sponsored by the Office of Naval Research.]
Diffraction of Acoustic Pulses by Obstacles of Arbitrary Shape with an Impedance-Boundary Condition
Authors: Shaw Richard Paul
Published: November 2005

The diffraction of an arbitrary acoustic pulse by an arbitrary scattering obstacle with an impedance-boundary condition is treated by the same technique used by the author in previous diffraction studies [“Diffraction of Acoustic Pulses by Obstacles of Arbitrary Shape with a Robin Boundary Condition,” J. Acoust. Soc. Am. 41 (to be published)]. The problem is formulated as an integrodifferential equation on surface values of pressure or velocity; this equation is then solved numerically for the specific geometry of a long cylinder of square cross section struck laterally by a step pulse in pressure. A useful economy is that the coefficients used in the approximation are independent of the boundary condition and are identical to those used for previous studies involving the same geometry. Results indicate that the surface pressure decreases from the rigid-body solution for infinite impedance to an almost constant level for the boundary impedance equal to the fluid impedance. [This work has been sponsored by the Office of Naval Research.]
Seismic and Acoustic Waves from a Meteor
Authors: Bayer Kenneth C. , Jordan James N.
Published: November 2005

On 1 April 1965, at 05:48 U.T., a meteor struck the earth in the Banff-Penticton area of British Columbia, Canada. The meteor was sighted and recorded by seismic and infrasonic equipment. The U. S. Coast and Geodetic Survey analyzed Canadian and United States seismograms from the immediate vicinity. Sufficient acoustic, surface, and body-wave seismic signals were recorded to outline an epicentral area of impact. This assisted the Canadian Government in carrying out an aerial photographic survey and on-site inspection tour. This represents the most geophysical data available on this unique event, and perhaps the best documented within recent historical times.
Observations of Bond Failure Using Low-Frequency Ultrasonic-Pulse Attenuation and Transmission Spectra
Authors: Kostyrko G. J.
Published: November 2005

Burst-continuous low-frequency ultrasound of 66 kHz frequency was used to examine the solid-propellant-to-liner bond as it undergoes failure due to constant-load application. Specimens with failure times as long as one week were studied. Piezoelectric-disk transducers of original design were used in a straight-through-transmission method. They were bolted to the sides of a circular-sandwich specimen; the solid propellant was bonded with flexible liner to the rubber insulation on one side and to an aluminum plate on the other. Failures in each case occurred in the flexible bond. Burst-continuous waves were sent through the specimen and the initial amplitude of the transmitted pulse was measured. The Fourier components of the transmitted pulse were obtained with an ultrasonic-spectrum analyzer and recorded on Polaroid film. In all cases tested, as the bond was failing, there was an increase in attenuation of the transmitted pulse and a shift in the characteristic “sonic” spectrum display. The results point the way for application of “sonic” spectroscopy to materials research.
Perceptual Study of English /l/ Allophones
Authors: Haggard Mark
Published: November 2005

Once the broad set of perceptual cues distinguishing utterances is isolated, speech synthesis can be further used to answer detailed questions about the process of perception. Such questions are basic to application of knowledge about speech to synthesis-by-rule. Improvement of synthesis rules may result from adjusting the rules to maximize quality of long utterances, but more restricted, detailed perceptual investigations are also necessary. The /l/ phoneme fits into no convincing matrix of feature oppositions and is difficult to synthesize; so five questions were examined for six /l/ allophones—initial and final in the contexts /i,a,u/. (1) How do the optimal patterns vary as a function of context? (2) What is the importance of spectral discontinuities? (3) Do the /l/ steady state and transition have interdependent perceptual effects? (4) Is the same priority of cues shown in quality judgments at high intelligibility levels and in effects on recognition of an ambiguous stimulus? (5) What modification do analysis data and preliminary synthesis experiments suggest for extension of answers to the above questions to other contexts? Results and some descriptive generalizations are given.
The Effects of Delayed Auditory Feedback on Ictal-Speech Automatisms
Authors: Chase Richard Allen , Cullen John K. , Niedermeyer Ernst F. L. , Blumer Dietrich P.
Published: November 2005

The experiments reported in this paper were designed to provide information about whether speech can be elaborated without closed-loop auditory-feedback control. The experiments involve precipiation of focal, psychomotor seizure activity in patients known to talk during their seizures (ictal-speech automatisms). Metrazol (pentylenetetrazol) is injected intravenously, under EEG control, in order to induce seizure activity. The effects of delayed auditory feedback on speech elaborated during seizure activity are compared to the effects of delayed auditory feedback on comparable speech samples obtained under normal speaking conditions. Observations made on one patient demonstrate that speech elaborated during seizure activity can sound quite normal; observations fail to show any evidence of the increase in phonation time and increase in mean sound-pressure level characteristic of speech under delayed auditory feedback. The same speech, elaborated before and after the seizure, shows marked prolongation of phonation time and increase in mean sound-pressure level under delayed auditory feedback conditions. From these observations we infer that the speech elaborated during psychomotor seizures can be organized in a normal fashion without closed-loop auditory-feedback control.
Confusions of Gravity and Diffuseness of Filtered Prevocalic /p,t,k/ and Postconsonantal /u,i,a/
Authors: Singh Sadanand , Morehead Donald M.
Published: November 2005

The relationship of /p/-/t/ according to Jakobson carries the opposition grave (low pitch) and acute (high pitch). Fischer-Jørgensen found that this opposition corresponds to a physical difference of relatively low and high frequencies. Further, compactness differentiates /p/ and /t/ from /k/. This opposition is relative to the concentration of energy in a narrow central part of either the higher or lower portion of the spectrum. The vowels /u,i,a/ are similarly contrasted. This experiment tests the relativeness of grave and acute and the distributions of spectrum for diffuseness. The speech spectrums of /p,t,k/ in a prevocalic syllabic context /u,i,a/ were recorded by one male and one female and filtered in 102 different frequency bands. Native speakers (English, N=205) listened in groups of five. Each group heard two bands in an open-choice situation at different times. The data were analyzed separately for correct identification and for substitutions. Contextual effects on perception were demonstrated. Optimal bands were also determined. Substitutions indicated general agreement but failed to demonstrate clearly the Jakobsonian distribution of relative frequency ranges. Optimal-intelligibility bands were found over a wide range of the spectrum.
Second-Order Fields near a Small Translating Source
Authors: Nyborg Wesley L. , Rooney James A.
Published: November 2005

Studies have been made of movements in liquid suspensions near small solid objects which become sound sources by being set into translatory oscillation at ultrasonic frequencies. Small-scale eddying movements are observed near such a source on which are superposed movements of suspended particles toward or away from the source. Available theories for near-boundary acoustic streaming and radiation pressure have been found useful in accounting for these movements. The radiation force can be accounted for intuitively in terms of gradients of Bernoulli pressure. Formal theory of particular relevance is that of Embleton [J. Acoust. Soc. Am. 26, 40 (1954)] for radiation pressure on a sphere in a spherical field. Approximate theory has been developed for generalizing the results. [This work was supported in part by grants from the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Subharmonic Generation in an Acoustic Interferometer
Authors: Bamberg Jack A. , Cook Bill D.
Published: November 2005

Korpel and Adler showed that above a certain energy-density threshold in an intense ultrasonic standing wave that subharmonics of the driving frequency were present [Appl. Phys. Letters, 7, 106 (1965)]. To study this effect, an acoustic Fabry-Perot interferometer was constructed using two air-backed x-cut quartz transducers submerged in water, driving one around its 3-MHz resonance, and examining the frequency spectrum across the other with a spectrum analyzer. An investigation of thresholds and frequencies of the subharmonic waves was conducted for various configurations of reflectors, driving frequencies, and distances between reflectors. All subharmonics observed had frequencies that are integer harmonics of the fundamental cavity resonance. The frequencies of the subharmonic “modes” occur in hands around 12, 13, and 14 of the driving frequency, but it should be noted that this does not necessarily imply that subharmonics occur at 1/n of the driving frequency. [Sponsored by the Office of Naval Research.]
Computer Simulation of Spatial Firing Pattern of 8th Nerve Fibers—A Preliminary Study
Authors: Khanna Shyam M. , Sears Richard E. , Tonndorf Juergen
Published: November 2005

The time pattern of nerve impulses in the 8th nerve fibers, in relation to signal intensity and frequency, represents but a limited aspect of the coding process employed in the auditory system. A study of spatial patterns should provide important additional information. However, the experimental approach in animals is quite difficult. As an alternative method, a computer simulation of the events in the cochlea and in the 8th nerve was attempted. Since the nature of the transduction process at the hair-cell level is not known, as a first step, the temporal and spatial patterns of firing for 120 uniformly spaced simulated nerve fibers were obtained, the assumption being that the mechanical stimulus might be directly responsible for neural triggering. The model includes the simulated effect of mechanical events in the middle ear and in the cochlea. Traveling waves and shear waves were generated and trigger fibers were connected to specified locations along the cochlea. [Work supported by grants from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Paucity of Unit Responses in the Accessory Superior Olive of Barbiturate-Anesthetized Cats
Authors: Guinan John J. , Norris Barbara E. , Swift Shelley H.
Published: November 2005

Platinum-tipped or fluid-filled electrodes (tip diameter 2.5–12 μ) were used to record extracellular unit responses to acoustic stimuli (e.g., tone bursts, noise bursts, or clicks, presented monauraly or binaurally). In data from approximately 40 electrode passes through the accessory superior olive (ASO), histology indicated that only 14 units (4 suitable for study) were encountered that were located within the ASO. Throughout the whole superior olivary region sampled by these passes, a total of 214 units (114 suitable for study) were encountered and histologically localized. The number of units found in the ASO seems disproportionately low considering the size of the ASO relative to the size of the region sampled. This paucity of unit responses suggests that previous data localizing units within the ASO might be profitably reexamined. [Supported in part by the Joint Services Electronics Program of the National Science Foundation, the National Institutes of Health, U. S. Department of Health, Education, and Welfare, and National Aeronautics and Space Administration.]
Histological Changes Accompanying Hearing Impairment following Subtotal Electrolytic Lesions to the Auditory-Nerve Region of the Guinea Pig
Authors: Liu J.-C. , Wilpizeski C. , Tanaka Y. , Harbert F.
Published: November 2005

Brainstems with attached cranial nerves were removed from guinea pigs sacrificed 13 weeks after placing electrolytic lesions in the auditory-nerve region. Tissue staining was done principally by the method of Kluver and Barrera, and sections were evaluated in terms of damage to fibers and cell bodies. Attempts were made to relate extent of histopathology to severity of hearing loss assessed by changes in absolute-threshold levels and above-threshold amplitudes of evoked potentials. Four additional groups of animals with no audiometric data were lesioned and sacrificed for histological study 24 h, and 1, 2, and 4 weeks following neural injury. [Work supported in part by National Institute of Neurological Diseases and Blindness.]
Determination of Resonant Modes in Piezoelectric Plates
Authors: Spencer W. J.
Published: November 2005

The wide usage of piezoelectric plates in ultrasonics and communication systems has stimulated considerable interest in the determination of the resonant modes of vibration of these plates. Experimentally, it is possible to measure the frequency, the reactance, and the loss associated with modes that may occur in a plate of arbitrary geometry. The determination of these parameters are generally not sufficient to identify a particular mode of vibration. The use of electrostatic probe measurements and x-ray diffraction topography can be used to determine the actual particle displacements associated with the resonant modes. All of these measurements may be used to compliment and extend the present approximations to anisotropic-plate vibrations. This paper reviews the techniques for the measurement of frequency, displacement, and electrical parameters in piezoelectric plates. These measurements are compared with the results computed from Mindlin's first-order theory for rectangular AT-cut quartz plates.
Speech Synthesis by Rule as a Research Technique
Authors: Mattingly Ignatius G.
Published: November 2005

A number of investigators, using various types of systems, have for some time been engaged in generating synthetic speech from a phonemic input. This work is not just an interesting curiosity but has practical applications and is a tool for linguistic research. Reasonably intelligible speech can now be produced, not only because of our growing understanding of the problems involved, but also because of technical improvements in synthesizers and the increased flexibility in experimentation that digital computers have made possible. But comparison of speech synthesized by rule with closely copied speech produced on the same system makes clear that the rules still need a great deal of correction and, perhaps, further elaboration. Areas in which further work is particularly needed include the prosodic features, rhythm and duration, “naturalness,” allophonic rules, and juncture. All of these topics are of great interest to phoneticians and phonologists. Speech synthesis by rule provides both an intellectual framework for consideration of these problems and an experimental method with which to investigate them.
On the Noise of Crowds
Authors: Connor William K.
Published: November 2005

The behavior of crowds of people as acoustical-noise sources is a matter concerning which there is little definitive information, in spite of an increasing need for such knowledge. Although quantitative data are available for individual talkers and listeners, analysis of an aggregate of individuals—i.e., a crowd—is complicated by the fact that the total acoustic output is influenced by the effect upon communication of the resultant noise level. A particular problem, discussed in several papers a few years ago under the heading “cocktail-party acoustics,” is the spontaneous increase of crowd noise to a rather high level under certain conditions. A simple model is given that attempts to define these conditions. This model assumes that (1) both direct and reverberant sound must be considered, although either may be dominant in a given case, and (2) if, in a specific situation, the noise level due to normal conversation is such as to inhibit communication, the level will increase to a certain maximum value, at which point talkers are exerting maximum speech effort short of shouting. Examples analyzed according to the model are given.
Ultrasonic Absorption in Aqueous Suspensions of Spherical Polystyrene Particles
Authors: Hawley S. A. , Dunn F.
Published: November 2005

The absorption of ultrasound in aqueous polystyrene lattices has been measured over the frequency range from 3–195 MHz for five suspensions with particle radii ranging from 0.044–3.5 μ. In three cases, the suspensions were monodisperse, representing particles of the type used as a secondary standard in electron microscopy. The acoustic attenuation in suspensions of all but the largest particles has been found to be at least an order of magnitude greater than is predicted from considerations of scattering and relative motion between particle and suspending liquid. In addition, an Arrhenius dependence of the absorption coefficient on temperature from 16°–50°C is observed. Since the glass transition temperature of polystyrene in this frequency range is above 100°C, it is not likely that acoustic losses result from viscous damping within the particle. Although the complete absorption mechanism has not been delineated, the experimental evidence indicates that the losses are related to the viscosity of the suspending liquid. [Supported by Institute of General Medical Sciences, National Institutes of Health, U. S. Department of Health, Education, and Welfare, and Acoustic Programs, U. S. Navy, Office of Naval Research.]
Semiautomatic Ultrasonic-Velocity and Absorption Instrumentation for Liquid Media
Authors: Kessler L. W. , Hawley S. A. , Dunn F.
Published: November 2005

A reliable semiautomatic pulse system for determining the velocity and absorption of ultrasound in liquids, over the frequency range from 1–200 MHz, includes a motor-driven lead screw that displaces the transmitting transducer relative to the receiving transducer. The amplitude of a selected received pulse is detected and fed to a chart recorder whose output is linearly related to the logarithm of the pulse amplitude. The chart recorder and the motor are synchronized to the line frequency and, therefore, the piston displacement is linearly related to the time axis of the chart paper. The ultrasonic velocity is determined from an interference pattern produced by employing either a double pulse or a pulse-CW configuration, which permits accurate characterization of the tracking between the transducer and the recorder-pen position. The velocity in aqueous materials has been determined with a precision of ±0.3%, limited by the linearity of the lead screw. The ultrasonic-absorption coefficient, over the entire frequency range considered, has a fractional standard deviation of ±0.3%. [Supported by Institute of General Medical Sciences, National Institutes of Health, U. S. Department of Health, Education, and Welfare, and Acoustic Programs, U. S. Navy, Office of Naval Research.]
Temperature Dependence of Ultrasonic Velocity in Some Relatively Simple Unassociated Liquids
Authors: Piercy J. E. , Rao M. G. Seshagiri
Published: November 2005

Measurements of the ultrasonic velocity in a liquid have generally exhibited a linear dependence on temperature, with certain exceptions (temperatures close to the freezing, boiling, or critical points), unless the liquid is associated (hydrogen-bonded). Deviation from linearity has, in fact, been used as a measure of association. We have measured the velocity in cyclopentane, methyl cyclopentane, and methyl cyclohexane over the extensive range of temperature for which they are liquid at atmospheric pressure. There can be no question of association in a saturated hydrocarbon, yet the velocity versus temperature plot, in each case, is plainly curved; the variation of velocity with temperature in methyl cyclohexane, for example, is −7.0 m/sec/°C below −70°C and −3.8 m/sec/°C above 30°C. The connection between the dependence of the velocity on temperature (Rao's relation) and molecular rotation in the liquid state is discussed.
Ultrasonic Relaxation in Divalent Sulfate Solutions
Authors: Goldfarb Louis , Yeager Ernest
Published: November 2005

Ultrasonic absorption has been measured in MgSO4, CoSO4, and CuSO4 solutions at frequencies in the range 45–550 MHz by the pulse-transmission technique. These measurements indicate that the high-frequency relaxation occurs at higher frequencies than reported by other workers, with the exception of Plass [Acustica 15, 601 (1965)], and is concentration-dependent—e.g., 320 MHz at 0.15 M and 200 MHz at 0.05 M for MgSO4 at ∼14°C. The data provide evidence for only a single relaxation at frequencies above 200 MHz. These results are interpreted in terms of multiple-step ion association, involving various types of ion pairs with the diffusion-controlled step corresponding to the observed high-frequency relaxation peak. [Research partially supported by the U. S. Navy, Office of Naval Research.]
Measurement of Dynamic Shear Impedance of Low Viscosity Liquids at Ultrasonic Frequencies
Authors: McSkimin H. J. , Andreatch P.
Published: November 2005

An instrument is described for measuring shear mechanical properties of liquids with viscosities as low as 0.5 cP. Operation is based on an ultrasonic shear-reflectance method previously used only for more viscous materials [W. P. Mason, et al., Phys. Rev. 75, 936–946 (1949)]. In the present apparatus, the considerable increase in sensitivity has resulted primarily from use of an improved method of determining small changes in phase shift for ultrasonic waves reflecting from the solid-liquid interface of the instrument. Results at 40 Mc/sec for complex shear impedance and dynamic viscosity are presented for a number of pure liquids. Application to studies of polymer solutions is illustrated by data for a series of polystyrene di-n-butyl phthalate solutions.
Comparison of Lateral Localization and Distance Estimation for Single- and Multiple-Source Speech Signals
Authors: Gardner Mark B.
Published: November 2005

Lateral localization of a single source of speech can be made to a relatively high degree of accuracy under anechoic room conditions. For multiple sources of equal intensities (loudspeakers arranged in a line, from left to right, in front of the listener), all of the energy, except for a slight lateral broadening, appears to come from the loudspeaker that is directly in front of the listener (Precedence Effect). The above results are independent of absolute level over a wide range. Distance estimation, on the other hand, is considerably affected by the level of the received speech and is therefore a much more difficult judgment to make. This is true for both single and multiple sources [loudspeakers arranged in lines of increasing distance from, and in front of, the listener]. The accuracy of distance estimation improves when a live voice is substituted for either of the above arrangements.
In-Head Localization of Acoustic Images
Authors: Toole F. E.
Published: November 2005

Under certain conditions of acoustic stimulation, a listener may perceive a sound image that is localized within the head. Different authors have attributed such in-head localizations to (a) a static relationship between head position and components of the acoustic signal at the two ears, (b) abnormal acoustic-impedance loading of the middle ear, (c) independent (and, therefore, slightly different) transmission paths to the two ears, and (d) other causes generally applicable to the binaural-earphone listening situation. Experiments in free-field localization have shown that convincing in-head localizations can be demonstrated under circumstances that apparently do not involve the above factors to an important extent. In fact, there are numerous single- and multiple-transducer arrays that can give rise to complex in-head and external localizations. These are described and discussed in the light of relevant interaural signal parameters and present theories of in-head localizations.
Effects of Intensity on Critical Bands for Tonal Stimuli as Determined by Band Limiting
Authors: Bourbon Walter T. , Evans Thomas R. , Deatherage Bruce H.
Published: November 2005

Four subjects were run in a 2-AFC psychophysical study in auditory masking. The signal consisted of a 100-msec tone burst delivered inphase to the two ears. Signal frequencies between 250–4000 Hz were used. Masking noise had spectrum levels of 45, 25, and 15 dB SPL. For each signal frequency, the signal level was found which produced P(c) of .54 in wideband noise at each spectrum level. The high- and low-frequency cutoffs of the noise were then varied independently (band-limited), and changes in detectability were observed. Detectability remained constant until the cutoff of the noise was raised or lowered to a critical value; from that point on, detectability improved. The function traced by improvement in detectability represents the “critical band” for the stimulus conditions used. The width of the critical band was directly related to stimulus intensity for all signal frequencies. [Work supported through a contract from the U. S. Navy Office of Naval Research, Physiological Psychology Branch.]
Auditory Afterimages Produced by Low-Pass, High-Pass, and Band-Rejected Noises
Authors: Guttman Newman , Lummis Robert C.
Published: November 2005

It has been previously shown that a stimulus consisting of band-rejected noise can produce a subjective tone heard after the stimulus is switched off. Present work indicates that steeply-cutoff high-pass or low-pass noise bands can also produce an afterimage, although the range of effective cutoff frequencies may be small. For a cutoff slope of 84 dB per octave, the ratio of pitch frequency of the subjective tone to noise-cutoff frequency is 1.2–1.7 for low-pass noise, and 0.5–0.7 for high-pass noise. If the low-pass and high-pass noises are added together at the same spectral level, to form the band-rejected noise used previously, the perception of the afterimage is considerably facilitated. Usually, a subjective tone is then heard associated with the low-pass noise band according to the ratio given above. Under certain conditions, a second subjective tone, associated with the high-pass noise band, can be heard simultaneously.
Some Effects of Cosine Amplitude Modulation on the Pitch of Tone Bursts
Authors: Mahaffey Robert B.
Published: November 2005

Subjects were asked to match the pitches of tone bursts of varying frequency, duration, and envelope contour. The tone-burst frequencies were 125, 250, 500, 1000, 2000, 4000, and 8000 Hz; and durations were varied in 5-msec steps around the minimum tone-burst durations required for reliable pitch perception at the respective frequencies. The envelopes of the stimuli were amplitude modulated, one cycle per tone burst, by a cosine wave and gated so as to resemble deviations of the Hamming Window Function. The percentages of cosine amplitude modulation were 0% (producing a rectangular tone burst), 15%, 30%, 50%, 70%, 85%, 92% (Hamming Window Function), and 100%. Analyses of these judgments revealed lower standard deviations of frequencies matched to highly modulated tone bursts than those matched to rectangular or near-rectangular tone bursts.
Temporary Threshold Shifts in Rhesus Monkeys Produced by Exposure to Octave Bands of Noise
Authors: Loeb Michel , Behar Isaac
Published: November 2005

Five rhesus monkeys were first tested by a simple avoidance technique at 1, 2, and 4 kHz, then exposed to a 110-dB, 600–1200-Hz noise and retested at intervals up to 4 h. This procedure was performed repetitively for each monkey. In subsequent sessions, the test tones were 3.15, 6.3, and 10 kHz and the exposure noise was 110 dB, 2400–4800 Hz. Contrary to most findings with humans, maximum shifts were observed for the frequency within the exposure band. They averaged 15–20 dB approximately 4 min after exposure and recovery was nearly complete within 4 h. These results are compared with those reported for comparable exposures in humans and other species.