bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic Investigation of the Lambda Point of Liquid Helium
Authors: Barmatz M. , Rudnick Isadore
Published: September 2005

The velocity and attenuation of first sound have been measured simultaneously to within microdegrees of the lambda transition of liquid helium. Measurements were made in the frequency range of 20–100 kcps. With the high-Q modes of the resonator, relative sound-velocity measurements of one part,in 105 could be obtained. Above the transition, the velocity of sound had the temperature dependence predicted by the Pippard theory out to 5 mdeg from the lambda point. The velocity of sound below the transition does not agree with the Pippard theory, except within a fraction of a millidegree of the transition. The added temperature dependence beyond that expected from the Pippard theory can be fit to a series expansion in |ΔT|. This additional dependence is postulated to be due to the effects of the order parameter. The minimum of the sound velocity at the lambda point was found to be finite and equal to 217.05 m/sec. Using the convective properties of the resonator, the position of the density maximum was found to be approximately 6.2 mdeg above the lambda point. [Work supported by the U. S. Office of Naval Research.]
Piezoresistive Coefficients of Noncubic Crystals
Authors: Ward Thomas L.
Published: September 2005

Piezoresistive effects in many semiconductors are quite large [C. S. Smith, Phys. Rev. 94, 42–49 (1954)] in comparison to those of metals. This has lead to their use in the measurement of force and torque [W. P. Mason and R. N. Thurston, J. Acoust. Soc. Am. 29, 1096–1101 (1957)1 and sound pressure [F. P. Burns, J. Acoust. Soc. Am. 29, 248–253 (1957)]. Silicon, which crystallizes in the cubic system, has been used almost exclusively for such applications. For cubic semiconductors, both Smith and Mason (op. cit.) normalized the functional relation between voltage gradient vector, resistivity tensor, and current density vector by dividing all three terms by the unstrained resistivity, or scalar resistivity, as it has been termed. This is not possible for noncubic semiconductors because the unstrained resistivity is not isotropic. If a generalized Ohm's law is written in matrix form, the resistivity tensor is a square, 3×3 matrix. The determinant of this matrix is invarient under axis rotation and has the dimensions of ohms squared. A new scalar resistivity is defined as the cube of the value of the determinant.
Some Properties of Longitudinal Shear Waves: A Study by Computer Simulation
Authors: Khanna S. M. , Sears Richard E. , Tonndorf Juergen
Published: September 2005

Shearing between basilar membrane and tectorial membrane is known to contribute towards mechanical processing of the auditory signals. The amplitude of the longitudinal shear wave has been given by von Békésy to be proportional to the product of the vertical amplitude of the basilar membrane and the first space derivative of the momentary position of the traveling wave along the basilar membrane. Traveling waves were generated on a digital computer, using a modified form of Flanagan's mathematical model. Shear waves were obtained from these by taking the 1st instantaneous space derivatives. Envelopes for the longitudinal-shear vibrations are compared to those of the traveling waves. These comparisons show that: (1) the maxima of the shear-wave envelopes are slightly closer to the helicotrema; (2) the shear waves are much more localized along the basilar membrane; (3) localization is much more pronounced at low frequencies than the equivalent entities of the traveling wave. Comparisons made between the resonance curves of traveling-wave vibrations and shear-wave vibrations show considerable sharpening of the shear-wave envelopes towards the low frequencies. Effects of middle-ear transmission on the resonance curves is shown. [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.]
Use of a New Photoelectric Device (Fotonic Sensor) for Vibration Measurements in the Ear
Authors: Jako G. J. , Hickman K. , Adkins H.
Published: September 2005

A new non-contact photoelectric device is described for displacement and vibration measurements. The device uses a bifurcated fiber-optic bundle as a probe. One part of the fiber-optic bundle is used as a light carrier and the other as a receiver of reflected light. The light source is a small incandescent light which is supplied by a dc current. The reflected light from the surface is transmitted through the receiver part of the bundle and sent through a sensitive photosensor. This signal, which is a direct linear function of distance to the surface, is amplified and displayed on an oscilloscope. The instrument is capable of resolving one micro-inch and the frequency responses go to the megacycle-per-second range. Direct calibration for any surface is achieved without contact and without any external precision-motion apparatus. The technique of calibration against various reflecting surfaces in the ear: tympanic membrane, stapedial footplate, round-window membrane, basilar membrane is described. The diameter of the probe used here is from 0.5 to 4 mm. Calibration for misalignment is also given.
Interpretation of Wall-Pressure Measurements under a Turbulent Boundary Layer
Authors: Chandiramani K. L.
Published: September 2005

Some aspects of the correlations and spectra of fluctuating wall pressure beneath a turbulent boundary layer are considered. The correlation function for the pressure field is represented by a hierarchy of mathematical models, each successive model more complex than the preceding one. These models are based on some mathematical inequalities that are applicable to a “convecting and decaying” stochastic process. Some of these models are used for estimating attenuation of the pressure spectrum measured by a transducer of finite size. The results indicate that, at high frequencies, temporal rather than spatial fluctuations of the pressure field contribute to the “fixed-microphone” spectrum as measured by a transducer of finite size. Some comments are included concerning the influence of transducer size on measured narrow-band crosscorrelations.
Relation between Turbulent-Flow Structure and Wall-Pressure Fluctuations in a Turbulent Boundary Layer
Authors: Willmarth William W.
Published: September 2005

Recent measurements show the relationship between the turbulent structure near the wall and the wall-pressure fluctuations. Detailed measurements of pressure-velocity and velocity-velocity correlations suggest a flow structure consisting of hairpin-shaped turbulent eddies originating near the wall that are elongated in the stream direction as they are swept down stream and move away from the wall. The model for the turbulent eddies supplies a qualitative description of the observed convection and decay of wall-pressure fluctuations. The accuracy and limitations of contemporary wall-pressure measurements are discussed, along with some suggestions for future experimental work. [Work supported by U. S. Office of Naval Research.]
Turbulent Boundary Layer of Space-Flight Vehicle
Authors: Lyon Richard H. , Chandiramani K. L.
Published: September 2005

The turbulent boundary layer (TBL) is an important aerodynamic environment for major portions of a space-vehicle structure. For most launch vehicles, the period of large dynamic pressure, and hence strong TBL excitation, coincides with supersonic flight. This implies high-speed convection of the pressure-field speeds generally in excess of the bending-wave speed on the structure. New procedures for calculating the response of cylindrical structures to a high-speed TBL have recently been developed at BBN. These procedures require information concerning the TBL pressure spectrum that can, in part, be related to flight data obtained from flush-mounted microphones. The use of these flight data for response estimation is the topic of this paper.
Effects of Lumber Facing Size on Sound Absorption
Authors: Goodfriend Lewis S.
Published: September 2005

Further tests on lumber as a facing for architectural acoustics uses have been performed. The sound absorption and its dependence on lumber spacing and dimensions are reported.
Measurement of Fast Sound-Decay Rates
Authors: Presti A. J. , Harvey F. K.
Published: September 2005

The automatic decay-rate meter described earlier [Paper 5A11, this meeting] is a promising tool for the measurement of sound-decay rates and reverberation times not only for auditoriums but especially for conference rooms. The fast decays associated with these smaller, often highly damped, enclosures generally requires measurements involving oscilloscope displays. However, the automatic decay-rate meter has proved to be an attractive alternative in this range and results obtained with it for a variety of enclosures appear to be more accurate and reproducible than those from several other more time-consuming methods.
Diffraction of Acoustic Transients in Air
Authors: Wright Wayne M.
Published: September 2005

A transient electrical discharge in air serves as a convenient source of acoustic impulses for studies in wave diffraction. Impulse waveforms resemble the letter N. A discharge energy of 0.05 J, which is convenient for laboratory experimentation, leads to peak acoustic amplitudes and signal durations of about 0.01 atm and 30 μsec, respectively, at a distance of 10 cm. For the present work, the transient sounds were detected with a capacitor microphone that had a flat sensitivity up to 500 kHz. The effects of diffraction by circular cylinders and narrow rectangular plates are demonstrated. Recorded waveforms are interpreted qualitatively in terms of the geometries of the scattering objects and the Fourier spectra of the N waves. [Work supported in part by the U. S. Office of Naval Research.]
Effect of Large Percentages of Water Vapor on the Ultrasonic Absorption in Carbon Dioxide
Authors: Higgs R. W. , Torborg R. H.
Published: September 2005

The ultrasonic absorption was measured in carbon-dioxide/water-vapor mixtures, using a pulse technique. The percent water vapor was varied from 0% to 50% and temperatures varied from 150° and 200°C. The frequencies used in this investigation were 1 to 14 MHz. The results show that in each case the absorption increases with increasing water-vapor content, reaches a maximum, and decreases as the water-vapor content approaches 50%. The percentage water vapor at which the absorption maximum occurs is a function of both frequency and temperature. The absorption in pure CO2 and at low percentages of water vapor compares favorably with previously published data. A discussion of the experimental apparatus, technique of measurement, and experimental results is presented. [Research supported by Consolidated Natural Gas Service Corporation, Cleveland, Ohio.]
Response of Panels to Oscillating Shock Waves
Authors: Crocker Malcolm J.
Published: September 2005

As a missile or aircraft accelerates at transonic speeds, shock waves that oscillate imposing severe structural loading form about the vehicle. Experimental evidence suggests that shocks can oscillate at discrete frequencies, and this is chosen as the principal theoretical model. Theory is formulated for the response of a flat rectangular simply supported panel to sinusoidally oscillating shocks. Initially, an approximate solution is found that is valid only for limited-shock-oscillation amplitudes, particularly for higher modes. This theory predicts that each mode can be excited by a forcing frequency equal to the resonant frequency ω and by the subharmonic ω/2; the theory also predicts first-mode dynamic-amplification factors of up to 25 for typical panel damping. An “exact” solution using Bessel functions is also formulated in which no restriction is placed on shock-oscillation amplitudes, and it is shown that each mode can actually be excited by an infinite number of subharmonic frequencies ω/2, ω/3, ω/4, ⋯. [Work supported by NASA-Marshall Space Flight Center, directed through Brown Engineering Company, Huntsville, Alabama.]
Defining the Induced Vibration of a Space Vehicle during Flight
Authors: Bies David Alan
Published: September 2005

A series of acoustic and vibration measurements has been made during flight tests on a pod carried on an Atlas missile. The flight data have been utilized to develop a procedure for estimating the vibration environment of a space-vehicle payload. Payload vibration levels appear to be controlled largely by missile-skin vibration levels rather than local excitation of the pod. The vibration spectrum in the missile skin is proportional to the acoustic or aerodynamic-pressure spectrum. The aerodynamic excitation at maximum dynamic pressure appears to be about 6 dB more efficient than the acoustic excitation, in line with the findings of previous work. The mass-loading effect of the payload attached to the skin has been experimentally investigated. Available data, together with the results of the present investigation, enable the designer to make a fairly reasonable estimate of the vibration environment of a new payload.
Experimental Confirmation of Circumferential Waves on Solid Cylinders
Authors: Bunney R. E. , Goodman R. R. , Marshall S. W.
Published: September 2005

Following the theory describing circumferential waves (presented in the preceding paper), an experimental investigation was undertaken to observe and measure these waves. The Rayleigh-type surface wave has been observed on elastic solid cylinders immersed in water. This wave was excited by an acoustical pulse of 10-μsec duration projected onto the cylinder at the excitation angle given by sin−1 (c0/c), where c is the velocity of the circumferential wave and c0 is the velocity of sound in water, and has been observed to make several circumnavigations of the cylinder. The waves can be detected since they continuously radiate acoustical energy into the water and have been observed on pure aluminum, 304 stainless steel, and various aluminum-alloy cylinders. Since the surface curvature gives rise to dispersion, cylinders of 3.5- to 6-in. diam were used and the frequency of the incident pulse was varied from 0.15 to 3.5 MHz. This corresponds to a radius-to-wavelength ratio of 10 to 400. Experimental and theoretical results will be presented and shown to compare favorably. Inhomogeneities in brass and in aluminum alloys are found to correlate with poor propagation characteristics for some of the cylinders. Examples will be shown.
Growth of Noisiness for Tones and Bands of Noise at Different Frequencies
Authors: Parry Hugh J. , Parnell John E. , Nagel David C.
Published: September 2005

Judgment tests have been conducted to measure the growth of noisiness as a function of sound-pressure level (SPL) for tones and bands of noise over a range of frequencies and reference SPL's. Adjustment-test results at 1000 Hz showed a mean value of 11.5 dB per doubling or noisiness except for the lowest reference level (50 dB SPL) where the mean was 16.7 dB. Magnitude-estimation results yielded values between 20 and 27 dB per doubling of noisiness. The specific value used for the growth of noisiness did not significantly affect the calculation of relative PNL values. Equal noisiness contours were obtained for: (1) pure tones in a free field, (2) 13-oct bands of noise in a free field, (3) 13-oct bands of noise in a diffuse field, (4) 1-sec and 4-sec stimulus durations, and (5) for loudness and noisiness instructions. No significant differences were found for the latter two conditions. [Research supported by the Federal Aviation Administration.]
Respiratory Mechanics during Speech Production
Authors: Hixon Thomas J. , Siebens Arthur A. , Ewanowski Stanley J.
Published: September 2005

The static pressure-volume characteristics of the lungs and thorax (diaphragm included) were measured throughout the vital capacity in five healthy adult males during breath holding with the airways open and during voluntary relaxation against an infinite resistance, respectively. Pressure—volume events were then recorded throughout most of the vital capacity during sustained [ɑ] productions at three different vocal-effort levels. Data were plotted in Campbell diagrams and analyzed to determine the alveolar pressures and the net forces developed by the respiratory muscles during the productions. Results indicated that a relatively steady alveolar pressure was provided by the respiratory system, the level of this pressure increasing with successive increases in vocal effort. Maintenance of a steady pressure throughout the lung volume required a continuously changing muscular effort in the face of changing elastic forces. At high lung volumes, the direction of airflow and the net muscular effort were often found to be opposite in sign. This suggests a braking action on the part of the inspiratory muscles.
Frequency Spectra of Forward-Scattered Sound from a Time-Varying Surface
Authors: Roderick William I. , Cron Benjamin F.
Published: September 2005

This study consists of a theoretical analysis, a model tank experiment, and an ocean experiment to determine the frequency spread of surface-reflected sound. The theoretical study is based on the concept that the surface waves' phase- and amplitude-modulate the acoustic signal. The amount of spreading is a function of the incident acoustic frequency, the surface wave spectrum, and the geometry of the experiment. The ocean experiment was conducted in winter off the coast of Bermuda. Two frequencies (750 and 1500 Hz) were simultaneously emitted from a fixed projector. The tones were surface reflected and received on a narrow-beam, fixed, bottom-mounted vertical array. Oceanographic and meteorological data were obtained in the vicinity of the insonified area. The time variation of the surface elevation was obtained from a wave staff, and this information has been processed to obtain the one-dimensional ocean spectrum. The experimental results are compared with theoretical predictions. It is shown that the comparison is excellent for both the model tank and the ocean experiments. Under all conditions for the ocean experiment, the frequency spread is less than 1.0 Hz; and under normal conditions, the spread is about 0.2 Hz.
Volume Reverberation in the North Atlantic Ocean
Authors: Adlington R. H. , Robinson A. E. , Chapman R. P.
Published: September 2005

Between November 1959 and April 1966, 13 experiments were carried out in the North Atlantic to measure the acoustic characteristics of deep scattering layers; measurements were made between Halifax and Puerto Rico, Halifax and Gibraltar, and St. John's and the Norwegian Sea. A quantity that has been found useful for investigating reverberation conditions over wide geographic areas and over a broad range of frequencies is the “scattering strength of the column.” A summary of measurements of this quantity in octave bands from 1.6 to 25.6 kHz is presented for both daytime and night-time conditions. Variations are discussed in terms of the responsible mechanism and in terms of oceanographic boundaries.
Spectral Analysis of Volume Reverberation between Newfoundland and Iceland
Authors: Bluy O. Z.
Published: September 2005

Measurements of volume reverberation were made in the North Atlantic between Newfoundland and Iceland. The sound source was a shallow explosive charge, while receivers consisted of two narrow-band hull-mounted directional transducers and an omnidirectional wide-band hydrophone suspended below the surface. Analysis of signals from the downward-looking transducers yielded scattering strength as a function of depth in their respective frequency bands. Swept filter analysis of the signal obtained with the omnidirectional hydrophone indicated the resonant frequencies and depths of prominent scattering layers, enabling determination of the sizes of the significant scatterers.
Experiments in the Fabrication of a Human-Size Cochlear Model
Authors: Jako Geza J. , Holly Sandor
Published: September 2005

Using present day thin-film technology, it is possible to fabricate small parts for a human-size artificial inner ear. A thin metal plate with a triangular window, 35 mm long and 500 μ, tapering to 100 μ in width serves to support a thin membrane, simulating on a 1:1 scale the human basilar membrane. Thin organic and inorganic films in various thicknesses are used for the vibrating basilar membrane. Variation of thickness of one (or two) materials are used to change the elastic properties of the artificial basilar membrane. To record the movements, photoelectric fiber optics system (fotonic sensor) is used. Thin-film piezoelectric layers as electromechanical transducers, deposited on the artificial basilar membrane, are also being investigated. The possibility of first-stage amplification by built-on integrated-circuit amplifiers is demonstrated. The high precision available through photoetching and present-day thin-film technology ensures small tolerances and consistency in fabrication and allows reproducible measurements even in such small dimensions. The significance of these experiments on the 1:1 scale linear model of the human cochlea is brought out by discussing some of the potential applications.
Using Linguistic Rules
Authors: McMahon L. E.
Published: September 2005

The difficulties and partial successes of applying linguistic rules to natural languages will be discussed. Work in mechanical parsing of English has uncovered its pervasive syntactic ambiguity; and attempts to deal mechanically with the meaning of utterances have been only partially successful. Work in generative grammars has made regularities in language more evident to linguists, and the strict formality of generative rules has led some to believe that they are ideally suited for computer realization; the pitfalls and promises of this view will be pointed out. Finally, a brief discussion of what kinds of language computers can and do understand will suggest some possible routes towards better use of linguistic rules and facts in automatic language processing.
Sound Transmission through Rectangular Slots of Finite Depth between Reverberant Rooms
Authors: Sauter August , Soroka Walter W.
Published: September 2005

An approximate theoretical relationship has been developed for the transmission of sound between two reverberant rooms through a connecting rectangular slot of finite depth. The theory makes use of impedance functions of rigid weightless rectangular pistons and assumes plane wave propagation through the slots. Slots having aspect ratios of 1, 2, 4 and 8, and depths of 12 in., were tested between two 1750-ft3 reverberation chambers. Three different slots for each aspect ratio were tested, and the slot dimensions were so chosen as to have the cross-sectional areas π/4, π, and 4π in.2 in each case to compare with previously published results on circular apertures having these areas. Numerical solutions on a digital computer are compared with the experimental results and the agreement found to be excellent over the range of the parameter, wavenumber times equivalent radius of a circular section having the same area as the rectangular section, from 0.1 to 3.2. [This research supported in part by the National Science Foundation.]
Acoustic Array of Concentric Rings
Authors: Ensign Thomas H.
Published: September 2005

The analysis of an acoustic array of concentric coplanar ring transducers in a rigid baffle is presented in this paper. The farfield directivity pattern is shown to be the summation of zero-order Bessel functions of the first kind. An orthogonal expansion technique is developed for choosing an appropriate amplitude and spacing distribution among the concentric rings to obtain a prescribed directivity pattern. Several even function prescriptions are described, and the amplitude, spacing coefficients are computed. It is shown that the total element requirement can be moderate for pattern prescriptions with continuous first derivatives. Two array designs with beamwidths of 4° and 40° and minor lobes suppressed at least 30 dB are illustrated. A tolerance analysis of both amplitude and phase errors is given for the two designs. A means of constructing an array of concentric rings is proposed making use of a piezoelectric quarter-wave thickness resonant plate with concentric-strip electrodes.
Computed Effects of a Concentric Shell on the Velocity Distribution of Transducer Elements in a Spherical Array
Authors: Moyer W. C.
Published: September 2005

A rectangular patch of elements mounted in a spherical array is assumed to radiate within a concentric spherical shell. Electrical input signals are prescribed such that the radiating elements are phased to a plane. Radiation loadings on each active element are computed, and these together with the input electrical signals and equivalent circuit for the element are used to compute the actual transducer element velocities. With these velocities, farfield beam patterns are computed. Results showing the effects of the shell on element radiation loadings, element velocities, and farfield beam patterns are included.
Theory of Compliant Tubes
Authors: Brigham G. A.
Published: September 2005

The static compressibility of oval tubes is calculated by directly integrating Love's force and moment equations for uniformly loaded oval tubes. The dynamic compressibility is next determined by inference from the author's previous work on the natural oval-bending frequencies. Finally, the radiation load is added and the farfield pressure scattered by the tube is estimated. Because the first oval-bending resonance occurs at frequencies where the acoustic wavelength in water is considerably larger than the oval periphery, the acoustic pressure reradiated by the tube in the near- and farfield is omnidirectional, leading to a relatively simple approach to the N-tube array problem.
Some Recent Information on Aircraft Vibration Due to Aerodynamic Sources
Authors: Runyan Harry L.
Published: September 2005

This paper is concerned with a survey of recent information on aircraft vibration with special attention being paid to vibration induced by aerodynamic sources. Certain aspects of the following topics as they bear on aircraft vibration will be discussed, including a general assessment of the state of the art in each of the areas: boundary-layer pressure fluctuations; buffet due to configuration and maneuver; vibratory response due to atmospheric gusts; engine noise as related to sonic fatigue; flutter with special mention of problems of coplanar wings; helicopters, including a brief mention of the major vibratory problems.
Primate Vocalizations and Human Linguistic Ability
Authors: Lieberman Philip
Published: September 2005

Some representative vocalizations of captive rhesus monkey, chimpanzee, and gorilla were recorded and analyzed by means of sound spectrograms and oscillograms. It was found that these animals' vocal mechanisms do not appear capable of producing human speech. A uniform-cross-section, schwalike configuration appeared to underlie all the vocalizations. No modifications of the supralaryngeal vocal tract occurred during a vocalization, except for epiglottal and possibly velar maneuvers. Format transitions occurred in some vocalizations, but they appeared to have been generated by means of laryngeal maneuvers. The laryngeal output was breathy, which apparently excited formats corresponding to both a closed and an open boundary condition at the glottis. The data suggest that speech cannot be viewed as an overlaid function that makes use of a vocal tract that has evolved solely for respiratory and deglutitious purposes; the skeletal evidence of human evolution shows a series of changes from the primate vocal tract that may have been, in part, for the purpose of generating speech. Articulate speech may not have been fully developed in some of man's immediate ancestors.
New Kind of Laryngeal Whistle
Authors: Allen George D.
Published: September 2005

A little-known laryngeal phenomenon is the production of two simultaneous vibrations at different frequencies, in the ratio of 5:6. The resulting sound, a minor third, is like a train whistle (not the “steam whistle” described by Abercrombie). Present-day models of laryngeal function cannot explain the production of this whistle. A subject with extremely good control of the production of this whistle was recorded under good conditions in his home. The subject articulated different vowels and phonetically complex sentences while phonating in this manner. Various simple tests were carried out to determine some of the physiological constraints on whistle production, such as the range of variation of pitch and amplitude, the possibility of producing the whistle with different laryngeal configurations, and the effect of increasing subglottal pressure. An edited tape recording will be played, and the results of acoustic measurements and the above-mentioned tests will be discussed. Explanatory suggestions are invited.
Effects of Task-Induced Stress on Speech
Authors: Hecker Michael H. L. , Stevens Kenneth N. , von Bismarck Gottfried , Williams Carl E.
Published: September 2005

A task involving the addition of numbers under time pressure was developed. The subject was required to read six meters and to announce the sum of his readings, together with a test phrase. By controlling the duration of the meter display, the experimenter could vary the level of stress induced in the subject. For each of 10 subjects, numerous verbal responses were obtained while the subject was under stress and while he was relaxed. The test phrases contained in these responses were analyzed with respect to level and fundamental frequency, and spectrograms of the test phrases were carefully examined. The results indicate that stress can produce a number of characteristic changes in the acoustic speech signal. Most of these changes are attributable to modifications in the amplitude, frequency, and detailed waveform of the glottal pulses. Other changes result from differences in articulation. [Research supported by the Air Force Cambridge Research Laboratories.]
Approach to More Efficient Segmentation and Classification of Speech Sounds
Authors: Beninghof William J. , Ross Myron Jay
Published: September 2005

The success of lumped-parameter analogs of the vocal tract suggests that speech spectra may be optimally approximated by a rational function. As a step in this direction, speech spectra have been approximated by a linear combination of Gram polynomials and have been found to be more efficient than a linear combination of trigonometric functions. The original spectra (100 samples in frequency) and the polynomial and trigonometric approximations have been represented by points in their respective Hilbert spaces, the distance between successive points being a measure of the dissimilarity of successive spectra. Segment boundaries are indicated where the distance between successive spectra exceeds a threshold. The effectiveness in segmentation of connected utterances using these spectral forms will be compared. Results will be presented and implications made for real-time machine recognition of speech. [This research was supported by NASA Fellowships and the Electrical Engineering Department at Northeastern University.]
Detection of the Voice Fundamental for Visual Pitch Detection
Authors: Phillips Nathan D.
Published: September 2005

The methods of voice fundamental detection used in various research problems are generally governed by the application for which the resulting signal is to be used. For visual pitch displays, the detection method is governed by simplicity and compactness of equipment, and clarity of the derived visual display. By applying the characteristics of (a) the limited range of the fundamental and (b) the limited rate of change o[ the fundamental, the output of the display can be limited to a clear indication of the intonation pattern being produced by the speaker. In order to make use of these limitations, a hybrid logic system that operates on the output of a peak-detector type pitch extractor was developed. The design of this system will be discussed, and the degree of success of error suppression will be presented in quantitative terms. [This investigation was supported, in part, by a research grant from the Social and Rehabilitation Service, Department of Health, Eduction, and Welfare, Washington, D. C. 20201.]
Rhythmic Fission and Perceptual Organization
Authors: Dowling W. J.
Published: September 2005

Tone sequences presented at rates of about 10 tones/sec and constructed such that successive tones have large, and alternate tones small, frequency intervals between them, are heard as two simultaneous melodic patterns formed of the alternate tones. This effect, called rhythmic fission, can also be effected by intensity differences or stereophonic separation between the patterns. (1) The intensity difference can be in either direction. The softer, as well as the louder, of the two patterns can be attended to as “figure.” (2) More stereo separation is required to make a melody distinct from a random background than from most melodically patterned backgrounds. This is true even though the random sequences were already more separate from the melodies in terms of frequency differences between successive notes than were the other melodic patterns. (3) Embedding a melody in alternate tones of the same intensity and randomly selected from the same frequency range produces a meaningless jumble. However, when told what melody to listen for, an observer comes to hear it distinctly after a few repetitions. No observer reported hearing any melody after misinformation about which melody it was.
Can the Binaural System Preserve Temporal Information for Detection of Jitter?
Authors: Pollack Irwin
Published: September 2005

Thresholds for the detection of temporal irregularity or “jitter” were obtained under three conditions: (1) monaural presentation of auditory pulse trains; (2) binaural presentation of auditory pulse trains, where the pulses were randomly assigned to the two ears; and (3) monaural presentation of one of the binaural channels of Condition 2. Since the binaural system shows microsecond sensitivity to temporal differences for lateralization, might not the binaural system preserve temporal information for the judgment of jitter? If the binaural system preserved temporal information prior to the analysis of jitter, thresholds under Conditions 1 and 2 would be equivalent, and both would be superior to Condition 3. In fact, Conditions 2 and 3 yielded nearly equivalent thresholds and both were substantially inferior to Condition 1. This result suggests that the binaural system does not preserve temporal information in a manner that permits acute temporal resolution for discrimination of jitter. [This research was supported in part by a grant from National Science Foundation.]
Binaural Unmasking of Vocalic Signals
Authors: Mosko James D. , House Arthur S.
Published: September 2005

Binaural unmasking was studied using vowels as the target signals. The vowels /a/, /i/, and /u/—each produced naturally and by an electrical analog device at three vocal frequencies—were presented to listeners for detection in a variety of interaural signal-noise configurations. In all listening conditions, the noise was correlated, while the interaural phase relations of the signals were manipulated. A number of conditions were used in which the portion of the signal above or below three selected frequencies—250, 500, and 1000 Hz—was interaurally out of phase, while the remainder of the signal was normal. The data suggest that binaural unmasking of complex amplitude-varying stimuli is best accounted for by the amount of energy in the 250–500-Hz band of the signal relative to the characteristic spectral maxima in the signal. The data also suggest that interaural phase inversions outside the 250–500-Hz band have differential effects on unmasking depending upon the amplitude relations in the band and the energy outside it.
Manipulation of Criteria in Auditory Detection
Authors: Evans Thomas R.
Published: September 2005

This study examined the possibility of experimentally manipulating an observer's response criterion in an auditory detection task by imposing objectively determined “criteria” to which the observer may adjust his subjective criterion. The imposed “criteria” were different signal-to-noise (S/N) ratios representative of ratios that the observer would encounter in a detection task involving variable noise and a relatively invariable signal. A binary decision task was employed. The dependent variable was the position of the observer's criterion on the probability-density functions of noise and signal plus noise. The signal was a sinusoid of 500-Hz, 200 msec in duration. It occurred with an a priori probability of 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, or 0.65 for any block of 100 trials. The results demonstrate that as the S/N ratio in the criterion interval increases, the response criterion of the observer becomes more strict. A change in criterion is not accompanied by an appreciable change in detection. Neither the criterion nor the detectability of the signal is influenced by the a priori signal probabilities. [This research was supported by a contract from the Office of Naval Research.]
Stochastic Model of Signal Detection under Conditions of Temporal Uncertainty
Authors: Cronholm James N.
Published: September 2005

This paper describes a reformulation of the problem of analyzing detection data obtained when signal presentation times follow an arbitrary intersignal interval distribution. The approach is based on revised definitions of hits, misses, correct negatives, and false positives, that are natural in this situation. It permits the construction of functions analogous to the iso-sensitivity and isobias curves of classical detection theory directly from observed time series of signals and responses. A model of the processes underlying the generation of signal-response time series is described, and the probability densities of interval durations associated with hits, misses, correct negatives, and false positives are presented. The areas under these distributions, and two related densities, are interrelated. An expression for the expected number of responses per signal is given along with suitable estimation procedures. The proposed model incorporates arbitrary intersignal interval and response latency distributions, which were replaced, respectively, by exponential and triangular distributions in a test of the model using data obtained from a simple auditory-detection experiment in which signal rate and intensity were varied.
Psychometric Function from Rayleigh-Rayleigh ROC Curves
Authors: Whitmore John K. , Williams Paul I. , Ermey Harold L.
Published: September 2005

While a visiting professor at the University of Texas, Egan (1967) showed us how power-law ROC curves can be derived from overlapping Rayleigh distributions. Such distributions suggest immediately that detection performance for narrow-band noise signals should differ markedly from that for sinusoidal signals. Accordingly, the psychometric function for Rayleigh signals was derived. The equations governing the probability of being correct in a 2AFC experiment for sinusoidal and noise signals are: P(c) = 1 − 12(exp− σs2/2σn2), which is another way of expressing Marill's famous equation, and P(c) = (σn2+σs2)/(2σn2+σs2), respectively; σn and σs are the rms voltages of the effective masking noise and the signal. For these signals, both rating-scale and 2AFC experiments, appropriate to the tenets of detection theory, show that the shapes of human psychometric functions are predicted in detail by the mathematical models. [Work supported by National Institute of Mental Health, Naval Ship Systems Command, and National Aeronautics and Space Administration.]
Asymptotic Theory for the Vibration of Orthotropic Plates
Authors: Widera O. E.
Published: September 2005

A two-dimensional theory for the vibration of orthotropic elastic plates is derived in a systematic and consistent manner without making any of the usual a priori assumptions regarding the dependence of field variables on the thickness coordinate. The analysis consists of the application of the boundary-layer technique to the equations of three-dimensional orthotropic elasticity. This is done by first introducing plate dimensions and an as yet unspecified length scale via changes in the independent variables. An asymptotic expansion of the field variables as well as the length scale in terms of a small plate parameter λ (the ratio of thickness to a characteristic length) is then performed near λ = 0. By equating corresponding powers of the parameter, successive systems of differential equations are obtained. The lowest-order system, when integrated across the plate thickness and combined with the boundary conditions, yields the simplest thin-plate theory. The higher-order systems yield the higher-order terms in the expansions and constitute thickness corrections.
Commercial Keyboard Instruments
Authors: Le Caine Hugh
Published: September 2005

Our music has been profoundly influenced by the keyboard: Its influence extends from the texture of the sound to the innermost processes. The future of keyboard instruments depends as much upon maintaining the present good relation between instrument potentialities and the musical structures composers and audiences find interesting as it does upon the absolute efficiency of the performer-keyboard combination in handling information. Both aspects of this relation will be discussed. To give a broad picture of the keyboard, radical electronic music instruments of today, which use keyboards in surprising ways, and experimental instruments of earlier years will be included.
View of Digital Filtering
Authors: Helms Howard D.
Published: September 2005

Use of the term digital is motivated by today's increasingly common use of digital computers; use of the term “filtering” by today's widespread knowledge of techniques for programming a computer to carry out operations similar to those performed by ordinary electrical filters. Techniques for using a computer to perform filtering include the z transform, which has both standard and bilinear forms. One of the newer techniques for digital filtering is the fast-convolution application of the Fast Fourier Transform (the FFT is a recently developed method of computing discrete approximations to Fourier transforms). This technique makes efficient use of computation time and often provides an unusually simple procedure for designing the computer program. Specification of the filtering operation can be as simple as supplying a numerical or algebraic statement of its frequency response. Filters useful in spectrum analysis are most easily specified in this manner. These filters include Taylor weighting and Kaiser's windows. Other filters that are expressed most easily as an algebraic frequency response are chirp filters and Hilbert transform filters. Digital filtering appears to offer the advantages of easier maintainability due to elimination of the need for adjustments, more compactness (as large-scale integrated circuits become available), fewer constraints and modeling uncertainties, and greater possibility of using the same hardware to perform several functions. Implementations involving floating-point computations on general-purpose digital computers have a reputation for programming ease and filter accuracy.
Adjustable Gated Signal Repeater
Authors: Presti A. J.
Published: September 2005

The technique of magnetic-tape scanning for spectrographic purposes is well suited to automatic gating of a recorded signal for detailed study. A tape scanner has been developed that incorporates a variable gate during playback for repeated playing of isolated sounds. The gate duration is adjustable from 50 msec to 2.4 sec. The gate is adaptable to the sound spectrograph to facilitate aural monitoring of the signal and spectrographic display of the isolated sounds.
Late Responses to Speech Stimuli as Demonstrated by Electroencephalography Utilizing a Summing Computer Technique
Authors: Tobin Henry , Graham James T.
Published: September 2005

In the EEG literature relating to auditory functioning, there is a notable lack of studies in which response to speech stimuli is investigated. It is not inherently certain in what manner speech signals should be presented so that the EEG response can be effectively viewed. This study assumed that the speech signal that could be the most easily controlled and whose parameters could be specified in detail should be the vehicle of initial interest. The purpose of the study was to determine whether speech, considered to be a species-specific function, did in fact elicit different EEG behavior than nonlinguistic signals. The primary problem in the use of linguistic elements was to demonstrate that the EEG response differed in some systematic way from nonlinguistic elements of comparable duration, amplitude, amplitude variation, and rise time. A summing computer was employed in an attempt to identify differences in response parameters that were related to the linguistic relevance of the signal. Unique EEG findings in the after-discharge region as a result of the speech stimulus are reported.
Language Identification from Nonsegmental Cues
Authors: Atkinson Kay
Published: September 2005

Low-pass filtering was used to extract intonation and durational cues from a tape recording of short utterances drawn from English and Spanish poetry, prose, natural speech, nursery rhymes, and dramatic dialogues. This tape, which thereby excluded segmental information, was used in listening tests with both simple identification and ABX designs. Forty-three subjects were asked to discriminate between English and Spanish from these cues alone. Speaker differences, listener differences, lengths of utterances, and the order of presentation of utterances were considered in the experimental design. Results from the identification test indicate that subjects can significantly discriminate between languages without reference to segmental cues. These results demonstrate that different nonsegmental acoustic properties characterize different languages. Various factors, which contribute to the ease of identification, were also revealed, e.g., subjects made the smallest percentage of errors in identifying poetry and the greatest percentage of errors in response to prose and nursery rhymes. Possible reasons for this are suggested in the paper. Alternative hypotheses concerning the acoustic cues that signal the difference between the languages are also suggested.
Simulation of a Four-Element “Optimum” Sonar Array
Authors: Schmid Charles E.
Published: September 2005

Various optimization criteria for multichannel estimation and detection have led to solutions dependent upon measuring and then inverting the noise cross-spectral density matrix [Q(ω)]. This digital-computer simulation involves generating random-noise samples with known stationary statistics for four hydrophones, and thereafter, estimating the cross-spectral density matrices and the inverses at sample frequencies. The matrices are estimated by successively averaging periodograms [S(ωn)]*[S(ωn)]T, where [S(ωn)]4×1 is obtained with a fast Fourier transform of the four generated hydrophone time series. The inverse is initially calculated and subsequently updated via a standard matrix equation: [Q+S*ST]4×4−1 = Q−1−(1+STQ−1S*)−1Q−1S*STQ−1. The array gain, which is proportional to the sum of the elements of the inverse matrix, is calculated for the simulation and compared to theoretical gains using Gaussian samples and combinations of plane-wave coherent, incoherent, and isotropic noise fields. The difference between the theoretical and simulation is determined as a function of number of periodograms averaged.