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Journal of the Acoustical Society of America

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Nov 1962

Volume 34, Issue 11, pp. 1679-1791


Generalized Short‐Time Power Spectra and Autocorrelation Functions

M. R. Schroeder and B. S. Atal

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1679-1683 (1962); (5 pages) | Cited 4 times

Online Publication Date: 26 Jul 2005

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“Wiener's theorem” relating the autocorrelation function to the power spectrum of a time function has been modified and extended to the cases in which measurements are made with realizable filters having finite integration times. Similar relationships derived earlier by Fa no are valid only for the case when the power spectrum is measured by means of a bandpass filter with all impulse response e−αt cosωt or the auto‐correlation function is measured by averaging through a simple R‐C integrator. The generalized relationships derived in this paper are valid for integrators with arbitrary impulse responses. Several different forms of short time representations and their experimental realizations are also discussed. The emphasis in this paper is on physical realizability—not mathematical existence.

Amplitude Contour Display of Sound Spectrograms

A. J. Prestigiacomo

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1684-1688 (1962); (5 pages) | Cited 1 time

Online Publication Date: 26 Jul 2005

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Sound spectrographs typically displayed complex signals, such as speech, on teledeltos (facsimile) paper with frequency and time plotted along the ordinate and abscissa, and shades of gray to indicate the relative intensity of the frequency components. The gray scale is usually limited by the teledeltos paper to a marking range of 12 dB, whereas the signal may have amplitude variations of 40 to 50 db. A voltage quantizer has been designed which will plot equal‐level contours in the frequency/time plane. The equal‐level plateaus were selected at 6‐dB intervals over a 42‐db range. Gray‐scale compression is also obtained as a by‐product of this quantizer to shade each contour level such that a 42‐dB change in signal level causes a 12‐dB change in marking voltage. A discussion of the design and operating principles is given so that one can incorporate the circuit into a spectrograph or modify the circuit for other applications.

Methods for the Calculation and Use of the Articulation Index

Karl D. Kryter

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1689-1697 (1962); (9 pages) | Cited 42 times

Online Publication Date: 26 Jul 2005

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See Also: Erratum

Show Abstract
Speech‐intelligibility testing is an expensive and time‐consuming operation that requires laboratory test conditions. In an attempt to short‐cut or make unnecessary this type of testing, a procedure was developed by French and Steinberg [J. Acoust. Soc. Am. 19, 90–119 (1949)] for calculating from physical and acoustical measurements made on a communication system a measure that is indicative of the intelligibility scores that would be obtained for that system under actual test conditions. This measure is called the “Articulation Index” (AI). Methods of calculating AI have been improved and elaborated to the point where several methods for its calculation, herein reported, can be proposed for use in the evaluation of most speech communication systems.

Validation of the Articulation Index

Karl D. Kryter

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1698-1702 (1962); (5 pages) | Cited 19 times

Online Publication Date: 26 Jul 2005

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French and Steinberg proposed the basic concept and method of calculating the Articulation Index (AI) approximately 15 years ago. Although improvements and modifications of AI have been made over the years, it has not been generally accepted, perhaps because of insufficient evidence as to its validity. On the basis of studies reported in the literature and on new studies herein reported, it is shown that AI is a valid predictor of the intelligibility of speech under a wide variety of conditions of noise masking and speech distortion.

Apparatus for Measuring the Dynamic Mechanical Properties of Polymeric Materials between 4° and 300°K

J. M. Crissman and R. D. McCammon

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1703-1706 (1962); (4 pages) | Cited 6 times

Online Publication Date: 26 Jul 2005

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An apparatus to measure the dynamic mechanical behavior of polymeric materials from 4°K to room temperature and at frequencies in the mid‐audio range is described. The specimen is driven in its fundamental longitudinal mode of vibration by a transducer which is coupled to the sample by a glass fiber. The lower end of the sample, which hangs vertically, is coated with a thin layer of iron filings. A small permanent magnet is rigidly supported close to and directly below the lower end of the specimen, and a pickup coil detects the motion of the latter. This apparatus uses either the free decay or bandwidth method of determining the internal friction Q−1 and values as low as 6×10−6 have been obtained. Measurements from 8° to 300°K for lead and from 20° to 130°K for polystyrene are reported.

Cylindrical Wave in a Viscoelastic Solid

Jacob Lubliner

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1706-1710 (1962); (5 pages)

Online Publication Date: 26 Jul 2005

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The propagation of a cylindrical wave in an infinite viscoelastic (standard linear) solid is studied by means of the Laplace transformation. Numerical results are obtained over a time interval encompassing the most significant characteristics of wave propagation, namely, attenuation of the initial peak, formation of the delayed peak, and asymptotic decline to the steady state. It is found that no marked change in the wave shape occurs until the distance from the axis exceeds a certain characteristic length (which is infinite in a perfectly elastic solid) and that the change becomes more marked at greater distances.

Investigation of the Fluctuating Forces Acting on a Stationary Circular Cylinder in a Subsonic Stream and of the Associated Sound Field

Roger T. Keefe

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1711-1714 (1962); (4 pages)

Online Publication Date: 26 Jul 2005

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The principal parameters governing the generation of almost pure tones (Aeolian tones) by a roll in a wind have been identified and measured, guided by a theory due to Etkin. In particular, the connection between rms fluctuating lift and the correlation length of the shedding vortices has been recognized, and light has been shed on both by measurements. This has been a group program and has been partially reported elsewhere. Reported herein are the comprehensive measurements of the fluctuating forces on the rod and of the sound field they generate. Sealing or unsealing the ends and the addition of disks at various spacings are found to have major effects. Substitution of the measured parameters in the theoretical equation yields sound pressures in acceptable agreement with experiment. The experiments covered a Reynolds number range of approximately 3000⩽Re⩽100 000.

Mutual Interaction between Two Spheres in a Plane Sound Field

T. F. W. Embleton

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1714-1720 (1962); (7 pages) | Cited 2 times

Online Publication Date: 26 Jul 2005

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The mutual forces between two spheres having their line of centers parallel to the direction of propagation of traveling plane waves may be many times greater than the usual radiation forces of repulsion exerted on a single sphere. Expressions are derived for the forces on each sphere in terms of diverging wavefunctions and coordinate‐transformation functions. Numerical calculations show that the mean force on the sphere nearest the sound source has a value which oscillates with increasing amplitude as the separation between spheres is decreased, reaching a maximum value of repulsion from the source when the spheres are a quarter‐wavelength apart. At smaller separations mutual repulsion between the spheres dominates. For the other sphere, the forces are always of repulsion, but increase in magnitude as the spheres are brought together.

Backscattering of Explosive Sound from the Deep‐Sea Bed

R. J. Urick and D. S. Saling

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1721-1724 (1962); (4 pages)

Online Publication Date: 26 Jul 2005

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The return by the deep ocean bottom of the sound produced by an explosive charge consists of a decaying burst representing scattering at successively decreasing grazing angles with the bottom. An analysis of shot records at three deep‐water locations between Cape Hatteras and Bermuda has yielded the backscattering strength of the sea bottom over a range of frequencies and angles between 30° and 90°. In the range 30° to about 65° the bottom appears to behave as a diffuse backscatterer of sound; between 65° and 90° (normal incidence) an increased return may represent reflection from inclined flat facets of the sea bed or from sub‐bottom sediment layers. Analyses in several frequency bands between 0.5 and 8.0 kc indicate no frequency dependence of the scattering strength that could not be due to shock‐wave attenuation effects in the sea. The coefficients agree with those obtained with pulsed sinusoidal sound sources.

Perturbation Solution for the Axisymmetric Vibrations of Prolate Spheroidal Shells

N. Shiraishi and F. L. DiMaggio

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1725-1731 (1962); (7 pages) | Cited 1 time

Online Publication Date: 26 Jul 2005

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The nontorsional extensional axisymmetric modes and frequencies of elastic prolate spheroidal shells are obtained by a perturbation solution which converges rapidly for small ratios of major to minor axis.

Spatial‐Correlation Functions for Various Noise Models

Benjamin F. Cron and Charles H. Sherman

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1732-1736 (1962); (5 pages) | Cited 20 times

Online Publication Date: 26 Jul 2005

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Observations indicate that noise in the ocean is a superposition of an isotropic noise field and an anisotropic noise field originating at the surface. Models which produce such noise fields are described, and the spatial‐correlation functions are obtained. The volume‐noise model, which produces an isotropic noise field, consists of noise sources uniformly distributed within a sphere. A single‐frequency component of each noise source is considered; the mean‐square output of each is the same, the relative phases are random, and inverse spreading occurs. It is shown that for a very large sphere the spatial correlation is the same as that given by Marsh for a homogeneous isotropic noise field and by the Faran and Hills noise model, which consists of noise sources on the surface of a large sphere. The surface‐noise model consists of noise sources uniformly distributed on a large circular area of a plane. The noise sources are assumed to be directional, in addition to having the properties listed above. The spatial correlation is obtained as a function of the directionality of the noise sources, the spacing of the receivers and their orientation with respect to the surface, and the electrical delay.

Determination of Far‐Field Characteristics of Large Underwater Sound Transducers from Near‐Field Measurements

D. D. Baker

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1737-1744 (1962); (8 pages) | Cited 1 time

Online Publication Date: 26 Jul 2005

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It has recently become necessary to find a way to determine far‐field characteristics of large underwater sound transducers from measurements made in the near field of the transducer (at ranges small compared to the transducer dimensions). It is possible to compute far‐field directivity patterns and source levels from pressure amplitude and phase measurements made in the near field. This can be done by using Kirchhoff's formula with a simple approximation for the normal component of the pressure gradient. Pattern computations were made on line, plane‐array, dipole, and line‐and‐cone transducers from measurements made in open water. Extensive pattern and source level computations were made on a large, multistave cylindrical transducer from measurements made in open water and in a highly reflective tank. Agreement with measured far‐field patterns and source levels was good throughout and was within ±1 dB in the more recent work with the cylindrical transducer. Particularly significant is the fact that successful measurements were made in a tank of diameter only 2.9 times that of the transducer. These measurements were made near the leading edge of the received pulses in order to avoid interference due to reflections. Preliminary work on a simplified near‐field test for a cylindrical transducer has also been done. Such a test would enable one to use near‐field data to make certain judgments about the far‐field performance of a transducer without computations.

Extension of the Theory of Signal Detectability to Matching Procedures in Psychoacoustics

Robert D. Sorkin

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1745-1751 (1962); (7 pages) | Cited 3 times

Online Publication Date: 26 Jul 2005

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The theory of signal detectability is used to analyze experiments where the observer's task is to state, after two signal presentations, whether the signals were the same or different. A model is suggested for predicting human performance in auditory “matching” tasks using data from detection and discrimination experiments. Three experiments are discussed which lend support to the model's application. The first, a two‐alternative forced‐choice, pulsed‐carrier experiment, serves to determine each observer's efficiency. The efficiency η is assumed constant provided certain observation interval and signal characteristics are held fixed, as they were during the entire experimental sequence. The second was a simple matching task, where the first observation interval always contained specified signal and the second sometimes contained a signal identical to the first. In the third experiment the signal appearing in the first interval was randomly chosen from a set of possible signals, thus removing the long‐term memory requirement, and necessitating a comparison observation based on both intervals. The results are consistent with the assumption of constant efficiency across different tasks, and close agreement with the model's predictions for matching performance is demonstrated. Also discussed are stone interesting side issues raised by the experimental data which are relevant to current use of the matching procedure in other areas of psychology. Consideration is made of possible further applications of the matching procedure, such as in determining the value of ϴ in recognition experiments.

Effect of Phase on the Quality of a Two‐Component Tone

James H. Craig and Lloyd A. Jeffress

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1752-1760 (1962); (9 pages) | Cited 1 time

Online Publication Date: 26 Jul 2005

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Listener responses to monaurally presented two‐component stimuli (a 250‐cps tone and its octave, at various intensities and phase relations) reveal striking individual differences and unexpected patterns. With certain pairs of these stimuli, that stimulus which is consistently judged higher in pitch (or louder or purer) by one subject is just as consistently judged lower (or softer or less pure) by another. When the intensity of one of the stimulus components and the phase angle between the components are held constant, reversals of phase of the entire stimulus become discriminable as soon as the intensity of the second component is increased a little above threshold. With certain combinations, as the second component is further increased, phase discrimination for one subject reaches a maximum, decreases to chance, and then increases again. For another subject under the same set of conditions, phase discrimination does not fail, but rather, monotonically increases.
No single explanation accounts for the subjects' patterns of responses and for their sensory experiences. Rather, it seems that two or more of several suggested mechanisms are involved.

Effect of Reverberation on Assessment of Repetitive Impulse Noise

G. J. Thiessen and K. Subbarao

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1761-1763 (1962); (3 pages)

Online Publication Date: 26 Jul 2005

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Reverberation is found to decrease the acceptability of impulse noise even though directional effects resulting from head diffraction are eliminated by presenting the signals by means of earphones. Four clicks per second, with artificially added reverberation corresponding to r = 1.1 sec, were presented to the subjects, who could adjust the level until it matched the same signal without reverberation. Matching was done according to “annoyance,” “noisiness,” and “speech interference.” Reverberation had no appreciable effect when the instantaneous rms level of the reference signal was below about 35 dB re 0.0002 dyn/cm2. The maximum effect occurred in the 85‐ to 90‐dB region where it was equivalent to about 3, 4, and 8 dB, respectively, for the three criteria. The shape of the curve is somewhat different for experienced and naive subjects.

Growth of Loudness and Its Relationship to Intensity Discrimination under Various Levels of Auditory Fatigue

W. Riach, D. N. Elliott, and James C. Reed

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1764-1767 (1962); (4 pages)

Online Publication Date: 26 Jul 2005

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The relationship of growth of loudness to differential sensitivity for intensity has not been experimentally established. Alteration of the rate of loudness growth by auditory fatigue provided the means whereby this relationship could be systematically investigated. Loudness growth was determined by the method of magnitude estimation. Difference thresholds for intensity were obtained using a 3/sec amplitude‐modulated tone. Loudness growth and intensity difference thresholds were determined under normal conditions and under three levels of auditory fatigue, i.e., TTS's of 10, 20, and 30 db. In the area of hearing where recruitment manifests itself, it was found that loudness growth under any of the three fatigue conditions differed significantly from normal, and that, as severity of fatigue increased, there were significant systematic increases in the rate of loudness growth. On the other hand, while the intensity difference thresholds under any of the three fatigue conditions differed significantly from normal, there was no significant difference in the thresholds as severity of fatigue was increased. It is obvious that the relationship of growth of loudness to differential sensitivity for intensity is of only a most general nature.

Investigation of Some Parameters of the Cutaneous Threshold for Vibration

Ronald T. Verrillo

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1768-1773 (1962); (6 pages) | Cited 2 times

Online Publication Date: 26 Jul 2005

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Sensitivity to vibration on the hand was determined as a function of frequency, contactor dimensions, contactor configuration, and distance of the contactor from a rigid support. It was found that each of these parameters affects the threshold in a different way. In the frequency range between 25 and 640 cps, the absolute threshold as a function of frequency yields a U‐shaped curve that reaches a maximum of sensitivity in the region of 250 cps. The effect of the geometric parameters appears to be highly complex.

Condenser Earphones with Multiple Layers of Solid Dielectric

G. M. Sessler and J. E. West

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1774-1779 (1962); (6 pages)

Online Publication Date: 26 Jul 2005

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A condenser earphone with multiple layers of thin solid dielectric material between a metal backplate and a metallized foil is described. The multilayer system has the advantage of providing a more uniform air‐cushion between the electrodes, thus increasing efficiency and decreasing distortion.
The frequency response of this earphone has been measured on a standard 6‐cm3 coupler. The response is flat within ±1.5 dB between 25 and 14 000 cps and within ±3 dB between 20 and 16 500 cps. In this frequency range the harmonic distortion is less than 1% and the intermodulation distortion is less than 3% at 100 dB SPL. Because of the phase linearity, the pulse response of the earphone is an almost true image of the applied voltage for pulses not containing frequencies above 15 000 cps.
The frequency response of the earphone has also been measured at seven human ears by the outer‐ear canal method. The individual frequency response is flat within ±7 dB from 70 to 14 000 cps. For any one frequency, the sound‐pressure deviation between individual ears is within ±6 dB.
The high quality of this earphone makes it useful for many purposes where preservation of signal wave‐form is important, particularly in psycho‐acoustic experiments.

Calibration and Free‐Field Evaluation of a Pressure‐Gradient Microphone

G. B. Thurston and R. L. Heiserman

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1779-1786 (1962); (8 pages)

Online Publication Date: 26 Jul 2005

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The design, calibration procedure, and evaluation in a free field for a condenser‐type pressure‐gradient microphone are described. Procedures are carried out for determination of both magnitude and phase of the pressure gradient. The microphone responds to the differential action of the pressure at two closely spaced field points as communicated by two small probe tubes to either side of a sensing metal diaphragm. By means of a coupling‐chamber calibration procedure it is possible to obtain a sensitivity factor and an error factor which may be used both to describe the precision of the internal structure of the microphone as well as to correct for its imperfections. The free‐field studies analyze the directional characteristics and resolution capabilities of the microphone. The radiation characteristics of a circular orifice in a plane baffle as measured with the gradient microphone are compared with those predicted by simple field theory with regard to the relationship between the pressure‐gradient magnitude and phase and the pressure magnitude and phase.
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Self‐Biased Condenser Microphone with High Capacitance

G. M. Sessler and J. E. West

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1787-1788 (1962); (2 pages) | Cited 12 times

Online Publication Date: 26 Jul 2005

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A new kind of condenser microphone with solid dielectric between the electrodes is described. The system employs metallized dielectric foil electret and requires no external dc bias. The lower impedance eliminates the need of a cathode follower and allows the use of a long connecting cable. The frequency response of this system is flat within ±3 dB between 50 and 15 000 cps. The sensitivity of the system is −59 dBV for a sound pressure of 1 dyn/cm2 (74 db SPL).

Simple Modification of Attenuation Equipment to Measure Velocity

M. Levy, I. Rudnick, and R. Stern

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1788-1789 (1962); (2 pages) | Cited 1 time

Online Publication Date: 26 Jul 2005

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A simple modification for making velocity measurements using existing ultrasonic attenuation equipment is described.

Comments on “Generalized Form of the Sonar Equations” by R. J. Urick

H. W. Marsh

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1789-1789 (1962); (1 page)

Online Publication Date: 26 Jul 2005

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Abstract Unavailable

Author's Reply to Comments by H. W. Marsh

R. J. Urick

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1789-1790 (1962); (2 pages)

Online Publication Date: 26 Jul 2005

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Abstract Unavailable

Erratum: Preliminary Investigation of the Equivalence of Acoustically and Mechanically Induced Vibrations [J. Acoust. Soc. Am. 34, 674 (1962)]

L. Marin and R. C. Kroeger

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1790-1790 (1962); (1 page)

Online Publication Date: 26 Jul 2005

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Abstract Unavailable

Precise Calibration of Sea‐Going Velocimeters

Norman W. Lord

J. Acoust. Soc. Am. Volume 34, Issue 11, pp. 1790-1791 (1962); (2 pages)

Online Publication Date: 26 Jul 2005

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A method is suggested for separating sound propagation and instrumental delay times. In addition, the effect of environmental temperature changes on the circuit operation is measured.
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