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Journal of the Acoustical Society of America

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Jul 1946

Volume 18, Issue 1, pp. 1-255

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Introduction to Technical Discussions of Sound Portrayal

Ralph K. Potter

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 1-3 (1946); (3 pages) | Cited 1 time

Online Publication Date: 17 Jun 2005

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The Portrayal of Visible Speech

J. C. Steinberg and N. R. French

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 4-18 (1946); (15 pages)

Online Publication Date: 17 Jun 2005

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This paper discusses the objectives and requirements in the portrayal of visible patterns of speech from the viewpoint of their effects on the legibility of the patterns. The portrayal involves an intensity‐frequency‐time analysis of speech and the display of the results of the analysis to the eye. Procedures for accomplishing this are discussed in relation to information on the reading of print and on the characteristics of speech and its interpretation by the ear. Also methods of evaluating the legibility of the visible patterns are described.

The Sound Spectrograph

W. Koenig, H. K. Dunn, and L. Y. Lacy

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 19-49 (1946); (31 pages) | Cited 9 times

Online Publication Date: 17 Jun 2005

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The sound spectrograph is a wave analyzer which produces a permanent visual record showing the distribution of energy in both frequency and time. This paper describes the operation of this device, and shows the mechanical arrangements and the electrical circuits in a particular model. Some of the problems encountered in this type of analysis are discussed, particularly those arising from the necessity for handling and portraying a wide range of component levels in a complex wave such as speech. Spectrograms are shown for a wide variety of sounds, including voice sounds, animal and bird sounds, music, frequency modulations, and miscellaneous familiar sounds.

Visible Speech Cathode‐Ray Translator

R. R. Riesz and L. Schott

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 50-61 (1946); (12 pages)

Online Publication Date: 17 Jun 2005

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A system has been developed whereby speech analysis patterns are made continuously visible on the moving luminescent screen of a special cathode‐ray tube. The screen is a cylindrical band that rotates with the tube about a vertical axis. The electron beam always excites the screen in the same vertical plane. Because of the persistence of the screen phosphor and the rotation of the tube, the impressed patterns are spread out along a horizontal time axis so that speech over an interval of a second or more is always visible. The upper portion of the screen portrays a spectrum analysis and the lower portion a pitch analysis of the speech sounds. The frequency band up to 3500 cycles is divided into 12 contiguous sub‐bands by filters. The average speech energy in the sub‐bands is scanned and made to control the excitation of the screen by the electron beam which is swept synchronously across the screen in the vertical direction. A pitch analyzer produces a d.c. voltage proportional to the instantaneous fundamental frequency of the speech and this controls the width of a band of luminescence that the electron beam produces in the lower part of the screen. The translator has been used in a training program to study the readability of visible speech patterns.

Visible Speech Translators with External Phosphors

Homer Dudley and Otto O. Gruenz, Jr.

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 62-73 (1946); (12 pages)

Online Publication Date: 17 Jun 2005

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This paper describes some experimental apparatus built to give a passing display of visible speech patterns. These patterns show the analysis of speech on an intensity‐frequency‐time basis and move past the reader like a printed line. The apparatus has been called a translator as it converts speech intended for aural perception into a form suitable for visual perception. The phosphor employed is not in a cathode‐ray tube but in the open on a belt or drum.

Basic Phonetic Principles of Visible Speech

G. A. Kopp and H. C. Green

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 74-89 (1946); (16 pages)

Online Publication Date: 17 Jun 2005

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Abstract Unavailable

The Propagation of Sound in the Atmosphere—Attenuation and Fluctuations

Vern O. Knudsen

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 90-96 (1946); (7 pages) | Cited 2 times

Online Publication Date: 17 Jun 2005

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A Determination of the Wave Forms and Laws of Propagation and Dissipation of Ballistic Shock Waves

Jesse W. M. DuMond, E. Richard Cohen, W. K. H. Panofsky, and Edward Deeds

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 97-118 (1946); (22 pages) | Cited 11 times

Online Publication Date: 17 Jun 2005

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Experiments to ascertain the wave forms and laws of propagation and dissipation of ballistic shock waves to large distances (80 yards) from the bullet trajectory are described. Calibers 0.30, 0.50, 20 mm, and 40 mm were studied. In every case an N‐shaped wave profile was observed consisting of a sudden rise in pressure, the “head discontinuity,” followed by an approximately linear decline to a pressure about equally far below atmospheric and then a second sudden return, the “tail discontinuity,” to atmospheric pressure. The peak amplitudes of this disturbance are found to diminish about as the inverse ¾ power of the miss‐distance (perpendicular distance from the trajectory) while the period T′ (measured between the discontinuous fronts) increases about as the ¼ power of the miss‐distance for calibers 0.30, 0.50, and 20 mm. For 40‐mm shells the amplitude decays a little faster, about as the inverse 0.9 power of miss‐distance over the range studied. A theory taking account of the dissipation of the N‐wave energy into heat is developed to explain the observed behavior. A method of measuring absolute N‐wave amplitudes by observing the rate of change of period T′ with propagation is described. The theory leads to an absolute relationship at large distances between distance, amplitude, and period in which no arbitrary constants appear.

The Modulation of Sound Decay Curves

Robert B. Watson

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 119-129 (1946); (11 pages)

Online Publication Date: 17 Jun 2005

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Note on Normal Frequency Statistics for Rectangular Rooms

R. H. Bolt

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 130-133 (1946); (4 pages)

Online Publication Date: 17 Jun 2005

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Fluctuation Phenomena in Room Acoustics

Dah‐You Maa

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 134-139 (1946); (6 pages)

Online Publication Date: 17 Jun 2005

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Two types of fluctuation phenomena are discussed theoretically, utilizing the concept of normal modes of aerial vibration in the room. The fluctuation noise due to the random motion of air molecules is found to be a property of air alone and independent of the room. On the other hand, the fluctuation during reverberation depends on both the room dimensions and its reverberation characteristics. Practical formulae of the magnitudes of the fluctuations are presented, which are in good agreement with the experimental data obtained previously. The astonishing gift of the blind in estimating the room size with surprising accuracy is explained, and further investigations on the problem of room liveness as related to fluctuation phenomena as well as its effect on the acoustical design of a room are suggested.

The Design and Construction of Anechoic Sound Chambers

Leo L. Beranek and Harvey P. Sleeper, Jr.

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 140-150 (1946); (11 pages) | Cited 8 times

Online Publication Date: 17 Jun 2005

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Data on the performance of five different types of structures for use in echo‐free (anechoic) chambers are presented. The best one of these structures is shaped like a wedge and manufactured from glass fibers held together by a binding agent. When mounted in the room, the wedges are spaced out several inches from the walls, and the dihedrals of adjacent units are turned through 90°. Generalized specifications for the optimal design of structures made from glass fiber wedges are presented in terms of either (a) lowest frequency at which 99 percent or better absorption is desired or (b) maximum depth of treatment which may be installed in the room. The application of these specifications to two rectangular rooms is shown and inverse square law measurements performed in the two completed chambers are presented. In the larger chamber the deviations are within ±0.3 db out to 10 feet and ±1.0 db out to 30 feet from a point source of sound. In the smaller, the deviations are within ±1.0 db out to 10 feet.

Effects of Finite Baffles on Response of Source with Back Enclosed

Rudolph H. Nichols, Jr.

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 151-154 (1946); (4 pages)

Online Publication Date: 17 Jun 2005

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The effect of a finite circular baffle on the axial response‐frequency characteristic of a central sound source in which sound from the back side of the diaphragm is completely suppressed was found to consist of an orderly series of peaks and valleys. The magnitudes and characteristic frequencies of these peaks and valleys depend upon the diameter of the baffle and the distance at which the response is measured. Experimentally determined values of the frequencies agree with values computed on the hypothesis that the phenomenon is one of interference between sound which reaches the measuring microphone directly from the source and sound which travels radially along the baffle and is “reflected” from its edge to the microphone. This assumption also accounts qualitatively for the increase of magnitude of the peaks and valleys with increasing distance from the baffle. As might be expected, baffles which are not symmetrical with respect to the sound source produce an irregular effect on the response.

Motional Impedance Analysis Applied to a Dynamic Microphone

J. E. White

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 155-160 (1946); (6 pages)

Online Publication Date: 17 Jun 2005

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An article by R. D. Fay presents a method for calculating the complete performance at any frequency of an electro‐magnetic speaker from a plot of its electrical impedance measured when the speaker is loaded by a closed air column of variable length. The present article applies this method to a dynamic microphone, yielding pressure sensitivity at lower audiofrequencies and providing a means of calculating microphone mechanical impedance and other characteristics. Improvement in accuracy which may be achieved by proper choice of area for closed air column is discussed.

Problems of High Altitude Communication

J. Weichbrod

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 161-166 (1946); (6 pages)

Online Publication Date: 17 Jun 2005

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The use by the Army Air Forces of high altitude for strategic bombing made the long standing and complex problem of voice communications these high altitudes a matter of considerable urgency. The problems of high altitude communication and solutions thereto dealing with the various components in the system, namely, the microphone, interphone amplifier, and headset receivers are discussed in a general way.

A Just Scale for Music

Arthur Taber Jones

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 167-169 (1946); (3 pages)

Online Publication Date: 17 Jun 2005

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In addition to the well‐known just major scale, Robert Smith described another that he regarded as equally harmonious. The second scale is like the well‐known one except that its first two intervals are interchanged. It is now shown that this scale may be obtained from three consecutive minor triads, in a manner similar to that in which its well known counterpart is often obtained from major triads. A comparison and experimental test of the two scales shows little to choose between them. Sometimes one is preferred, and sometimes the other. A satisfactory scale should include the pitches from both.

Transmission, Reflection, and Guiding of an Exponential Pulse by a Steel Plate in Water. II. Experiment

M. F. M. Osborne and S. D. Hart

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 170-184 (1946); (15 pages) | Cited 2 times

Online Publication Date: 17 Jun 2005

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In this paper are given the results of an experimental study of the interaction of an explosion wave with a water‐backed steel plate. Data are given showing the dependence of the transmitted and reflected waves on the angle of incidence, and of the diffracted wave on position behind the plate. These data are illustrative of the use of the explosion wave in acoustical research. The plate acts as a filter, removing the high frequencies from the transmitted wave and the low frequencies from the reflected wave. The reflected wave is approximately constant in shape, or time scale, with varying angle of incidence. Its amplitude has a broad maximum at normal incidence. In addition to the reflected, transmitted, and diffracted waves, waves can travel along the plate, in which case the plate acts as a wave guide. As a consequence of dispersion in the guided waves, a precursor precedes the explosion wave as it travels along the plate. The dependence of the frequency, length, and amplitude of this precursor upon orientation of the plate, position, and time has been determined.

The Absorption of Ultrasonic Waves in Benzene

John Quinn

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 185-189 (1946); (5 pages) | Cited 3 times

Online Publication Date: 17 Jun 2005

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The coefficient of absorption of ultrasonic waves in benzene was measured as a function of the temperature by means of the sonic interferometer. The frequency‐free coefficient varies from 0.66 × 10−14 to 0.85 × 10−14 over the temperature range from 7.2°C to 73.5°C. It appears that the absorption of ultrasonic waves in liquids is effected by two causes, viz., the viscosity effect deduced by Stokes, and a second effect of uncertain origin. In benzene, the second effect pre‐dominates overwhelmingly and determines the over‐all temperature dependence of the absorption coefficient.

The Velocity of Dilatation and Rayleigh Waves in Metal Bars

J. Howard McMillen

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 190-199 (1946); (10 pages)

Online Publication Date: 17 Jun 2005

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Single elastic waves in rock and metal specimens were studied by partially immersing the specimen in water and observing the body waves in the water by means of spark shadowgrams. The waves were started by impact from a fast moving steel sphere. Waves in the water were observed to come from the dilatation body wave and the Rayleigh surface‐wave in the solid. Using the slope of the wave front in water, the dilatation wave velocities were measured for cold‐rolled steel, yellow brass, and an aluminum alloy, as well as for two rock specimens, a marble and a diabase. These agreed well with the velocities calculated from the elastic constants. The velocity of the first wave or pulse was found to correspond to the velocity of a dilatation wave in an infinite medium, while the wave velocities which were measured when the bar was in resonant oscillation were observed to have values characteristic of a dilatation wave in a narrow bar. The Rayleigh surface wave velocities were measured in steel, brass, and an aluminum alloy and showed good agreement with the theory. None of the surface waves was strong enough in the rock specimens to be observed. Spark shadowgrams were also made, showing that a Rayleigh wave is produced when a dilatation wave passes through an interface at nearly normal incidence. Rayleigh waves were also observed to produce a second Rayleigh wave at a square corner, demonstrating that the Rayleigh wave has a component of displacements which is parallel to the surface.

Refinements in Supersonic Reflectoscopy. Polarized Sound

Floyd A. Firestone and Julian R. Frederick

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 200-211 (1946); (12 pages) | Cited 4 times

Online Publication Date: 17 Jun 2005

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One form of simple circuit for the generation of the short duration high frequency voltage trains and in the supersonic reflectoscope is shown. The required band width of the system, including the crystal, is discussed. Techniques for the radiation of longitudinal, shear, and Rayleigh waves are set forth. Either longitudinal or shear waves can be used to establish various modes of thickness resonance through a plate for measuring velocity of propagation or thickness. Shear waves have some of the properties of polarized light, for instance, double refraction has been measured by three methods in elastically aeolotropic solids and a technique for the direct indication of the amount of elastic aeolotropy developed. By means of a quarter‐wave plate, circularly polarized sound can be produced.

Standing Wave Technique of Thickness Measurements

John B. Butler and James B. Vernon

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 212-215 (1946); (4 pages)

Online Publication Date: 17 Jun 2005

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On the Vibrations of a Whirling Wire

A. Victor Maskei

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 216-216 (1946); (1 page)

Online Publication Date: 17 Jun 2005

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The Sound Spectrograph

W. Koenig, H. K. Dunn, and L. Y. Lacy

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 244-244 (1946); (1 page)

Online Publication Date: 17 Jun 2005

Full Text: | Download PDF

Show Abstract
The sound spectrograph is a wave analyzer which produces a permanent visual record showing the distribution of energy in both frequency and time. This paper describes the operation of this device and shows the mechanical arrangements and the electrical circuits in a particular model. Some of the problems encountered in this type of analysis are discussed, particularly those arising from the necessity for handling and portraying a wide range of component levels in a complex wave such as speech. Spectrograms are shown for a wide variety of sounds, including voice sounds, animal and bird sounds, music, frequency modulations, and miscellaneous familiar sounds.
FREE

Translators with External Phosphors (A)

Homer Dudley and Otto O. Gruenz, Jr.

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 244-244 (1946); (1 page)

Online Publication Date: 17 Jun 2005

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Two translators are described which display instantaneously on a moving external phosphor the essential characteristics of sound waves, such as speech. There is thus presented to the eye a parade of speech patterns as though a printed line were passing by. The pattern of intensity vs. frequency vs. time remains in view long enough to permit the eye to observe pattern groups as an aid to speech interpretation. Typical applications are portraying the phonetics of speech and aiding the deaf to understand speech and to build up their own speech. The goal in the speech pattern portrayal is to show the stronger speech components simply but accurately as a function of frequency and time. The speech is equalized to bring out the stronger components over the frequency range. Next automatic volume control is applied to iron out level differences on a time basis. Then the 3500 cycle speech band is analyzed by twelve filters of about 300 cycles each and the resultant component powers applied to the excitation of a phosphor. The smaller translator employs twelve incandescent grain‐of‐wheat lamps for phosphor excitation, generating a pattern 1″ high and 5″ long and the larger translator sets up a pattern 7″ high and 47″ long. The patterns remain in the field of view for about two seconds.
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The Cathode‐Ray Translator (A)

R. R. Riesz and L. Schott

J. Acoust. Soc. Am. Volume 18, Issue 1, pp. 244-244 (1946); (1 page)

Online Publication Date: 17 Jun 2005

Full Text: | Download PDF

Show Abstract
A system has been developed whereby speech analysis patterns are made continuously visible on the moving luminescent screen of a special cathode‐ray tube. The screen is a cylindrical band that rotates with the tube about a vertical axis. The electron beam always excites the screen in the same vertical plane. Because of the persistence of the screen phosphor and the rotation of the tube, the impressed patterns are spread out along a horizontal time axis so that speech over an interval of a second or more is always visible. The upper portion of the screen portrays a spectrum analysis and the lower portion a pitch analysis of the speech sounds. The frequency band up to 3500 cycles is divided into 12 contiguous sub‐bands by filters. The average speech energy in the sub‐bands is scanned and made to control the excitation of the screen by the electron beam which is swept synchronously across the screen in the vertical direction. A pitch detector produces a d.c. voltage proportional to the instantaneous fundamental frequency of the speech and this controls the width of a band of luminescence that the electron beam produces in the lower part of the screen. The translator has been used in a training program to study the readability of visible speech patterns.
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