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Journal of the Acoustical Society of America

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Mar 1954

Volume 26, Issue 2, pp. 151-258

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Perforated Facing and Sound Absorption

Uno Ingard

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 151-154 (1954); (4 pages) | Cited 2 times

Online Publication Date: 29 Jun 2005

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In the analysis of the absorption characteristics of a porous layer with perforated facing, it is usually assumed that the facing contributes only a mass reactance to the total impedance. In the present paper it is shown that the facing also causes an additional acoustic resistance which is often larger than the acoustic resistance of the porous layer itself. This resistance obtained only when the porous material is in close contact with the facing and becomes practically zero when the air space between facing and material exceeds approximately one perforation diameter. The effect is due to the near field (higher mode) losses in the porous material around the perforations. The resulting effect on the absorption characteristics considerable, as demonstrated in some examples, and may at least partly explain reported disagreement between measurements and previous calculations.

Information of Elementary Multidimensional Auditory Displays

Irwin Pollack and Lawrence Ficks

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 155-158 (1954); (4 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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The information transmission associated with elementary auditory displays consisting of a large number of independent stimulus aspects, e.g., the frequency or the sound level of a tone, was examined. In general, multiple stimulus encoding is a satisfactory procedure for increasing the information transmission associated with elementary auditory displays. Further, extreme subdivision of each stimulus aspect fails to produce substantial improvement in the information transmission.

Characteristics of Radiating Variable Resonant Frequency Crystal Systems

Walter Welkowitz and William J. Fry

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 159-165 (1954); (7 pages)

Online Publication Date: 29 Jun 2005

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Calculations based on the usual one‐dimensional theory of piezoelectric crystal systems have been carried out for several particular variable resonant frequency crystal systems radiating into water. Curves are presented showing the (1) power output as a function of frequency for operation both on and off resonance, (2) resonant frequency shift as a function of backing length, and (3) relative band width as a function of frequency. The validity of certain approximations is checked so that the operating characteristics of systems made up of different materials can be quickly estimated. The curves indicate that a variable resonant frequency system of crystals all of equal free‐free resonant frequency operating with an allowable power variation for fixed applied field strength of 2:1 can have a continuous variation of resonant frequency of about 2.3:1. A system half the crystals of which have twice the free‐free resonant frequency of the others for the same allowable field strength variation can operate over a frequency range of about 5.3:1.

The Lowest Resonant Frequency of a Water‐Loaded Circular Plate

William H. Peake and Edward G. Thurston

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 166-168 (1954); (3 pages) | Cited 2 times

Online Publication Date: 29 Jun 2005

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The resonant frequency for the lowest mode of a circular plate is calculated for the conditions of concentrated mass loading at the center, water loading on one side, simply supported and clamped at the edge. These results are compared with those of Lamb and others.

Sound Field of a Moving Cylinder and a Moving Sphere

Henry Zatzkis

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 169-173 (1954); (5 pages)

Online Publication Date: 29 Jun 2005

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Most investigations of the sound field of a moving source deal only with point sources. We have examined the sound field of finite sources, moving with constant velocity. The simplest possible vibrators have been chosen, viz., a pulsating circular cylinder and a pulsating sphere. The solution is an infinite series in terms of Mathieu functions in the two‐dimensional case, and in terms of prolate ellipsoidal functions in the three‐dimensional case. Besides the rigorous solutions, asymptotic formulas valid for large distances away from the source are given.

Self‐Maintained Oscillations of the Jet in a Jet‐Edge System. I

Wesley L. Nyborg

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 174-182 (1954); (9 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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A theory is presented for the self‐maintained transverse oscillations which arise in a low‐velocity jet as it plays upon an obstacle, thus generating edge tones. It is assumed that transverse forces act on each particle of the jet as it travels toward an obstacle, and that this force is due to “sources” of hydrodynamic origin localized near the obstacle. The law of motion is set up in the form of an integral equation involving unknown functions for the force field. It is shown that a number of important properties of jet‐edge systems, and of the edge tones they produce, can be deduced from the equation, even for highly simplifying trial assumptions about the unknown functions.

On the Dissipative Viscoelastic Constants of Higher Order

Leon Knopoff

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 183-186 (1954); (4 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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The limitations imposed upon the usual elastic and viscoelastic constants are reinvestigated. Defining viscoelastic properties of a higher order, it is found that methods which have been used for the first‐order quantities are insufficient to determine relationships between the higher‐order constants. Necessary but non‐sufficient criteria are arrived at by means of arguments involving energies in dissipative processes.

Wave Propagation in a Randomly Inhomogeneous Medium. III

David Mintzer

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 186-190 (1954); (5 pages) | Cited 3 times

Online Publication Date: 29 Jun 2005

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The coefficient of variation for a series of sound pulses and the correlation function for successively received sound pulses are evaluated for arbitrary pulse length, using the assumption that the correlation function of the refractive index inhomogeneities is expressible as the product of time‐ and space‐dependent functions. For the case of pulse length much less than the time constant of refractive index correlation function, the coefficient of variation is found to be independent of the pulse length, and the pulse‐correlation function is found to be identical with the time‐dependent part of the refractive index correlation function. Comparison is made with data obtained from Sheehy. An approximate calculation shows that the motion of source and receiver will distort the pulse‐correlation function so that little information can be obtained from the data concerning the time dependance of the refractive index.

On Nonspecular Reflection at a Rough Surface

John W. Miles

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 191-199 (1954); (9 pages) | Cited 4 times

Online Publication Date: 29 Jun 2005

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The reflection of a plane wave at a rough interface separating two fluid media is examined in the approximation of “small roughness,” such that second‐order terms in the magnitude of the roughness may be neglected. Exact solutions are obtained when the roughness is harmonic, while asymptotic results are obtained for arbitrary distributions. The analysis deals principally with an incident wave that is harmonic in time, but the problem of the reflection of a pulse from a perfectly reflecting, sinusoidal boundary is solved. It is found that such a boundary acts as a band‐pass filter of the nonspecular components of the reflected wave. Outisde of this pass band the reflection is not only specular but distortionless. Rather less generality is possible when the boundary is not perfectly reflecting, but the pass band is found to be independent of the properties of the reflecting medium.

On the Theory of Sound Reflection in an Open‐Ended Cylindrical Tube

Harold Levine

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 200-211 (1954); (12 pages)

Online Publication Date: 29 Jun 2005

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The propagation of dominant mode plane sound waves within a cylindrical tube having arbitrary cross section and extending indefinitely from an open end is studied theoretically. A quantity of special interest is the end correction, which characterizes the reflection coefficient at wave lengths large compared to the transverse tube dimensions. The reflection coefficient and end correction fit naturally into a boundary value formulation of the wave propagation problem, whose solution hinges on that of one or more integral equations. Since the integral equations do not in general admit of exact solution, practical techniques for approximately determining the physical quantities are important. Among these are the stationary or variational principles, which can be cast into a variety of independent forms, corresponding to the different nature of boundary distributions. Another technique is based on initial modification of an integral equation so as to utilize the possibility of explicit and rigorous solution. Approximate forms of the reflection coefficient and end correction are obtained in this manner, with the distinction of yielding exact results when the tube cross section is circular. A brief comparison of the different procedures is included.

Visual Contribution to Speech Intelligibility in Noise

W. H. Sumby and Irwin Pollack

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 212-215 (1954); (4 pages) | Cited 32 times

Online Publication Date: 29 Jun 2005

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Oral speech intelligibility tests were conducted with, and without, supplementary visual observation of the speaker's facial and lip movements. The difference between these two conditions was examined as a function of the speech‐to‐noise ratio and of the size of the vocabulary under test. The visual contribution to oral speech intelligibility (relative to its possible contribution) is, to a first approximation, independent of the speech‐to‐noise ratio under test. However, since there is a much greater opportunity for the visual contribution at low speech‐to‐noise ratios, its absolute contribution can be exploited most profitably under these conditions.

Laboratory Evaluation of Field Measurements of the Loudness of Truck Exhaust Noise

D. B. Callaway and H. H. Hall

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 216-220 (1954); (5 pages)

Online Publication Date: 29 Jun 2005

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Simple loudness judgment tests were performed by a jury of 15 observers on the recorded noises of approximately 100 highway trucks. The loudness of the noises calculated by a modification of the equivalent tone method proposed by Beranek and co‐workers ranges from about 20 to 200 sones. Observers were instructed to rank the noises in six loudness classes and were allowed to listen to a sample of class 1 and class 6 after each 20 recordings. The calculated loudnesses were then divided into six classes with class limits set by a 40 percent loudness increase per class. Although the subjective tests were conducted with no elaborate controls, a correlation coefficient of 0.94 was found between the average judgment of the group and the calculated loudness class. The correlation coefficient between average judgment and total sound pressure level was 0.78, whereas the correlation coefficient between the average judgment and the level on the A‐network of the sound level meter was 0.83. Experimental techniques and the capabilities and limitations of the loudness‐calculation methods are discussed.

An Anechoic Tank for Underwater Sound Measurements under High Hydrostatic Pressures

Charles L. Darner

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 221-222 (1954); (2 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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The new USRL tank for making acoustic measurements under hydrostatic pressures up to 1000 psig and controlled temperatures from near freezing to near boiling is described. The internal treatment of the tank with wedges of Insulkrete, a sound absorbing material composed of pine sawdust and Portland cement, is pictured. Oscillograms of the pulsed signal show the reduction in reverberation level effected by Insulkrete. The conversion by Insulkrete of high‐frequency sound energy into heat is illustrated by schlieren photographs.

Measurements of Sound Absorption in Aqueous Salt Solutions by a Resonator Method

O. B. Wilson, Jr. and Robert W. Leonard

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 223-226 (1954); (4 pages) | Cited 7 times

Online Publication Date: 29 Jun 2005

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This paper presents the results of measurements of the sound absorption in aqueous solutions of several salts. While magnesium sulfate is the salt of primary interest in this case, some results for sea water at different temperatures, solutions of magnesium acetate, zinc sulfate, and beryllium sulfate are given. The frequency range of the measurements is approximately 50 to 500 kc. Although the resonator method used is not very precise, it is the only known laboratory method which is able to give reliable absorption measurements in water and water solutions in this low‐frequency range where the sound absorption in these liquids is extremely small.

Sound Velocity in Some Aqueous Solutions as a Function of Concentration and Temperature

Romard Barthel

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 227-230 (1954); (4 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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Precision sound velocity measurements are reported in sucrose solutions in the concentration range up to 3 molal, and in solutions of NaCl and Pb(NO3)2 up to 2 molal. Measurements were made at three temperatures−24.76°C, 40.37°C, and 59.60°C−using 15‐Mc sound. For sucrose and NaCl the velocity vs molality relation is linear out to about 1 molal, where a slight decrease in slope sets in. For Pb(NO3)2 the velocity vs molality relation has a negative slope, and a rise from linearity is already evident at 0.5 molal.
A simple theory of the concentration dependence of the sound velocity in solutions is developed and correlated with experimental data.

The Backscattering of Sound from a Harbor Bottom

R. J. Urick

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 231-235 (1954); (5 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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When underwater sound strikes the bottom of the sea in shallow or deep water, a portion of its intensity is scattered back toward the source of sound. A study of the backscattering from the bottom as a function of pulse length, frequency, and tilt‐angle at several locations in a harbor along the East Coast, was made by using a tiltable transducer mounted on a barge. The results are expressed in terms of quantity called the “scattering strength” of a unit area of bottom.
The results suggest that the backscattering of sound from a natural bottom is due more to its roughness rather than to the fact that it consists of sedimentary particles. Even at normal incidence the bottom of a sea or bay appears sufficiently rough so that little sound is returned by specular reflection. Some evidence in support of these conclusions is given.

Ultrasound and Medicine. A Survey of Experimental Studies

J. F. Herrick and Frank H. Krusen

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 236-240 (1954); (5 pages)

Online Publication Date: 29 Jun 2005

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Experimental investigations indicate that ultrasound may prove useful for therapy, for diagnosis, and for biologic measurement.
Ultrasound, although it may be dangerous in unskilled hands, is an excellent agent for the structural heating of living tissues. The term “structural heating” is used to denote heating at abrupt interfaces.The living organism presents numerous abrupt interfaces.
Ultrasound promises to become a reliable diagnostic tool. Either the transmitted or the reflected ultrasonic energy can be used in this application. Tumors, gallstones, kidney stones, stones in the salivary glands, foreign bodies, and abnormal collections of fluid have been located accurately.
Preliminary observations on the use of ultrasound for certain biologic measurements are encouraging. Instrumentation for biologic measurement includes ultrasonic flowmeters, devices for measuring thickness of some tissue structures, and equipment for measuring the viscosity of blood.

The Processing Possibilities of Ultrasonics

Oskar Mattiat

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 241-243 (1954); (3 pages)

Online Publication Date: 29 Jun 2005

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Ultrasonic processing possibilities are limited mainly by the economic factors of high first cost of equipment and high‐power cost per unit of processed material. In addition transducers suitable for large volume applications have only recently been developed. Processing possibilities which have led to industrial applications or which seem quite promising are reviewed. Among them are ultrasonic maturing of liquids, extraction, dispersing of dyes and pigments, emulsification, floatation ore dressing, degassing of water, oil and glass, soldering of aluminum, drilling, and cleaning of metal parts.

Uses of Ultrasonics in Degreasing Processes

Thomas J. Kearney

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 244-246 (1954); (3 pages)

Online Publication Date: 29 Jun 2005

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Ultrasonics is one of the newest tools to be applied to metal cleaning. Through the years abrasives, soaps, compounded alkaline materials, and solvents have been used to remove soils from metals. Trichlorethylene Solvent degreasing has had a wide reception in industry since its introduction in 1930. The Detrex Soniclean process combines sound energy and trichlorethylene solvent degreasing for metal cleaning. This is accomplished by immersing especially treated barium titanate transducers in chlorinated solvents producing cleaning results previously unobtainable. Crossrod, conveyorized equipment incorporating constant distillation and filtration of the solvent in the sonics chamber and providing a final vapor rinse and drying is now producing as many as 8000 parts per hour in industrial plants.

The Dispersion of the Velocity of Sound in Water between 500 and 1500 Kilocycles

T. King McCubbin, Jr.

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 247-249 (1954); (3 pages)

Online Publication Date: 29 Jun 2005

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Dispersion of the velocity of sound was measured by simultaneously transmitting continuous trains of sound waves of the two frequencies through water. One transducer was used to generate the two signals and a second transducer, which could be moved in the direction of the sound beam, received the signals. Dispersion was determined by measuring the change in the relative phase of the two received signals as the length of path between the transducers was varied. These measurements indicated that the velocity of sound at 500 kc was equal to the velocity at 1500 kc to within one part in 290 000.

The Study of a Sound Field by Means of Optical Refraction Effects

J. Kolb and A. P. Loeber

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 249-251 (1954); (3 pages)

Online Publication Date: 29 Jun 2005

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An optical effect of an ultrasonic field discovered by R. Lucas and P. Biquard, namely the broadening of a slit image, can be computed in a simple way which is based on a method by Wiener. It is useful in the frequency range below 1 Mc/sec for the point by point study of the pressure distribution in a stationary sound wave. Photographic records of this distribution were made. A simple method of measuring the wavelength is described.
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Note on Longitudinal Vibrational Amplitudes of Solid Conical Horns

Robert H. Quint

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 252-252 (1954); (1 page)

Online Publication Date: 29 Jun 2005

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An equation is given for the amplitude multiplication factor of a longitudinally vibrating solid resonant cone; showing, that from simple theory, as one of the diameters reduces to zero, the amplitude multiplication factor remains nonzero.

On Axi‐Symmetrical Vibrations of Circular Plates of Uniform Thickness; Including the Effects of Transverse Shear Deformation and Rotatory Inertia

Eric Reissner

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 252-253 (1954); (2 pages)

Online Publication Date: 29 Jun 2005

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Vibrations of Evaporating Liquid Drops

N. J. Holter and W. R. Glasscock

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 253-253 (1954); (1 page)

Online Publication Date: 29 Jun 2005

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Finite Amplitude Sound Produced by a Piston in a Closed Tube

Joseph B. Keller

J. Acoust. Soc. Am. Volume 26, Issue 2, pp. 253-254 (1954); (2 pages)

Online Publication Date: 29 Jun 2005

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The problem stated in the title is solved for a gas with γ = − 1 by the method of a previous paper. First an arbitrary piston motion is considered. Then more detailed results are given for the sinusoidal case.
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