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Journal of the Acoustical Society of America

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Nov 1956

Volume 28, Issue 6, pp. 1016-1293

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Viscous Dissipation Caused by a Sphere

C. A. Lane

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1194-1196 (1956); (3 pages)

Online Publication Date: 29 Jun 2005

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Recent studies have led to a satisfactory solution to the problem of acoustic streaming in the vicinity of a sphere for s/a≪1, where s is the oscillation amplitude, and a is the radius of the sphere. The results of these studies have now been applied to the calculation of the inherent energy losses. The energies in the dc vortices and in the primary ac vortices have been computed, and it is shown that the energy in the former is negligible in comparison with the energy in the latter. The results are restricted to cases where s/a≪1, and a(ω/2ν)½≫1, where ν is the kinematic viscosity and ω is the frequency of oscillation.

Physical Acoustics and the Properties of Solids

Warren P. Mason

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1197-1206 (1956); (10 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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The techniques of physical acoustics have been applied in determining the elastic properties and internal friction of polycrystal and single crystal metals, glasses, nonmetallic crystals, high polymer materials, and ceramics. They have been used as tools in investigating such solid state phenomena as grain and domain boundary effects in metals and ferromagnetic and ferroelectric materials, in the diffusion of atoms, molecules and vacancies through a solid, in the motion of imperfections such as dislocations and have even detected an interaction between the lattice sound vibrations and free electrons in metals at low temperatures.
These effects are studied by techniques varying from the vibrations of torsional pendulums at frequencies below 1 cy to frequencies as high as 300 Mc by ultrasonic pulsing methods and have employed strain values from 10−8 to 10−2. Four examples of these techniques are discussed in the present paper. These include diffusions of nitrogen and carbon atoms in iron, the motion of domain walls in ferromagnetic nickel, the interaction of lattice vibrations with free electrons at low temperatures and the use of high strain values in studying internal friction and fatigue in metals. These examples were chosen because they result in definitely explained effects which are indicative of typical processes occurring in solids.

Internal Friction and Fatigue in Metals at Large Strain Amplitudes

W. P. Mason

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1207-1218 (1956); (12 pages) | Cited 7 times

Online Publication Date: 29 Jun 2005

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A barium titanate transducer coupled to an exponential horn can produce large strains in metals. By using a final horn with a necked down section, it is possible to concentrate the strains in a small specimen. Measurements of the impressed voltage and a voltage from a pick up electrode on the titanate make it possible to calibrate the device so that the internal friction, change in elastic constant, and the strain in the sample are all determined.
The measured internal friction can be divided into three strain regions. From 10−6 to 10−5 the internal friction is approximately independent of the strain. For strains from 10−5 to from 2 × 10−4 to 2 × 10−3, depending on the material, the internal friction increases with strain in a reversible anelastic manner. Above this range the internal friction increases very rapidly and for strains twice as large as those for the initial rise, the metal fatigues in a very short time.
It appears that the anelastic range is caused by the reversible production of unstable Frank‐Read loops. The shape of the internal friction curve allows one to evaluate the dislocation distribution with results in accord with etch pit methods. The final phase appears to be due to irreversible production of Frank‐Read loops caused by dislocations cutting through other dislocations. This process produces jogs in the dislocations and vacancies in the metal. These vacancies accumulate to produce fatigue cracks in accord with a theory of Mott's. Temperature and time effects result from the lowering of the activation energy by the applied stress. At liquid nitrogen temperature, the fatigue stress increases until the activation energy for diffusion is nearly zero.

Determination of the Elastic Constants of Optical Glasses by an Ultrasonic Method

James M. Barnes and E. A. Hiedemann

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1218-1221 (1956); (4 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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The values of the elastic constants of twelve samples of optical glass commercially produced in the United States and a sample of fused silica were calculated from the results of measurements made on these samples. The method used was a combination of the ultrasonic method developed by Schaefer‐Bergmann with that of Hiedemann.
The accuracies of the experimentally determined values of the longitudinal and shear wave velocities were 0.13% and 0.25%, respectively, while the accuracies in determining the elastic constants were 0.5% for the shear modulus, Lame's modulus, and the bulk modulus, 0.7% for Poisson's ratio, and 0.8% for Young's modulus. The values of the surface tensions of the samples were calculated using the results of the measurements and Auerbach's equation.

Application of Two Ultrasonic Methods to the Determination of the Ratio p/q of the Photoelastic Constants of Optical Glasses

H. F. Gates and E. A. Hiedemann

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1222-1227 (1956); (6 pages)

Online Publication Date: 29 Jun 2005

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The ultrasonic methods of Bergmann and Fues and of Mueller for the determination of the ratio p/q of the photoelastic constants of glasses were applied to a series of American optical glasses and to fused silica. Mueller's method gave significant results which are given in tables.

Attenuation of Ultrasonic Waves of Finite Amplitude in Liquids

V. Narasimhan and R. T. Beyer

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1233-1236 (1956); (4 pages)

Online Publication Date: 29 Jun 2005

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Measurements are reported for the effect of finite amplitude on the attenuation of the fundamental component of an ultrasonic wave in water and in aqueous solutions of acetic acid and manganous sulfate. A two crystal continuous wave method was employed. The results in water indicate that the rate of increase of α/ν2 with pressure becomes less with increasing frequency. This result is in contrast to earlier results of Towle and Lindsay. The rate of increase of α/ν2 with pressure was lowered in the aqueous solutions as the concentration was increased.

Small‐Scale Acoustic Streaming in Liquids

Josef Kolb and Wesley L. Nyborg

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1237-1242 (1956); (6 pages) | Cited 1 time

Online Publication Date: 29 Jun 2005

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By using special acoustical and optical arrangements, vortex motions are discovered in the vicinity of small vibrating sources in liquids. Of particular importance is the vigorous eddying that typically takes place near a vibrating gas bubble when it rests on a boundary. This bubble‐associated streaming has been observed under a variety of circumstances, and apparently occurs quite generally. Especially violent and chaotic motions appear near bubbles of resonant size. The attendant highly localized convection and viscous stresses are probably very important as intermediate physical mechanisms for sonic irradiation effects.

Acoustic Properties of the Ocean Bottom at Bahia Todos Santos, Lower California

C. W. Horton

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1243-1247 (1956); (5 pages)

Online Publication Date: 29 Jun 2005

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The transmission data which were obtained at Bahia Todos Santos, Lower California, by the University of California, Division of War Research, have been analyzed. It is shown that at a frequency of 200 cy/sec the observed propagation agrees quite well with a formula developed by Camp and Eckart. This formula, which is based on the assumption that the bottom acts like an acoustic impedance, predicts that the observed pressure should decrease with the three‐fourths power of the distance. When the data are fitted with the formula, one obtains an average value of 1.25 for the ratio of (ρc of the bottom/ρc of the water).

Theory of the Shadow Zone Diffraction of Underwater Sound

William J. Noble

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1247-1252 (1956); (6 pages)

Online Publication Date: 29 Jun 2005

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The problem of the shadow zone diffraction of underwater sound is reduced to that of diffraction by a dark half‐plane and an asymptotic expansion of the edge wave used to calculate the transmission anomaly. This theory explains the general shape and the observed break of the transmission anomaly curve. The dependence of the calculated values on range, wavelength, and depth, is shown to agree with observations made during and after the Second World War.

On the Pressure Dependence of Sound Absorption in Liquids

Leonard Liebermann

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1253-1255 (1956); (3 pages) | Cited 2 times

Online Publication Date: 29 Jun 2005

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The theory of the dependence of sound absorption pressure is given for liquids in which absorption significantly depends on the two coefficients of viscosity: bulk viscosity and shear viscosity. The bulk viscosity, and therefore sound absorption, is shown to be related to the equation of state. The equation of state is derived for a liquid model in which the volume is determined by molecular distribution within two states. This equation of state possesses two characteristic constants; these can be numerically evaluated for an actual liquid by comparing the theoretical equation of state with pressure‐volume relations available in tables. As an example, the characteristic constants of water are evaluated and used to compute the effect of pressure on sound absorption. The theoretical prediction is in agreement with published observations. As a further example, ethyl alcohol is also treated.

Speech Communications in Noise: Some Equipment Problems

Mones E. Hawley

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1256-1260 (1956); (5 pages)

Online Publication Date: 29 Jun 2005

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The design of a speech communication system begins with an operations analysis of the communication problem. When speech has been chosen as the means and when the needed linkages have been determined, the designer chooses the best compromises among the frequently conflicting factors of intelligibility, safety, comfort, quality, reliability, and economy. It is particularly important to provide good quality as well as adequate intelligibility. The latter may be predicted with reasonable accuracy if the noise and signal levels and the transfer characteristics throughout the system are known. Pressure gradient microphones, especially with noise shields, noise attenuating earcaps, and earplugs, are the primary acoustical devices that can be used to obtain high intelligibility through improvement of signal‐to‐noise ratios. If the listeners are in intense noise, headsets presently pose the major systems limitation. Automatic volume control and peak clipping are the audio techniques most frequently used to complement the transducers. Typical values and limitations for these kinds of processing are given. Optiomum results can be obtained only if the whole system is designed together.

Note on Pitch‐Synchronous Processing of Speech

E. E. David, Jr. and H. S. McDonald

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1261-1266 (1956); (6 pages)

Online Publication Date: 29 Jun 2005

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Voiced portions of speech waveforms are quasi‐periodic in nature. This property arises from repeated excitation of the slowly changing vocal cavities by glottal puffs. Knowledge of this periodicity affords a means for reducing the channel capacity necessary to transmit a speech signal. One proposal to this end involves eliminating N − 1 of every N pitch periods before transmission, where N is chosen small enough so that variations important to the ear‐cortex in the intraperiod wave form are preserved. Thus, provided consonants are similarly chopped, the channel capacity in bits/second can be reduced by 1/N. At the receiver, missing parts are restored by interpolating them in a predetermined way, for example, by simply repeating each of the received periods N − 1 times.
Circuits for operating on monotone speech demonstrating this principle have been constructed. Experiments with N = 2, 3, and 4 indicate that minor distortion, which appears as submultiples of the pitch harmonics, is thereby introduced. Consonants are little affected by the chopping.
A similar scheme which involves eliminating portions of the wave form in each period was also investigated. Less satisfactory results were obtained here, since the intraperiod wave form carries the phonemic information.

Source and Receiver Behavior in the Use of a Criterion

James P. Egan and Frank R. Clarke

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1267-1269 (1956); (3 pages)

Online Publication Date: 29 Jun 2005

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A listener in an articulation test is confident of some of his responses and dubious about others. On the basis of this fact, it is reasonable to require that a receiver decide whether or not his response is correct. If he adopts various criteria from test to test, a receiver operating characteristic may be obtained which will be one way of describing quantitatively this type of behavior. The curve showing the confirming and rejecting behavior of the receiver is compared to that of the source using the same test materials and the same speech‐to‐noise ratio.

Determination of the Speech Spectrum through Measurements of Superposed Samples

T. H. Tarnózy

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1270-1275 (1956); (6 pages)

Online Publication Date: 29 Jun 2005

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By recording on one magnetic tape the simultaneous utterances of several speakers saying unrelated things, we have obtained noise which is essentially time‐invariant, has a continuous spectrum, and displays the average spectral properties of speech much more readily than methods employed heretofore. Spectral analysis of this speech noise has been performed.
The advantages of the method are (1) the integration time needed for determining the long‐time spectrum of speech can be reduced to a few seconds; (2) the combination of speech wave forms can be treated as a statistical noise constant in time; (3) this noise does not contain any line spectrum elements; (4) with normal speaking levels, better signal‐to‐noise ratios are obtained.
The experiments suggest that different languages may be characterized by differences in the long‐time average spectra. Spectra obtained by the present method were used to compute the average loudness level of a single speaker. The method is adaptable to measurement of the spectrum of a speech sound or of an individual mode of pronunciation.

Effect of Visual Factors on the Intelligibility of Speech

Keith K. Neely

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1275-1277 (1956); (3 pages)

Online Publication Date: 29 Jun 2005

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Research has indicated the important role that vision plays in face‐to‐face voice communication. This study was an attempt to quantify further the visual contribution to speech intelligibility in a high intensity noise environment in terms of the angle and distance from the listener to the speaker.
Results indicated that (1) visual cues resulted in a significant increase in listener‐intelligibility scores, (2) the angle at which the listeners observed the speaker influenced their listener‐intelligibility scores, and (3) the distance of the listener from the speaker did not have a significant effect on listener‐intelligibility scores within three to nine‐foot limits.
The importance of speech‐reading training and the use of visual cues is evident where face‐to‐face voice communication has to be conducted in high intensity noise environment.

Response of the Human Skull to Mechanical Vibrations

Ernst K. Franke

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1277-1284 (1956); (8 pages) | Cited 4 times

Online Publication Date: 29 Jun 2005

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Measurements of the mechanical impedance and of the vibration pattern of the human skull are described. In the frequency range from 200 to 1600 cps the skull was excited to vibrations by means of an electrodynamically actuated piston with small contact area. Data were obtained from living subjects, a dry skull preparation, and a human cadaver. The modulus of elasticity of skull bone, calculated from the resonance frequency of the skull, was found consistent with the value obtained by static methods. The propagation velocity of flexural waves in the skull bones, as calculated from the natural frequencies, agrees satisfactorily with the experimentally determined velocity. It is shown, finally, that a vibrating spherical shell is a suitable model for the skull and describes its vibration patterns with good approximation.

Analog Circuit Representation for Wall Panels

Albert D. Frost

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1285-1291 (1956); (7 pages)

Online Publication Date: 29 Jun 2005

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A new approximate equivalent analog circuit representation for wall panels is proposed. This circuit is in the form of an extended network of interconnected mesh structures. Solutions for the fractional energy transfer through the system are given for various source and boundary conditions. Experiments on a lightweight panel using a simulated plane‐wave source give values of transmission loss which are comparable to those using coupled chamber techniques.
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Determination of the Elastic Constants of Ice Single Crystals by an Ultrasonic Pulse Method

Robert E. Green, Jr. and Lachlan Mackinnon

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1292-1292 (1956); (1 page) | Cited 1 time

Online Publication Date: 29 Jun 2005

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The elastic constants c11, c12, c13, c33, c44 of single crystals of ice have been determined through the measurement of elastic wave velocities by an ultrasonic pulse method.

On Brain Lesions by Focused Ultrasound

H. T. Ballantine, Jr., W. C. Cotter, and T. F. Hueter

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1292-1293 (1956); (2 pages)

Online Publication Date: 29 Jun 2005

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Abstract Unavailable

Errata: Acoustical Streaming in the Vicinity of a Sphere [J. Acoust. Soc. Am. 27, 1082 (1955)]

C. A. Lane

J. Acoust. Soc. Am. Volume 28, Issue 6, pp. 1293-1293 (1956); (1 page)

Online Publication Date: 29 Jun 2005

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Abstract Unavailable
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