bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffraction of Elastic Waves
Authors: Knopoff L. 
Published: September 2005

An integral solution to the differential equations of elastodynamics is given. The solution for the displacement at any point in an isotropic homogeneous, elastic medium is obtained in terms of the initial distribution of body forces within a given volume and the initial distribution of displacements and stresses over the bounding surface of the volume. These quantities appear in the solutions as retarded displacements, stresses, and body forces, with two types of retardation depending upon the velocities of longitudinal and transverse waves.
From the integral solution the diffraction of elastic waves through large apertures bounded by opaque walls in solid materials is formulated. The incident wave motions may be either of longitudinal or transverse polarizations. The expected shear-compression interaction is obtained in the course of the computation. By analogy with optical procedure, Fraunhofer diffraction of elastic waves may be investigated as a special case.
In the example of diffraction by a slit, an incident compression wave is diffracted into (1) a compression wave with the “ordinary” spatial distribution similar to that obtained in the corresponding optical problem and (2) a weaker shear wave with an “extraordinary” distribution. In the case of incident shear waves, there is obtained a diffracted shear wave with an ordinary distribution, and a possible weak compression wave with the extraordinary distribution. The presence of the diffracted compression wave depends upon the polarization of the incident shear wave.
Opacity in the Kirchhoff sense is a property of materials which are perfectly rigid.
Organ-Pipe Oscillations in a Burner with Deep Ports
Authors: Putnam Abbott A. , Dennis William R. 
Published: September 2005

Data are presented on acoustic oscillations produced by a burner using a hexagonal bank of hypodermic tubes as deep ports. Most of the tests were made with ethane as the fuel, but some tests were run with methane and propane, for comparison. Both the diameter and length of the combustion chamber were varied.
It was found that the combustion chamber could be considered as a driver which forced the slugs of gas in the ports to oscillate. Burning of the incremental pulses of combustible mixture periodically issuing from the ports furnished energy to drive the oscillations when the pulses burned in phase with the oscillating component of the pressure in the chamber. The phasing depended on a time-lag factor which was a function of the velocity of the gases through a space, similar to dark space, between the burner ports and the mean burning points, and the width of the space itself.
The oscillations not only ceased when there was a failure to satisfy the timing criterion, but also ceased upon approach to either rich or lean blowoff limits of the conventional type. This premature cessation apparently results from the flame burning from fewer ports as the limits are approached, less driving energy being available.
High Power Operation of a Magnetostrictive Transducer
Authors: Hoover R. M. 
Published: September 2005

As a result of the nonlinear properties of magnetostrictive transducers their impedance and efficiency is a function of the amplitude of the driving field. Earlier studies of high power operation of magnetostrictive transducers at the Harvard Underwater Sound Laboratory showed the need for further study of this subject. This earlier study has been extended by the use of a high power amplifier recently installed at the ORL Black Moshannon Calibration Station.
Impedance and efficiency data obtained on a nickel ring stack transducer operated with and without polarization are presented for a driving field range of 0.1 to 100 oersteds. The efficiency of the unpolarized transducer is shown to be comparable to that of the polarized transducer at high driving powers.
Input current wave form was also observed in this study, and data are presented to show the dependence of wave form on current level. With the unpolarized transducer it is shown that the wave form is a function of nonlinear coupling as well as nonlinear magnetic properties.
Both the experimental procedure used in this study, and the importance of the results to transducer operation at high power levels are discussed.
An Experimental Pitch Indicator for Training Deaf Scholars
Authors: Anderson F. 
Published: September 2005

An instrument is described which extracts from the complex speech wave, as produced by the deaf child or its teacher, information related to the subjective pitch of the sound. It then displays this information on the long-persistence screen of a revolving cathode-ray tube in such a manner that a continuous graph of pitch vs time is obtained. The deaf child is, therefore, enabled to compare visually the pitch patterns produced by its own voice with the standard as produced by the teacher and to correct defects in the pitch changes, rhythm, and phrasing of his speech.
An experimental model of this instrument is being used successfully, but some deficiencies exist which require further study before an improved design can be finalized.
Vibrational Relaxation in N2O - H2O and N2O - D2O Mixtures
Authors: Wight Howard M. 
Published: September 2005

Ultrasonic absorption measurements were made to compare the relative effectiveness of H2O and D2O molecules in influencing thermal vibrational relaxation in N2O molecules. The displacement rates of the absorption per wavelength maxima induced by H2O and D2O were compared in N2O - H2O and N2O - D2O mixtures. Experimental apparatus was constructed for these measurements which utilized the “direct” absorption technique in conjunction with pulsed sound waves, having a frequency of approximately 113 kc. The parameter of frequency/pressure was varied by changing the gas pressure.
The data were taken at a temperature of 21°C in the frequency/pressure range of 100–700 kc/atmos. The maximum amplitude of the molecular absorption coefficient per wavelength in dry N2O was 0.153 and this occurred at 210 kc/atmos. Measurements were taken in N2O - H2O and N2O - D2O mixtures at H2O-vapor and D2O-vapor concentrations of 0.39%, 0.77%, and 1.14%.
The usual single relaxation time theoretical absorption curve could be fitted to the data for dried N2O. However, in the mixtures there was some evidence of two separate relaxation times, one possibly associated with N2O - N2O collisions and the other with N2O - H2O or N2O - D2O collisions. The maximum absorption coefficient in the mixtures was somewhat less than that observed in the dried N2O. The H2O molecules were 1.72 times more effective than the D2O molecules in shifting the frequency associated with the absorption maximum.
Absorption of Sound in Manganous Sulfate Solutions
Authors: Smithson J. R. , Litovitz T. A. 
Published: September 2005

The absorption of sound in MnSO4 solutions was studied over the frequency range 1 to 55 Mc as a function of concentration, temperature, dielectric constant, and with D2O as solvent. The absorption maximum in the range 1 to 10 Mc was verified, and also a secondary relaxation peak, not previously reported, was observed near 30 Mc. The primary relaxation frequency was decreased when the dielectric constant was lowered, while the secondary relaxation frequency was increased. The absorption cross section was increased when the dielectric constant was decreased. The primary relaxation frequency increased with increasing temperature following Arrhenius' equation. The activation energy was determined for both isodielectric and isocomposition solutions. Substitution of D2O as a solvent had no effect on the primary relaxation frequency but increased the absorption cross section. The secondary relaxation was not observed in D2O solutions.
These results indicate that the hydrogen ion is not involved in the rate-determining reaction causing the observed relaxation effects. Furthermore, the results seem to rule out the reaction between two ions of unlike sign as the rate determining step in the primary relaxation process and to make the reaction between ions of like sign improbable. All observed data can be explained on the assumption that the reaction is between two dipole molecules.
Detection of Signals in Noise: A Comparison between the Human Detector and an Electronic Detector
Authors: Sherwin Chalmers W. , Kodman Frank , Kovaly John J. , Prothe Wilbert C. , Melrose Jay 
Published: September 2005

The observer's responses to aural signals in noise are compared to the output of an electronic detection system whose constants are intended to be close to those of the human auditory detection system.
Of the four variations of an electronic detector tested, the best correlation between the detector and the observer occurred for signals of duration 0. 3 second, band pass 60 cps (single tuned RLC circuit), square law detector, output filter time constant, 0.15 second.
The incomplete correlation between the signal responses of the observer and the detector can be explained by assuming that the observer's threshold fluctuates randomly about a mean value with a dispersion of about 20% of the mean, or alternatively that there is internal noise with this dispersion generated inside the observer's detection system.
The observer's false alarms appear to be caused by noise fluctuations (as measured by the electronic detector) of the same average magnitude and dispersion as those calculated for a detector with the same threshold fluctuation. However, the observer's false alarm rate is about an order of magnitude lower than that calculated for the fluctuating threshold detector so it is clear that the model is deficient in some important respects.
Observations of the Stability of a Normal Mode Sound Field in an Intermediate Scale Model
Authors: Scrimger Joseph A. 
Published: September 2005

Spectra of sound-pressure amplitude versus frequency in the range 1.1 to 2.4 kc have been obtained at regular intervals in shallow (10 ft) water during two periods of extended observation. The acoustical data have been presented in the form of contour diagrams of sound-pressure amplitude versus frequency and time as coordinates and compared with water conditions.
The form of the contour diagrams permits differentiation between field-structure variation and variation in attenuation although differentiation between the associated processes has not been possible. Temporal variation in the vertical sound-velocity profile produced only small changes in the gross features of the field structure, as inferred from the contour diagram, for up to the first three modes of propagation. For frequencies above 1.6 kc (i.e., when three or four modes were stimulated) the variations in field structure were prominent. Attempts have been made, with little success, to explain periods when the received signal was strongly attenuated in terms of vertical sound-velocity structure.
Sensitive Electrodynamic Balance for Measurement of Absorption of Ultrasonic Waves in Liquids
Authors: Mokhtar M. , Youssef H. 
Published: September 2005

In this paper a new method for measurement of absorption of ultrasonic waves in liquids is developed. Its main feature is a low frequency (L.F.) modulated ultrasonic transducer actuating a thin circular disk which is placed at some distance above it within the ultrasonic cell. The disk is suspended by a glass rod from a metallic reed which forms one plate of a small air condenser. The vibrations of the suspended system, which are resonant with the L.F. modulating component, are detected by a crystal controlled oscillator, working at the steep portion of its crevasse. The output of the oscillator is applied to a wave analyzer whose output gives directly a measure of the ultrasonic pressure on the disk.
In a further development in the detecting end, a null method is used in which the reed is brought to rest by a L.F. balancing voltage supplied by the same modulator and the zero reading is adjusted by the aid of a cathode-ray oscillograph.
Two liquids are chosen for testing the apparatus, namely, benzene and water representing both high and low absorptive liquids, respectively. The values obtained are, 2α/v2 = 16.2×10−16 sec2 cm−1 for benzene, and 2α/v2 = 52×10−17 sec2 cm−1 for water, which compare favorably with the values obtained by the more elaborate pulse method. Moreover, the high sensitivity of the method eliminates all the complications which usually accompany high-power ultrasonic beams.
Reflection of Plane Sound Waves from an Irregular Surface
Authors: Parker J. G. 
Published: September 2005

A plane sound wave is assumed to be incident upon an irregular pressure release surface z=ζ (x,y). The solution for the reflected field is regarded as a superposition of plane waves having an amplitude spectrum A (k1,k2). Next, the Fourier transform G(x,y) of A (k1,k2) is introduced and subjected to the boundary condition on ζ This leads to an integral equation for G(x,y) that cannot be readily solved. However, if one causes G(x,y) to depend exponentially on a function u(x,y), then a differential equation may be derived from this integral equation, the solution of which gives an approximate form of u(x,y); the degree of approximation involved depends on the smallness of ζ.
This method is applied to the problem of sound scattering from a one-dimensional sinusoidally corrugated surface and the results compared with experimental measurements of LaCasce and Tamarkin and also with the results of a theory due to Rayleigh. This comparison shows the predictions of the theory presented here to be as good as the Rayleigh theory in all cases and closer in the majority of cases.
Effect of Alcohol Impurity on Ultrasonic Vibrational Relaxation in Liquid CS2
Authors: Slie W. M. , Litovitz T. A. 
Published: September 2005

Ultrasonic attenuation measurements were made in liquid carbon disulfide-alcohol mixtures over a frequency range from 5 to 155 Mc at a temperature of −63°C. From these measurements the vibrational relaxation frequency for the liquid was calculated. Methyl, propyl, and butyl alcohol were added in various concentrations up to 0.6 mole percent. In every case the relaxation frequency increased with the addition of the impurity. This increase was found to be a linear function of the impurity concentration which is consistent with the assumption that the vibrational-translational energy transfer is a binary collision process. The shifts in relaxation frequency per mol % of impurity were found to be a linear function of the molecular weight of the impurity molecules for both the gas and liquid data.
A comparison was made of the ratio of collision efficiency of like to unlike molecules in both the gas and liquid state. It was found that within experimental error this ratio is the same in both states. This was interpreted as meaning that the vibrational relaxation process for unlike collisions was the same in both liquids and gases. Further, it appears that the efficiency of an AB-type collision is more strongly temperature dependent than for the AA-type collisions.
Reduction of the Response to Vibration of Structures Possessing Finite Mechanical Impedance
Authors: Snowdon J. C. 
Published: September 2005

Expressions have been derived from which the isolation provided by a simple mounting system when supported by any nonrigid foundation may be determined, if the mechanical impedance of the foundation is known. As an example, the mechanical impedance of a damped beam at its midpoint has been employed to simulate the behavior of such a foundation. Knowledge of the dynamic mechanical properties of natural rubber and a high-damping synthetic rubber has enabled the behavior of antivibration mountings to be described realistically.
If the ratio of the mass of the mounted item to the mass of the foundation is large, the isolation afforded by a mounting is found to be much less than that predicted by its transmissibility curve, which relates to an ideally rigid foundation. It is shown, however, that the isolation provided by a mounting can be increased significantly at high frequencies if an additional mass is employed to load the foundation, the greatest isolation then being provided by a low-damping rubber such as natural rubber. Damping of the foundation is found to have little influence upon the over all level of the isolation afforded by the mounting system.
Annoyance Threshold Judgments of Bands of Noise
Authors: Spieth Walter 
Published: September 2005

Annoyance threshold judgments were obtained by exposing an individual to noise for three minutes and asking him to adjust the intensity to the level which, if any louder, would annoy him if it were present most of the time where he was working.
In one experiment, 21 people made judgments about 13 bands of noise which covered the frequency range of 50 to 13 000 cps, and subsequently made sets of equal loudness matches. No differences were found between annoyance threshold curves and equal loudness curves. In a second experiment, each of 162 people made one annoyance judgment. When these annoyance thresholds were transformed into equivalent loudness terms, the resultant annoyance threshold curve varied reliably with frequency only in that the threshold on the highest band (6600–9000 cps) was reliably lower than those on lower frequency bands.
Office workers who had once worked in noisy situations as well as those working in noisy situations at the time of the experiment gave thresholds about 15 db higher than did people who had only worked in office-type situations.
Within a group who had worked only in quiet situations, those who tried to imagine themselves in an actual working situation gave thresholds that averaged about 15 db higher than the thresholds of those who did not.
Ultrasonic Double Refraction in Worked Metals
Authors: Sullivan Paul F. , Papadakis Emmanuel P. 
Published: September 2005

In the first part of this work the double refraction observed while measuring the attenuation of ultrasonic transverse waves in heat-treated 4150 steel was investigated. Although the data are not complete, they suggest that this double refraction phenomenon can be utilized to detect the amount of preferred orientation of the crystallites in rolled steel when this orientation is small. Calculated values of fractional velocity differences are given.
In the second part the theory of ultrasonic wave propagation in polycrystalline metal is discussed, and the effect of preferential orientation of crystallites on fractional velocity changes is indicated. The use of ultrasonic double refraction data for determining the extent of preferential orientation is discussed.
Ultrasonic Attenuation at Low Temperatures for Metals in the Normal and Superconducting States
Authors: Mason W. P. , Bömmel H. E. 
Published: September 2005

At very low temperatures the mean free paths of electrons in metals become so large with respect to their values at room temperature that they can acquire momentum from collisions with lattice vibrations which result in ultrasonic attenuation when the electrons are in the normal state. This attenuation drops to zero in the superconducting state. Original measurements in impure lead, tin, and copper showed an attenuation proportional to the square of the frequency which could be directly related to the electron viscosity calculated from the number N, the mass m, the mean free path l and the mean velocity 0 of the electrons.
Recently some very pure tin samples have been obtained and much larger effects have been measured due to the increased conductivity at low temperatures. Six oriented samples have been measured and from the measurements the six elastic constants and six viscosity coefficients have been obtained. These correspond to those for a tetragonal crystal. As the mean free path becomes longer than the acoustic wavelength, the loss is determined by a scattering process and the loss for a given frequency approaches a limiting value in agreement with a theoretical prediction of Pippard. The loss for longitudinal waves is from 2.5 to 7.5 times the predicted value while that for shear waves is about 1.5 times the theoretical value of Pippard's.
Measurements of the elastic constants have been made through the super conducting range and the only discontinuity that occurs is that due to the thermodynamically predicted value. The change for a longitudinal wave is less than that predicted for a volume change in agreement with a theoretical derivation. No relaxation effect occurs for the measured velocity even for very pure tin.
Noise in Magnetic Recording Tapes
Authors: Howling D. H. 
Published: September 2005

A theoretical and experimental investigation is made into the mechanism of noise in magnetic media as used in magnetic recording. It is shown that the basic noise in a wow and flutter free system arises from the fact that the domain size in metals or the particle size of oxides is finite, and improvement in the lower limit of noise can only be made by reduction of particle or domain size. The effect of impressed ac and dc magnetization on the noise level is also examined.
A theoretical value for the tape noise arising from the particle nature of an oxide medium has been derived by taking into account the modern theories of magnetism of the iron oxides and evaluating exactly the mathematical function f(x) which appears in the noise equation. Good agreement with the observed noise voltage is obtained.
It is also shown that the basic wide-band unmagnetized tape noise level of 0.6 μv for the head employed is extremely low and that for the ideal system the theoretical signal/wide-band unmagnetized tape noise ratio is independent of tape velocity and varies as the square root of the track width.
Performance of Ceramic Ferrite Resonators as Transducers and Filter Elements
Authors: van der Burgt Cornelis M. 
Published: September 2005

In recent experiments the compositions and methods of preparation of various ferrites were varied with the aim of achieving optimum mechanical and piezomagnetic performance. Essential improvements were obtained by small cobalt substitutions in the chemical composition and by suitable modifications of the mechanical and thermal treatments.
In CW operation, appropriate ferrites can excite radiation intensities up to at least 10 w/cm2, with an electroacoustic efficiency of more than 75% up to 50 kc/sec. So they are highly promising for underwater transmission and processing, in spite of their brittleness (ultimate tensile strength up to about 6 kg/mm2). Wide-band hydrophones with linear frequency response and high pressure-sensitivity can also be built from such ferrites having magnetomechanical coupling coefficients at remanence up to almost 0.25, like Permendur.
The total variation of the mechanical resonant and antiresonant frequencies of ferrite filter elements in the temperature range from +20 to +50°C, being 0.1–0.25% for existing commercial ferrites, has been lowered to 0.03% and less. Since the mechanical quality factors are usually much better than 2000, such ferrites can be profitably applied to the construction of electrical and electromechanical band filters.