Showing papers on "Acoustic interferometer published in 1969"
TL;DR: In this article, an optical-spatial filtering technique for studying complex, high frequency, standing and traveling acoustic surface waves is described, and the relative amplitude distribution is directly displayed and the wavelength and velocity are accurately measured.
Abstract: An optical‐spatial filtering technique for studying complex, high frequency, standing and traveling acoustic surface waves is described. The relative amplitude distribution is directly displayed, and the wavelength and velocity are accurately measured. The velocity for z propagation on a y‐cut LiNbO3 crystal is found to be 3472.5 ± 1.5 m‐sec−1.
31 citations
TL;DR: In this article, the authors investigate the internal waves that are produced in a stratified fluid having constant Brunt-Vaisala frequency by a cylinder which executes small vibrations at a lower frequency.
Abstract: The paper describes an investigation of the internal waves that are produced in a stratified fluid having constant Brunt—Vaisala frequency by a cylinder which executes small vibrations at a lower frequency. Explicit solutions are found for slender cylinders having arbitrary cross-sections. When the cross-sectional area of the cylinder varies with time it is found necessary in calculating the surface pressures and power output to take account of terms in the governing equations that are significant only at distances from the cylinder comparable to or larger than the scale height of the density variations. For this case a simple expression for the power output is obtained in terms of the rate of change of the cross-sectional area of the cylinder. When the vibrating cylinder is rigid its cross-sectional area is independent of time and then the expression for the power output is very similar to von Karman's expression for the drag of a body of revolution in supersonic flow. In both the above cases it is found that one quarter of the power is radiated in each of the four directions that are inclined at a particular angle to the horizontal.
26 citations
TL;DR: In this article, a macroscopic theory is presented to explain the electromagnetic generation of acoustic waves in a metal in the presence of a steady magnetic field, and to account for the effect of these acoustic waves on the surface impedance.
Abstract: A macroscopic theory is presented to explain the electromagnetic generation of acoustic waves in a metal in the presence of a steady magnetic field, and to account for the effect of these acoustic waves on the surface impedance. The theory is valid for the limiting case where the skin depth is much smaller than the wavelength of sound. In particular, the size and shape of the surface impedance singularities at frequencies corresponding to the formation of standing acoustic waves in a metal plate are calculated. Absolute measurements of the surface resistance and reactance of gallium single crystals are reported which are in quantitative agreement with the predictions of the theory.
22 citations
TL;DR: In this article, the ability of devices based on the phenomena of magnetoelastic waves, acoustic bulk wave, acoustic surface waves, and the optoacoustic interaction to fulfill the requirements for a dispersive filter for a pulse compression RADAR are reviewed.
Abstract: The ability of devices based on the phenomena of magnetoelastic waves, acoustic bulk waves, acoustic surface waves, and the optoacoustic interaction to fulfill the requirements for a dispersive filter for a pulse compression RADAR are reviewed. The performance and current limitations of devices that use techniques employing these effects are described. The discussion is generally limited to devices which have been operated in the frequency range above 100 MHz. For comparison, other solid-state techniques that do not employ acoustic waves which can be used to make dispersive filter are described.
14 citations
TL;DR: In this article, the attenuations of acoustic waves propagating along the crystalline axes were measured near the transition points in NaNO 2, and it was found that the attenuation for longitudinal waves shows a sharp maximum at the Neel point.
13 citations
TL;DR: In this article, a method for determining the losses in a rocket chamber during (combustion instability) is proposed based on acoustic measurements at room temperature, which permits the losses to be determined from experiments in a small-scale model of the actual chamber.
Abstract: A promising method for determining the losses in a rocket chamber during (combustioninstability is based on acoustic measurements at room temperature. This method permits the losses to be determined from experiments in a small-scale model of the actual chamber. The calculations presented here treat the acoustics of a chamber with mean flow; they are intended to be used in the design of such experiments and in the interpretation of data.
11 citations
Patent•
17 Feb 1969
TL;DR: In this paper, a flat plate, pierced with openings at regular intervals evenly distributed and arranged in parallel relation disposed at a very short distance from the vibrant surface of the vibrating surface, is presented.
Abstract: Device for increasing the acoustic power radiated in a gas by the solid vibrating surface of a source of sonic or ultrasonic waves, constituted by a flat plate, pierced with openings at regular intervals evenly distributed and arranged in parallel relation disposed at a very short distance from the vibrant surface.
8 citations
8 citations
TL;DR: Giant quantum oscillations and large amplitude, low field resonances, of the electromagnetically generated acoustic shear waves in bismuth are observed at helium temperatures as discussed by the authors, which is the state of the art.
5 citations
TL;DR: LF sound velocity measurement in carbon dioxide near critical point, noting existence of logarithmic divergence was performed by as mentioned in this paper, where they found that the LF sound velocities were near the critical point.
Abstract: LF sound velocity measurement in carbon dioxide near critical point, noting existence of logarithmic divergence
TL;DR: In this paper, the construction and operation of an ultrasonic interferometer and its application to the analysis of gas mixtures are described, and a possible pulse method is discussed.
Abstract: It is suggested that many binary or pseudo-binary gas mixtures may be analysed by measuring their acoustic velocities. The construction and operation of an ultrasonic interferometer and its application to the analysis of gas mixtures are described, and a possible pulse method is discussed.
Book•
01 Jan 1969
TL;DR: In this paper, it was shown that the critical value of the relative characteristic impedance above which the attenuation of the sound waves becomes sharp depends upon the nature of the gas and the ionic charge.
Abstract: The electron temperature and the velocity of sound waves in a Lorentz plasma have been determined by transmitting sonic signals in the range 4 to 40 kc/s through it. It has also been observed that although the reflections of the sound waves at the plasma—air interfaces occur when the relative characteristic impedance of plasma with respect to air exceeds unity, the reflected or transmitted pressure amplitudes do not change appreciably until the relative characteristic impedance exceeds the value (Z + 1)1/2, where Z is the charge of the ion. Thus the critical value of the relative characteristic impedance above which the attenuation of the sound waves becomes sharp depends upon the nature of the gas and the ionic charge. This method is also useful for exploring the pre-glow/Townsend discharge condition of the ionized media. The plasma parameters may be measured even in very weak ionizations where other existing techniques, viz. the microwave/ultrasonic probing or spectroscopic methods, are not suited. The ...
01 Mar 1969
TL;DR: In this article, an ultrasonic, pulse-echo technique was used to determine the velocities of sound waves propogating in a heated region of rod-shaped specimens.
Abstract: Ultrasonic method is used to determine the elastic moduli of materials used in components of high-temperature nuclear reactors. An ultrasonic, pulse-echo technique determines the velocity of sound waves propogating in a heated region of rod-shaped specimens. From these velocities, the elastic moduli are calculated.
TL;DR: In this article, the authors measured the attenuation of liquid argon, nitrogen, and oxygen at their boiling points with a variable path-length two-crystal acoustic interferometer.
Abstract: The ultrasonic attenuation at 1 GHz was measured in liquid argon, nitrogen, and oxygen at their boiling points with a variable‐path‐length two‐crystal acoustic interferometer. The attenuation in argon shows an absorption in excess of the value calculated from the classical Stokes‐Kirchhoff equation for shear viscosity and thermal conductivity. The excess absorption can be attributed to a volume viscosity predicted by Gray and Rice, and is in good agreement with the lower‐frequency measurements of others such as Naugle and Squire. The attenuation measurement in nitrogen shows a similar excess absorption and is in good agreement with the lower frequency values of Singer and Lunsford. The ultrasonic attenuation measurements in oxygen indicate that it may also have a volume viscosity. In the process of aligning the apparatus, some data were obtained in methanol that give a lower volume viscosity than that observed at lower frequencies.
TL;DR: With a quartz-crystal acoustic light modulator, 600 spots have been obtained by only varying the frequency of the longitudinal acoustic waves as mentioned in this paper, where the center frequency of acoustic waves was 780 MHz.
Abstract: With a quartz-crystal acoustic light modulator, 600 spots have been obtained by only varying the frequency of the longitudinal acoustic waves. The center frequency of the acoustic waves was 780 MHz.
01 Jan 1969
TL;DR: In this article, an ion-energy analyzer was used to detect the wave mode among wave-like fluctuations in a grid immersed in a streaming ion plasma, and the comparison between the experimental results and the theory about the effects on the higher-order modes is made.
Abstract: Ion acoustic waves are excited in a streaming-ion plasma. The comparison between the experimental results and the theory about the effects on the higher-order modes is made. Discussions on the wave mode and the ballistic mode are described in detail. On the basis of the discussions, we succeed in detecting of the wave mode among wave-like fluctuations by an ion-energy analyzer. Waves are excited by a grid immersed in a plasma. When the voltage applied to the grid is increased, oscillations of the amplitude are observed. In the course of the amplitude oscillations, multiple exchange of energy between resonant ions and the wave is detected by the ion-energy analyzer.