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Employing principles outlined previously by the authors, quartz-cavity resonators were built which operate in the 3- and 10-Gc/sec regions at room temperature. Their properties agree well with theory. In order to resonate, the crystals must be very thin and accurately plane-parallel. There is no dispersion in the longitudinal velocity of sound in X-cut quartz to 10 Gc/sec within 0.005%. The attenuation is (4±0.4) Np/cm at 3.2 Gc/sec and (33±6) Np/cm at 9.6 Gc/sec. The specific acoustic impedance of water is (1.5±0.6) × 106 g·cm-2 sec-1 at 3.2 Gc/sec. The efficiency for radiation into water is 10%. Sound has been transmitted into water through an aluminum film 3 μ thick. [ABSTRACT FROM AUTHOR]

A series-equivalent circuit for a quartz plate driven at high harmonics is given, and a simple analysis developed for the re-entrant cylindrical microwave cavity with an X-cut crystal in the gap. Expressions are derived for the efficiency and sensitivity of such a system as a hypersonic transducer for use with liquids at room temperature and 3 Gc/sec. Design equations are developed for the crystal and cavity dimensions which maximize the efficiency. These show that the crystal should be less than 100 μ thick and plane-parallel to one-fiftieth of an optical wavelength to minimize the absorption and alignment losses, respectively. The cavity should have a 'square' cross section with a post height e2 times the post radius. Efficiencies of 40% and 65% are theoretically possible with quartz crystals 100 μ and 35 μ thick radiating into water at room temperature. A companion paper will discuss experimental results. [ABSTRACT FROM AUTHOR]

The acoustic transmission of a sandwich consisting of a pair of plane parallel solid plates immersed in a liquid has been investigated theoretically and experimentally. Not only the dilatational waves, but also the shear waves, are considered. Results show greatly improved transmission characteristics over those of single thick metal plates with respect to dependence on both frequency and angle of incidence. Theoretical transmission curves for a sandwich of two steel plates have been prepared to exhibit the dependence of transmission on frequency, on ratio of plate thickness to wavelength and separation to wavelength, and on angle of incidence, respectively. Calculated transmission curves for single steel plates, including half-wave plates, are shown for comparison. An experimental test was made on a steel sandwich with lateral dimensions of the order of two wavelengths and plate thickness-to-wavelength (in the steel) ratio equal to 0.05. The measured transmission losses are within ±4 db of the calculated values. [ABSTRACT FROM AUTHOR]

Data are presented on the dispersion of the velocity of sound and on the effect of impurities upon the rotational relaxation times determined therefrom. The attenuation due to the relaxation is shown to agree with the theory, with some evidence of multiple relaxation. Anomalous dispersions of the classical attenuation and of the Herzfeld reflection coefficient are predicted. The latter is confirmed experimentally and also yields a determination of the accommodation coefficient. [ABSTRACT FROM AUTHOR]

The first part is the description of a circuit employing rf amplification which converts an ultrasonic interferometer into a sensitive self-recording instrument whose records can be simply analyzed to yield a rapid determination of the attenuation and reflection coefficients of gases at low pressures. The second part is a summary of the sources of error in ultrasonic interferometry, their detection and their correction. In the third part, some data on the velocity, attenuation, and reflection in helium in the region two to sixty Mc/atmos are presented to illustrate the range, precision, and absolute errors of the instrument. [ABSTRACT FROM AUTHOR]