An ultrasonic image-converter system is described which provides two-dimensional visual images of incident-sound fields. The system is based on an electronically operated image-converter tube, similar to a television-camera tube, except that the photosensitive surface is replaced by a slab of piezoelectric x-cut quartz. The spatial distribution of sound pressure produces a similar distribution of piezoelectric potential at the ungrounded quartz surface which is scanned by a 500-v electron beam. The output of the converter, dependent upon secondary emission from the quartz, is used to generate a cathode-ray tube display of the sound field. Constructional details of the continuously pumped converter tube are described, including electrode configurations, crystal bonding, and vacuum techniques. With the water-immersed converter face irradiated by a pulsed 7-Mc/sec collimated sound beam directed normally to the face, a 12-mm-diam metallic wire intercepting the sound beam is easily discernable on the cathode-ray tube display. Laminar-type defects measuring 0.75 mm diam and 0.01 mm thick, simulated in a steel plate and oriented normal to the sound beam, are resolved by suitable electronic processing of the converter output pulses. Applications to flaw detection and medical diagnostics are discussed.

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An experimental method has been developed for measuring attenuation of Rayleigh waves propagating in metal plates. Rayleigh waves are generated at one end of a plate using either a y-cut crystal or an x-cut crystal mounted on a Lucite wedge. The waves propagate along the plate, the lower part of which is immersed in water. Mode conversion occurs at the water-plate interface, and the resulting compressional wave is detected by an x-cut quartz crystal. The path length of the Rayleigh wave in the plate is varied by changing the plate position relative to the water level. Attenuation data are presented for several common metals, and the effect of heat treatment on attenuation in steel samples is discussed. The attenuation produced by several machined slots of different geometries is also shown. [This research was sponsored in part by Aeronautical Systems Division, U. S. Air Force.]

The normal absorption coefficient and the normal specific acoustic impedance of the following several materials were measured as a function of temperature for temperatures up to 1500°F and frequencies up to 1800 cps. The specific acoustic impedance of all materials measured increased with temperature and caused a variation in absorption which is dependent upon the variation of the specific acoustic impedance of the material relative to the specific characteristic impedance of air. An acoustic impedance tube with the sample holder inserted into an electric furnace was used for the measurements. Both longitudinal and vertical temperature gradients were present in the tube. Empirical corrections were made to the data, but the detailed effect of the gradients on the measured absorptions and impedances has not yet been completely determined. (This research was supported by Wright Air Development Center).