Variations of the Ultrasonic Pulse-Superposition Method for Increasing the Sensitivity of Delay-Time Measurements

Abstract

A number of methods are described for increasing the sensitivity of a measuring technique that has proven to be particularly useful for determining 3rd-order moduli and other quantities from measured changes in ultrasonic delay times [J. Acoust. Soc. Am. 33, 12 16(1961)]. Pulse cancellation, phase comparison, and methods involving either pulse position or frequency modulation have been examined. Two of the circuits developed are amenable to automatic frequency control, with precisions better than one part in 106.