Circuit improvements for a method of measuring ultrasonic delay times or velocities [H. J. McSkimin, J. Acoust. Soc. Am. 37, 864–871 (1965)] have resulted in attained resolutions of approximately one part in 107 for high-Q materials, and with compatible long-term stability. By way of illustration, some results are presented for delay-time variations as a function of low (<250 psi) uniaxial stress in single crystals of Si and Ge. For the latter, the data are combined with results obtained previously through use of hydrostatic pressure to yield the six 3rd-order stiffness moduli. The satisfactory agreement with literature values demonstrates the usefulness of the method for materials that might be damaged by large uniaxial loads.
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McSkimin et al. (1967) studied this question.