INTERFEROMETRIC MEASUREMENT OF ULTRASONIC VELOCITY IN LIQUIDS - EFFECT OF DIFFRACTION

The effect of diffraction on Sound velocity measurements in liquids was studied in the low frequency range, 0.6 to 3.0 MHz, using a single crystal interferometer. The excess velocity ΔC over the plane wave velocity C was found to follow the relation [formulla omitted] where ⋔ is the wavelength, d the beam diameter, and D is the distance from the source at which measurements were made. The diffraction effects are 3.2 times the values envisaged theoretically [from Bass and Williams cited in H. J. McSkimin, J. Acoust. Soc. Amer. 33, 539 (L) (1961)]. © 1969, Acoustical Society of America. All rights reserved.