Effect of surface voids on the precise determination of the velocity of ultrasound in solids

Accurate and reproducible values of ultrasonic phase velocity in solid specimens are obtained only if all surface voids and irregularities are filled by the material bonding the specimen under investigation to the buffer delay line. Experimental results are given which show that considerable attention to surface finish and bonding technique is necessary to obtain velocity accuracies better than within 1 in 104. With careful bonding, and by operation at high frequencies, results reproducible to within 3 parts in 105 can be obtained.