On transducer and bond corrections for velocity measurements using continuous-wave ultrasound

The perturbing effect of an ultrasonic transducer on determination of sound velocity by continuous-wave methods is reanalyzed. The Bolef–Menes (1+δ) formula is found usually to apply only within a very narrow frequency range around the transducer’s resonant frequencies. Thus it should be regarded as a ‘‘near-transducer’’ rather than a ‘‘thin-transducer’’ correction. Outside the applicable frequency range, it is more appropriate to multiply δ by the square of the ratio of the specimen’s mechanical impedance to that of the transducer. The effect of the bond between specimen and transducer is assessed.