The determination of the speed of sound in liquids using acoustic resonance in piezoelectric tubes

A methodology based on acoustic resonance has been developed for determination of the speed of sound in various liquids. A frequency sweep of an annular piezoelectric transducer (tube), performed using an impedance analyser, reveals the structural resonance frequency. Upon immersing the tube in a liquid, the impedance curve obtained from the frequency sweep has an additional resonance peak. The peak is the result of the acoustic resonance in the tube that feeds back to the piezoelectric structure. By using the fundamental acoustic mode in pipes, and accounting for end corrections and for the compliance of the piezoelectric tube, a formula for the intrinsic speed of sound in a liquid was determined. Several liquids were tested and the speed of sound was obtained. Comparison of the values obtained with literature data showed that the difference was less than 3%. (Original abstract)