High-Q plano-concave resonator with and without Straubel quartz for ultrasonic absorption measurements of liquids

A resonator technique for the measurement of the sound absorption coefficient of liquids is described. It is designed for use at low frequencies with reasonably small sample values. The construction of a high-precision cylindrically shaped specimens cell is shown and results for different versions of the resonator are presented. The relative merits of using a Straubel quartz instead of a disc-shaped quartz as the transmitter crystal and of using a concave instead of a plane reflector as the opposite face of the cavity are discussed. The accuracy of the method is illustrated by results of measurements which have been performed at frequencies down to 80 kHz on a low-loss 0.1-M aqueous solution of magnesium sulfate