A novel phase locked cavity resonator for B/A measurements in fluids

A new technique for the measurement in fluids of the acoustic non-linearity parameter BIA is presented, together with measured BIA values for several fluids. The non-linearity parameter is measured by phase locking radial mod es within a PZT cylinder. The system, which implements the isentropic phase technique, uses continuous wave phase locking to measure the change in sou nd velocity that is typically associated with a change in ambient pressure under constant entropy. The method provides a means of measuring BIA in vit ro both accurately and simply without the typical problems involved in time -of-flight systems. Fluid samples can remain small due to the nature of the cavity resonator, so the system is well suited to small volume, biological samples. (C) 2000 Elsevier Science B.V. All rights reserved.