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 B/A is presented, together with measured B/A values for several fluids. The non-linearity parameter is measured by phase locking radial modes within a PZT cylinder. The system, which implements the isentropic phase technique, uses continuous wave phase locking to measure the change in sound velocity that is typically associated with a change in ambient pressure under constant entropy. The method provides a means of measuring B/A in vitro 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.
Davies
JR
Department of Electrical Engineering, University of Cape Town, Rondebosch, South Africa. jdavies@eleceng.uct.ac.za
Tapson
J
Mortimer
BJ