  Previous studies of Barkhausen noise in PZT have been limited to the energy
spectrum (slew rate response voltages versus time), showing agreement with
avalanche models; in barium titanate other exponents have been measured
acoustically, but only at ambient temperatures. In the present study we report
the Omori exponent (-0.95$\pm$0.03) for aftershocks in PZT and extend the
barium titanate studies to a wider range of temperature.
