Fig. 7(a) shows the vibration velocity distribution on the PPSbased
bar at a frequency of 28.30 kHz and driving voltage of
100 V. The maximum vibration velocity reached 280 mm/s. The
spectrum of the vibration velocity is shown Fig. 7(b). The propagating
wavenumber k0 was approximately 0.616 mm1 (k = 10.2 mm)
at 28.30 kHz. The cut-off wavenumber of the low-pass filter was
set to 0.9 mm1
. Fig. 7(c) and (d) shows the reactive-energy distribution
DEk(z) and the local-dissipated-energy distribution DP(z)
along the z axis. Clearly, the reactive energy and the local