When a piezoelectric materialis exposed to an AC electric field with increasing frequency itstarts to vibrate, and this vibration peaks at the mechanical reso-nance frequency with the absolute value of its impedance beingthe minimum (short circuit condition). This mechanical reso-nance frequency is determined by the geometry of the specimenalong the observed vibration axis. This mechanical vibration diesaway with further increasing driving frequency due to anotherresonance with electrical capacitance, which is commonly called‘antiresonance’ (open circuit condition). The larger the distance