Experiments with Piezo Ceramics (2)

Piezo ceramics are everywhere. Manufacturers have produced special ceramics optimised for different applications: one example is the thin discshaped piezo sound transducer used in the experiments described here.How do piezo transducers manage to make such a loud noise when the movement they make is so small? Here is the trick: the ceramic is always bonded to a thin sheet of metal. The ceramic disc stretches while the metal does not, and so a relatively large bending motion is produced (Figure 1). Also, the stiffness and mass of the materials are chosen so as to produce a resonance at a frequency of a few kilohertz.Since ordinary piezo transducers (Figure 2) operate on the same principle as we have already explored in capacitors, we ought to be able to repeat all the experiments we described using the capacitor, and get much better results.