Interesting, I only knew the piezo diaphragms that need a frequent pulse drive to vibrate, probably because the energy need and loss in the process is much bigger for the amplitudes needed by audible vibration.
Piezoelectric effect can be applied differently to have different applications. In the piezo diaphragm case, the electric pulse is the frequency driver. If the electric pulse runs at once per second, the diaphragm is moved once per second (bending and unbending once per second). If the pulse runs at 1000/sec, the diaphragm is moved at 1000/sec (1kHz), producing a different pitch of sound. With different frequencies of electric pulse, you can produce different frequencies of diaphragm movement and different pitches of sound.