These piezo transducers can be used for all kinds of applications involving music or speech, such as electronic drums, knock sensors...
If you are connecting the piezo to an analogue input on a MCU such as Arduino, we recommend to add a 1 MOhm resistor between ground and the analogue input to bleed off the voltage generated. You can also add a 5.1v zener diode in parallel to ensure that no larger voltages will make it into the Arduino and blow it out.
Specifications
Max Input Voltage: 30VResonant Frequency: 2.6 ±0.5 KhzResonant Impedance(MAX): 200 OhmCapacitance at 1kHz: 33nF ±30%