Review on Enhanced Performance: uxcell 5V 85dB Industrial Active Electronic Alarm Buzzer - Set of 15 by Terry Keown

Tested 5 so far, none worked at 5 volts until I got frustrated with one and upped the voltage to try and kill it. It wouldn't die! And the best part is that it now runs on 5 volts, I think I taught it a lesson lol. I've tried many different voltages, but the best thing that worked for me was increasing it to 12V, then decreasing it to 0V, then back to 12V and then turning it off. All of them, after this procedure, began to work at 5 V. I don't know if it weakens the surface there or what, I'm not a piezo expert, but it does something!