So I am looking to make an audio device to control raccoons and rats passing through my property. I would like to experiment with high freq sound, and have picked up some piezos. I have a few questions if anybody has knowledge of this. Firstly, is the resonant frequency which a piezo operates determined by the size of the brass disk diameter, thickness etc? Could altering the diameter or the like 'tune' for efficiency at a specific freq? How much heat can be applied while soldering before damage occurs? Most importantly, how do you figure safe operating limits at a given freq? I picked up a few of these > https://www.fasttech.com/products/1453503 but there is no mention of specs which seems to be common for these devices.