So the whole problem revolves around the fact, that i need to drive the piezo to the highest possible DB-level from a 3v battery. I've designed and 3D-printed a resonance chamber which seems to work okay. My biggest succes has come from driving around 4.6kHz from the output arduino pin to a transistor and from there to a parallel setup with a 4.7kH inductor and the piezo. The piezo is measured as 18.5nF which by my calculations should result in a ressonance frequency around 17068Hz. However this is far from where i get my highest voltage when measuring vAC. Around 4.6kHz is where i get the highest voltage (around 6.2vAC). Any suggestions on how to increase the voltage across the piezo? My current setup just doesn't seem to cut it. It needs to be louder 
(it's for an alarm)
Thanks again for inputs!