allanhurst:
Presumably you don't mean 4.7kH ( 4700H)What value is it?
Allan
Sorry, i mean 4.7mH ofcourse!
allanhurst:
Putting about 80mH in series with the piezo would give a reasonable current through it at 4kHz - see enclosed.The voltage depends on the internal resistance of the piezo.
Allan
I don't have a 80mH inductor unfortuanently. Only have 56mH 
But why would you put it in series? According to what i've found
they should be in parallel? 
For some weird reason my calculations of ressonance frequency don't seem to match the reality of what i'm measuring