Will air pressure induce a voltage of a piezoelectric crystal or does it need to be mechanically compressed? My guess is that it would depend on the permeability of the crystal
Thread re-opened on request to keep this duplicate and close the other.
@Adamant, per my PM, please provide more detail about the setup you are describing. Piezoelectrics are indeed used as absolute pressure sensors, but my suspicion is that you are after something that works differently and won't produce a piezoelectric effect.