In poled piezoelectric ceramic lead zirconate:lead titanate (PZT) compositions, the non zero components of the piezoelectric tensor are d33, d31 = d32, d15 = d24 (Bornstein, 1981). When the positive directions of the three axis in the ceramic is taken as the poling direction and a tensile stress is considered positive, d33 is a positive coefficient and d31 is negative (Jaffe, Cook, Jaffe, 1971). For the very high coupling compositions with zirconia titania ratio close to that of the morphotropic phase boundary between tetragonal an rhombohedral ferroelectric phases (Zr/Ti = 53/48) in the PZT phase diagram there is an unfortunate effect that d33 ∼ 2d31 (Setter and Cola, 1993). Thus in attempting to use monolithic PZT as a hydrostatic pressure wave sensor dh = h33 + 2d31 is unusually small. For all PZTs, the dielectric permittivity ε33 is large (Herbert, 1982) so that the hydrostatic voltage coefficient gh = dh/ε33 is now very small. For many hydrophone applications the product dhgh is often taken as a figure of merit and so monolithic PZT in spite of its very high individual coefficients is useless as a hydrostatic sensor.