A high performance PZT type material used as sensor for an audio high frequency piezoelectric siren

A high quality PZT type material was designed and produced in order to be used as sensor for a high internsity siren. Two disks from this materials were assembled into a parallel bimorph type transducer with an intermediate metallic plate. This assembly behaves like an acoustic resonator in the high frequency audio range. The fundamental of the flexural mode for a free resonator is taken into account. Its frequency dependence on the geometry of the system and on its material properties is computed using the results for a circular plate with clamped edges and an observation on the equivalence between the movement of a particular part of a resonator in a stationary state and the movement of that part separated from the resonator but with the same border conditions. Acoustical and impedance measurements were made in order to appreciate the influence of the metallic plate on the frequency. In order to increase the acoustic emission a frontal cardboard horn was added to the resonator.