Soft type PZT material used to fabricate a high intensity air siren

A high quality soft type PZT material was designed and produced in order to be used as sensor for a high intensity air siren. Two thin disks from this material were assembled into a parallel bimorph type sensor with an intermediate metallic plate for the siren. This assembly behaves like an acoustic resonator in the high frequency audio range. This structure transforms the radial mode of vibration into a flexural one, with a much lower frequency. A mechanical impedance adapter was used in order to assure a good match between the oscillating ceramic and the surrounding air. A theoretical approach was outlined, which allows the evaluation of the resonance frequency for the working transducer. The theoretical and experimental data agree to a satisfactory degree up to the input errors assumed by the model. Acoustical and impedance measurements were made in order to appreciate the influence of the metallic plate on the frequency. The bimorph necessary for making the siren was designed as a parallel structure and the corresponding transducer was measured and evaluated. In order to increase the acoustic emission a frontal cardboard horn was added to the resonator.