Eigen frequencies and directivity patterns of a spherical acoustic transducer

International audience; In this work, a spherical acoustic sensor has been developed, and is composed of two Plexiglas half-spheres and a PZ26 piezoelectric ring that can be either used as an exciter or as a sensor. The resonance of the spherical shell is studied analytically, numerically by finite elements modeling in COMSOL Multiphysics, and verified by experimental analysis using an impedance analyzer (Wayne Kerr 6520). The results obtained show a good agreement between the three methods, the first four resonant frequencies of the spherical sensor are respectively 18, 22, 35 and 43.6 KHz, the last frequency corresponds to the breathing mode. And finally the frequency response, surface displacements and directivity patterns have been measured using the Laser Doppler Vibrometry technique (LDV).