The objective of this paper is to predict the ultrasonic field radiated by piezoelectric transducers with finite dimensions in an isotropic plate. This prediction allows a good understanding of physical phenomenon of Lamb wave propagation used on the Integrated Structural Health Monitoring System. In order to describe correctly the radiated field, the stress field in the length direction of the transducer has been supposed to have a parabolic shape. The displacement field generated at the surface of an aluminum plate by a surface-mounted PZT transducer excited by a 5-cycle, Hanning-windowed sinusoid signal, has been measured for different directions, using a laser interferometer. Experimental and numerical results are successfully compared.