A detailed modal analysis of several axisymmetrical or fully three‐dimensional Tonpilz transducers is carried out, both with a plane wave approach and with the finite element method. It allows identification and classification of the modes in a broad frequency range (longitudinal modes of the ceramic stack, flexural modes of the head mass, and longitudinal modes of the stress rod) and demonstrates that the motion of the ceramic part of the structure remains essentially of plane wave type. Following this conclusion, a mixed finite element–plane wave method is proposed and described, which gives fairly good results and uses the computational resources efficiently. Moreover, it is likely to be applied to other types of projectors.