Effect of a voltage shading of the ceramic stack on the bandwidth of a radiating Tonpilz transducer

In addition to the main resonance, the analysis of classical Tonpilz transducers points out the existence of several maxima of the transmitting voltage response which are associated to various structural modes (dilational modes of the stack, flexural modes of the headmass). However, though the electromechanical coupling of the first mode is large, the other modes are generally less effective. In this paper, the effectiveness of a particular mode is shown to depend upon a simple relation, for each ceramic ring of the stack, between the phase of its electrical excitation and the sign of its longitudinal strain. This fact is clearly demonstrated with the help of a finite element modeling, using the ATILA code [J. N. Decarpigny et al., J. Acoust. Soc. Am. 78, 1499 (1985)]. These results suggest various voltage shadings of the ceramic stack which reinforce particular modes. Thus various frequency ranges can be effectively obtained with the same transducer, as confirmed by a detailed study that is based on numerical simulations as well as in‐water measurements.