Abstract: A broadband piezoelectric sandwich transducer with semi-perforated structure has been developed previously. It is formed by drilling holes longitudinally in the radiating head, and has been shown experimentaly to possess a bandwidth approximately twice that of a conventional non-perforated transducer, while its electroacoustic efficiency remains almost undeteriorated.
In this paper a theoretical model for th'e broadband structure is proposed. The frequency characteristics of the input electrica'l admittance of the transducer and the input mechanical impedance of radiating head loaded by water, are calculated both as functions of the relative cross-section a of the bored part and the relative depth of the holes βof radiating head. Some theoretical results are compared with measured ones, the two agree fairly well. Furthermore, the dependence of' input mechanical impedance of loaded radiating head on phase length has been examined and explained by means of bilinear transformation of complex variables.