Analysis of broad-band piezoelectric sandwich transducer with perforated structure

Pre-stressed piezoelectric sandwich transducers are used widely as sonic source for many low frequency ultrasonic applications, notably in the fields of macrosonics sand sonar. For certain applications a broader bandwidth is necessary. The sandwich transducer with perforated structure developed by us is formed by drilling holes longitudinally in the radiating head, and has been shown experimentally to possess a bandwidth approximately double that of a conventional nonperforated transducer, while its electroacoustie efficiency remains almost undeteriorated [1].
In this paper a theoretical model for the broadband structure is proposed. The frequency characteristics of the input electrical admittance of the trans¬ducer and the input mechanical impedance of the 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 /3 of the radiating head. Some theoretical results are compared with measured ones, the two fairly well agree.