Cymbal transducers: a review

The cymbal transducers consist of a piezoelectric disk (poled in the thickness direction) sandwiched between two cymbal-shaped metal end caps. The metal caps serve as a mechanical transformer which transforms the high impedance, small extensional motion of the ceramic into low impedance, large flexural motion of the shell. The cymbal was originally designed as an actuator, which provides a sizable displacement as well as a large generative force, bridging the gap between the two most common actuators, the bimorph and the multilayer. It was later proposed as a shallow water sound projector and receiver. Single elements are characterized by high Q, low efficiency and medium power output capability. Their low cost and thin profile allow the transducer to be assembled into large flexible arrays. A 5/spl times/20 prototype array was built and tested. It has a broadband response in the frequency range between 17 kHz and 100 kHz. The array is flexible and easily conforms to a curved surface. Finite element code ATILA was used successfully in modeling and optimizing the single element transducer. Several modifications were investigated for various applications with the aid of computer modeling. Among them are the double-dipper (deep submergence), the double-driver (unidirective beam pattern) and the smart caps (adjustable resonance frequency).