Design and fabrication of a wideband Tonpilz transducer with a void head mass

A new Tonpilz transducer structure has been developed to achieve a frequency bandwidth much wider than that of a conventional transducer. The mechanical quality factor of a Tonpilz transducer is proportional to the weight of its head mass. Here, the internal space of the head mass was made void to reduce the weight drastically, which produces a low mechanical quality factor, and thus a wide bandwidth. The concept of this new wideband Tonpilz transducer with a void head mass was presented by the authors [1]. This paper is about the experimental validation of the concept. First, the effect of the void head mass structure on the transducer performance was investigated by the finite element method. To achieve the wide frequency bandwidth, we optimized the structure of the Tonpilz transducer through regression analysis of the calculation results and genetic algorithm. The optimized transducer had a fractional bandwidth of 130% that confirmed the efficacy of the void head mass in widening the frequency bandwidth. The validity of the design is confirmed by manufacturing and characterizing a prototype transducer of the optimized structure.