A number of Tonpilz piezoelectric transducers generally form a large matrix array. They may be required to be only light in weight, or both miniaturized and light in weight as well as to have high-power capability, according to their use. This paper describes the results obtained in an investigation of miniaturized, light-weight Tonpilz piezoelectric transducers with high-power capability. An electromechanical energy conversion system and mechanical vibration system for the transducer are theoretically investigated on transducer configuration, using a Martin equivalent circuit and distributed-constant equivalent mechanical circuits. For simplification of the theoretical analysis, the transducer was considered as being divided into a front-half section, from the head mass end to the vibration nodal section, and a rear-half section, from the vibration nodal section to the tail mass end. Figures of merits, FMm for the front-half section and FM'm for the rear-half section, are calculated to achieve lightening as well as high-power capability. In addition, figures of merits FMml for the front-half section and FM'ml for the rear-half section are calculated to achieve miniaturization and lightening as well as high-power capability. To corroborate the theoretical results obtained, three kinds of Tonpilz transducers having the same 30 kHz resonant frequency but different configurations were built. Then, three kinds of 33 matrix arrays composed of nine Tonpilz transducers with the same configuration were fabricated. To evaluate the high-power characteristics for the arrays, a water tank to which high hydraulic pressure can be applied was adopted and a high-power test was carried out. As a result, it was found that transducers with high FMm and FM'm figures of merits are light in weight and exhibit high performance in high-power handling capability. Also, it was found that transducers with high FMml and FM'ml figures of merits are miniaturized and light in weight and exhibit high performance in high-power handling capability.

Tonpilz piezoelectric transducers are one style of transducers for high-power sound generation. However, the transducers have mainly been designed by the trial-and-error method. The object of this paper is to precisely estimate the transducer performances beforehand by a equivalent circuit analysis. The precise electro-mechano-acoustical equivalent circuit is derived for the transducer, including housing, an acoustic rubber layer and a bolt, and its transmission matrix is presented. To improve the calculation accuracy, the effects of adhesive layers in a piezoelectric ceramic stack part and compressive stress by bolting them together are included into the electrical and mechanical equivalent constants for the ceramic stack. Also, to accurately evaluate any errors between theoretical values and measured values, transducer performances are expressed as absolute values by MKS units. Then, based on this analysis, a Tonpilz transducer has been built. Transmitting and receiving voltage sensitivities for the transducer, as well as the respective resonant frequencies, mechanical quality factors and free admittance loci in air and in water, have been measured. As a result, a good agreement between theoretical values and experimental results has been achieved.

Wide-band, low-ripple underwater transducers with high-power acoustic radiation capability have been designed on the basis of multiple-mode filter synthesis theory. They are composed of triple acoustic matching plates and double backing plates with optimized specific acoustic impedances,besides piezoelectric ceramic elements. One of the backing plates employs a Fe damping-alloy to suppress unwanted response peaks in the frequency range above the passband region. Two 33 array transducers were fabricated, each with a center frequency of 200 kHz, one as a transmitter and the other as a receiver. The two transducers show high-sensitivity, low-ripple and wide-band transmitting and receiving responses. Then, the transducers were applied in a color video picture digital transmission system.Clear color video pictures, composed of 256240 pixels, were successfully received within one second.