Multilayer piezocomposite ultrasonic transducers operating below 50 kHz

Ultrasonic transducers operating below 50 kHz have applications in sonar, process ultrasound, and low frequency nondestructive evaluation. The most common structure is the Tonpilz mass-spring design. In contrast, multilayer piezocomposite transducers are reported here. The electrical impedance of these devices can be controlled by the number and thickness of layers and the acoustic impedance by ceramic volume fraction. The transducers described in this paper have been designed using finite element analysis and linear systems modeling. Typical design output is presented and results from prototype devices are presented. These show that it is not easy to obtain a quality factor less than 5, but that excellent sensitivity is possible. It is concluded that multilayer piezocomposites have benefits, for example in terms of sensitivity, and costs, for example in terms of increased manufacturing complexity.