Development of the new shape PZT ceramics sounder suitable for a sound source of artificial larynx

Various speech production substitutes, which aim to reconstruct speech functions, have been developed and used practically by speech impaired individuals. However, conventional speech production substitutes have various drawbacks; therefore, perfect speech production substitutes are expected to be developed. We focused on the PZT ceramics sounder as a sound source in an electric drive artificial larynx. We first developed the artificial larynx that uses a PZT ceramic sounder and then evaluated its performance. The vocalized sound of the artificial larynx user shows good characteristics at the formant frequency, which is important for vowel discrimination. The characteristic feature of our artificial larynx is its individual structure, and this typical structure implies that the sound source and the implant are separated. This structure facilitates a high biocompatibility in our artificial larynx. In our previous work, the improvement in the acoustic characteristics of the sound source was described. The improvement is achieved by the optimization of the electric control and its structure. In this paper, we present the results of shape optimization and new shape PZT ceramics sounder evaluation. The optimized shape is decided on FEM analysis, and prototype PZT ceramics sounder based on above analysis is manufactured by way of trial. Additionally, the performance of prototype sounder is evaluated by acoustic analysis. Until now, we have researched about the immobilization of biomolecules onto the metal surface. It is believed that biomolecular immobilization on the sound source surface improves its biocompatibility. In the future, we aim to realize implantable sound sources that employ biomolecular immobilization technology.