We aim to develop the easy-to-use artificial larynx with high tone quality. We focus on using a PZT
ceramics sounder as its sound source, because it is small size, low power consumption, and
harmless to humans. But conventional PZT ceramics sounder have the problem that it cannot
generate an enough sound in the low frequency range, thus they cannot be used for artificial larynx.
Then, we aim to develop the PZT ceramics sounder which can generate enough volume in the low
frequency range. If we can lower the resonance frequency of the sounder, it can generate low pitch
sound easily. Therefore I created the new diaphragm with low resonance frequency. In addition, we
could obtain the high amplitude by changing method of driving. This time, we report on the
characteristic comparison of this new PZT ceramics sounder and conventional one. Furthermore,
for this new one, we analyzed the best alignment of PZT ceramics and the shape of the diaphragm
to obtain low resonance frequency and big amplitude. In fact we analyzed the optimization of the
structure. The analysis is done by computer simulation of ANSYS and Laser Doppler Vibrometer.
In the future, we will add intonation to the generated sound by input wave form which is developed
concurrently, and implant the sounder inside of the body by the method of fixing metal to
biomolecule which is done too. And so high tone quality and convenient artificial larynx will be
completed.
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.
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