Text-to-speech of a talking robot for interactive speech training of hearing impaired

The authors are developing a talking robot which is a mechanical vocalization system modeling the human articulatory system. The talking robot is constructed with mechanical parts that are made by referring to human vocal organs biologically and functionally. In this study, a newly redesign artificial vocal cord is developed for the purpose of extending the speaking capability of the talking robot. The artificial vocal cord is developed using functional approach. A thin layer of rubber band with a width of 7mm is attached on a plastic body in a sealed chamber creates an artificial sound source. The fundamental frequency of the sound source vary from 80Hz to 280 Hz depending on the pressure to the rubber band and the curving shape of the rubber band. The curving shape of the rubber band is adjustable by an innovative design mechanism driven by a servo motor. The amount of air pressure applied to the rubber band is controlled by another servo motor which is referred as volume motor in this study. The experiment to verify the speak capability of the talking robot with this newly redesigned vocal cord is conducted by letting the robot generating five vowel sounds with difference combination of 20 levels of rubber band shape and 10 levels of air pressure input. The pitch and volume of each sound is extracted to determine the effect of the rubber band shape and the pressure input on the output sound. The result shows that this newly redesigned vocal cord greatly increase the speaking capability of the talking robot, especially its singing performance.