Mechanical reproduction of human-like expressive speech using a talking robot

The authors have developed a talking robot by reconstructing a human vocal system mechanically based on the physical model of human vocal organs. The robotic system consists of motor-controlled vocal organs such as vocal cords, a vocal tract and a nasal cavity to generate a natural voice imitating a human vocalization. By applying the technique of the mechanical construction and its adaptive control, the robot is able to autonomously reproduce a human-like vocal articulation using its vocal organs. In vocalization, the vibration of vocal cords generates a source sound, and then the sound wave is led to a vocal tract, which works as a resonance filter to determine the spectrum envelope. For the autonomous acquisition of the robot's vocalization skills, an adaptive learning using an auditory feedback control is introduced. In this study, a human-like expressive speech production by the talking robot is introduced. A human generates speech by controlling their own vocal organs for changing the speech expressions such as the volume and the intonations. To realize the human-like expressive speech production, a control method for the mechanical organs has to be established. In the first part of the paper, the construction of the talking robot and the acquisition of the vocalization will be described, and then the control method for producing human-like speech with various expressions will be introduced.