2015 Volume 14 Issue 2 Pages 95-102
Various vocal sounds are generated by the complex articulations of human vocal organs under the feedback control mechanisms using the auditory system. By reconstructing a human vocal system mechanically, the authors have developed a talking robot based on the physical models of vocal organs. The robotic system consists of motor-controlled vocal organs such as vocal cords, a vocal tract, a nasal cavity and an auditory system to generate a natural voice imitating a human vocalization. By introducing an auditory feedback learning of the mechanical systems, the robot is able to autonomously reproduce a human-like vocal articulation using its vocal organs to generate human-like vocal sounds. 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 vocal articulation skills, the resonance characteristics given by the articulatory motions are adaptively acquired by the auditory feedback control. In this study, a human-like expressive speech production by the talking robot is introduced for the vocal communication with a human. 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, a suitable 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 autonomous acquisition of the vocalization using a self-organizing map will be described, and then the articulatory motions for producing human-like speech with various expressions will be introduced for realizing expressive speech communication with a human.