We developed an anthropomorphic talking robot, Waseda Talker No. 6 (WT-6), which
generates speech sounds by mechanically simulating articulatory motions and aero-acoustic
phenomena. WT-6 possesses 17 degrees of freedom (DOF): a 5-DOF tongue, 1-DOF jaws, 4-DOF
lips, a nasal cavity, and a 1-DOF soft palate as articulators; and 5-DOF vocal cords and 1-DOF lungs
as vocal organs. The vocal cords, tongue, and lips are made from the thermoplastic rubber Septon,
whose elasticity is similar to that of human tissue. WT-6 has three-dimensional (3D) lips, tongue, jaw,
and velum, which form the vocal tract structure. It also has an independent jaw opening/closing
mechanism. The previous robot in the series had a two-dimensional tongue and could not produce
human-like tongue shape. The new tongue can form 3D shapes, and thus, is able to produce more
realistic vocal tract shapes. The vocal cord model consists of two folds, and is constructed with a
structure similar to the biomechanical structure of human vocal cords. These vocal cords can vibrate
in complex phases, similar to those of a human. With these mechanisms, the robot can reproduce
human speech in a more biomechanical manner, and thus, can produce a voice closer to that of a
human.