Takayuki Arai(Sophia University)
In 2017 and 2018, two types of vocal-tract models with physical materials were developed that resemble anatomical models and can physically produce human-like speech sounds. The 2017 model is a static-model, and its vocal-tract configuration is set to produce the vowel /a/. The 2018 model is a dynamic-model, and portions of the articulators including the top surface of the tongue are made of a gel-type material. This allows a user to manipulate the shape of the tongue and articulate different vowels and a certain set of consonants. However, the mandible of the model is fixed, making it difficult to manipulate different sounds with different jaw openings, such as high vs. low vowels. Therefore, in 2019, two types were developed by adding an additional mandible mechanism to the 2018 model. For the first type, the mandible was designed to move between the open and closed positions by creating an arc-shape rail. For the second type, the mandible moves the same trajectory with an additional support. As a result, various speech sounds with a flexible-tongue and moveable mandible can be easily produced. These models are more realistic than the anatomical models proposed in 2017 and 2018 in terms of articulatory movements.