Human palate and related structures: their articulatory consequences

The vowel space reflects the right-angled shape of the vocal tract, and many consonants exploit the palatal wall. These two facts suggest the importance of the geometry of peripheral structure in speech production. In this study, the relationship between geometry and articulatory variation was examined using a database of English and Japanese speakers. The geometry of each speaker's vocal tract was defined by a quadrilateral bounded by the palatal plane and other rigid structures. This quadrilateral, whose area we refer to as the articulatory (or A) space, provides indices of pharyngeal distance, lower facial height, mandibular position and inclination, and head rotation. The A-spaces of different speakers vary in size and form: the speakers with longer pharyngeal distance tend to have shorter lower facial height. There is also significant variation among speakers in the degree of inclination of the mandibular symphysis. Qualitative comparisons suggested that speakers' vowel articulations adapt to the form of their respective A-space, while consonant articulations seem to be independent of the A-space.