This paper presents three-dimensional tongue surfaces reconstructed from multiple
coronal cross-sectional slices of the tongue. Surfaces were reconstructed for sustained
vocalizations of the American English sounds [symbol: see text]. Electropalatography
(EPG) data were also collected for the sounds to compare tongue surface shapes with
tongue-palate contact patterns. The study was interested also in whether 3-D surface
shapes of the tongue were different for consonants and vowels. Previous research and
speculation had found that there were differences in production, acoustics, and linguistic
usage between the two groups. The present study found that four classes of tongue
shape were adequate to categorize all the sounds measured. These classes were front
raising, complete groove, back raising, and two-point displacement. The first and
third classes have been documented before in the midsagittal plane [cf. R. Harshman,
P. Ladefoged, and L. Goldstein, J. Acoust. Soc. Am. 62, 693-707 (1976)]. The first
three classes contained both vowels and consonants, the last only consonants. Electropalatographic
patterns of the sounds indicated three categories of tongue-palate contact: bilateral,
cross-sectional, and combination of the two. Vowels used only the first pattern, consonants
used all three. The EPG data provided an observable distinction in contact pattern
between consonants and vowels. The ultrasound tongue surface data did not. The conclusion
was that the tongue actually has a limited repertoire of shapes and positions them
against the palate in different ways for consonants versus vowels to create narrow
channels, divert airflow, and produce sound.