Articulation from acoustics: Estimating constriction degree from the acoustic signal.

Abstract

Voiced stops in Spanish (/b/, /d/, /g/) are often realized as approximants with incomplete supralaryngeal closure. A number of studies have shown that these are not allophonic variants but rather form part of a continuum of productions, influenced by a number of segmental and prosodic factors. Most work on this topic has used indirect acoustic measurements to estimate articulatory constriction degree. These methods include energy difference in CV (intensity minimum of the consonant over intensity maximum of adjacent vowels), spectral tilt, and maximum rising velocity of the intensity envelope in the CV transition [Kingston, LASP 3, (2008)]. These acoustic measures of constriction, while generally showing the same overall patterns, at times show significant differences in exact results [Hualde et al., LSRL (2010)]. The current study tests the accuracy of all three measures by comparing the acoustic results with articulatorily constriction degree, measured via electromagnetic articulometry (EMA). Comparisons are conducted using only /b/, as calculation of articulatory constriction degree using EMA is more accurate for bilabials than for coronals or velars. The results show for the first time the relative accuracy of three widely used acoustic tools for estimating articulatory constriction degree.