Articulatory idiosyncrasy inferred from relative size and mobility of the tongue

Abstract

Origins of individual characteristics of speech sounds have been a mystery. Individual patterns of higher spectra could be attributed to quasi-static hypopharyngeal-cavity resonance, while those of lower spectra are puzzling because both spectra and vocal-tract shapes radically change during speech. A possible clue to look into articulatory idiosyncrasy may be the relation between relative size and mobility of the tongue in the oropharyngeal cavity. To this end, combined cine- and tagged-MRI collected from four Chinese speakers producing two-syllable words were processed. The relative tongue size was indexed by midsagittal tongue area divided by tongue plus airway area both measured above the level of the superior genial tubercle in static MRI during /i/. The mobility of the tongue was measured by average velocity of tag points located along the oral and pharyngeal surface of the tongue. In the result, the velocity monotonically decreased with the relative tongue size, suggesting that the smaller the tongue the faster the movement according to a speaker-specific anatomical constraint derived from the space available for tongue articulation in vowel production. [Work supported by National NSF Programs (No. 61573254 and 61304250), and National One-Thousand Program (WQ20111200010) in China.]