A cine MRI-based study of sibilant fricatives production in post-glossectomy speakers

Glossectomy changes properties of the tongue and negatively affects patients' speech production. Among the most difficult consonants to produce in the post-glossectomy speakers, the sibilant fricatives /s/ and /sh/ are often problematic. To better understand these problems in production, this study analyzed acoustic and articulatory data of /s/ and /sh/ from three subjects: one normal speaker and two post-glossectomy speakers with abnormal /s/ or /sh. Based on cine magnetic resonance images, three dimensional vocal tract reconstructions, tongue surface shapes behind constrictions, and area functions were analyzed. Our results show that in each patient, contrary to normal, /s/ and /sh/ were quite similar in acoustic spectra, tongue surface shapes, and constriction locations. In the abnormal /s/, the missing unilateral tongue tissue created an air flow bypass which made the constriction further backward. The abnormal /sh/ may be explained by the lack of precise tongue control after surgery. In addition, the tongue surfaces in the patients were more asymmetric in the back and were not grooved for /s/ anterior to the constriction.