Vocal Tract Morphology in Inhaling Singing: Characteristics During Vowel Production—A Case Study in a Professional Singer

Abstract

A professional singer produced various vowels on a comfortable loudness and pitch in an inspiratory and expiratory phonation manner. The present study investigates the morphological differences and tries to find a link with the acoustical characteristics. We hypothesize that features, constantly present over all vowels, characterize inhaling phonation and that the formant frequencies reflect the morphological findings. A prospective case study was carried out. A female singer uttered the vowels /a/, /e/, /i/, /o/, and /u/ in a supine position under magnetic resonance imaging, on a comfortable loudness and pitch, in both inhaling and exhaling manner. The exact same parameters as in previous reports were measured (1-3). Acoustical analysis was performed with Praat. Wilcoxon directional testing demonstrates a statistically significant difference in (1) the distance between the lips, (2) the antero-posterior tongue diameter, (3) the distance between the lips and the tip of the tongue, (4) the distance between the epiglottis and the posterior pharyngeal wall, (5) the narrowing of the subglottic space, and (6) the oropharyngeal and the hypopharyngeal areas. Acoustical analysis reveals slightly more noise and irregularity during reverse phonation. The central frequency of F0 and F1 is identical, whereas that of F2 and F3 increases, and that of F4 varies. A smaller mouth opening, a narrowing of the subglottic space, a larger supralaryngeal inlet, and a smaller antero-posterior tongue diameter can be considered as morphological characteristics for reverse phonation. Acoustically, reverse phonation discretely contains more noise and perturbation. The formant frequency distribution concurs with a mouth narrowing and pharyngeal widening during inhaling.