Changes in glottal contact quotient during resonance tube phonation and phonation with vibrato

Phonating into narrow hard-walled tubes of varying diameters and length as an extension of the vocal tract is considered a semioccluded vocal tract exercise. Semioccluded vocal tract postures have been postulated to have a therapeutic effect during the treatment of the dysphonic patient. They appear to affect at least two components of the voice source (1) glottal flow pulse and (2) vibrational characteristics of the vocal folds. Vibrato also has been described as a possible therapeutic tool and may decrease phonatory hyperfunction. The aim of this study was to determine the influence of resonance tubes and phonation with vibrato on the closed quotient. Thirty-six adult classical singers were recruited for this study. Subjects were asked to produce four phonatory tasks at comfortable pitch and loudness: sustained vowel [a:] without vibrato, sustained vowel [a:] with vibrato, sustained phonation into a straw without vibrato, and sustained phonation into a straw with vibrato. Computer analysis of the contact quotient (CQ) was performed for each type of phonation in every participant. An increase in CQ variability was observed during tube phonation when compared with vowel phonation. Although there was a decrease in the mean CQ values when comparing vowel phonation without vibrato with the other three phonatory tasks, the difference was not statistically significant. Intrasubject analysis demonstrated a decrease in the CQ during tube and vibrato phonation in most of the participants. Although a causal relationship is not proven, this finding suggests that the use of straws and vibrato during phonation may have potential therapeutic value in the treatment of patients with hyperfunctional voice disorders.