The effect of resonance tubes on glottal contact quotient with and without task instruction: a comparison of trained and untrained voices.

Phonation into narrow tubes or straws has been used as a voice training and voice therapy technique and belongs to a group of techniques known as semi-occluded vocal tract exercises. The use of what are called resonance tubes has received renewed attention in the voice research literature, in both theoretical and empirical studies. The assumption is that the partially occluded and lengthened vocal tract alters supraglottal acoustics in such a way as to allow phonation near a lowered first vocal tract formant, which has been suggested as a way to bring about a more efficient glottal closure pattern for sustained oscillation. In this study, two groups of male participants, 10 with no vocal training and 10 with classical vocal training, phonated into a resonance tube for approximately 1 minute. Electroglottography was used to estimate glottal contact quotient (CQ) during spoken /a/ vowels before tube phonation, during tube phonation, and again during spoken /a/ vowels after tube phonation. Half of each group of participants was made to keep pitch and loudness consistent for all phases of the experiment, replicating the method of a previous study by this author. The other half was instructed to practice phonating into the resonance tube before collecting data and was encouraged to find a pitch and loudness combination that maximized ease of phonation and a sense of forward oral resonance. Glottal CQ altered considerably from baseline for almost all participants during tube phonation, with a larger variability than that during vowel production. Small differences in glottal CQ were found as a function of training and instruction, with most participants' CQ increasing during tube phonation. A small post-tube phonation effect was found primarily for the trained and instructed group. Secondary single-subject analyses revealed large intersubject variation, highlighting the highly individualized response to the resonance tube task. Continued study of resonance tubes is recommended, comparing both male and female as well as vocally trained and untrained participants. Future studies should continue to examine systematic variations in task instruction, length of practice, and resonance tube dimensions.