Oral vibratory sensation at different laryngeal and semi-occluded vocal tract configurations during voice production

Voice therapy aimed at improving vocal efficiency, such as resonant voice therapy or semi-occluded vocal tract exercises, often emphasizes vibratory sensations in the front part of the vocal tract during phonation. It remains unclear what laryngeal and vocal tract adjustments are elicited in patients by this emphasis on oral vibratory sensations and how these adjustments improve voice production. This study aims to identify laryngeal and vocal tract adjustments that maximize oral vibratory sensations during phonation, as quantified by the oral sound pressure level (SPL), at different laryngeal and semi-occluded vocal tract conditions in a three-dimensional phonation model. Results show that maximum oral SPL is reached at intermediate vocal fold adduction conditions. Epilaryngeal tube narrowing further increases the oral SPL in an open vocal tract, but this effect is much reduced and even reversed in a semi-occluded vocal tract, due to the reduced sensitivity of the first formant to epilaryngeal manipulation in a constricted vocal tract. These findings suggest that emphasis on oral vibratory sensations generally elicits a laryngeal configuration that is neither too tight nor too open. In a semi-occluded vocal tract, this emphasis may also reduce the degree of epilaryngeal narrowing as often observed in recent imaging studies.