Background
Semi-occluded vocal tract exercises (SOVTE) are widely used in both clinical rehabilitation as well as habilitation of voice for pathological and healthy professional voice users. SOVTEs have been shown particularly useful in the treatment of dysphonia. However, potential contraindications for SOVTEs are sparsely studied, with some clinical results suggesting that fatigue and tiredness may result from SOVTEs in both patients and singers, at least short-term. Recent studies document epilaryngeal expansion during and after SOVTEs, which may be counterproductive for learning sounds requiring narrowing in this vocal tract region.
Objective:
To study the effects of four common SOVTEs in 2 healthy professional singers, one male and one female, producing a variety of voice conditions at various loudness levels and qualities.
Methods:
Double-case nasostroboscopic study of a male and a female singer. Both singers performed sustained vowels for a total of 8 different singing sounds varying in loudness and qualities for four specific SOVTE interventions, including 3mm straw, 10cmH20 Water Resistance Therapy, Shaker Deluxe at 5cmH20, and a voiced vvvf-fricative. Nasoendoscopic stroboscopy and simultaneous EGG and audio from a head-mounted microphone were obtained before, during, and after the SOVTE intervention to document the effects of each SOVTE for each of the 8 tested conditions. Auditory perceptual assessment for each condition before and after each SOVTE was performed by a trained singing teacher simultanesly to ensure accuracy in task. Singers filled in baseline SVHI and VTDS questionnaires prior to interventions as well as an adapted VTDS (only severity of symptom) for each intervention.
Results:
All SOVTEs resulted in epilaryngeal expasion for both participants. This was particularly visible during phonations with marked epilaryngeal narrowing prior to the intervention. For the female participant, 3mm, 10cmH20 WRT, and Shake Deluxe at 5cmH20 interventions destabilised the voice source and changed vocal fold vibratory pattern as observed by EGG wavegram traces, which was not the case for the voice fricative. For the male participant, 3 of 4 SOVTE interventions caused marked epilaryngeal expansion and pronounced vocal fatigue, though with less dramatic EGG-wavegram trace changes. For both participants, samples requiring more initial epilaryngeal narrowing and firmer adduction coupled with SOVTEs were associated with increased VTDS symptom severity.
Conclusions:
Epilaryngeal expansion during and lingering after SOVTE intervention, as described in previous studies, were visible for a variety of different vocal coordinations in professional singing voice. Some sounds, particularly those requiring epilaryngeal narrowing, seem mismatched with high resistance SOVTEs, whereas sounds less reliant on epilaryngeal narrowing may benefit from the increase flow and adduction control provided by SOVTEs. More research into the alignment between target singing output in terms of loudness and sound quality and appropriate SOVTE for the specific sound is warranted.