Where SOVTEs tend to fall short and narrowing wins

„What narrowing?“, might be the first question that comes to mind.

Undoubtedly, Semi Occluded Vocal Tract Exercises¹ have success stories to tell. They have helped patients with diagnosed MTD and hyper functional adduction as they can solve uncontrolled pharyngeal narrowing relatively easy. (Hijleh, K., & Pinto, C. 2021)

But are they also the best choice to re-establish a fully functional speaking voice or are we maybe missing something?

Let’s first ask Dr. Ingo Titze.
Already in 2006 he gave the answer in part when he described the necessity of transferring the SOVTE’s benefits to free speech:

“As in any training program that uses exercises outside the norm of behavior, one must question transfer, or carryover, to normal behavior. Ultimately, phonation in normal speech or singing must be improved, and since speech does not maintain a constancy of semi-occluded vocal tract shapes (i.e., closed vowels, nasals, or bilabial obstruents are only intermittent), a residual effect must be demonstrated for portions of speech where the vocal tract is not occluded. This is especially the case for singers and speakers who speak loudly before audiences, using a wider-than-normal mouth opening.” (p.3)

Interestingly, both Titze (2006) and Guzman (2013) postulated a correlation between a wider pharynx and a narrow epiglottic area already when SOVTEs were in use, also in a vocal lay population with hyperfunctional adduction.²

What we might learn from these observations

1. According to the literature mentioned SOVTEs seem to prepare epilaryngeal narrowing but to maintain the benefit we need more of it or at least a strategy to maintain it.
2. Perhaps, by reducing uncontrolled constrictions in vocal lay populations with hyperfunctional adduction through SOVTEs, the voice reestablishes an increased degree of epilaryngeal narrowing. The voice “knows” what is healthy – it naturally tends to return to efficient, inertive conditions once dysfunctional behavior is resolved.
3. Moreover, epilaryngeal narrowing is a component of any form of singing training, functioning as a natural amplifier within the vocal tract. Could E-P narrowing in these populations rather be a habitual aspect of phonation itself than an effect of the SOVTE?
   

It’s worth pointing out that …

Apfelbach and Guzman (2021) reviewed the scientific research on semi-occluded vocal tract exercises in vocally untrained adults both with and without dysphonia over the last decades, stating that

„Although few studies examined the duration of these changes post exercise, several RTCs [Randomized Controlled Trials] support the assertion that SOVTE’s effects can be sustained with regular practice over weeks or months, regardless of current vocal health status.“ (p.1)

Unfortunately, the exact references to these studies could not be found in the article. On the other hand the authors mention the limits of SOVTEs themselves, when stating

„[…] the sensation of inertive reactance may also help patients experience vibrations in the facial tissues, then use this sensory experience to recreate economical resonant voicing patterns once the semi-occluded stimulus has been withdrawn. (p.19)

In other words, unless the patient learns to recreate inertive reactance without an SOVTE tool, he’s doomed to eternal straw-bubbling. I still see him sitting there ten years later… ironymodeoff.

Do SOVTEs have a positive long term effect in healthy voices?

As to the current knowledge of the author more research is needed to fully answer this question.

However, after investigating the effects of sustained SOVTEs in healthy voices over a duration of four weeks Jakob R. Holm et al. (2025) observed „a significant difference between weeks four and five, coupled with no difference between weeks zero and five, suggests that the effects of SOVTEs do not persist one week after discontinuation“ (p.7).

This is what they did: The treatment was carried out over four consecutive weeks, during which the participants showed an improvement in voice quality. In week five, however, the twenty-two participants were asked to stop the SOVTEs to assess any lingering effects of the exercises. That week, the results were the same as at the start of the treatment, indicating that no lasting effects were observed once the treatment had ended.

The authors concluded that „prolonged straw phonation resulted in decreased PTP [Phonation Threshold Pressure] over four weeks of use… For effective results, continued straw phonation is required to maintain benefits from SOVTEs“ (p.10)

Therefore, according to this study SOVTEs lack a positive long term effect in healthy voices, once stopped.

Introducing a new perspective with a different approach

We either need an additional type of treatment after SOVTEs, or a different therapeutical approach that covers all these needs.

CVT Voice Rehabilitation³ offers a new perspective and a 3-step approach how to enhance and maintain inertive reactance in both, trained and untrained voice users.

The systematic approach, guided by an Authorised Complete Vocal Technique teacher who further specialized in CVT Voice Therapy, is a training method that raises both vocal awareness and vocal regulatory abilities in the patients during their vocal recovery journey.

The 3-step approach in CVT voice rehabilitation

Step 1: Releasing uncontrolled pharyngeal constrictions (e.g. through SOVTEs, or other exercises that both lower the Phonation Threshold Pressure and enhance the learning effect in the voice user)
Step 2: Additional help in maintaining or increasing epilaryngeal narrowing with the use of vowels [æ] or [e], instead of [u], [i], and [a]
Step 3: working dynamically with more and less anterior-posterior narrowing, using the practice vowels on single words, in planned speech and in free speech.

Aspects to be aware of:

• Steps 2 and 3 are always implemented in consideration of step 1, thereby providing a hierarchical approach in working safely with the patient’s voice.
• Steps 2 and 3 with the right choice of vowels depend on the voice user and the diagnosis.
• Step 3: Every setting seems to have a specific type of PTP – condition under which it operates best – depending on narrowing, vocal fold closure, occlusions, choice of vowel, etc.

Why these vowels?

Both vowels [æ] and [e] can be easily produced with epilaryngeal narrowing and both with and without A–P (pharyngeal) narrowing (with ventricular fold activation), allowing for a gradual increase in A–P narrowing without triggering symptoms of MTD or hyper adduction.

This kind of training will help the speaker reestablish a functional and dynamic voice and it will give him the freedom to deliberately adapt his voice use to different situations and surroundings.

Conclusions:

1. Lower-tract narrowing is an important factor in maintaining inertive reactance, and SOVTEs tend to fall short in this regard. In CVT voice rehabilitation, both its timing and type must be tailored to the diagnosis, often involving a back-and-forth between steps to allow the process to unfold its full benefits.
2. CVT voice rehabilitation is a training method that makes the voice user independent from any gadgets and tools. Instead it teaches him to become his own voice trainer and vocal supervisor.

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Footnotes:

1. In this article: straw phonation or straw in water therapy ↩︎
2. Hijleh, K., & Pinto, C. (2021). Realizing the benefits of SOVTEs: A reflection on the research… p.335 ↩︎
3. Complete Vocal Technique is a science-informed method of working with the voice, developed by Catherine Sadolin. For further information please visit the official website of Complete Vocal Institute.  ↩︎

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References:

Apfelbach, C. S., & Guzmán, M. (2021). Acoustic, aerodynamic, morphometric, and perceptual changes during and after semi-occluded vocal tract exercise: An integrative review. Journal of Voice, 38(2), 404–425. https://doi.org/10.1016/j.jvoice.2021.09.031

Hijleh, K., & Pinto, C. (2021). Realizing the benefits of SOVTEs: A reflection on the research. Journal of Singing: the Official Journal of the National Association of Teachers of Singing, 77(3), 333–344.

Holm, J. R., Wischhoff, O. P., Gilvydis, T. K., Prosser, B. D., Bhowmik, A., Bienhold, G. J., & Jiang, J. J. (2025). Effects of sustained semi-occluded vocal tract exercises in non-disordered populations. Journal of Voice, 38(2), 404–425. https://doi.org/10.1016/j.jvoice.2025.04.003

McGlashan, J., Aaen, M., White, A., Saccente-Kennedy, B., Tempesta, M., & Sadolin, C. (in press). Feasibility and acceptability of Complete Vocal Technique-Voice Therapy as a treatment for primary muscle tension dysphonia: A feasibility trial. Journal of Voice. https://doi.org/10.1016/j.jvoice.2025.07.044

Titze, I. R. (2006). Voice training and therapy with a semi-occluded vocal tract: Rationale and scientific underpinnings. Journal of Speech, Language, and Hearing Research, 49(2), 448–459. https://doi.org/10.1044/1092-4388(2006/035)