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Comparing Straw-Based Semi-Occluded Vocal Tract Exercises (SOVTEs): From Air Phonation to Water Resistance Therapy-A
Ralph Haddad1, Dario Ebode1, Alexia Mattei1
1Department of Oto-Rhino-Laryngology and Head and Neck Surgery, AP-HM, La Conception University Hospital, Marseille, France.
Objectives:
Semi-Occluded Vocal Tract Exercises (SOVTEs) are fundamental in voice therapy, yet the mechanical and clinical distinctions between straw phonation in air and Water Resistance Therapy (WRT) remain insufficiently synthesized. This scoping review aims to map the literature on these two modalities, analyze their physiological principles, and compare their efficacy on acoustic, aerodynamic, and laryngeal outcomes.
Methods:
A systematic search was conducted in Medline and Cochrane databases up to September 2025, following PRISMA guidelines. Studies involving adults (healthy or dysphonic) using straw phonation (in air) or WRT (tube in water) were included. Data were extracted regarding physiological mechanisms, exercise parameters (diameter, length, water depth), and clinical effects.
Results:
Out of 1378 records, 107 studies were included. Straw phonation in air acts as a single-source system providing stable back pressure. It is highly effective at reducing mediolateral supraglottic compression and vocal fold impact stress, particularly with small-diameter straws (≤3 mm). WRT serves as a double-source system; water depth dictates hydrostatic pressure, while bubbling creates a pulsatile pressure (15-40 Hz), providing a "massage-like effect." While WRT effectively lowers vibration amplitude and encourages respiratory conditioning, it may introduce vibratory irregularity. Direct comparisons suggest straw phonation is superior for immediate reduction of hyperfunctional patterns, whereas WRT (at varying depths) is highly adjustable for both recovery (shallow) and hypofunctional compensation (deep).
Conclusions:
Both techniques enhance vocal economy by optimizing the oral-to-subglottal pressure ratio, but they serve distinct clinical goals. Straw phonation in air is preferred for stabilizing hyperfunction, while WRT offers unique pulsatile tissue stimulation and adjustable resistance for respiratory drive. Clinical dosing - specifically straw diameter and water depth - is critical for therapeutic success.
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