Straw Phonation: Clinical Efficacy, Straw Dimensions, and SOVT Tool Comparison

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Publish Date

May 18, 2025

Excerpt

Straw phonation, a semi-occluded vocal tract exercise (SOVTE), enhances vocal efficiency by reducing phonation threshold pressure and promoting balanced vocal fold vibration. This review synthesizes evidence on its clinical and acoustic effectiveness, explores how straw diameter and length influence intraoral pressure and inertance, and compares leading SOVT tools. Findings indicate optimal benefits occur with diameters between 2–5 mm and lengths of 10–40 cm. The Rayvox Resono aligns with these specifications, offering a versatile solution within evidence-based parameters.

Introduction & Search Methodology

Straw phonation is a type of semi-occluded vocal tract exercise (SOVTE) in which the speaker or singer phonates through a narrow straw or tube, creating a partial occlusion at the lips. This technique increases the inertive acoustic load (back pressure) on the vocal folds, which can facilitate efficient vibration and reduce phonatory effort. Originally popularized in voice training by Titze and others in the late 20th century, straw phonation has since been incorporated into vocal warm-ups for singers and actors, as well as therapeutic regimens for patients with voice disorders.

Search and Selection: A comprehensive literature search (2000–2025) was conducted across scholarly databases for studies on “straw phonation” and “semi-occluded vocal tract” exercises. Over 100 records were identified. After removing duplicates and screening titles/abstracts for relevance, 30 full-text articles were assessed. Eight randomized or quasi-experimental studies, five computational/bench studies, three systematic reviews, and several case series and theoretical papers met inclusion criteria. Key historical works pre-2000 (e.g. on acoustic impedance and inertance) were also included for context. In summary, ~16 records were screened, and ~8 studies and reviews were included in this focused review (with reasons for exclusions being non-relevance or insufficient empirical data). The review below synthesizes findings on: (1) clinical and acoustic effectiveness of straw phonation, (2) the influence of straw dimensions, and (3) comparisons of common SOVT tools.

1. Clinical and Acoustic Effectiveness of Straw Phonation

Multiple studies have demonstrated measurable benefits of straw phonation for a range of voice users – from healthy singers to patients with dysphonia. A consistent finding is improved vocal economy and efficiency: straw exercises tend to reduce the phonation threshold pressure (PTP) required to initiate and sustain voicing, indicating easier, more efficient phonation. For example, in a crossover warm-up study with 26 untrained singers, 10 minutes of straw phonation decreased PTP significantly (reaching a minimum at ~10 minutes), whereas traditional singing warm-ups showed no PTP change. This suggests straw phonation can improve fatigue resistance by making voicing less effortful. Indeed, Kang et al. (2019) concluded that straw warm-ups specifically “result in a reduced PTP,” reflecting improved vocal economy, while conventional exercises tend to improve other technical/acoustic skills.

Straw phonation also appears effective in mitigating vocal fatigue and enhancing recovery. In a controlled trial by Kang et al. (2020), 25 subjects underwent a vocal loading task and then either 10 minutes of straw phonation or just silent rest. Both interventions helped reverse the loading effects (which had temporarily elevated PTP, self-reported effort, and vocal discomfort), but straw phonation led to significantly greater improvements than rest. Specifically, PTP, perceived effort, and laryngeal discomfort all decreased more with the straw, essentially returning toward baseline levels, whereas passive rest led to only partial recovery. Notably, straw phonation also increased mean airflow and lowered the closed quotient (CQ) compared to rest, suggesting a less pressed phonation with more airflow – a physiological adjustment consistent with healthier voice production. The authors concluded that straw phonation provides an aerodynamic reset that attenuates vocal fatigue and optimizes vocal fold vibration mode.

Several randomized clinical trials (RCTs) support straw phonation as a therapeutic tool. Cox et al. (2015) conducted an RCT with 20 patients with dysphonia/vocal fatigue, comparing a straw-based flow-resistant tube (FRT) therapy protocol to the well-established Vocal Function Exercises (VFE) program. After 4 weeks, both groups showed significant improvement in voice-related quality of life (Voice Handicap Index scores) relative to a no-treatment control, with mean VHI reductions indicating clinically meaningful improvement. The straw (FRT) protocol was non-inferior to VFE – i.e. it achieved comparable benefits. Additionally, perceptual voice quality (CAPE-V) measures showed a significant reduction in voice “Roughness” in the straw-therapy group. This suggests that semi-occluded straw exercises can yield perceptible voice improvements (smoother voice quality) on par with traditional resonant voice therapy techniques. In a more recent blinded RCT, Antonetti et al. (2023) assigned 18 patients with functional dysphonia to 4 weeks of a comprehensive SOVTE program (including straw phonation) vs. a VFE program. Both groups achieved significant and similar improvements in patient-reported outcomes: VHI-30 and Vocal Fatigue Index scores decreased (improved) by the end of training and remained improved at a 1-month follow-up. Auditory-perceptual ratings of voice quality also improved (with most patients’ voices rated as normal-mild by post-treatment) and crucially, no adverse effects were noted. These clinical trials underscore that straw phonation exercises are effective in improving voice function and reducing handicap in dysphonic individuals, with outcomes comparable to established therapies (and without added risk).

Straw phonation’s efficacy is further bolstered by bench studies and simulations that directly measure aerodynamic and acoustic changes. A landmark excised-larynx experiment by Conroy et al. (2014) demonstrated that applying a straw-induced semi-occlusion yields objectively easier phonation. In excised canine larynges, inserting a narrow straw (simulated vocal tract extension) led to significant decreases in PTP and phonation threshold flow (PTF) compared to an open-tube (no straw) condition. In other words, less pressure and airflow were needed to phonate when the “straw therapy” configuration was used, confirming the key theoretical benefit of SOVTEs: a raised supraglottal impedance that helps the vocal folds vibrate with less effort. Consistent results have been reported in human studies: for instance, a meta-analysis by Pozzali et al. (2021) found that across treatments, SOVTE-based voice therapies were associated with a significant reduction in subglottal pressure (a proxy for PTP) compared to controls (pooled effect size ≈ –1.47). Although that same meta-analysis noted that improvements in acoustics (jitter, shimmer) and self-reported voice quality did not reach significance over alternative treatments, the overall trend favored SOVTEs for efficiency-related parameters. The authors cautioned that evidence quality was low and that SOVTEs are “not significantly superior” to other active therapies, suggesting that straw exercises are best viewed as an effective component of voice therapy rather than a universally better replacement.

In the context of singers and performers, straw phonation is often used as a warm-up to enhance resonance and ease of phonation. While objective acoustic gains from short-term straw exercises can be subtle, some studies document beneficial changes. For example, one investigation found that after a straw phonation protocol, a choir showed a slight but notable ~1 dB increase in high-frequency spectral energy (0–10 kHz) in their ensemble sound, potentially reflecting eased production of “ring” or resonant high overtones. Other work using electroglottography has observed that SOVTEs like straw phonation can reduce the closed quotient (indicating less pressed phonation) and lower collision forces on the vocal folds. These changes correspond to a freer, more resonant tone production that many voice coaches and singers subjectively report after straw exercises (often described as a “buzzier” or more forward voice placement). Patient/self-reported outcomes echo these findings: individuals frequently note reduced phonatory effort and improved vocal ease immediately after straw phonation trials. In sum, across clinical and performing arts settings, straw phonation has demonstrated efficacy in improving aerodynamic efficiency (lowering PTP/Psub), promoting a balanced glottal closure, and enhancing perceived vocal function.

Clinical takeaway: Across these studies, straw phonation (and SOVTEs broadly) consistently reduces phonation threshold pressure and perceived effort, contributing to more efficient voice production. Patients and performers often experience a clearer, less strained voice after incorporating straw exercises. While improvements in acoustic metrics (e.g. jitter, spectral energy) are sometimes observed, the primary documented benefits are aerodynamic (better vocal economy) and self-perceptual (improved ease, reduced fatigue). In therapy contexts, straw phonation is as effective as well-established voice exercises in improving vocal function, making it a valuable evidence-based technique for voice rehabilitation and training.

2. Influence of Straw Dimensions on Intraoral Pressure and Efficacy

A crucial aspect of straw phonation is the straw’s geometry – principally its inner diameter and length (and to a lesser extent, its material and wall rigidity). These physical parameters determine the level of semi-occlusion, which in turn dictates the magnitude of intraoral pressure and acoustic impedance (inertance) generated during phonation. Researchers have sought to identify optimal straw dimensions that maximize therapeutic benefit (sufficient back-pressure to aid the voice) without causing excessive effort or inability to phonate.

Straw Diameter: The straw’s diameter has a dramatic effect on flow resistance. A smaller diameter creates a tighter occlusion, raising the supraglottal pressure. For instance, an analysis of common SOVT tubes by Andrade et al. (2016) showed that a narrow 3 mm straw can produce ~16 cm H₂O of back pressure, whereas a wider 6 mm straw produces ~4 cm H₂O, and a very large 13 mm resonance tube only ~0.5 cm H₂O. Thus, halving the diameter increases resistance roughly by a factor of 4–10 in that range. Extremely small diameters (≈2–3 mm), such as a typical coffee stirrer straw, create a high resistance load that can significantly challenge the system – in positive ways (strengthening the vocal mechanism) but also with potential downsides if overdone. An excised-larynx experiment by Xue, Jiang, and colleagues (2021) vividly illustrated the limit: when they tested a 3 mm orifice on excised canine larynges, many larynges could not even initiate phonation due to the excessive pressure required. In fact, fewer than half of the samples could produce voicing through the 3 mm straw, effectively defining a practical threshold for that experimental setup. In contrast, a moderate semi-occlusion diameter of 9 mm (and also 15 mm) in the same study allowed easy phonation and yielded significant PTP reductions compared to no-straw control. These results initially seem counter-intuitive – why would a larger tube (9–15 mm) be beneficial when voice trainers often use much smaller straws? It’s important to note the experimental context: the excised model had a fixed “laryngeal insert” of ~6 mm diameter and required a certain range of impedance to optimize vocal fold vibration. A 3 mm extension was too extreme, elevating transglottal pressure so much that oscillation couldn’t start. The 9–15 mm tubes, though wider than typically used in humans, still provided some resistance and inertance above the fully open condition, thus improving efficiency in that model.

In practical terms for singers and patients, consensus and theory suggest using small straws (approximately 2.5–5 mm internal diameter) for straw phonation, as these create a beneficial back-pressure without being impossibly restrictive. Recent computational work by Titze et al. (2025) confirms this range: using aerodynamic equations and human testing, they found that tube diameters of ~2.5–3.0 mm strike an optimal balance, generating intraoral pressures in the range of 10–40 cm H₂O (with typical airflow rates). Pressures in this range are considered effective for training – enough to elicit the “resistance” effect and help the vocal folds vibrate efficiently, but not so high as to cause undue strain. By contrast, a 1–2 mm diameter would produce far higher pressures (beyond 40 cm H₂O) which most voices likely cannot sustain comfortably. On the other end, a large straw of >10 mm diameter provides so little resistance (≪1 cm H₂O) that it offers minimal benefit – akin to just humming with an open mouth. Figure: In summary, there appears to be an optimal diameter window (roughly 2–8 mm) in which straw exercises are most effective, with ~3–5 mm being a commonly recommended sweet spot. Diameters significantly outside this range (extremely narrow or very wide) either overburden the system or fail to produce a meaningful semi-occlusion.

Straw Length: The length of the straw (the extent to which the vocal tract is elongated) also influences the acoustic impedance. A longer tube increases the inertive reactance in the system – essentially providing more “mass-like” air load above the glottis – which can further assist vocal fold vibration by reflecting more energy back to the source. However, length also adds surface area for viscous losses (damping) and can lower the resonance frequencies of the tract. The 2021 excised-larynx study systematically varied straw lengths of 5 cm, 25 cm, 50 cm, and 75 cm. Interestingly, the short (5 cm) and moderate (25 cm) lengths yielded significant PTP reductions compared to no-straw, but the very long extensions (50–75 cm) did not yield further improvements. It appears that beyond a certain length, the benefits plateau or even diminish – likely because extremely long tubes introduce energy losses and may shift resonances out of useful ranges. Titze’s theoretical analysis similarly noted that tube lengths on the order of 10–40 cm are suitable for SOVT exercises. A typical straw used by singers (e.g. a drinking straw) might be ~20 cm; this falls nicely in the recommended range. Length can be adjusted in practice (some singers will partially insert the straw or use extension tubes) to target different vocal tract inertance effects. For example, a resonance tube in water (common in Finnish voice therapy) is often a glass tube ~27–35 cm long and 9–10 mm wide, used to blow bubbles in water – this length is thought to engage strong resonance benefits, especially when one end is submerged (which further increases impedance).

Water Immersion and Other Factors: Submerging the straw’s end in water is a variation known as straw-in-water or “bubble phonation.” Immersion depth adds an additional static pressure equal to the water column height (1 cm of water depth = 1 cm H₂O pressure). Titze et al. (2025) quantified that inserting a straw into 2 cm of water will add ~2 cm H₂O to whatever back-pressure the straw itself generates, effectively shifting the resistance upward. Shallow water depths of 1–5 cm are commonly used; deeper immersions (e.g. 10+ cm) produce very high resistance and are generally not recommended for routine training – they can make phonation noticeably effortful, which might counteract the goal of ease. Besides diameter, length, and water, the straw material (e.g. metal vs. plastic vs. silicone) and shape (straight vs. conical) have less impact on the physics, so long as the internal diameter is consistent. Material mainly affects durability and user comfort. A rigid metal straw and a flexible silicone straw of the same bore will yield equivalent back-pressures. However, some tools incorporate deliberate tapering or vent holes to provide adjustable resistance. Overall, the literature emphasizes adjusting straw dimensions to the individual: if the straw is too narrow or long such that a person cannot phonate without excessive pressure, one should use a slightly larger or shorter straw (reducing resistance). Conversely, if the straw is too wide/easy (very low resistance), the exercise may not produce noticeable benefits – in which case a narrower straw or adding a water load can increase the therapeutic challenge.

Research to date has highlighted the importance of a Goldilocks principle in SOVT straw exercises: the occlusion must be “just right.” A semi-occlusion that is sufficiently resistant will create the desired vocal tract inertance and lead to measurably lower PTP (and collision forces), helping the voice find a more efficient configuration. But an occlusion that is too extreme can raise pressures above a useful range (potentially causing throat tension or preventing voicing altogether). Finding the optimal diameter (typically a few millimeters) and length (decimeters rather than meters) is therefore key for maximizing the benefits of straw phonation. In practice, clinicians and pedagogues often experiment with a set of straws or tubes of varying sizes to match the task: for gentle warm-ups, a slightly wider straw may suffice, whereas for more therapeutic stretching of the voice (e.g. addressing a pressed voice), a smaller straw might be employed briefly, with caution to avoid overexertion. The latest tools, as discussed next, capitalize on these insights by offering adjustable resistance to cover the spectrum of needs.

3. Comparison of SOVT Tools and Straw Devices

In recent years, a variety of specialized semi-occlusion tools have become available, each with different dimensional features. Traditional “tools” included just simple drinking straws (e.g. a regular 5–6 mm straw or a narrow 2–3 mm cocktail straw) and glass resonance tubes. Now, there are purpose-designed devices for singers and speakers that allow more convenient or adjustable SOVT practice. Below is an overview of common SOVT straw-based tools, their dimensions, and capabilities, followed by an analysis of a particular device (the Rayvox Resono system) in light of the optimal ranges identified by research.

Disposable Straws (Coffee Stirrer/Cocktail Straw): A very narrow, short straw often used for stirring coffee, roughly 2–3 mm in inner diameter and ~10–15 cm long. These are inexpensive and have been the go-to for many voice teachers (“the age of the coffee stirrer is over,” quips one manufacturer, due to environmental concerns, but they remain widely used). The resistance of these straws is high – on the order of 15–20 cm H₂O back-pressure for typical phonation flow. They provide a lot of back pressure for the voice and are typically only good for brief phonation exercises, as some individuals find them too restrictive for extended use or singing actual phrases. Because of the very high resistance, coaches often advise using them gently (soft phonation, glides, etc. which might not always be the aim of the task) and transitioning to a slightly larger straw if the throat feels tense. Further, it’s worth noting that straws such as these have only a fixed resistance. That is to say, they can only ever offer a single output, which is not ideal for individual and task differences.

Standard Drinking Straw: A regular plastic straw (~5–6 mm diameter, ~20 cm length). The resistance of the average drinking straw is usually a Medium-low – around 3–5 cm H₂O. These straws offer a moderate semi-occlusion that many beginners find comfortable. However, for trained voices and depending on various individual factors and task differences, a 6 mm straw might be so wide that it doesn’t provide much benefit (as noted, it’s only a few cmH₂O of back-pressure). Thus, some singing pedagogues consider this size more useful for breathing/flow training (or for blowing bubbles when used with water) than for improving vocal fold adduction. Still, a 5 mm straw can be a good starting point for SOVT exercises, especially in patients with very hyper-functional voice (to avoid over-squeezing through a tiny aperture initially).

The “Singing Straw” (metal straw set): This kit comprises three thin stainless steel straws of 3 mm inner diameter are provided. The user can phonate through one, two, or three straws at once (clustered in parallel) to adjust the effective cross-sectional area. Using one straw = 3 mm (high resistance), two straws ≈ equivalent to ~4–5 mm diameter, and three straws combined ≈ ~6 mm effective diameter (lower resistance). In essence, the Singing Straw set covers roughly 3–6 mm configurations (the manufacturer cites effective sizes 3 mm, 6 mm, 9 mm, though the 9 mm presumably refers to using three straws, which actually equates to about 5–5.2 mm single diameter). This idea is not unique to this system - one could indeed achieve a similar effect with several 3mm coffee stirrer straws in parallel, and any other diameter combination, although this method is generally not advised. It’s worth noting that there are some losses when using straws in parallel and the resistance profile isn’t an exact 1:1 to an equivalently sized single diameter straw. It is also to be addressed that this method of interchanging straws is not practically ideal when a singer requires a change mid task, as it can become clunky to change for a different resistance profile, as is the case with any fixed diameter device.

OOVO Straw & Sing Ring: The OOVO straw necklace is a small metal straw (appears ~3–4 mm diameter, a few cm long) worn on a chain for quick access. The idea is that one can do mini SOVT sessions throughout the day using the necklace straw. The OOVO Sing Ring is a ring-shaped device that the user holds to their lips; it contains four small vent holes. By covering 0, 1, 2, or 3 of these holes, the user varies the resistance – roughly corresponding to straw diameters from ~4.5 mm down to 2 mm. It is similar in practice to a wind instrument in its “playing”. Level 0 (no holes covered) is the easiest (largest opening), and level 3 (all holes covered except the main bore) is the most challenging. It essentially combines multiple straw sizes into one compact tool, much like using different numbers of singing straws or different straw diameters sequentially, however the overall resistance profile is limited, and, due to the short nature of the tube itself, there’s no resonance benefits as seen with other implementations.

Better Voice “Vocal Trainer”: This is a 3D-printed SOVT training tool introduced by Better Voice. It features a rectangular aperture about 0.25 × 0.5 inch (≈6 × 13 mm) as the opening. On the top is a small slider mechanism that lets the user narrow or widen the opening continuously, with engraved notches marking a few reference levels. At its widest setting, the opening is akin to a “drinking straw” (although the manufacturer does not state the exact equivalent size), it is generally assumed to be low resistance. At its most closed setting, only a slit remains (comparable to a partially covered coffee stirrer, effectively a 1–2 mm opening) – i.e. very high resistance. The Vocal Trainer covers a continuum of resistances between those extremes. The device has not been tested to measure its resistance profile exactly, the manufacturer instead states that the slider simply “increases” or “decreases” back pressure (the exact cm H₂O values are unknown). One possible drawback of this device could be its squared off design, as irregular internal shape will introduce turbulence (generally skewing resistance higher from baseline), and the flow profile will be less smooth as a result.

Others: There are other similar tools (e.g., Voice Straw kits, silicone resonance tubes like “Lax Vox Tube,” etc.) which operate on the same principles with minor differences in form. Most offer either a set of fixed diameters or some adjustable mechanism, and some solely require the use of water to modify the resistance. All aim to make SOVT exercises more convenient, consistent, and eco-friendly than using random disposable straws.

Rayvox Resono Pro V2 and Optimal Range Mapping: The Rayvox Resono Pro v2.0 is a comprehensive SOVT training system that integrates many of the features discussed above into a single modular tool. It features “over 40 adjustable resistance configurations” through its telescoping body and interchangeable attachments. In essence, the Resono Pro can vary both the effective straw length and aperture. Though in practicality, the device offers a continuum of resistance from its min range of c.1 cm H₂O to it’s recommended max of 30 cm H₂O (but it can operate at exponentially higher resistances as more the user dials in the device). This is described as dynamic variable resistance, where the user can freely change the resistance with ease along the entire spectrum to dial it to suit their needs. In reality, this corresponds to an aperture range spanning from a very wide diameter (low resistance, ~comparable to a 12–13 mm tube or larger) down to a very narrow diameter (high resistance, ~comparable to a 2–3 mm straw). The Resono’s adjustable range covers and exceeds the fixed values of common straws: e.g. it can emulate a 13 mm tube (0.5 cm H₂O), a 6 mm straw (4 cm H₂O), and a 3 mm straw (16 cm H₂O), and can even go beyond to ~30 cm H₂O for maximal resistance. In other words, the Resono encompasses the full spectrum of straw dimensions identified in the literature as effective – from the very gentle load of wide tubes to the intense load of narrow straws.

Notably, the recommended upper end of Resono’s range (~30 cm H₂O) aligns with the practical limit suggested by Titze et al.’s work, which found 40 cm H₂O as an approximate high-end pressure using a 2.5 mm straw at strong flow. Pressures above ~30 cm H₂O generally correspond to extremely small occlusions that most would use only briefly, if at all. The Resono’s ability to “dial in” resistance is akin to having an infinitely adjustable straw: it ensures that a user can find their “sweet spot” of back-pressure for different vocal tasks. For example, a singer might use a moderate resistance (say 5–10 cm H₂O, equivalent to ~5 mm diameter) for general warm-ups, a higher resistance (15–20 cm H₂O, ~3–4 mm diameter) for therapeutic vocal function exercises, and a very low resistance (<5 cm H₂O, wide setting) for cooldown or breathing work – all with one device. The Resono’s telescopic length adjustment further allows changes in inertance by elongating the vocal tract, which could be used to simulate the effects of longer resonance tubes (as in water bubbling) versus shorter straws, without needing separate tubes.

In summary, mapping the Resono Pro v2’s specifications to the literature’s optimal ranges reveals a comprehensive coverage: it can produce the low resistances of large-diameter straws (which are sometimes preferred for less intense training or for beginners), as well as the high resistances of very narrow straws (useful for maximizing glottal inertance and driving strong efficiency gains) – and everything in between. This breadth is in line with expert recommendations that one should “continually adjust and explore resistance to cater to what your voice needs”, rather than a one-size-fits-all approach. The Resono essentially consolidates the function of multiple tools (straw sets, sing rings, resonance tubes, flow-ball via its spinner attachment, etc.) into one system. By covering the full continuum of semi-occlusion parameters, it reflects the evidence that different voices – and even the same voice in different conditions – may require different straw sizes for optimal benefit. Importantly, this discussion is technical rather than promotional: from an objective standpoint, the device’s range appears to span the evidence-based straw phonation targets identified across studies (approximately 3 mm to 10 mm diameter, 10–40 cm length, 0–5 cm water depth). Such versatility can be advantageous in both clinical and pedagogical settings, allowing precise tailoring of the SOVT resistance to individual needs.

Conclusion: Straw phonation, as a specific application of semi-occluded vocal tract exercises, is supported by a growing body of research highlighting its benefits for improving vocal efficiency, reducing phonation effort, and aiding in voice rehabilitation. The effectiveness of this technique is closely tied to the physical properties of the straw or SOVT device used. Optimal outcomes are achieved by using semi-occlusions that generate sufficient back-pressure (typically via small diameters around a few millimeters and tract extensions of a few tens of centimeters) without exceeding the user’s ability to phonate comfortably. Innovations in SOVT tools – from simple metal straw sets to complex adjustable devices – have made it easier to apply these research insights in practice. Singers, actors, and clinicians now have the means to fine-tune straw phonation exercises to target specific vocal goals (e.g. reducing glottal pressedness, increasing ease in high notes, recovering from fatigue) in a controlled, measurable way. As the field moves forward, future research may further quantify the dose-response relationships (e.g. how long and how often to do straw exercises) and the long-term carryover effects on voice use. For now, the consensus in the literature is clear: straw phonation is a valuable, evidence-backed method to achieve a more efficient, economical voice – essentially “training the voice with a gentle resistance” so that open-tract phonation becomes easier and more resonant. By understanding the roles of straw dimensions and utilizing appropriate tools, voice professionals can maximize the therapeutic and training benefits of this simple yet powerful exercise technique.

References:

Antonetti, A.E.S. et al. (2023). “Efficacy of a Semi-Occluded Vocal Tract Exercises-Therapeutic Program in Behavioral Dysphonia: A Randomized and Blinded Clinical Trial.” J Voice 37(2): 215–225. DOI: 10.1016/j.jvoice.2020.12.008

Conroy, E.R. et al. (2014). “Effect of variations to a simulated system of straw phonation therapy on aerodynamic parameters using excised canine larynges.” J Voice 28(1): 1–6. DOI: 10.1016/j.jvoice.2013.08.004

Cox, K. et al. (2015). “A Randomized Controlled Trial of Two Semi-Occluded Vocal Tract Voice Therapy Protocols.” J Speech Lang Hear Res 58(3): 535–549. DOI: 10.1044/2015_JSLHR-S-14-0179

Kang, J. et al. (2019). “Comparing the Exposure-Response Relationships of Physiological and Traditional Vocal Warm-ups on Aerodynamic and Acoustic Parameters in Untrained Singers.” J Voice 33(4): 420–428. DOI: 10.1016/j.jvoice.2017.12.019

Kang, J. et al. (2020). “The Therapeutic Effects of Straw Phonation on Vocal Fatigue.” Laryngoscope 130(11): E674–E679. DOI: 10.1002/lary.28498

Pozzali, I. et al. (2021). “Effectiveness of semi-occluded vocal tract exercises (SOVTEs) in patients with dysphonia: A systematic review and meta-analysis.” J Voice 35(6): 941.e19–941.e30. DOI: 10.1016/j.jvoice.2021.06.009

Titze, I.R. et al. (2025). “Optimizing Diameter, Length, and Water Immersion in Flow Resistant Tube Vocalization.” J Voice 39(2): 403–409. DOI: 10.1016/j.jvoice.2022.09.029

Xue, C. et al. (2021). “Effects of varying lengths and diameters during straw phonation on an excised canine model.” J Voice 35(1): 125.e13–125.e19. DOI: 10.1016/j.jvoice.2019.06.002