Voice Disorders
Conditions
Keywords
voice, semi-occluded vocal tract, larynx, randomized controlled trial, efficacy study
Brief summary
1. The first objective of this research is to investigate the immediate effects of three semi-occluded vocal tract (SOVT) exercises (straw phonation in air, straw phonation in 2cm water, and straw phonation in 5cm water) on (supra)glottic activity of vocally healthy participants and patients with voice disorders (dysphonia) visualized with laryngovideostroboscopy. Participants will receive a flexible laryngovideostroboscopy, both during normal phonation and during the specific SOVT exercise. These videos will be randomly and blindly evaluated by two experts using the Voice-Vibratory Assessment with Laryngeal Imaging (VALI) rating form (Poburka et al., 2017). Researchers will compare the effects of these SOVT exercises on the (supra)glottic activity with the effects found in a control group producing /u/ phonation, using a randomized controlled trial. 2. The second objective of this research is to investigate the short- and long-term effects of the three SOVT therapy approaches on the (supra)glottic activity, voice quality and self-report of patients with voice disorders (dysphonia). Participants will receive a short-term intensive therapy with the specific SOVT exercise across four weeks. Immediately after the therapy program and at 1 and 3 months follow-up, the voice of the participants will be re-evaluated.
Interventions
BEHAVIORALStraw phonation in air
Phonation (/u/ vowel) through a stirring straw (3 mm diameter, 20cm length) in air
BEHAVIORALstraw phonation in water
Phonation (/u/ vowel) through a stirring straw (3 mm diameter, 20cm length) in 2 cm or 5 cm water
BEHAVIORAL/u/ phonation
/u/ phonation without a straw, control condition
Sponsors
Research Foundation Flanders
University Ghent
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
SINGLE (Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
17 Years to 50 Years
Healthy volunteers
Yes
Inclusion criteria
Patients: Inclusion criteria are aged between 17 and 50 years, and diagnosed with dysphonia by an otorhinolaryngologist and SLP experienced in voice diagnostics.
Exclusion criteria
are previous or current participation in voice therapy, previous phonosurgical interventions, pregnancy, smoking, nasal or ear diseases, and neurological disorders. Vocally healthy participants: Inclusion criteria are aged between 17 and 50 years.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| (Supra)Glottic Activity: Amplitude of Vibration | baseline (before the intervention) | Laryngeal function determined with the Voice-Vibratory Assessment with Laryngeal Imaging (VALI) rating form (Poburka et al., 2017). Amplitude of vibration: magnitude of lateral movement of the vocal folds. This is a visual-perceptual evaluation based on the video samples of the strobovideolaryngoscopy. Raters score the magnitude of lateral movement of the vocal folds based on the graphic of the VALI form ranging from 0 to 10, this number is then multiplied by 10 to obtain a percentage. Lower percentages mean a smaller amplitude of vibration, higher percentages mean a larger amplitude of vibration. |
| Supraglottic Activity: Anteroposterior Compression | baseline (before the intervention) | Laryngeal function determined with the VALI form (Poburka et al, 2017). Anteroposterior supraglottic compression: constriction of the supraglottic structures in the anteroposterior dimension. This is a visual-perceptual evaluation based on the video samples of the strobovideolaryngoscopy. Raters score the supraglottic compression based on the graphic of the VALI form on a scale ranging from 0 to 5 (with the aid of concentric circles). The higher the number, the more supraglottic compression. More supraglottic compression is often seen as a negative outcome, however it might be a beneficial effect seen in SOVT phonation studied here. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Self-report 1: Voice Handicap Index (VHI) | baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up | VHI: A lower index indicates less impact of the voice impairment on the quality of life. The VHI ranges from 0 to 120. |
| Voice Quality Index 1: Dysphonia Severity Index (DSI) | baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up | DSI: A higher index indicates a better voice quality. The index ranges from -5 to +5 for severely dysphonic to normal voices. A more negative index indicates a worse voice quality. Values \> +5 are possible in subjects with excellent vocal capacities. A DSI = +1.6 is the threshold separating normophonic from dysphonic persons. |
| Self-report 3: Vocal Fatigue Index (VFI) | baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up | VFI: A lower index indicates less vocal fatigue. The index ranges from 0 to 76. |
| Self-report 2: Vocal Tract Discomfort Scale (VTDS) | baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up | VTDS: A lower index indicates less discomfort in the vocal tract. The index ranges from 0 to 96. |
| Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up | A lower AVQI indicates a better voice quality. The index ranges from 0 to 10 for normal to severely dysphonic voices. An AVQI of 2.95 is the threshold separating normophonic from dysphonic persons. |
Countries
Belgium
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Straw Phonation in Air Participants will be asked to phonate an /u/ vowel through a stirring straw in air with slightly pursed lips and a soft voice onset.
Straw phonation in air: Phonation (/u/ vowel) through a stirring straw (3 mm diameter, 20cm length) in air | 15 |
| Straw Phonation in 2 cm Water Participants will be asked to phonate an /u/ vowel through a stirring straw, placed 2 cm below the water surface, with slightly pursed lips and a soft voice onset.
straw phonation in water: Phonation (/u/ vowel) through a stirring straw (3 mm diameter, 20cm length) in 2 cm or 5 cm water | 15 |
| Straw Phonation in 5 cm Water Participants will be asked to phonate an /u/ vowel through a stirring straw, placed 5 cm below the water surface, with slightly pursed lips and a soft voice onset.
straw phonation in water: Phonation (/u/ vowel) through a stirring straw (3 mm diameter, 20cm length) in 2 cm or 5 cm water | 14 |
| /u/ Control Condition Participants will be asked to phonate an /u/ vowel with slightly pursed lips and a soft voice onset but without a straw.
/u/ phonation: /u/ phonation without a straw, control condition | 14 |
| Total | 58 |
Baseline characteristics
| Characteristic | Straw Phonation in Air | Straw Phonation in 2 cm Water | Straw Phonation in 5 cm Water | /u/ Control Condition | Total |
|---|---|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical Between 18 and 65 years | 15 Participants | 15 Participants | 14 Participants | 14 Participants | 58 Participants |
| Age, Continuous | 18.7 years | 18.7 years | 18.7 years | 18.7 years | 18.7 years |
| organic vocal fold pathology | 0 Participants | 1 Participants | 1 Participants | 1 Participants | 3 Participants |
| Race and Ethnicity Not Collected | — | — | — | — | 0 Participants |
| Region of Enrollment Belgium | 15 Participants | 15 Participants | 14 Participants | 14 Participants | 58 Participants |
| Sex: Female, Male Female | 15 Participants | 15 Participants | 14 Participants | 14 Participants | 58 Participants |
| Sex: Female, Male Male | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| smoking | 1 Participants | 0 Participants | 0 Participants | 0 Participants | 1 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk |
|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 14 | 0 / 13 | 0 / 13 | 0 / 12 |
| other Total, other adverse events | 0 / 14 | 0 / 13 | 0 / 13 | 0 / 12 |
| serious Total, serious adverse events | 0 / 14 | 0 / 13 | 0 / 13 | 0 / 12 |
Outcome results
Primary
(Supra)Glottic Activity: Amplitude of Vibration
Laryngeal function determined with the Voice-Vibratory Assessment with Laryngeal Imaging (VALI) rating form (Poburka et al., 2017). Amplitude of vibration: magnitude of lateral movement of the vocal folds. This is a visual-perceptual evaluation based on the video samples of the strobovideolaryngoscopy. Raters score the magnitude of lateral movement of the vocal folds based on the graphic of the VALI form ranging from 0 to 10, this number is then multiplied by 10 to obtain a percentage. Lower percentages mean a smaller amplitude of vibration, higher percentages mean a larger amplitude of vibration.
Time frame: baseline (before the intervention)
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | (Supra)Glottic Activity: Amplitude of Vibration | habitual phonation | 36.7 percentage |
| Straw Phonation in Air | (Supra)Glottic Activity: Amplitude of Vibration | SOVT phonation | 37.7 percentage |
| Straw Phonation in 2 cm Water | (Supra)Glottic Activity: Amplitude of Vibration | SOVT phonation | 32.5 percentage |
| Straw Phonation in 2 cm Water | (Supra)Glottic Activity: Amplitude of Vibration | habitual phonation | 39.6 percentage |
| Straw Phonation in 5 cm Water | (Supra)Glottic Activity: Amplitude of Vibration | habitual phonation | 40.0 percentage |
| Straw Phonation in 5 cm Water | (Supra)Glottic Activity: Amplitude of Vibration | SOVT phonation | 28.8 percentage |
| /u/ Control Condition | (Supra)Glottic Activity: Amplitude of Vibration | habitual phonation | 34.6 percentage |
| /u/ Control Condition | (Supra)Glottic Activity: Amplitude of Vibration | SOVT phonation | 37.1 percentage |
Primary
Supraglottic Activity: Anteroposterior Compression
Laryngeal function determined with the VALI form (Poburka et al, 2017). Anteroposterior supraglottic compression: constriction of the supraglottic structures in the anteroposterior dimension. This is a visual-perceptual evaluation based on the video samples of the strobovideolaryngoscopy. Raters score the supraglottic compression based on the graphic of the VALI form on a scale ranging from 0 to 5 (with the aid of concentric circles). The higher the number, the more supraglottic compression. More supraglottic compression is often seen as a negative outcome, however it might be a beneficial effect seen in SOVT phonation studied here.
Time frame: baseline (before the intervention)
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | Supraglottic Activity: Anteroposterior Compression | SOVT phonation | 2.6 units on a scale |
| Straw Phonation in Air | Supraglottic Activity: Anteroposterior Compression | habitual phonation | 1.2 units on a scale |
| Straw Phonation in 2 cm Water | Supraglottic Activity: Anteroposterior Compression | habitual phonation | 1.0 units on a scale |
| Straw Phonation in 2 cm Water | Supraglottic Activity: Anteroposterior Compression | SOVT phonation | 2.3 units on a scale |
| Straw Phonation in 5 cm Water | Supraglottic Activity: Anteroposterior Compression | SOVT phonation | 2.9 units on a scale |
| Straw Phonation in 5 cm Water | Supraglottic Activity: Anteroposterior Compression | habitual phonation | 1.4 units on a scale |
| /u/ Control Condition | Supraglottic Activity: Anteroposterior Compression | SOVT phonation | 1.3 units on a scale |
| /u/ Control Condition | Supraglottic Activity: Anteroposterior Compression | habitual phonation | 1.4 units on a scale |
Secondary
Self-report 1: Voice Handicap Index (VHI)
VHI: A lower index indicates less impact of the voice impairment on the quality of life. The VHI ranges from 0 to 120.
Time frame: baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | Self-report 1: Voice Handicap Index (VHI) | baseline | 9 score on a scale |
| Straw Phonation in Air | Self-report 1: Voice Handicap Index (VHI) | 1 month | 7 score on a scale |
| Straw Phonation in Air | Self-report 1: Voice Handicap Index (VHI) | 1 month follow-up | 9 score on a scale |
| Straw Phonation in Air | Self-report 1: Voice Handicap Index (VHI) | 3 months follow-up | 11 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 1: Voice Handicap Index (VHI) | 1 month | 12 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 1: Voice Handicap Index (VHI) | 1 month follow-up | 11 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 1: Voice Handicap Index (VHI) | 3 months follow-up | 16 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 1: Voice Handicap Index (VHI) | baseline | 12 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 1: Voice Handicap Index (VHI) | 1 month follow-up | 18 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 1: Voice Handicap Index (VHI) | 1 month | 17 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 1: Voice Handicap Index (VHI) | 3 months follow-up | 18 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 1: Voice Handicap Index (VHI) | baseline | 19 score on a scale |
| /u/ Control Condition | Self-report 1: Voice Handicap Index (VHI) | 3 months follow-up | 11 score on a scale |
| /u/ Control Condition | Self-report 1: Voice Handicap Index (VHI) | 1 month | 13 score on a scale |
| /u/ Control Condition | Self-report 1: Voice Handicap Index (VHI) | baseline | 13 score on a scale |
| /u/ Control Condition | Self-report 1: Voice Handicap Index (VHI) | 1 month follow-up | 9 score on a scale |
Secondary
Self-report 2: Vocal Tract Discomfort Scale (VTDS)
VTDS: A lower index indicates less discomfort in the vocal tract. The index ranges from 0 to 96.
Time frame: baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | baseline | 16 score on a scale |
| Straw Phonation in Air | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month | 13 score on a scale |
| Straw Phonation in Air | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month follow-up | 13 score on a scale |
| Straw Phonation in Air | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 3 months follow-up | 13 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month | 19 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month follow-up | 16 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 3 months follow-up | 18 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | baseline | 21 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month follow-up | 19 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month | 21 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 3 months follow-up | 20 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | baseline | 25 score on a scale |
| /u/ Control Condition | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 3 months follow-up | 12 score on a scale |
| /u/ Control Condition | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month | 16 score on a scale |
| /u/ Control Condition | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | baseline | 16 score on a scale |
| /u/ Control Condition | Self-report 2: Vocal Tract Discomfort Scale (VTDS) | 1 month follow-up | 21 score on a scale |
Secondary
Self-report 3: Vocal Fatigue Index (VFI)
VFI: A lower index indicates less vocal fatigue. The index ranges from 0 to 76.
Time frame: baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | Self-report 3: Vocal Fatigue Index (VFI) | baseline | 14 score on a scale |
| Straw Phonation in Air | Self-report 3: Vocal Fatigue Index (VFI) | 1 month | 11 score on a scale |
| Straw Phonation in Air | Self-report 3: Vocal Fatigue Index (VFI) | 1 month follow-up | 11 score on a scale |
| Straw Phonation in Air | Self-report 3: Vocal Fatigue Index (VFI) | 3 months follow-up | 13 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | 1 month | 14 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | 1 month follow-up | 12 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | 3 months follow-up | 17 score on a scale |
| Straw Phonation in 2 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | baseline | 20 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | 1 month follow-up | 17 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | 1 month | 16 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | 3 months follow-up | 19 score on a scale |
| Straw Phonation in 5 cm Water | Self-report 3: Vocal Fatigue Index (VFI) | baseline | 19 score on a scale |
| /u/ Control Condition | Self-report 3: Vocal Fatigue Index (VFI) | 3 months follow-up | 15 score on a scale |
| /u/ Control Condition | Self-report 3: Vocal Fatigue Index (VFI) | 1 month | 15 score on a scale |
| /u/ Control Condition | Self-report 3: Vocal Fatigue Index (VFI) | baseline | 15 score on a scale |
| /u/ Control Condition | Self-report 3: Vocal Fatigue Index (VFI) | 1 month follow-up | 14 score on a scale |
Secondary
Voice Quality Index 1: Dysphonia Severity Index (DSI)
DSI: A higher index indicates a better voice quality. The index ranges from -5 to +5 for severely dysphonic to normal voices. A more negative index indicates a worse voice quality. Values \> +5 are possible in subjects with excellent vocal capacities. A DSI = +1.6 is the threshold separating normophonic from dysphonic persons.
Time frame: baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | Voice Quality Index 1: Dysphonia Severity Index (DSI) | Baseline | 1.0 score on a scale |
| Straw Phonation in Air | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month (immediately after the intervention) | 1.7 score on a scale |
| Straw Phonation in Air | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month follow-up | 2.4 score on a scale |
| Straw Phonation in Air | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 3 months follow-up | 2.3 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month (immediately after the intervention) | 1.2 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month follow-up | 3.0 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 3 months follow-up | 2.5 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | Baseline | 1.3 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month follow-up | 2.3 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month (immediately after the intervention) | 0.9 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 3 months follow-up | 1.9 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 1: Dysphonia Severity Index (DSI) | Baseline | 0.7 score on a scale |
| /u/ Control Condition | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 3 months follow-up | 1.5 score on a scale |
| /u/ Control Condition | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month (immediately after the intervention) | 0.9 score on a scale |
| /u/ Control Condition | Voice Quality Index 1: Dysphonia Severity Index (DSI) | Baseline | 1.0 score on a scale |
| /u/ Control Condition | Voice Quality Index 1: Dysphonia Severity Index (DSI) | 1 month follow-up | 1.3 score on a scale |
Secondary
Voice Quality Index 2: Acoustic Voice Quality Index (AVQI)
A lower AVQI indicates a better voice quality. The index ranges from 0 to 10 for normal to severely dysphonic voices. An AVQI of 2.95 is the threshold separating normophonic from dysphonic persons.
Time frame: baseline (before the intervention), 1 month (immediately after the intervention), 1 month follow-up, 3 months follow-up
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Straw Phonation in Air | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month | 3.86 score on a scale |
| Straw Phonation in Air | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month follow-up | 3.64 score on a scale |
| Straw Phonation in Air | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 3 months follow-up | 3.84 score on a scale |
| Straw Phonation in Air | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | baseline | 3.63 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | baseline | 3.69 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month follow-up | 3.22 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 3 months follow-up | 3.22 score on a scale |
| Straw Phonation in 2 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month | 3.12 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | baseline | 4.12 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month | 3.73 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 3 months follow-up | 3.86 score on a scale |
| Straw Phonation in 5 cm Water | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month follow-up | 3.74 score on a scale |
| /u/ Control Condition | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month follow-up | 3.57 score on a scale |
| /u/ Control Condition | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 3 months follow-up | 3.15 score on a scale |
| /u/ Control Condition | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | 1 month | 3.41 score on a scale |
| /u/ Control Condition | Voice Quality Index 2: Acoustic Voice Quality Index (AVQI) | baseline | 3.70 score on a scale |