An interventional study of Condition A and Condition B in Voice Alteration, sponsored by Aveiro University. Completed at 1 site in Portugal. Open to participants aged 18 Years to 55 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-08-19.
Sponsored by Aveiro University · Not applicable, Interventional, and Health services research
This clinical trial aimed to evaluate the effects of the semi-occluded vocal tract exercise Finger Kazoo (FK), with and without oropharyngeal expansion, on the singing voice. Fifteen classically trained singers, screened using the Singing Voice Handicap Index-10 (SVHI-10), participated in a randomized, single-blind, crossover trial with two experimental sessions separated by 48 hours. Participants were randomized via Sealed Envelope to start in Condition A (without oropharyngeal expansion) or Condition B (with oropharyngeal expansion). In each session, standardized recordings were obtained before and after the intervention, including maximum phonation time for the vowels /a/ and /i/, and an operatic aria excerpt. Acoustic analysis (PRAAT) extracted fundamental frequency (F0), jitter, and shimmer. Comparisons between baseline and experimental conditions were performed using paired-samples t-tests, Wilcoxon tests, robust paired t-tests, and Friedman ANOVA with Durbin-Conover, Tukey, Bonferroni, and Holm post hoc corrections, with a 95% confidence interval. Auditory-perceptual evaluation was conducted by 15 blinded experts using the EAI Scale Form, with balanced sample distribution among raters. Self-perceptual evaluation was also performed by participants using the same scale.
131 studies on the registry are indexed under Dysphonia; 34 are open to participants now.
This study's enrollment of 15 is below the median of 39 across 94 interventional studies indexed under Dysphonia.
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Exclusion Criteria:
Without Oropharyngeal Enlargement
Behavioral: Condition A · Behavioral: Condition B
With Oropharyngeal Enlargement
Behavioral: Condition A · Behavioral: Condition B
Condition 0 (Baseline) consists of producing the target vocal tasks without any semi-occlusion or intentional oropharyngeal modification just a pre vocal warmup.
Behavioral: Condition A · Behavioral: Condition B
Condition A consists of performing the Finger Kazoo exercise without inducing oropharyngeal enlargement. In this condition, participants place the index finger vertically in front of the lips to partially occlude the vocal tract, producing a semi-occluded vocal tract configuration, but without modifying tongue position, soft palate height, or pharyngeal wall expansion to increase the oropharyngeal space.
Also known as: Whitout Oropharyngeal Enlargement
Condition B consists of performing the Finger Kazoo exercise with intentional oropharyngeal enlargement. In this condition, participants place the index finger vertically in front of the lips to partially occlude the vocal tract, producing a semi-occluded vocal tract configuration, while simultaneously modifying tongue position, elevating the soft palate, and expanding the pharyngeal walls to increase the oropharyngeal space.
Also known as: With Oropharyngeal Enlargement
Maximum Phonation Time (MPT) variation between conditions without and with oropharyngeal enlargement.
Assessment of the difference in maximum phonation time (in seconds) between two experimental conditions: without oropharyngeal enlargement (Condition A) and with oropharyngeal enlargement (Condition B), during sustained vowel phonation. Data Collection Method: Acoustic recordings obtained using Praat software. The MPT was measured from the onset of phonation to cessation, with participants instructed to sustain the vowel at comfortable pitch and loudness. Analysis Method: Robust Paired Samples T-Test comparing MPT between Condition A and Condition B. Effect sizes calculated using Cohen's d. Results Summary: Mean MPT was significantly higher in Condition B (+7.9 s; p \< .001; d = 0.46), indicating improved phonatory efficiency.
Time frame: Baseline and 48 hours after first session (allowing return to baseline before second session).
Change in Fundamental Frequency Stability (ΔF0) between conditions without and with oropharyngeal enlargement.
Evaluation of the mean variation in fundamental frequency (in Hz) from onset to end of sustained vowel phonation, comparing Condition A and Condition B. Data Collection Method: Praat software pitch analysis, extracting F0 mean values for initial and final 3 seconds of the sustained vowel, then calculating the difference (ΔF0). Analysis Method: Robust Paired Samples T-Test. Results Summary: ΔF0 was significantly lower in Condition B (-7.6 Hz; p \< .001; d = 0.39), indicating greater pitch stability.
Time frame: Baseline and 48 hours after first session (allowing return to baseline before second session).
Change in Jitter between conditions without and with oropharyngeal enlargement.
Percentage variation in jitter between the initial and final segments of sustained vowel phonation. Data Collection Method: Jitter (%) extracted from Praat software and compared between initial and final segments. ΔJitter calculated as final - initial. Analysis Method: Robust Paired Samples T-Test. Results Summary: ΔJitter was significantly reduced in Condition B (-1.3%; p \< .001; d = 0.54), indicating improved micro-frequency stability.
Time frame: Baseline and 48 hours after first session (allowing return to baseline before second session).
Change in Shimmer between conditions without and with oropharyngeal enlargement.
Percentage variation in shimmer between the initial and final segments of sustained vowel phonation. Data Collection Method: Shimmer (%) extracted from Praat software and compared between initial and final segments. ΔShimmer calculated as final - initial. Analysis Method: Robust Paired Samples T-Test. Results Summary: ΔShimmer was significantly reduced in Condition B (-2.1%; p \< .001; d = 0.57), suggesting improved amplitude stability.
Time frame: Baseline and 48 hours after first session (allowing return to baseline before second session).
Plan to share: No — Individual participant data will not be shared due to institutional and legal restrictions on data privacy and protection as per the data protection agreement signed with the University of Aveiro.
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Aveiro University