Immediate Effects of the High-Frequency Oral Oscillation Technique with the Acapella® Device in Popular Singers

To analyze the immediate effects of the voiced high-frequency oral oscillation technique (VHFOO) with Acapella® resistance settings (A3 and A5) on voice self-assessment and acoustic measures in female popular singers with and without voice problems.

Experimental, clinical, crossover, two-arm, blind study with a 1-week washout between interventions, including 42 female popular singers - 22 with (PG) and 20 without voice problems (NPG). They performed VHFOO with Acapella® at both settings (in randomized order, blinded to participants) at different times. The study verified acoustic measures and general voice self-assessments (visual analog scale and qualitative self-assessment of effects) before and after the intervention. The data were analyzed with the Wilcoxon (P ≤ 0.05) and Mann-Whitney (P ≤ 0.05) tests. The qualitative analysis used word clouds developed in Wordcloud.

The comparison of pre and postintervention measures in the two settings found an increase in PG's voice self-assessment measures before the intervention (P < 0.001). PG's fundamental frequency (F0), cepstral peak prominence-smoothed for vowels (CPPSv), and number counting (CPPSc) increased, and the other acoustic measures decreased (P < 0.001). NPG's voice self-assessment improved after the intervention (P < 0.001). NPG's F0 and CPPSv increased, and the other acoustic measures decreased with A3. Their F0 (P <;0.002), shimmer, amplitude perturbation quotient, noise-to-harmonic ratio (NHR), and CPPSv decreased (P < 0.001), and jitter, pitch perturbation quotient (PPQ), and CPPSc increased (P < 0.001) with A5. Group comparison before and after intervention regarding settings found no statistically significant differences in PG. In NPG, jitter (P <;0.045) and PPQ (P < 0.012) decreased more with A3 than with A5. NHR decreased more with A5 (P < 0.031).

Among the female singers with and without voice problems who participated in this study, an immediate self-perceived improvement in vocal quality was observed during VHFOO with Acapella®, regardless of resistance setting. Qualitative descriptions of both groups and settings highlight the term "clear," reflecting a clearer voice self-assessment. Setting 3 provided greater vocal stability, reduced vocal fold vibration aperiodicity, and improved vocal quality in both groups. These effects were immediate, and acoustic measures in the group without voice problems using the VHFOO Acapella®/A5 technique differed, requiring caution when using this setting in female singers.