Immediate Effects of Traditional Vocal Warm-up With and Without the Voiced High-Frequency Oscillation Technique Using...

Evaluate the immediate effects of traditional vocal warm-up and its variation with the voiced high-frequency oscillation (VHFO) technique using the Shaker Classic device in vocally healthy female choristers in vocal self-perception, auditory-perceptual analyses (APA) of speaking and singing voice, and acoustic measures.

Single-blinded crossover longitudinal clinical trial with a one-week washout period and a sample of 30 vocally healthy female choristers. The participants completed two vocal warm-up protocols: traditional vocal warm-up (TVW) and its variation, switching from phonation through a narrow straw to the VHFO technique with the Shaker Classic (SVW), one week apart, in a randomized order, each lasting 10 minutes. The outcome variables were vocal self-assessment, assessed through the voice self-perception visual analog scale (V-VAS) and the Brazilian version of the Evaluation of Ability to Sing Easily protocol (EASE-BR), APA, and acoustic measures. Statistical analysis was conducted in R (v4.4.1), in which the pre- and post-intragroup differences in paired samples were analyzed using the Wilcoxon signed-rank test and paired t test, with a 5% significance level. The Fleiss' Kappa was used for the inter-rater analysis of APA (speaking and singing voice). Effect sizes were calculated using Cohen's d for the paired t-test and the coefficient r for the nonparametric Wilcoxon test.

Statistically significant results were found for both groups on the V-VAS and EASE-BR. The TVW group presented statistically substantial associations for f₀, Jitter percent, Period Perturbation Quotient, and Smoothed Cepstral Peak Prominence for the Number Counting. By comparison, the SVW group for f₀, Jitter percent, Period Perturbation Quotient, Shimmer percent, Amplitude Perturbation Quotient, and Smoothed Cepstral Peak Prominence for the vowel /a/. The APA findings revealed that most of the experts identified improvement in speaking and singing voice quality, highlighting statistically significant inter-rater agreement for SVW. The two vocal warm-ups appear to be reliable and effective for vocally healthy female choristers, as they led to improvements in self-assessment of vocal quality and ease of singing with statistical significance.

The results reveal enhancements in the acoustic measures of both groups. The TVW increases both the fundamental frequency level and regularity, along with enhancing cepstral quality. The SVW triggers a broader scope of acoustic measures optimization, including greater stability and a rise in fundamental frequency, as well as improvements in vocal amplitude stability and cepstral quality. Large effects emerged for speaking-voice self-perception, perceived vocal ease in singing, and vibratory-frequency stability, with SVW additionally yielding strong source-signal amplitude-stability gains. The APA data reveal positive immediate effects in each group, with particular emphasis on SVW. This study was registered in the Brazilian Clinical Trials Registry (REBEC) under the number RBR-6DGN572.