Vocal Intensity and Pitch Effects on Cepstral Peak Prominence and Formant Frequencies in Sustained and Extracted Vowels from a Song of Trained Popular Singers and Non-Singers

Singers are elite voice professionals who frequently develop vocal complaints related to altered voice sound quality, causing serious occupational harm. Although a significant influence of speaking voice intensity, fundamental frequency, and vocal task has been shown for several instrumental acoustic measures when applying clinical assessment guidelines, it is unclear if similar effects are present in Cepstral Peak Prominence (CPP) and Formant frequencies 1-4 (F1-F4) in trained popular singers (TPS) as compared to non-singers (NS). Especially in singers heavily relying on vocal output, reliable acoustic benchmark data is crucial to estimate the extent of vocal deviation in voice diagnostics. Objective: To determine the effects of voice intensity and pitch on CPP and F1-F4 in TPS and NS. Methods: In this cross-sectional study fourteen TPS and sixteen NS, 23 women and 7 men with a mean age of 31 years (SD 10.3), participated. Task samples were a) sustained vowel /a/ in three subjective intensities (SI, soft/comfortable/loud), and three subjective pitches (SP, low/comfortable/high), b) vowels /a:/ (lower-pitch) and /Ɛ/ (higher-pitch) extracted from “Happy Birthday” in Brazilian Portuguese in two SI (comfortable/loud). CPP and F1-F4 were measured with the PRAAT program. Statistical analysis comprised Friedman’s test (with Holm post-hoc analysis) and Wilcoxon Signed Rank Test for three and two repeated measures respectively. Results: Generally, there were no significant differences between groups TPS and NS for all measures (p>0.05). For all participants, SI and SP had a significant effect on CPP and F1-F4 in sustained vowels (p<0.05). CPP and F1-F2 values increased as the SI level rose, while F3-F4 decreased. Furthermore, CPP increased and F1-F4 decreased in lower SP compared to higher SP. In both /a:/ and /Ɛ/ vowels from the song, CPP and F1 were higher in loud as compared to comfortable SI (p<0.05). Conclusion: In both singers and non-singers, there was a similar relationship between CPP and F1-F4 with vocal intensity and pitch over most tasks, indicating a stable relation between vocal tract configuration and vocal sound quality regardless of voice use and training level. A larger study on singers and non-singers should confirm these effects and their application in clinical assessments.