Fundamental Frequency and Intensity Effects on Cepstral Measures in Vowels from Connected Speech of Speakers with Voice Disorders

Objective. Cepstral peak prominence (CPP) and smoothed CPP (CPPS) have been described as reliable parameters to detect overall dysphonia in standardized connected speech samples. Recent studies indicate that vocal intensity (sound pressure level, SPL) and fundamental frequency (f(o)) changes may influence cepstral measurement results in healthy speakers. The main aim of the present work was to investigate the effects of prosody related SPL and fo variations on cepstral measures in speech of adults with voice disorders. Study design. Retrospective cross-sectional study. Methods. Recordings of CAPE-V sentences from 27 voice disordered Brazilian Portuguese speakers (19 women, eight men) with a mean age of 45 years (SD = 13) were investigated. Five /a/ vowels were manually extracted from stressed syllables in different positions. Voice f(o) (Hz), SPL (dBA), CPP (dB), and CPPS (dB) were computed using PRAAT. Statistical analysis included Linear Mixed Models with ANCOVA and Bonferroni post hoc tests. Results. Voice SPL as single factor and combined with fo had a highly significant effect (P < 0.001), while f(o) alone had no significant impact on both CPP and CPPS (P >= 0.77). Voice f(o), SPL, CPP, and CPPS of the first vowel were all significantly lower than of the last vowel (P <= 0.03). Conclusion. In vowel samples from connected speech of adults with voice disorders, we observed better CPP and CPPS in higher voice SPL alone and combined with higher fo. Further, the vowel position influenced the present results. A larger clinical study should confirm how prosody related SPL and fo and vowel position effects could be controlled for in connected speech samples.