RESUMO
OBJECTIVE: Cepstrum-based voice measures, such as smoothed cepstral peak prominence (CPPS), are influenced by voice sound pressure level (SPL) in vocally healthy adults. Since it is unclear if similar effects hold in voice disordered adults and how these interact with natural fundamental frequency (fo) changes, this study examines voice SPL and fo effects on CPPS in women with vocal hyperfunction and vocally healthy controls. STUDY DESIGN: Retrospective matched case-control study. METHODS: Fifty-eight women with vocal hyperfunction were individually matched with 58 vocally healthy women for occupation and approximate age. The patient group comprised women exhibiting phonotraumatic vocal hyperfunction associated with vocal fold nodules (n = 39) or polyps (n = 5), and nonphonotraumatic vocal hyperfunction associated with primary muscle tension dysphonia (n = 14). All participants sustained the vowel /a/ at soft, comfortable, and loud loudness conditions. Voice SPL, fo, and CPPS (dB) were computed from acoustic voice recordings using Praat. The effects of loudness condition, measured voice SPL, and fo on CPPS were assessed with linear mixed models. Pairwise correlations among voice SPL, fo, and CPPS were assessed using multiple regression analysis. RESULTS: Increasing voice SPL correlated significantly (P < 0.001) with higher CPPS in both patient (r2 = 0.53) and normative groups (r2 = 0.45). fo had statistically significant effects on CPPS (P < 0.001), but with a weak relation for the patient (r2 = 0.02) and control groups (r2 = 0.05). CONCLUSIONS: In women with and without voice disorder, CPPS is highly affected by the individual's voice SPL in vowel phonation. Future studies could investigate how these effects should be controlled for to improve the diagnostic value of acoustic-based cepstral measures.