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Cepstral Peak Prominence: Normative Values for Clinical Voice Assessment-A Systematic Review and Meta-analysis
Irena Yanushevskaya1, Ciarán Kenny1
1School of Linguistic, Speech and Communication Sciences, Trinity College Dublin, Dublin, Ireland.
Objective:
This systematic review aimed to synthesize evidence on Cepstral Peak Prominence (CPP) and its smoothed version (CPPS) values reported in the literature for normophonic adults, as well as normative CPP/CPPS values proposed for clinical voice assessment. Specifically, it examined reported effects of sex, age, language, speech task, software, and recording conditions on cepstral measures, and performed meta-analyses of data by sex across different software platforms.
Methods:
A systematic search of PubMed, CINHAL, Embase, and Web of Science was conducted without time restrictions for studies reporting CPP/CPPS in vocally healthy adults. Included were peer-reviewed studies aimed at collecting normative data in adult speakers or experimental studies of any design, which involved normophonic adults without limitations on language, sex, or age. Data were extracted in Covidence and synthesized according to demographics, speech tasks, software, and recording conditions. Methodological quality was assessed using the Downs & Black checklist.
Results:
A total of 122 studies met inclusion criteria and were categorized as: (i) studies collecting normative CPP/CPPS data and/or reporting cutoff CPP/CPPS values for clinical voice assessment (k = 20, 16%), (ii) studies investigating speech of normophonic participants in which CPP/CPPS were reported (k = 53, 43%), and (iii) studies examining vocally healthy controls alongside participants with voice disorders (k = 49, 40%). Substantial methodological heterogeneity limited comparability across studies. Normative CPP/CPPS values were available for sustained [a] for males and females in five languages, and for females only in two languages; proposed clinical cutoffs were reported in 11 studies. Meta-analyses of sustained vowel [a] indicated a significant effect of sex (higher CPP/CPPS in males).
Conclusion:
The evidence base for CPP/CPPS is limited by inconsistent methodological approaches and a lack of standardization. Reliable normative data cannot be meaningfully established without the adoption of standardized recording and analysis protocols, which require a concerted effort and international collaboration.
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