Main and Interactive Effects of Age, Gender, and Speech Task on Cepstral Measures in Persian-Speaking Adults With...

This study investigated the main and interactive effects of age, gender, and speech task on Cepstral Peak Prominence (CPP) and Smoothed Cepstral Peak Prominence (CPPs) in healthy Persian-speaking adults.

A sample of 156 vocally healthy Persian speakers (78 males, 78 females) aged 20-50 years was classified into three age decades. Participants performed sustained vowels, sentence reading, conversational speech, and counting. CPP and CPPs were extracted using Praat software. To study main effects, data were analyzed using nonparametric tests. The main and interactive effects were also examined using the nonparametric version of repeated-measures ANOVA, and the ANOVA-Type Statistic (ATS) was reported. To measure effect size, Cliff's Delta was calculated for pairwise comparisons.

The effect of age was statistically significant for CPP and CPPs across nearly all tasks (P < 0.001), with a stronger effect on CPP (ATS=442.78, df=1, P < 0.0001). A significant gender effect was observed for both cepstral measures in most tasks (P < 0.001 and P < 0.05, respectively), with a stronger effect on CPPs (ATS=325.16, df=1.83, P < 0.0001). Also, a highly significant main effect of speech task was observed on CPP and CPPs (P < 0.001), indicating a comparable degree of influence on both measures based on the ATS. All two-way interactions were significant (P < 0.0001), with the age ⁕ speech task interaction emerging as the most robust (CPP: ATS=17,729.43, df=2.14; CPPs: ATS=21,826.13, df=2.94). Crucially, the three-way interaction was statistically significant (P < 0.0001; CPP: ATS= 366.75, df=2.8; CPPs: ATS= 516.61, df=3.63) and Cliff's Delta mostly represented strong (≤ 0.474) or perfect separation (+1 or -1) of two independent variables.

Findings demonstrate that age, gender, and speech tasks operate interdependently to influence vocal quality in healthy Persian-speaking adults. These complex interactions should be considered when interpreting cepstral measures for Persian-speaking adults.