Acoustic Analysis of Normal Voice Patterns in Italian Adults by Using Praat

This study was designed to identify the physiological vocal parameters of Italian adult subjects by means of Praat software, differentiated by gender and age. The vocal parameters analyzed were mean pitch, Jitter local %, Jitter local absolute, Jitter rap, Jitter ppq5, Jitter ddp, Shimmer local %, Shimmer local dB, Shimmer apq3, Shimmer apq5, Shimmer apq11, Shimmer dda, Harmonicity Mean autocorrelation, Harmonicity Mean noise-to-harmonics ratio, Harmonicity Mean harmonics-to-noise ratio, and the maximum phonatory time. The volunteers were 123 (58 men and 65 women) and were recruited among students and employees of the University of Eastern Piedmont and of the University Hospital Maggiore della Carità Novara, among family members and researchers' acquaintances. The group of subjects was divided according to gender and age categories, ie, 18-30, 31-40, 41-50, 51-60, and 61-70 years. The voice samples were recorded in the same silent room to minimize the differences in background noise. The measurement was repeated twice on different days to evaluate the reproducibility of the vocal analysis with the Praat software. The comparisons of the vocal values obtained were carried out by stratifying the group of volunteers both by gender and age. After analyzing the variables for skewness, kurtosis, normality distribution through Shapiro-Wilk test, and the equality of variances by Levene test, parametric or nonparametric statistical tests were used when appropriated assuming a confidence level of 0.05. The Bland-Altman test has been used to evaluate the data reproducibility. The analysis of the stratified data for both gender and age showed a good repeatability of all the vocal parameters (except the maximum phonatory time in the age groups 18-30, 31-40, and 41-50 of the women where the Pvalue was less than 0.05). Gender differences were significant in all the vocal parameters, in particular, the variables related to the fundamental frequency and jitter local absolute were statistically significant in all categories. From the analysis of the data of the participants divided by age groups grouped there emerged a substantial difference among individuals belonging to different ages (with the exception of men aged between 18 and 50 years), thus making it impossible to compare and defining an important difference in vocal parameters throughout life.