Developmental Changes in Acoustic Characteristics of Speech of Estonian Adolescents

Abstract

The paper introduces the Estonian Adolescent Speech Corpus and explores the developmental changes in speech production based on acoustic characteristics of fundamental frequency (F0), formant frequencies, and speech tempo as a function of age and gender. Age- and gender-related anatomic changes in adolescence have implications for speech acoustics: a sudden drop of F0 at puberty in boys, and an almost gradual decrease of the acoustic vowels space. In parallel with anatomic changes, the development of the speech motor system is manifested as the increase of speaking rate. The analysis of fundamental frequency (F0) shows that in both male and female speakers, the F0 decreases gradually at the age from 9 to 12 years, then in males F0 drops ca by 100 Hz at the age of 12–15 due to puberty voice change, and becomes stable at the age of 15–18; in female speakers, a gradual decrease of F0 continues till the age 18. The formant frequencies of vowels decrease gradually from 10 to 15 years in both genders and the quality of vowels stabilizes at the age of 15–18 years, gender-specific differences emerge at the age of 12–13. Speech rate increases from 4 syllables per second in 9–10 years to 5.1 syllables per second in 14 years and becomes stable between the ages of 15 and 18, gender differences are not significant. The results of the current study can be considered as reference data that are typical for Estonian-speaking individuals aged 9–18 years with normal language development.