Russian-language material was used to study the dynamics of the acoustic characteristics of vowel-like sounds and vowels in the words of 115 children aged from three months to seven years. Significant decreases in the duration and frequency of the fundamental tone were seen by seven years of age. Our studies provide the first demonstration that vowel stressing, typical of the Russian language, whereby the stressed vowel has a longer duration than unstressed vowels, forms by age seven years. The articulatory model of vowels is not fully formed. The data presented here on the dynamics of the duration and frequency characteristics of vowels on the one hand confirm the general pattern of establishment of the acoustic aspects of speech during ontogeny and, on the other, are new results, as they reflect the child’s assimilation of articulations occurring in Russian speech