Spectral characteristics of vowel-like sounds in children of the first year of life and speech development

To study the continuity in speech development, an investigation of vowel-like sounds recorded in the course of longitudinal research of speech formation was carried out in 12 infants beginning with the first month up to 12 months of their life. It was revealed that features ensuring separation of vowel-like sounds are specific by their amplitude relation and frequency location of the most expressed spectral maxima, including the maxima corresponding to the fundamental frequency. As fundamental frequency increased, the vowel-like sounds a], u], i] began to exhibit specific changes of the amplitude ratios of the spectral maxima. It was established that peculiarities of frequency positions of spectral maxima and relations of their amplitudes may be the very features on the bases of which children compare their own vowel-like sounds to the vowels of the adults in sound imitation. These findings and literature data corroborated the opinion of continuity in speech development, beginning with the early preverbal vocalizations.