Allophonic variation of stressed vowels in 3-year-olds' speech (based on acoustic analysis)

The aim of this research is to study the acoustic characteristics of six vowels in different consonant environment and identify the formation of phonological oppositions of vowels in child speech. The experiment was conducted in two kindergartens located in Blagoveshchensk, Amur Oblast. The subjects were native speakers of Russian aged from three years and one month to three years and three months old. To analyze phonological acquisition the method of minimal pairs was used. 126 words that formed 63 word pairs were chosen for the study. The children were asked to repeat a word after the interviewer but if the word was not pronounced correctly the child was asked to repeat the same word the second time and, if it was possible, the third one. As a result 3,942 words were obtained. The speech samples were recorded on a Samsung YP - VP1AB digital voice recorder. The perceptual study of words with elision and substitution was performed first. The native speakers were given the task to listen to the stimuli and write them down using the letters of the Latin alphabet. It was important to understand if it was a phonological or a phonetic substitution and elision. A phonological change was considered true if 75% of the native speakers perceived it and could not recognize the word. This made it possible to distribute the vowels in accordance with the actual combinatorial position for further acoustic analysis. The acoustic study was performed in the computer program Praat. The results obtained during the present study enabled to conclude that FI and FII values of six vowels in child speech exceed the generally known values of the corresponding vowels in adult speech. However, all vowels have a primarily analogous position relative to each other in the FI-FII plane compared to adult speech. FI and FII values, which are acoustic correlates of differential characteristics of vowel height and backness, evenly go up, demonstrating the immaturity of the child's vocal apparatus. Although FI and FII values are higher than in adult speech, their analogue position relative to each other allow concluding that phonological oppositions of vowels in 3-year-olds' speech are formed. Vowel /a/ has the longest duration, which is better demonstrated after soft consonants. In contrast to adult speech, in child speech /u/ is the second longest vowel. Duration and intensity are not interdependent.

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