Description of maternal speech characteristics addressed to infants of third and sixth months and adults was made. As a result of instrumental analysis of stressed vowel sounds of maternal speech there were found differences in the time-value and frequencies of vowel sounds in the speech addressed to infants and adults. Dynamics of maternal speech parameters was traced. The outspread of vocalic-speech communicative sphere of mother before infant's six months was shown. It is concluded that maternal speech has educative function and acoustic characteristics of maternal speech addressed to infants are universal.