Choose a sound that you have heard your child babble frequently. Repeat this sound many times during the day, using it in words, songs, or babbling it yourself. For example. “Ba” is a common early sound. Sing “Bah Bah Black Sheep”, play with a “ball”, sit in a “box”, drink from a “bottle”, etc. Stress the sound as you talk about what you are doing during the day.
Babies under 6 months respond to a high pitched voice. By four months they are noticing the individual sounds you make and repeating them often. They are learning how vowel and consonant sounds are used together. For children over 6 months avoid using “baby talk” but make your voice very rhythmic. After 6 or 7 months your child may make a game of imitating your sounds of speech.