At this age your baby's repertoire of sounds may include squeals, bubbling noises, operatic octave changes and babbling. About half of all six month olds babble, repeating one syllable, such as "ba" or "ma", over and over again. Try listening to your baby and see how many sounds you can hear. Does he babble quickly or slowly? Softly or loudly? Are the sounds high or low? You can encourage his budding language skills by babbling along with him and making a game of it. He reacts to different tones in your voice now, too. You may notice him going quiet if you talk to him crossly or laughing when you play games with him.