when do babies become able to distinguish different speech sounds
Phonological development Infants as young as 1 month perceive some speech sounds as speech categories (they display categorical perception of speech). For example, the sounds /b/ and /p/ differ in the amount of breathiness that follows the opening of the lips. Using a computer generated continuum in breathiness between /b/ and /p/, Eimas et al. (1971) showed that English-learning infants paid more attention to differences near the boundary between /b/ and /p/ than to equal-sized differences within the /b/-category or within the /p/-category.[4] Their measure, monitoring infant sucking-rate, became a major experimental method for studying infant speech perception.
Articulatory phonetics Consonants are produced with some form of restriction or closing in the vocal tract that hinders the airflow from the lungs. Consonants are classified according to where in the vocal tract the airflow has been restricted. This is also known as the place of articulation.