The phonemic system of a language is something that we learn: it is worth pausing at this point for a note on the learning process.
The newborn child is capable of producing sounds, and is likely to make one not unlike cardinal [ s] very shortly after birth. But he speaks no particular language, and the noises that he makes are often not at all clearly related to the categories of the International Phonetic Alphabet: hence it is often not easy to describe them. During the first two months oflife, front vowels (in the general region of [i] and [ E]) and back consonants (resembling [h] and the glottal stop) are reported to predominate. As the child develops, the number of different sounds which he is able to make will gradually increase; at the age of two months the average American infant is said to have a repertoire of about seven distinguishable sounds, and at the age of a year, this number will have risen to about fifteen (Irwin, 1957).