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What is First sound by child is: and explain in detail?
Most children are able to produce the bilabial sounds (made with the lips) of “b, p, m, w” ﬁrst, since these are sounds visible on the lips. 
They may also produce sounds (linguo-alveolar) such as “d, n, t” early on as well.
These sounds are called linguo-alveolar, since they are produced with the tongue behind the teeth against the alveolar ridge in the mouth.