Q: How can I get a two-year-old to produce bi-labials? He substitutes /d/ for all of them.

It is my observation that the bilabials emerge because the jaw goes up-and-down, not because the lips do anything. A baby begins to babble with bilabials by banging his jaw up-and-down while he is cooing (prolonging his voice).

So when I am trying to get the bilabials, I get the child to produce voice, to prolong it, and then I stimulate the jaw to go up-and-down while he is prolonging this vocalization. The voiced phonemes –– /m/, or /b/, or /w/ –– should emerge, depending upon what he is doing with his velum, and how hard he is banging the lips together.

Once the basic CV emerges, I help him shape the lips more, with a focus on the vowel that follows—Boo-boo-boo, mah-mah-mah, wee-wee-wee, and so forth.

Work all the bilabials together, and follow along with whichever one emerges.

I also teach these little guys to make bi-labial raspberries as a way to wake up those lips. A raspberry made in the same place usually comes in right before the consonants do, and therefore becomes a springboard for the consonants.