Consonants are frequently assimilated to neighboring consonants.
A consonant cluster is a group of two, three or even four consonants pronounced together.
This is because if you only have eight consonants and five vowels, as Hawaiian does, you're going to get lots of homophones.
Perhaps the most exotic sounds are clicks-technically "non-pulmonic" consonants that do not use the airstream from the lungs for their articulation.
The consonants in babble mean the baby is practicing, shaping different sounds by learning to maneuver the mouth and tongue, and listening to the results.
They argue that altering the physical production of speech — the movements of the tongue, lips and mouth — makes the pronunciation of vowels and consonants sound foreign.
