The easiest sounds for a child to begin with are vowels. Generally, the first consonants that a child produces include the /m/, /n/, /h/, /w/, /p/, /b/, /k/, and /d/. Other sounds, such as /t/, /g/, and /sh/ come later. The most difficult sounds for children to master include /th/ (as in thumb) and /zh/ (as in measure).
Here is some information about articulation of speech sounds:
- Consonant sounds are made by either stopping the flow of air in the oral cavity ("stops", such as the sounds /p/, /b/, /t/, /d/, /k/, and /g/) or by letting the air flow through restricted areas which are formed by changing the position of the lips, tongue, teeth and palate ("fricatives", such as the sounds /f/, /v/, /s/, /z/, and /th/. Some sounds, called affricates, are a combination of a stop and a fricative; examples include /j/ and /ch/.
- Nasal sounds (/n/, /m/, and the /ng/ at the end of the word "sing") are made by forcing air through the nasal cavity.
- Sounds that are produced by vibrating the vocal cords are called "voiced", while sounds that are produced without vibrating the vocal cords are called "unvoiced" or "voiceless". There are many pairs of consonants that are identical in every feature except for the voicing; examples of these pairs include /p/ and /b/, /t/ and /d/, /d/ and /g/, /f/, and /v/, /th/ and /th/, /sh/ and /j/, /s/ and /z/. Try pronouncing each of the pairs while touching your throat; you will be able to feel your vocal cords vibrating for one sound in each pair.
To learn more, check out this blog post.