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My child's speech sounds are not fully developed. How do I know if their speech is developing normally?

All children have some errors in their speech until they are about 6 or 7 years of age. There is a wide variation in when children develop their sounds. However it is important that most errors have resolved before starting school. Below is information which will give you an idea of whether your child's speech is developing as expected.

As a guide according to the Atkins Fishure Articulation Survey, 75% of children have developed the following sounds by the following ages [1]:

  • By 3;6 years: h, p, m, ng, n, w, b, k, g, d, t, j.
  • By 4;0 years: f, l, sh, ch, and z (as in measure)
  • By 4;6 years: s*, z, dz (as in judge)
  • By 5;0 - 6;0 years: r
  • Around 6;0 - 7;0 years years: th as in this and th as in thing

* NB: Most children have a fronted /s/ (lisp) when they first start to say the /s/ sound. However this usually resolves into a mature /s/ sound by the age of 4;6 years. The fronted /s/, however, is usually present by 3;6 months.

Clusters are where two speech sounds occur together without a vowel in between. For example 'st', 'bl', 'cr'. Although a child may be able to say a sound, their ability to say it in a cluster occurs later. According to McLeod et. al's [2] review of the literature around cluster development, 75% of children tend to develop their clusters by the following ages.

  • 3;6 years: tw, kw
  • 4;0 - 5;0 years: sp, st, sk, pl, bl, kl, gl, fl
  • 5;0 years: pr, br, tr, dr, kr, gr, fr
  • 6;0 years: thr, skw, spl
  • 8 years: spr, str, skr


NB: there is significant variation in the literature regarding when cluster are fully developed. The decision about whether a child may or may not need speech therapy is often made by considering additional factors such as those described below.

Overall speech intelligibility improves as develop. As a general rule

  • By 2 years, a child's speech is about 50% intelligible, and intelligible mainly to family
  • By 3 years, a child's speech is about 75% intelligible
  • By 4 years, anyone should be able to understand a child's speech, even though the child will continue to have some speech sound errors.

Phonological Processes

When children first start to speak, they simplify their speech using predictable patterns, called processes. E.g. a child may leave the final sound off all words (e.g. 'hat' becomes 'ha'). This processes is called final consontant deletion. A process affects a number of sounds rather than a single sound.

Phonological processes are typically gone by these ages (in years ; months)

Table from

Bowen, C. (1998). Developmental phonological disorders. A practical guide for families and teachers. Melbourne: ACER Press.

Grunwell, P. (1997). Natural phonology. In M. Ball & R. Kent (Eds.), The new phonologies: Developments in clinical linguistics. San Deigo, CA: Singular Publishing Group, Inc.

When should I seek assistance?

A delay in developing speech sounds is common in young children. Speech therapy can assist children catch up to their peers. Consider speech therapy for your child if:

  • They are more than 6 months behind in any of the milestones listed above
  • They are self conscious of their speech, are frustrated when not understood an/or are being teased
  • They are in kinder and have multiple speech errors. Ideally children have most of their speech sounds before they enter school so they are ready to learn to read and write.

In some cases, children have a speech sound disorder such as childhood apraxia of speech, or a developmental disability that affects speech development such as dysarthria. In these cases, warning signs might include:

  • weakness or slurring of speech sounds
  • difficulty eating, chewing, swallowing, sucking
  • inconsistent speech errors
  • vowel distortions and errors
  • very few consonants present
  • If you suspect your child may have a speech sound disorder, early intervention is important.

[1] Atkin N.& Fisher J., (1996) Articulation Survey, Royal Children’s Hospital, Melbourne
[2] Smit et al. (1990) cited in McLeod, S., van Doorn, J., and Reed, V. R., (2001) Normal Acquisition of Consonant Clusters. American Journal of Speech-Language Pathology 10, 99-110.