Ask any speech pathologist this question and you will probably get the same answer–/r/, /s/, and /z/!  These sounds are tough for many children and are often not mastered until 5, 6, or 7 years old. There are many other common errors as well. Children tend to make the same types of errors on each of these sounds.  Here is a list of common speech sound errors:

/k/ and /g/…………These sounds are usually mastered by age 4, but some children substitute /t/ for /k/ and /d/ for /g/.

/th/…………………./f/ and /d/ are commonly substituted for the /th/ sound.

/s/ and /z/ ………./th/  is typically substituted for these sounds. Other children distort /s/ and /z/ by allowing the airflow to come around the sides of the tongue instead of channeling it over the top of the tongue, resulting in a slushy-sounding /s/ or /z/.

/r/…………………../w/ is most commonly substituted for the /r/ sound. Sometimes /r/ is omitted, especially at the ends of words.

/ch/………………../t/ or /sh/ may be substituted for /ch/ or the /ch/ may be distorted.

/j/…………………. /d/ may be substituted for /j/ or the /j/ may be distorted.

/sh/………………../t/ or /s/ may be substituted for /sh/ or the /sh/ may be distorted.

-F and V…………../b/ is often substituted for /v/.  /p/ may be substituted for /f/.

-/l/…………………./w/ and /y/ are the sounds typically substituted for /l/.  /l/ is usually omitted at the end of the word.

The more errors a child has, the more difficult he will be to understand. Likewise, the more severe the child’s errors are, the more his intelligibility will be affected. For example, omitting consonants is a more severe problem than simply distorting the correct sound.