Speech Sound Development

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Speech Sound Delays and Disorders

‘Speech sound delay’ or ‘speech sound disorder’ (SSD) are umbrella terms for a number of speech difficulties that children may have. A ‘delay’ is used to describe speech sound difficulties that still follow the normal developmental pattern, but that are immature for a child’s chronological age. A ‘disorder’ describes difficulties that are not considered ‘normal’ at any stage of development. SSDs are further divided into the following categories:

  • Articulation delay (e.g., difficulty saying /r/ after age 7)

  • Articulation disorder (e.g., lateral lisp at any age)

  • Phonological delay (example of a type of error: if a child says ‘tape’ instead of ‘cape’ after age 3 ½ years)

  • Phonological disorder (example of a type of error: if a child says ‘cape’ instead of ‘tape’)

  • Speech sound disorders with an organic or structural cause (e.g., cleft lip/palate)

  • Speech sound patterns associated with significant hearing impairment

  • Motor speech disorders (e.g., developmental dysarthria or childhood apraxia of speech)


A speech-language pathologist is able to evaluate and diagnose SSDs and answer the following questions:

  • What is the nature of the child’s speech difficulties? (e.g., is the child’s lisp a dentalized, interdental, unilateral, bilateral, or palatal lisp?)

  • Is this child’s speech errors normal for his/her age or are they consistent with a delay/disorder? (e.g., if a child cannot yet say ‘r’ is that normal for their age?)

  • What type of speech sound delay/disorder is the child exhibiting? (this is critical to the type of treatment procedure selected)

  • How severe is the delay/disorder?

  • What is the child’s prognosis for improvement with intervention?

  • What therapeutic approach and procedures are appropriate to treat the delay/disorder? (e.g., there are different procedures for articulation, phonological, and motor speech difficulties)


Assessment typically involves:

  • Interview with parents and collection of case history

  • Hearing screening

  • Expressive and receptive language screening

  • Examination of the oral cavity

  • Standardized assessment of speech sound productions (compares an individual child's performance to other children their age)

  • Analysis of samples of natural speech and responses from standardized assessment

  • Probe for response to treatment strategies



Children do not ‘grow out of’ either delays or disorders of speech. Specialized intervention by a speech-language pathologist is required if a child is to improve their speech. The earlier a child is seen, the better. An evaluation will give a child’s parents accurate information specific to their child so that they can make informed decisions.

Typical Speech Sound Development

Normative data charts on speech sound acquisition can sometimes appear to be different. The data is actually generally similar but may appear to be different based on how the data is reported. For example, a chart may indicate the age when a sound starts to emerge (i.e., the child sometimes says the sound accurately) and/or mastered (the child says the sound accurately over 90% of the time). Mastery can also be defined as anywhere between 80-90% correct or 80-90% of a given group of children. Furthermore, sounds are developed at different ages depending on the position in the word (e.g., at the beginning, middle, or end of the word).


These sound development charts are meant to provide guidance for referrals and for parent counselling. Interpretations about whether or not a child’s errors are age-appropriate or developmental should only be made following consultation with a speech-language pathologist, and usually after a comprehensive clinical evaluation using norm-referenced standardized assessments, speech sample analysis, and other valid and reliable clinical tools and procedures. Although these guides are helpful, that they are indeed just that – guides – and that they have limitations and do not replace a clinical evaluation.

Early Speech Development

This handout describes the very early (birth to 2 years) development of speech.

Speech Sound Development: A Guide for Parents 

This chart displays the ages when specific speech sounds are developed.

Phonological Process Chart from Mommy Speech Therapy

When to Refer to Speech-Language Pathology


A speech-language pathology referral is warranted when: 

  1. A parent, education or health professional has concerns about a child’s speech development, particularly if there is a family history, hearing impairment, history of chronic ear infections, or the child is experiencing frustration. If a parent is concerned, an evaluation will either affirm that their child’s speech development is age appropriate (while giving them accurate, individualized information), identify if a child is at risk and should be monitored (while also providing the parents with recommendations to facilitate further speech development), or identify a child that is genuinely in need of intervention. If there is hesitation about whether or not a referral for a full assessment is warranted, a parent can start with a brief screening test.

  2. If, using the guides for speech development, a child does not appear to be reaching milestones.

  3. If a child exhibits any of the following:

    1. lateral lisps – s, z, sh sounds slushy or spitty

    2. palatal lisps – midline of tongue touches roof of mouth too far back

    3. backing – a sound made at the front of the mouth is replaced by a sound made at the back of the mouth (tape >> cape; Dan >> gan)

    4. initial consonant deletion – the first consonant in a sound is omitted (two >> oo)

  4. If, using the guidelines below, a child is less intelligible than would be expected for their age to an unfamiliar person. People familiar with a child (especially their parents) will understand more of what their child says than someone who is relatively unfamiliar with the child.

             19-24 months       25-50% of the child’s speech is understood

             2-3 years              50-75%

             4-5 years              75-90%

             5+ years               90-100%


Lisps affect 'sibilant' sounds as in Sue, zoo, shoe, measure. They also affect other sounds as in choo and jump. Lisps result from incorrect tongue placement that distorts the sound.

The /s/ sound is produced by placing the tip of the tongue very close to the hard palate  behind the upper front teeth. You can feel the location in your mouth - feel for the bumpy ridge of the hard palate behind your teeth. This is called the 'alveolar ridge'. At the same time, the sides of the tongue raise up and touch the hard palate and inner sides of the molars. This tongue position creates a narrow groove or channel along the middle of the tongue. Air then comes up from the lungs and passes through this narrow constriction. The air flow becomes turbulent, creating a 'hissing' quality.

s drawing other orientation.png

Dentalized and Interdental Lisps

Sometimes a lisp is a normal part of speech development. Children may produce a dentalized or interdental lisp (aka frontal lisp) while learning to say 's', 'z', and 'sh'. When a child continues to produce these kinds of lisps after age 4 1/2, however, it may be considered a speech sound delay.

With a dentalized lisp, the tongue tip is too far forward. Instead of being close to the alveolar ridge, it rests behind the upper front teeth.

With an interdental lisp, the tongue tip is even farther forward. It rests between the front teeth. This type of lisp may sound similar to 'th'.

Hear and see a frontal lisp produced by an S-LP here.

interdental b.png
interdental c.png
dentalized b.png
interdental 6y old AC 2.png

Lateral and Palatal Lisps

Other lisps are not part of normal speech development at any age. 'Lateral lisps' (bilateral and unilateral) and a 'palatal lisp' are considered speech sounds disorders and will not fade on their own.

With a lateral lisp, the tongue is incorrectly placed along it's middle and sides. There are different types of lateral lisps. With a unilateral lisp, the tongue moves away from the centre and off to one side of the mouth. Air escapes along the side of the tongue, creating a 'slushy' quality.

Hear and see a lateral lisp produced by an S-LP here.

Hear a unilateral lisp produced by a 4-year old child here:

unilateral lisp 4yo - Unknown Artist
unilateral lisp 4yo.png

With a palatal lisp, the tongue is too far back in the mouth. The mid-section raises up and touches the back of the hard palate or even the front of the soft palate. Air escapes around the sides of the tongue. This is the least common type of lisp.


Hear and see a palatal lisp produced by an S-LP here.

palatal lisp pam.png


All types of lisps are treatable by a speech-language pathologist. Treatment should be started as early as possible.

If your child is exhibiting a lisp and you would like to speak with one of our speech-language pathologists, contact us.



View as pdf.

Motor Speech Disorders

In motor speech disorders, the brain's control of speech is affected. Motor speech disorders include childhood dysarthria, childhood apraxia of speech, and motor speech disorder not otherwise specified.

Childhood Dysarthria

In childhood dysarthria, children have difficulty producing intelligible speech due to neuromuscular difficulties that impact execution of speech movements. These difficulties may be due to increased or decreased muscle tone, reduced drive to muscles, reduced force of muscle contraction, delayed initiation of movement, reduced speed of movement, restricted range of motion, or incoordination between speech systems such as respiration and phonation. These impairments can result in speech differences such as abnormal loudness, pitch, articulatory precision, resonance, voice quality, and breath support. Ultimately, a person's speech sounds distorted and less clear.

Childhood Apraxia of Speech

Childhood apraxia of speech occurs when a child has difficulty planning/programming speech movements at the level of the brain. The child has difficulty sequencing volitional muscle movements to produce speech. Visible groping with the mouth may be observed as the child attempts to produce the required movements. Errors tend to be inconsistent (a word may be produced in error a different way each time they say the word). Their speech becomes difficult to understand.

Learn more here.


Tongue Tie


Tongue tie ('ankloglossia') describes a condition present at birth in which the piece of tissue that runs from the floor of the mouth to the underside of the tongue ('lingual frenulum') is larger than usual. The lingual frenulum typically attaches to the underside of the tongue about halfway down its length. In the case of ankloglossia, this excess tissue means that the attachment extends too far forward, closer to the tongue tip. This can restrict the movement of the tongue (e.g., forward protrusion, elevation to the hard palate). Although there can be difficulties with breastfeeding and clearing food from the mouth, it typically does not affect speech except for in severe cases. Parents should speak with their doctor if they have questions about ankloglossia. A speech-language pathologist can evaluate implications for speech production.

tongue tie.png

Ankloglossia. Image from "Netter's Head and Neck Anatomy for Dentistry" p. 420.