Speech Sound Disorder: Causes, Signs, Treatment

Speech sound disorder refers to any difficulty with the perception, motor production, or phonological representation of speech sounds and speech segments and can be organic or functional. Organic speech sound disorders are caused by underlying motor/neurological, structural, or sensory/perceptual issues, while functional speech sound disorders are idiopathic and can be related to motor production or linguistic aspects of speech production. Articulation disorders focus on individual speech sound errors, while phonological disorders focus on predictable, rule-based errors affecting multiple sounds. 

This post will cover functional speech sound disorders only and uses the broad term “speech sound disorders” throughout.


Speech sound disorder can affect school-aged children, with prevalence rates ranging from 2.3% to 24.6%. Boys are more likely to have speech sound disorders than girls, with estimates of 1.5:1.0 to 1.8:1.0. Children with speech sound disorders may also have language impairment, and poor speech sound production skills in kindergarten may lead to lower literacy outcomes. Estimates also suggest a greater likelihood of reading disorders in children with a preschool history of speech sound disorders.


Functional speech sound disorders can affect a child’s ability to accurately produce speech sounds and speech segments. Signs and symptoms of these disorders may include:

Omissions and deletions 

Omissions and deletions of sounds can occur in various ways and can affect different sounds or sound sequences in a word. For example, a child may leave off the final sound of a word, such as saying “ca” instead of “cat,” or omitting the initial sound, such as saying “at” instead of “cat.” They may also leave out consonant blends, such as saying “un” for “spun” or “top” for “stop.”

Another common omission is the deletion of unstressed syllables, which can result in a shortened or simplified pronunciation of a word. For example, a child may say “nana” instead of “banana” or “puter” instead of “computer.”

In more severe cases, entire syllables or words may be deleted, making the child’s speech difficult to understand. For instance, a child may say “ack” instead of “backpack” or “een” instead of “green.”


Substitutions refer to the replacement of a sound with another sound. For instance, instead of producing the “s” sound in “sing,” a person with a speech sound disorder may substitute it with a “th” sound and say “thing.” Similarly, they may replace the “r” sound with a “w” sound and say “wabbit” instead of “rabbit.” These substitutions may lead to a loss of phonemic contrast, which means that two or more words that differ in only one sound can be mistaken for each other. For example, if a person substitutes the “s” sound in “sit” with a “th” sound and says “thit” instead, they may confuse “sit” with “thick” or “thick” with “sick.”

Additions or insertions

Additions or insertions are common speech sound errors in children with functional speech sound disorders. They involve adding an extra sound or syllable to a word, which changes its meaning and makes it sound different from the target word.

For instance, a child might say “buhlack” instead of “black” or “plam” instead of “palm.” Another example is adding an extra syllable to a word, such as saying “peaple” instead of “people.”


Distortions refer to when a child alters or changes a sound, resulting in an incorrect sound that is different from both the target sound and other known speech sounds. For example, a child may produce a lateral “s” sound, which is produced with air flowing over the sides of the tongue instead of over the center of the tongue. 

Other examples of distortion include lisping, in which the “s” and “z” sounds are produced with a hissing sound due to air escaping between the tongue and teeth, and nasalization, in which a non-nasal sound is produced with air flowing through the nose, resulting in a nasal-sounding speech. Children may also have difficulty with voice onset time, which refers to the timing between the release of a consonant sound and the onset of vocal cord vibration. For example, a child may produce a voiceless sound as a voice or vice versa.

Syllable-level errors 

Syllable-level errors refer to the deletion or substitution of weak syllables in a word. For example, a child with a speech sound disorder may say “tephone” instead of “telephone” by omitting the weak syllable “le.” Another example might be saying “nana” instead of “banana” by omitting the weak syllable “ba.” 

This type of error can make it difficult for the listener to understand the intended word, especially in longer or more complex words. Children with this type of error may also have difficulty with multi-syllable words in general, as they struggle to correctly produce all of the syllables.

The signs and symptoms of speech sound disorders can occur as independent articulation errors or as phonological rule-based error patterns. In addition, idiosyncratic error patterns can also occur, resulting in homonyms. Accents and dialects can influence the pronunciation of speech sounds and the acquisition of phonotactic rules in subsequently acquired languages. SLPs must distinguish between dialectal differences and communicative disorders, understand dialects’ rules and linguistic features, and be familiar with nondiscriminatory testing and dynamic assessment procedures. It is important to recognize that dialects are rule-governed linguistic systems, and accents are a natural part of spoken language and do not reflect speech or language disorders.


The exact cause of functional speech sound disorders is not currently understood, but several risk factors have been identified through research. These risk factors include:

  • Gender: Males have a higher incidence of speech sound disorders than females (Shriberg et al., 1999).
  • Pre- and perinatal problems: Factors such as maternal stress or infections during pregnancy, complications during delivery, preterm delivery, and low birth weight have been associated with delayed speech sound acquisition and speech sound disorders (Howard, 2002).
  • Family history: Children who have family members with speech and/or language difficulties, such as parents or siblings, are more likely to develop a speech disorder (Campbell et al., 2003)
  • Persistent otitis media with effusion: This condition, often associated with hearing loss, has been linked to impaired speech development (Fox et al., 2002)

It is important to note that these risk factors do not necessarily cause functional speech sound disorders but may increase the likelihood of their occurrence. Further research is needed to fully understand the causes of these disorders.

Role of Speech Therapists

woman teaching child to speak

Speech therapists are responsible for screening, assessing, diagnosing, and treating speech sound disorders. Their professional roles include clinical/educational services, prevention and advocacy, and education, administration, and research. Appropriate roles for speech therapists involve providing prevention information, educating other professionals, screening individuals, conducting comprehensive assessments, diagnosing speech sound disorders, collaborating with other professionals, developing treatment plans, counseling persons with speech sound disorders and their families, serving as an integral member of an interdisciplinary team, consulting and collaborating with professionals, remaining informed of research, and advocating for individuals with speech sound disorders and their families.”


Screening is conducted to identify individuals who require further speech-language assessment and/or referral for other professional services. The comprehensive assessment protocol for speech sound disorders may include evaluation of spoken and written language skills if indicated. The case history includes gathering information about the family’s concerns about the child’s speech, history of middle ear infections, family history of speech and language difficulties, languages used in the home, and the teacher’s perception of the child’s intelligibility and participation in the school setting. Assessment results may lead to a diagnosis of a speech or spoken language disorder, identification of written language problems, referral for multi-tiered systems of support, and referral to other professionals as needed.


The comprehensive speech sound assessment includes oral mechanism examination, hearing screening, speech sound assessment, severity assessment, and intelligibility assessment. The speech sound assessment evaluates speech production, including accurate production, speech sound errors, error patterns, and other factors such as sound combinations and syllable shapes. Severity and intelligibility assessments evaluate the impact of the speech sound disorder on functional communication. Severity assessment can be determined by a rating scale or quantitative measures such as the percentage of consonants correct. Intelligibility is a perceptual judgment of how much of the child’s speech the listener understands, and it can vary depending on various factors, including the number and types of speech sound errors, linguistic factors, and communication environment.

Language Assessment

Language testing is important in a comprehensive speech sound assessment, as speech sound disorders are often associated with language problems. Spoken language assessments usually begin with a screening of expressive and receptive skills, followed by a full battery if necessary. Written language assessments are also necessary, as difficulties in speech processing can impact reading and writing skills. The components of a written language assessment depend on the child’s age and stage of development and include print awareness, alphabet knowledge, sound-symbol correspondence, reading decoding, spelling, reading fluency, and reading comprehension.

Phonological processing Assessment

Phonological processing refers to the use of sounds to process spoken and written language and includes phonological awareness, phonological working memory, and phonological retrieval. Phonological awareness is the conscious analysis and manipulation of the sound structure of language. Phonological working memory involves storing phoneme information in short-term memory for manipulation, while phonological retrieval is the ability to retrieve phonological information from long-term memory. Assessing phonological processing skills is important for speech production and the development of spoken and written language skills, particularly for children with phonological processing difficulties.

Treatment Options

There are different approaches for treating speech sound disorders in children. The choice of approach depends on the age of the child, the type of speech sound errors, and the severity of the disorder. The following approaches are:

  • Contextual Utilization Approaches: These approaches use syllable-based contexts to facilitate the correct production of a particular sound and may be helpful for children who use a sound inconsistently.
  • Phonological Contrast Approaches: These approaches focus on improving phonemic contrasts in a child’s speech by emphasizing sound contrasts necessary to differentiate one word from another. There are four types of contrastive approaches: minimal oppositions, maximal oppositions, treatment of the empty set, and multiple oppositions.
  • Complexity Approach: This approach is based on the view that the use of more complex linguistic stimuli promotes generalization to untreated but related targets. The complexity of targets is determined based on hierarchies of complexity and stimulability, and whole-word production is used.
  • Core Vocabulary Approach: This approach focuses on whole-word production and is used for children with inconsistent speech sound production who may be resistant to more traditional therapy approaches.
  • Cycles Approach: This approach targets phonological pattern errors and is designed for children with highly unintelligible speech who have extensive omissions, some substitutions, and restricted use of consonants. Treatment is scheduled in cycles ranging from a few weeks to several months.


These are four different speech therapy approaches for children with phonological disorders: Distinctive Feature Therapy, Metaphon Therapy, Naturalistic Speech Intelligibility Intervention, and Nonspeech Oral-Motor Therapy.

  • Distinctive Feature Therapy focuses on identifying and targeting specific phonetic features lacking in a child’s speech and uses minimal pairs to compare target sounds with their substitutions. 
  • Metaphon Therapy teaches metaphonological awareness to children with phonological disorders and focuses on sound properties that need to be contrasted. 
  • Nonspeech Oral-Motor Therapy uses oral-motor training prior to or as a supplement to sound instruction to address poor articulation caused by immature or deficient oral-motor control.
  • Naturalistic Speech Intelligibility Intervention addresses targeted sounds in naturalistic activities without imitative prompts or direct motor training.  Watch how is it done in this video (1:34)

Speech sound perception training

Speech sound perception training aims to help children acquire a stable perceptual representation of target phonemes or phonological structures, using procedures such as auditory bombardment and identification tasks that progress from judging speech produced by others to judging one’s own speech.

Treatment techniques and technologies

Treatment techniques and technologies for speech sound disorders include using mirrors for visual feedback, gestural cueing, ultrasound imaging, palatography, amplifying target sounds, and providing spectral and tactile biofeedback. When treating bilingual or multilingual individuals, the clinician must consider the sound systems of each language and whether any observed differences are due to a communication disorder or variations in speech associated with another language the child speaks. The SLP must also determine if specially designed instruction and/or related services are needed to help the student make progress in the general education curriculum when working with children with speech sound disorders in schools.

IDEA Accommodation

To determine if a child is eligible for services under IDEA, the SLP must consider if the child has a speech sound disorder, if there is an adverse effect on educational performance resulting from the disability, and if specially designed instruction and/or related services and supports are needed. If a child is not eligible for services under IDEA, they may still be eligible to receive services under the Rehabilitation Act of 1973, Section 504. Children with persisting speech difficulties vary in etiology, severity, and nature of speech difficulties. Therapy goals should be individualized and functional, considering the child’s communication needs and academic demands.