The following is a brief revision of speech disorders. Please refer to the texts directly for a full explanation.



Speech is the physical production of sounds. 'Speech' is therefore composed of air pressure waves (or 'sound' as it is commonly known) which can be detected by the human ear and audio equipment such as microphones. Speech sounds may be described by a phonetician (or speech and language therapist) in one of two ways. Firstly a PHONETIC description and secondly a PHONOLOGICAL description.

Grunwell summarizes the difference 'In a phonetic analysis one is describing what types of sound the human individual is, or is capable of, producing...In contrast...the aim of a phonological analysis is to provide a description and classification of the sound differences in speech on the basis of their communicative function and organisation in the spoken medium of language' (1987: 2-3).

Speech production

Speech production is highly complex, requiring the mapping of spoken language onto motor movements which result in air being manipulated in the human vocal tract. In addition, the speaker monitors speech production using their hearing system.


'A phonological analysis of a speech sample will describe the organisation of the speech units with reference to their function of 'transmitting the messages' of the language' (Grunwell 1987: 12). A phonological system is therefore a description of how the language maps meaning onto speech. The phoneme is the smallest unit of contrast. For example, in British standard English, /s/ and /t/ are phonemes as to substitute one for the other would bring about a change in meaning:
'sack' / 'tack'; 'bus'/'but'; 'saucer'/'sorter' (note that English orthography does not always relate to the sounds produced).

It is important to note that a phoneme is not a sound. A phoneme is not a physical sound wave produced during speech. Rather, phonemes are concepts. Take for example, the British English phoneme /p/. This can be produced as a bilabial voiceless plosive with aspiration at the start of a word such as 'pea', or as a bilabial voiceless plosive without aspiration in a word such as 'spoon'. The phoneme has two allophones. Lancaster and Pope define an allophone as '...the concrete realisation of a phoneme...' (1990: 5)

Transcription and IPAInformation on IPA and transcription page.

Transcription is the conversion of sounds into symbols. The symbols used are found in the International Phonetic Alphabet. The reason for using this alphabet is that one sound maps to one symbol. Any transcription can therefore be read and understood by another phonetician or speech and language therapist. For example, in English 'sh' is written with two symbols in words such as 'shop', and yet, 'sh' is only one sound. It is therefore written as /ʃ/.

Slant brackets denote a phonological transcription. Square brackets denote a phonetic transcription.
For example /t/ is produced as [th]

Typically, when transcribing a child's speech, target words are written in slant brackets with the actual realisation written in square brackets:
Target 'sock' realisation
/sɒk/ [dɒk]

However, for individual attempts at sounds, square brackets are used for both target and realisation, as the target is merely a phone when produced as a single sound and therefore does not signal meaning. The ability to produce a single sound is articulation and there is often a discrepancy between a child's articulatory ability and the phonological system. That is to say, a child may be able to produce the phone [s] as a single sound but not know how to use this sound in the context of a word to signal meaning. Therefore the same child who said [dɒk] for 'sock' may be able to say [s] on it's own with ease. In fact, this is one of the key tests to differentiate articulation from phonological disorders.

Terminology and common errors

Many students and professionals mistakenly use the word 'phonology' as short-hand for 'phonological disorder', 'speech disorder' and 'speech assessment'. This appears to have originated from an emphasis on phonological theory in the 1980s. Many children present with speech disorders which have both articulatory and phonological involvement. It is for this reason that some researchers have sought to clarify speech disorder diagnosis (see diagnostic categories, below).

  • Speech - the physical sound waves produced
  • Phonology* - the system of meaning signaled by contrasting phonemes for a particular language
  • Phone - a single sound (used when describing articulation of individual sounds rather than a sound in the context of a word)
  • Phoneme - the smallest unit of contrast in a language
  • Delay - developing in the same way as typically developing children, but at a slower rate
  • Disorder - (1) A difficulty, (2) developing in a manner which is not found in the speech of typically developing children
  • Articulation - the physical production of sounds

*Parents may have heard the word 'phonology' to refer to literacy skills. It is important to help them to understand that sounds and letter knowledge are related, but different skills.

Diagnostic Terminology

There is still debate on the nature of speech disorder in children. For this summary I will use the model proposed by Dodd and her team. There are other models of both typical and atypical speech processing and production which a brief literature search will show.

Speech disorder

This generic label covers all other diagnostic labels. It refers to the presence of speech errors which are cause for concern. For example, 'This 6 years old boy was referred to the speech and language therapy service with speech disorder. Following assessment this was confirmed as phonological delay'. The decision as to whether a child has a speech disorder (or not) is not as easy as it may first appear. Children go from cries and babble as babies to adult speech sound systems. At what point should the speech and language therapist be concerned? This depends on the norm for the particular population and also the criteria used to assess the child. The use of norms applicable to the population in which the child is acquiring speech is essential. The danger is that typically developing children are labelled as speech disordered when they are simply at a normal stage of speech development which does not yet include the full adult inventory of sounds.

Dodd proposes a classification of subgroups of functional speech disorders. See Dodd (2005 :9) for a full explanation and discussion of these subgroups.

1. Articulation disorder

The child has a difficulty physically producing the sound in all contexts. That is, as a single sound, when attempting to imitate an adult, in words and in spoken utterances.

2. Phonological delay

Young children may only have a few contrasts in their phonological system. They therefore use one sound for several. For example, children may use [t] for both /t/ and /k/, E.g. 'tar' (the sticky black stuff to mend roads) and 'car' (the things you drive on roads) are produced by the child as [tɑ]. The child does not decide to say 'k' words as 't' word, rather, s/he has not realised that they run the risk of being misunderstood if they do not signal a contrast between these two groups of words.

These patterns are repeatedly found in children who go on to develop normal speech. Children who retain these early patterns are therefore described as having phonological delay, as their system is developing along typical lines, but at a slower rate.

The speech and language therapist can differentiate phonological delay from articulation disorder by asking the child to imitate single sounds. If the child cannot say a sound in isolation then this is an articulation difficulty. If the child can say the sound in isolation, but not in the context of a word then this is a phonological difficulty. Note that a child may have both an articulation difficulty and a phonological difficulty.

3. Consistent phonological disorder

The child's speech contains unusual patterns not found in the speech of younger, typically developing children. These patterns are consistent and do not vary from production to production. As Dodd highlights, the child may have some unusual error patterns and some delayed patterns, but the child's speech would still be considered disordered.

4. Inconsistent phonological disorder

The child's speech shows a high degree of variability (40% or more). The child will therefore often produce the same word in different ways.


Children with developmental dyspraxia can have dyspraxic speech as a part of this condition. Developmental verbal dyspraxia (DVD), specific to speech is more controversial as it is a diagnosis of exclusion, often given to children with severe speech disorder who do not appear to respond to traditional therapy approaches. Inconsistent speech disorder may be confused with dyspraxia. Dyspraxia appears to be extremely rare compared with the other speech diagnoses. See Stackhouse, J. 1992, Developmental verbal dyspraxia I: A review and critique. International Journal of Language & Communication Disorders 27 (1) 19–34.

Why does the diagnostic label matter?

The diagnostic label is based on a theory of speech development and phonological organisation. If the diagnosis is correct and the appropriate therapy administered, the child will have a good opportunity to resolve their difficulties.

Language and vocabulary assessment

It is important that speech assessment does not take place in isolation. It may seem obvious if a child is referred to speech and language therapy with a speech difficulty that this should be the focus of the assessment and treatment. However, failure to assess the child's communication skills profile may lead to mis-diagnosis. For children to have a phonological system, they must have many examples of lexical items (words) and understand their meaning. Remember, phonology is the interface between meaning and speech. If a child has a very small vocabulary, then s/he will not understand the principles of minimal pair based therapy and other word-based techniques. If a child has delayed language development, they may not understand the descriptions of sounds used by the speech and language therapist. Language therapy and advice on building up the child's vocabulary may therefore be a pre-cursor to therapy for speech disorder. Alternatively, therapy focusing on speech and language together may be indicated.


Children with hearing impairments may be unable to perceive sounds and therefore not attempt to say them. Even a mild hearing loss caused by an upper respiratory infection or similar can prevent a child from receiving the full spectrum required to acquire speech. A referral to the Audiology Service for a hearing test is essential before confirming a diagnosis of speech disorder.

Speech Systems Examination (SSE)

A speech systems examination is an inspection of the vocal tract, often accompanied by a motor assessment (examining the movements of articulators such as the lips and tongue) and a brief articulation assessment (saying single sounds). The aim of the SSE is to rule out articulatory difficulties and gross anatomical problems such as cleft palate.


As with much speech and language therapy, although there are many approaches there is little definitive research to say which therapy packages are the most effective.

Resources listed below fall into two categories, a programme or scheme and resources which support sound production and awareness.

Evidence Review by students at the School of Human Communication Sciences at La Trobe University, Melbourne, Australia



Armstrong, S. and Ainley, M., 2008, South Tyneside Assessment of Phonology (STAP 2). (Ponteland: STASS Publications)

Clear Phonology Screen. (Spilsby: Clear Resources)

Dodd, B., Zhu Hua, Crosbie, S., Holm, A., and Ozanne, A., 2002, Diagnostic Evaluation of Articulation and Phonology (London: Harcourt Assessment, Inc.)

Phonological awareness assessment:
Dodd, B., Crosbie, S., McIntosh, B. Teitzel, T. and Ozanne, A. 2000, Preschool and Primary Inventory of Phonological Awareness (The Psychological Corporation)

Advice leaflets

Afasic Glossary 14 - Phonological problems


For articulation disorders and as part of therapy for other speech disorders:
Traditional articulation therapy.

For phonological delay and disorder:
METAPHON, Minimal pair therapy, Maximal pair therapy, phonological therapy.

For inconsistent phonological disorder:

Dodd, B., Crosbie, S. and Holm, A., 2004, Core Vocabulary Therapy. (Perinatal Research Centre). ISBN 0-646-43909-X

For dyspraxia / motor difficulties:
2007, Nuffield Dyspraxia Programme (NDP3), (Nuffield Centre Dyspraxia Programme Ltd).

See Caroline Bowen's 'Children's Speech Sound Disorders Questions and Answers' web page and the reference list for further information.

Therapy picture resources

Black Sheep Press publishes CDs of consonant worksheets, pairs in pictures and phonological awareness sheets.

Passy, J., 2007, Cued Articulation and Cued Vowels. (Ponteland: STASS Publications). Booklets, DVD, Cards and wallcharts on how to 'see a sound'.

Hughes, S. and Ramsay, N., Bigmouth Sound Pack (Ponteland: STASS). A friendly character who shows children how to produce sounds (articulograms).


Dodd, B. (Ed), 2005, Differential diagnosis and treatment of children with speech disorder. Second Edition (Chicester: Whurr)

Grunwell, P., 1987, Clinical Phonology, Second Edition. (London: Chapman & Hall)

Lancaster, G. and Pope, L., 1990, Working with children's phonology. (Oxon: Winslow Press)