What are Speech Sound Disorders and Types of SSD

Speech Sound Disorders include different types of speech disorders in which a client does not produce speech sounds correctly or even omit them. As a result of this, intelligibility becomes compromised. 

Speech Sound Disorders, Articulation Disorder, Phonological Disorder

It is important to note that, the term SSD is a blanket term. We can classify it in the two following categories.

• Functional
• Organic

1. Functional Speech Sound Disorder

These include those impediments which don't have known cause. Here is the overview to understand the concept.

Children start expressing after birth through cry. It takes years to learn all the phonemes including vowels and constants. They learn to speak easier sounds like vowels and bilabial consonants at an early age. During this process of learning, some sounds are easier for them and some are difficult.

In some cases, children show difficulty to articulate particular phonemes beyond the expected age. Such cases might fall under the category of SSD.

I recommend you to take a look at the Speech Sound Development Chart which shows age norms.

This category has two types of impairments. You can also get an idea about symptoms of speech sound disorders. 

Articulation Disorder

In this case, a client was not able to learn the correct way to use articulators* for pronouncing a sound. For instance, a child is saying tup instead of a cup.

*Articulators are the structures that we use to speak. These are as follows.

• Tongue
• Palate
• Velum
• Jaws
• Lips
• Glottis

The mispronunciations, in this case, is called Articulation Errors. It has four following types (Types of articulation disorders).

• Omission: Omitting a sound from a word (Dink instead of Drink).
• Addition: Addition of sound in a word (Blue for Blueh). 
• Distortion: Production of a sound with imprecise manner (Nasalized /n/ in Pencil)
• Substitution: Replacing a sound with another (Tap for cap).

It is one of the common speech impairments. It is also known as Phonetic Disorder. 

Assessment includes various methods including Single word test and Connected Speech. Later one includes picture description, conversation, story, etc.

A Speech Pathologist will evaluate the following aspects.

• Consistency of errors. 
• Accuracy at different positions of a word and levels of a syllable, consonant clusters, and vowel combinations.
• Types of Errors
• Severity
• Stimulability (Imitation of sound) 
• Intelligibility

Phonological Disorder

In this case, a client fails to differentiate the contrasts between the speech sounds. As we know, children learn phonemes with time. During the learning phase, they try to simplify their pronunciation according to their age. As a result of this, we can observe patterns of errors in their conversation.

They are also called Phonemic Disorder.

These patterns are Phonological Processes. It is normal for a developing child. These errors can persist beyond the age at which others, usually overcome them. In this case, a child may have this problem.

People Also Search For Development Milestones For Language

Phonological Processes

Substitution	Definition	Examples	Approx. Age of Elimination (in Years)
Affrication	Substitution of non-affricates with affricates	Joor for Door	3
Stopping	Substitution of fricatives or affricates with stop consonants	Pun for Fun Dune for June Den for Then	A) /f/ /s/ by 3 B) /v/ /z/ by 3.5 C) /tʃ/ /ʃ/ /dʒ/ by 4.5 D) /θ/ by 5
Fronting	Substitution of velar or palatal sounds with alveolar.	Tap for Cap	3.5
Deaffrication	Substitution of affricates with non-affricates.	Ships for Chips	4
Deplatization	Non-palatal sound in place of palatals.	Fit for Fish	5
Alveolarization	Alveolar sounds instead of non-alveolars.	Tues for Shoes	5
Gliding	/r/ and /l/ becomes /w/ and /dʒ/ or /w/ respectively	Wocket for Rocket	6
Labialization	Labial sounds instead of non-labials.	Pen for Ten	6
Backing	Substitution of alveolar sounds with velars.	Gog for Dog	---
Vowelization	Replacement of /l/ or /ɚ/ with vowels.	Appo for Apple	---

Assimilation
Denasalization	Nasal consonants become non-nasal consonants.	Bouce for Mouse	2.5
Reduplication	Repetition of a syllable (complete or incomplete).	Baba for Bear	3
Final Consonant Devoicing	Voiceless consonants replace voiced consonants at the final position of a word.	Pick for Pig	3
Assimilation	Consonant sounds like another sound in a word.	Bub for Bus	3
Prevocalic Voicing	Voiced consonant instead of voiceless consonant at the initial position of a word.	Domb for Comb	6
Coalescence	Substitution of a sound with phoneme having similar features.	Foon for Spoon	---

Syllable Structure
Final Consonant Deletion	Ommission of consonant at the final position in a word.	Boar for Board	3
Weak Syllable Deletion	Deletion of a weak syllable in a word.	Nana for Banana	4
Cluster Reduction	Reduction of a consonant cluster into a single consonant.	Pane for Plane	5
Epenthesis	Addition of a sound between two consonants.	Blue for Blue	8
Initial Consonant Deletion	Ommission of consonant at the beginning of a word.	Ion for Lion	---

Assessment includes the following areas. 

• Phonological Awareness (Awareness of sound and its manipulation at different levels like syllable, word, etc.)
• Phonological Retrieval (To retrieve information from memory through different tasks like the naming of objects)
• Phonological Working Memory (Relying on short term memory. SLP can ask the client to repeat a given word)

Residual Errors

Some speech errors may persist during adulthood after successful treatment. These may be resolved on their own. In this case, such errors are called Residual Errors. 

Mixed

In this case, clients face both phonetic and phonemic disorders together. 

Read More: Relationship between SSD and Literacy

2. Organic Speech Sound Disorders

This category includes those disorders which result from various medical conditions. These are as follows. 

• Neurological problems can cause Dysarthria or Apraxia of speech.
• Abnormality in Structural development like cleft palate or velopharyngeal insufficiency.
• Sensory Deficits like hearing impairment. 

Speech Sound Disorder DSM 5 criteria

Causes of Speech Sound Disorder

There is no known cause for functional SSD. It is assumed that the child failed to learn the correct method of pronunciation. Or a child could not understand the rules of speech sounds.

While organic disorders may have different causes behind them. A few of the examples are as follows. 

• Brain Injury 
• Genetic Disorders
• Developmental Issues

Read More: Childhood Apraxia of Speech

Conclusion

SSD can affect social interaction, academic or occupational performances. Articulation disorder and Phonological Disorder are not rare problems. You can take look at the age norms for a guide (not for assessment). 

It is necessary to consult an SLP for "Speech Sound Disorder" treatment. Otherwise, the client may face difficulties in verbal communication of daily life.