Unintelligible speech is often mistakenly attributed to low intelligence or lack of environmental stimulation, and the child may be labelled as “slow”.
It is often thought that the longer the tongue, the better the speech clarity; however, only severe tongue-tie causes poor articulation.
Unintelligible speech may be due to an undetected hearing loss or disorders of language, articulation, voice and resonance.
Early detection and treatment of these problems is needed for optimal speech outcomes.
A resonance problem, in particular, is easily missed and there is a lack of awareness among the public that this can be helped.
Resonance disorders include hypernasal speech, hyponasal speech or a combination of both.
Hypernasality & Hyponasality can result in unintelligible speech
A glass that is half full when hit with a spoon sounds different from that of a glass three quarters full. The resonance is different.
Resonance problems can cause speech unintelligibility by abnormally decreasing or increasing the space within which sound vibrates during speech.
Hyponasal speech sounds like that when one is having a blocked nose due to a cold. Hypernasal speech sounds like that of a person talking through the nose, where an abnormal air leak accompanies non-nasal sounds.
Causes of hypernasality
Hypernasality is commonly associated with children who have a cleft palate.
However, many children and adults with poor oro-facial muscle tone, craniofacial disproportions and short, scarred or undetected hard palate defects may have velopharyngeal insufficiency or incompetence (VPI) that results in hypernasality and reduced speech intelligibility.
This may be due to an inability of the soft palate to close off the nose for non-nasal sounds such as /s/, /z/, /k/, /g/.
Children, for example, with a global developmental delay or subtle neurological weakness often have difficulty closing the velopharynx area completely due to weak muscles in the soft palate.
VPI is also sometimes due to very large tonsils, or may be revealed after adenoid surgery. VPI needs a formal examination to be diagnosed, and speech therapy alone may not be able to correct it.