The palate comprises two parts, the hard palate (palatum durum) and the soft palate (palatum molle), which is connected to the uvula. The movements of the soft palate and the uvula are made possible by the velopharyngeal sphincter. During speech or swallowing, the soft palate lifts against the back throat wall to close the nasal cavity. When producing nasal consonants (such as "m", "n", and "ng"), the soft palate remains relaxed, thereby enabling the air to go through the nose.
The Eustachian tube, which opens near the velopharyngeal sphincter, connects the middle ear and nasal pharynx. Normally, the tube ensures aeration and drainage (of secretions) of the middle ear. Narrow and closed at rest, it opens during swallowing and yawning, controlled by the tensor veli palatini and the levator veli palatini (muscles of the soft palate). Children with a cleft palate have difficulties controlling these muscles and thus are unable to open the Eustachian tube. Secretions accumulate in the middle ear when the tube remains dysfunctional over a long period of time, which cause hearing loss and middle ear infections. Ultimately, hearing loss can lead to impaired speech and language development.
The general term for disorders of the velopharyngeal valve is velopharyngeal dysfunction (VPD). It includes three subterms: velopharyngeal insufficiency, velopharyngeal inadequacy, and velopharyngeal mislearning.
There are several methods for diagnosing hypernasality.
Hypernasality is generally segmented into so-called 'resonance' effects in vowels and some voiced or sonorant consonants and the effects of excess nasal airflow during those consonants requiring a buildup of oral air pressure, such as stop consonants (as /p/) or sibilants (as /s/). The latter nasal airflow problem is termed 'nasal emission', and acts to prevent the buildup of air pressure and thus prevent the normal production of the consonant. In testing for resonance effects without the aid of technology, speech pathologists are asked to rate the speech by listening to a recorded sentence or paragraph, though there is much variability in such subjective ratings, for at least two reasons. First, the acoustic effect of a given velopharyngeal opening varies greatly depending on the degree of occlusion of the nasal passageways. (This is the reason why a stuffy nose from an allergy or cold will sound more nasal than when the nose is clear.) Secondly, for many persons with hypernasal speech, especially hearing impaired, there are also mispronunciations of the articulation of the vowels. It is extremely difficult to separate the acoustic effects of hypernasality from the acoustic effects of mispronounced vowels (examples). Of course, in speech training of the hearing impaired, there is little possibility of making nasality judgments aurally, and holding a finger to the side of the nose, to feel voice frequency vibration, is sometimes recommended.