There are three types of resonance disorders: hypernasality, hyponasality and cul-de-sac resonance.
Hypernasality occurs when too much sound resonates (vibrates) in the nasal cavity (nose) during speech. This type of resonance makes the patient sound as if she is talking through the nose. When there is severe hypernasality, other abnormal speech characteristic can occur. For example, nasal air emission (air that escapes out of nose) can be heard during production of certain consonants (such as / p /,/ t /, / k /, / s /, / sh / and / ch /). When there is nasal emission, the consonants become weak or omitted. In addition, the child may use abnormal speech sounds (such as a hard “uh” instead of the consonant sound / g /) because of the lack of air pressure in the mouth.
Hypernasality is due to an abnormal opening between the nose and the mouth during speech. This is usually due to a form of velopharyngeal dysfunction (velopharyngeal insufficiency or velopharyngeal incompetence). Common causes include a history of cleft palate or submucous cleft palate. Hypernasality can occur after adenoidectomy in some cases. Some neurological problems can cause poor movement of the velopharyngeal structures, resulting in hypernasality.
Hyponasality occurs when there is not enough sound resonating in the nasal cavity (nose) during speech. This type of resonance makes the patient sound “stopped up.” It can be due to blockage or congestion in the throat or nose. Enlarged tonsils or adenoids are often the cause.
Cul-de-sac resonance occurs when sound resonates in the throat or nose, and is trapped in that area with no outlet. The speech may sound muffled as a result. It may also seem as if the child is “mumbling” or not speaking up. The cause of cul-de-sac resonance can vary, but it is usually due to an area of blockage somewhere in the throat or nose.