Resonance Disorders

The scope of this page is resonance disorders in children and adults. Resonance disorders—specifically hypernasality—are also discussed in ASHA’s Practice Portal page on Cleft Lip and Palate as they relate to clefting.

Velopharyngeal dysfunction (VPD) is discussed in this page as it relates to resonance disorders. See Possible Causes of Hypernasality and/or Nasal Emission. For a discussion of articulation disorders that may co-occur with VPD and resonance disorders, see ASHA’s Practice Portal page on Cleft Lip and Palate.

Resonance disorders are not voice disorders, although they are often mislabeled as such. Resonance disorders should not be confused with conditions targeted by resonant voice therapy, an approach that emphasizes phonation with the least effort and impact on the vocal folds. See ASHA’s Practice Portal page on Voice Disorders. Resonance, however, depends upon voicing as discussed below.

See the Velopharyngeal Dysfunction Evidence Map for summaries of available research on this topic as it relates to resonance disorders.

Resonance is the modification of sound from the vocal folds and is determined by the size and shape of the vocal tract, including the pharyngeal, oral, and nasal cavities.

Speech resonance is the result of the transfer of sound produced by the vocal folds (source) through the vocal tract (filter). The vocal tract selectively enhances harmonics of the source (voicing) based on the size and/or shape of the supralaryngeal cavities, the pharynx, and the oral and nasal cavities.

The velopharyngeal valve is integral to achieving appropriate speech resonance; however, other aspects of the vocal tract also contribute to perceived resonance. These include

  • the size and shape of the resonating cavities (pharynx, oral cavity, and nasal cavity);
  • the position of the tongue; and
  • the degree of mouth opening and lip rounding.

Normal resonance is achieved through an appropriate balance of oral and nasal sound energy, based on the intended speech sound. Resonance varies for vowels, voiced oral consonants, and nasal consonants as well as across languages and dialects. Most vowels and vocalic consonants in the English language are predominantly oral, meaning they are produced with the velopharyngeal port closed or nearly closed. Normal resonance has a range of acceptability and is perceived along a continuum (Peterson-Falzone et al., 2010).

Resonance disorders result from too much or too little nasal and/or oral sound energy in the speech signal. They can result from structural or functional (e.g., neurogenic) causes. Speech-language pathologists (SLPs) use differential diagnosis to determine if issues are related to structural and/or functional causes or if the errors are due to mislearning as the different etiologies require different treatment plans. Articulation errors due to mislearning may be misinterpreted as a resonance disorder.

Resonance disorders should not be confused with nasal airflow errors or distortions. Nasal airflow errors are related to articulation when there is an inappropriate escape or release of air through the nasal cavity during production of pressure consonants—consonants that are produced by bursts of streamed air (i.e., /p, b, t, d, k, g, f, v, s, z, ʃ, t͡ʃ, θ, d͡ʒ, ʒ, ð/). Nasal airflow errors may be categorized into one of the following error types:

  • learned errors—maladaptive articulation errors that are produced through the nose and used to replace oral fricatives (e.g., nasal fricatives, pharyngeal fricatives, and phoneme-specific nasal emission)
  • obligatory errors—exist due to structural abnormalities that result in velopharyngeal insufficiency and oral structural deviations (e.g., oronasal fistulas, dental deviations, or malocclusions)
  • compensatory errors—actively learned maladaptive articulations that develop in response to abnormal structures found in VPD

See ASHA’s Practice Portal page on Cleft Lip and Palate for further discussion.

Resonance disorders include the following:

  • Hypernasality—occurs when there is abnormal sound energy in the nasal cavity during production of voiced, oral sounds. Hypernasality is primarily a vowel phenomenon but can occur on other voiced sounds.
  • Hyponasality—occurs when there is reduced nasal resonance or energy associated with nasal sounds, typically due to a blockage or an obstruction in the nasopharynx or nasal cavity or related to a neurological condition.
  • Cul-de-sac resonance—occurs when sound circulates within a cavity (oral, nasal, or pharyngeal) being “trapped” and unable to exit, typically because of an obstruction within the vocal tract. As described below, different types of cul-de-sac resonance are possible depending on the location of the obstruction.
  • Mixed resonance—presence of hypernasal, hyponasal, and/or cul-de-sac resonance in the same speaker depending on the intended speech sound.

Hypernasality should not be confused with nasal air emission. Although some clinicians may use these terms interchangeably, they are distinct symptoms of VPD that typically occur on different speech sounds. Hypernasality is a resonance phenomenon that occurs primarily on vowels, and nasal air emission is an aerodynamic phenomenon that occurs primarily on oral pressure consonants, especially voiceless consonants (Zajac & Vallino, 2016). When VPD is present, both hypernasality and nasal air emission can occur in the same speaker, but they are different entities.

See ASHA’s Practice Portal page on Cleft Lip and Palate for further discussion of nasal air emission, including learned nasal fricatives.

Content Disclaimer: The Practice Portal, ASHA policy documents, and guidelines contain information for use in all settings; however, members must consider all applicable local, state and federal requirements when applying the information in their specific work setting.

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