Speech resonance is the result of the transfer of sound produced by the vocal folds through the vocal tract comprised of the pharynx, oral cavity, and nasal cavity (Kummer, 2020a; Peterson-Falzone, Trost-Cardamone, Karnell, & Hardin-Jones, 2017). The vocal tract filters this sound, selectively enhancing harmonics based on the size and/or shape of the vocal tract. Perceived resonance is the result of this filtered tone.
The velopharyngeal (VP) valve plays an integral role in determining speech resonance; however, other aspects of the vocal tract also contribute to the perceived sound. 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. Opening and closing of valves along the vocal tract (e.g., vocal cords, VP valve, and place of articulation) contribute to the size and shape of the vocal tract.
Normal resonance is achieved through an appropriate balance of oral and nasal sound energy, based on the intended speech sound. Resonance varies for vowels, oral consonants, and nasal consonants and also varies across languages and dialects. Most vowels and vocalic consonants in the English language are predominantly oral. Normal resonance has a range of acceptability and is perceived along a continuum (Peterson-Falzone, Hardin-Jones, & Karnell, 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 and occasionally are due to mislearning (e.g., articulation errors that can lead to the perception of a resonance disorder).
Resonance is a function of sound—not airflow. 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 of air through the nasal cavity during production of pressure consonants. Nasal airflow “errors” may be learned (e.g., nasal fricatives, pharyngeal fricatives, and phoneme-specific nasal emission), or they may be obligatory due to a palatal fistula or VPD. See ASHA's Practice Portal Page on Cleft Lip and Palate for further discussion.
Resonance disorders include the following:
Incidence is the number of new cases of a disorder or condition identified in a specific time period. Prevalence is the number of individuals who are living with the disorder or condition in a given time period.
Given the various etiologies and presentations of resonance disorders, overall incidence and prevalence are unknown. Incidence and prevalence estimates for one cause of resonance disorders—VPD—is reported in the literature for the following disorders and conditions.
References below are made to both VPD and velopharyngeal insufficiency; for clarification between terms, see Classification of Velopharyngeal Dysfunction.
Signs and symptoms of resonance disorders can vary depending on a number of factors, including the type of resonance disorder and the severity of the condition causing the disorder. Signs and symptoms associated with each type of resonance disorder are listed below.
There are a number of causes of resonance disorders, including velopharyngeal dysfunction, oronasal fistulas, obstruction in the nasal or pharyngeal cavity, and hearing loss. Specific causes are grouped below by type of resonance disorder.
Speech-language pathologists (SLPs) play a central role in the screening, assessment, diagnosis, and treatment of persons with resonance disorders. The professional roles and activities in speech-language pathology include clinical/educational services (diagnosis, assessment, planning, and treatment), prevention and advocacy, and education, administration, and research. See ASHA's Scope of Practice in Speech-Language Pathology (ASHA, 2016b).
For further information regarding the role of the SLP in the management of persons with cleft lip and palate and associated craniofacial conditions, which includes VPD, the reader is referred to ASHA's Practice Portal page on Cleft Lip and Palate.
In cases of resonance disorders in other (noncleft) populations, appropriate roles for SLPs include, but are not limited to, the following:
As indicated in ASHA's Code of Ethics (ASHA, 2016a), SLPs who serve this population should be specifically educated and appropriately trained to do so.
Assessment and treatment of resonance disorders may require use of appropriate personal protective equipment.
Assessment includes evaluation of oral, nasal, and velopharyngeal function for speech production. The goal is to help determine if an individual would benefit from speech therapy and/or if medical (i.e., surgical or prosthetic) intervention might be warranted. The SLP conducts the assessment alone or as a member of a collaborative team that may include family members or caregivers, and other relevant professionals (e.g., otolaryngologist, surgeon, or prosthodontist).
Differential diagnosis is important during assessment to distinguish velopharyngeal mislearning from other causes of VPD. This will ensure that appropriate treatment follows. If differential diagnosis cannot be determined during initial assessment, referral to an appropriate team (e.g., craniofacial, cleft palate, or VPD team) would be necessary.
Screening for suspected resonance disorders does not provide a diagnosis but, rather, identifies the need for additional and/or more comprehensive assessment. Clinicians must take into account the norms of a particular language spoken and consider linguistic variance and/or influence when screening an individual's speech for signs of resonance disorder.
Screening typically includes the following:
See the Assessment section of ASHA's Practice Portal page on Cleft Lip and Palate for further details related to screening in persons with cleft lip and palate.
See ASHA's Practice Portal pages on Adult Hearing Screening and Childhood Hearing Screening for information about hearing screenings. The outcome of a hearing screening may result in referral for a comprehensive hearing evaluation by an audiologist.
See Comprehensive Assessment for Resonance Disorders: Typical Components. Some components of the Comprehensive Assessment for Resonance Disorders are similar to those for cleft lip and palate. See Comprehensive Assessment for Cleft Lip and Palate: Typical Components.
Consistent with the World Health Organization's (WHO) International Classification of Functioning, Disability and Health (ICF) framework (ASHA, 2016a; WHO, 2001), assessment is conducted to identify and describe
See ASHA's resource on the International Classification of Functioning, Disability, and Health (ICF) for examples of ICF handouts specific to selected disorders.
Clinicians must take into account the norms of a particular language spoken and consider linguistic variance and/or influence when evaluating an individual's speech for signs of resonance disorder.
Individuals who speak a dialect or whose speech is influenced by native languages other than English may speak with a different tone or nasality than native English speakers or speakers of Standard English dialect. These differences (e.g., glottalized tones or nasalized vowels) may affect perceptual judgements of nasality. Consequently, clinicians who are unfamiliar with the linguistic characteristics of the individual's dialect or accent may have difficulty distinguishing a resonance difference from a resonance disorder (Lee, Brown, & Gibbon, 2008).
Regardless of the language spoken, vowels (particularly high vowels) and pressure consonants are most vulnerable to velopharyngeal dysfunction. Clinicians need to consider the presence and frequency of occurrence of these sounds in a particular language, as well as the degree of nasality produced by typical speakers of that language (Cordero, 2008; Willadsen & Henningsson, 2011). The presence of lexical tones (e.g., in tonal languages such as Cantonese) should also be taken into consideration when assessing possible VPD (Cordero, 2008).
Individuals who are deaf or hard of hearing often exhibit resonance disorders characterized by hypernasality or hyponasality, mixed resonance, or cul-de-sac resonance. In most cases, these resonance problems result from poor control of the VP valve due to the lack of auditory feedback. Despite having normal structure and muscle movement, the VP valve may lack rhythm and timing. These individuals may have speech characteristics including abnormal resonance on vowels and nasal consonants (Coelho, Medved, & Brasolotto, 2015). It is important that other anatomical causes of resonance disorder be ruled out, particularly if hearing loss is secondary to a syndrome.
Treatment is indicated for individuals of all ages when their ability to communicate effectively is impaired because of resonance and related articulation disorders.
Consistent with the WHO (2001) framework, treatment is designed to
The goal of treatment is to achieve improved resonance and improved articulation sufficient to allow for functional oral communication.
Treatment procedures and approaches discussed below include
Treatment selection considers the cause of the resonance disorder; the appropriateness of treatment for the individual's chronological and developmental age; and the individual's medical status, physical and sensory abilities, cognitive status, and cultural and linguistic background. Goals for individuals who speak a language other than English take into consideration their linguistic background.
Surgical management is the most common treatment for hypernasal speech due to velopharyngeal insufficiency (structural) and may also be used to treat oronasal fistulas that are symptomatic for speech. Procedures include the following:
Surgical management for hyponasality involves procedures to correct anatomical sources of obstruction. Procedures include
Prosthetic management is used for correcting resonance problems that result in hypernasality when there are no surgical options or when the individual is unable or unwilling to undergo surgery. SLPs may collaborate with prosthodontists to assist in prosthetic design, positioning, or adjustments for optimal speech and swallowing function (Jackson, 2015).
Prosthetic management may include
Pharmacologic management is sometimes indicated when swelling or inflammation in the nasal cavity due to allergies or other irritants is causing or contributing to hyponasality. Medications include antihistamines or steroids delivered via nasal sprays or oral medication.
Behavioral speech therapy cannot correct resonance disorders that are due to structural causes. Therapy is considered if it has been determined through an evaluation that the abnormal resonance and/or nasal emission is due to misarticulation rather than structural causes.
Behavioral speech therapy is appropriate for the following:
Individuals who are deaf or hard of hearing often have difficulty monitoring VP function due to lack of, or decreased, auditory feedback. Hearing aids and cochlear implants serve to assist the individual's auditory feedback mechanisms, thereby improving self-monitoring skills.
Cochlear implants have been shown to increase understanding of speech and help improve the resonance of oral speakers (Sebastian et al., 2015). Improved nasalance scores following cochlear implantation demonstrate the role of auditory feedback in helping monitor velopharyngeal function (Hassan et al., 2012; Nguyen, Allegro, Low, Papsin, & Campisi, 2008).
After obtaining hearing aids or receiving cochlear implantation, individuals often benefit from aural (re)habilitation to improve listening and communication skills. Additional goals may address speech (e.g., improving consonant production) and resonance, taking advantage of improved auditory feedback. For information on aural (re)habilitation in children with cochlear implants, see ASHA's Practice Portal page on Cochlear Implants.
Individuals who are profoundly deaf may benefit from visual and tactile feedback to normalize hypernasal speech (Nguyen et al., 2008).
These feedback techniques may include
Community-based SLPs—including private practitioners and school SLPs—who are involved in the treatment of individuals with resonance disorders are encouraged to collaborate with cleft palate/craniofacial teams and other appropriate professionals, including otolaryngologists and plastic/craniofacial surgeons, to maximize speech outcomes. School and private practice/clinic-based SLPs are encouraged to refer to these teams as needed to ensure quality of care. See also ASHA's resources on collaboration and teaming and interprofessional education/interprofessional practice (IPE/IPP).
In addition to determining the type of speech and language treatment that is optimal for individuals with resonance disorders, SLPs consider other service delivery variables—including format, provider, dosage, timing, and setting—that may affect treatment outcomes.
This list of resources is not exhaustive and the inclusion of any specific resource does not imply endorsement from ASHA.
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Content for ASHA's Practice Portal is developed through a comprehensive process that includes multiple rounds of subject matter expert input and review. ASHA extends its gratitude to the following subject matter experts who were involved in the development of the Resonance Disorders page:
The recommended citation for this Practice Portal page is:
American Speech-Language-Hearing Association. (n.d.). Resonance Disorders. (Practice Portal). Retrieved month, day, year, from www.asha.org/Practice-Portal/Clinical-Topics/Resonance-Disorders/.