Cul de sac resonance is an increasingly prevalent voice disorder that causes your speech to sound muffled and trapped, often due to structural or functional reasons.
Assimilation occurs when one or more vocal tract cavities become blocked during speech production, leading to reduced nasal escape and hypernasality on voice oral consonants and high vowels.
Oral Resonance
Resonance refers to how our vocal folds (vocal cords) create sound which travels through our mouth, nasal cavity and pharynx in order to filter the sound produced with them. Factors like soft palate shape and position as well as how far open our mouth are are all essential in controlling resonance during speech production.
Speech therapy is vital for treating these types of disorders. If there is an imbalance between how much oral and nasal sound energy you produce when speaking, and the distortion it creates in your voice, others may struggle to understand what you are saying. Speech therapy provides effective solutions.
Your child’s speech therapist will teach them to use the muscles in their mouth and throat to produce more oral resonance while speaking, without changing sounds or pitches of words they say. Furthermore, they’ll demonstrate how to use their nose and pharynx for producing increased nasal resonance during speech.
Your child with hyponasality, cul-de-sac resonance or mixed resonance should aim to use an equal mixture of nasal and oral sound energy when speaking; this will allow them to more easily understand what other people are saying.
Speech therapy for resonance disorders should ideally be provided by a speech-language pathologist with expertise in this area, like CHOP’s SLPs. However, all SLPs must possess some knowledge on how to evaluate and treat such conditions.
Cul-de-sac resonance occurs when sound becomes trapped within one of your child’s mouth or nasal cavities during speech, creating an echo effect that interferes with normal speech production. It may be the result of either a structural issue such as cleft palate or narrow pharynx, or simply temporary issues like enlarged tonsils or nasal congestion causing this condition; should your child’s cul de sac resonance stem from such issues, they may require surgery in order to resolve it.
Nasal Resonance
Resonance disorders occur when sound doesn’t travel correctly through the mouth, nose and throat while speaking; this could be caused by blockage in one area (blockage), lack of movement in another (lack of movement) or inconsistent movement. There are four types of resonance disorders: hypernasality, hyponasality, pharyngeal or cul-de-sac resonance and mixed resonance.
Hypernasal resonance occurs when children use their nasal passages for airflow when speaking or singing, creating too much resonance in the nasal tract and making a voice muffled and hard to understand – especially consonant sounds such as /m/, /n/ and /g/. Children suffering from this condition may also have difficulty breathing through their nose, making taking in food or beverages challenging.
Prior to developing a treatment plan for your child’s speech issue, it’s crucial that a speech evaluation includes an assessment for either hypernasality or hyponasality. You can quickly detect this through listening and assessing connected speech as well as pressure on both nasal and oral sounds; if nasal sounds sound louder than oral ones then that suggests hypernasality; vice versa for hyponasality.
Pharyngeal or “cul-de-sac” resonance disorder is one of the most frequently experienced forms of resonance disturbance and occurs when sound cannot pass from entering to exit the pharynx during speech, making the voice appear muffled or low in volume. This issue often stems from having large tonsils which restrict oropharyngeal opening.
Listen for changes in sound pressure in the mouth and nose when a child says plosives, fricatives and affricates. If these sounds differ between plosives and fricatives, that may indicate a pharyngeal or cul-de-sac issue.
As part of a clinical trial, raters were able to distinguish accurately between various concentrations of sound pressure in nasal and pharyngeal compartments; however, during the first round of ratings the raters became confused in judging cul-de-sac resonance locations and could not reliably discriminate among them; even though all raters were experienced clinicians, their confusion prevented accurate assessment and possibly led to low intrarater reliability for this rating scale.
Pharyngeal Resonance
Cleft palates can lead to various resonance disorders. These range from the ability to produce nasal vowels (i and o), and consonants such as “g,” to reduced voice vibrations passing through the nose; commonly referred to as non-nasal speech sounds may sound tight, breathy or dry in production – characteristics which may or may not exist for every individual producing speech; furthermore articulation errors related to clefting can sometimes accompany such issues which ASHA’s Practice Portal page on Cleft Lip and Palate as related to Clefting for further details.
Mixed resonance is a type of speech disorder, where hyponasal and hypernasal speech coexist within one person – it may occur due to learned misarticulation, nasal airway blockage or movement problems with the soft palate.
Speech therapy techniques aim to achieve harmony among respiration, phonation and resonance. A speech therapist may employ facilitative techniques in order to improve respiration-phonation relationships as well as voice awareness techniques and conversational narrative to enrich vocal quality and quality of timbre. Studies have demonstrated these approaches can reduce symptoms such as straining of low volume speech or muffled sound quality in speech production.
Increased vibration of the uvula during speech is another strategy to improve voice quality, often in combination with velopharyngeal implants or pharyngeal obturators. A study of 30 patients diagnosed with velopharyngeal dysfunction demonstrated that those wearing such devices performed significantly better on various speech evaluation tests compared to those without them.
Ask the person to produce nasal and oral sounds such as “ng” for nasal sounds and “ah” for oral. Gently touch their cheeks during these sounds to detect any movement of their velum; if there is, this indicates hypernasality; a narrow palatal vault, large tonsils or small mouth opening may also contribute. These issues can be corrected with VPD treatment or using a pharyngeal obturator device.
Mixed Resonance
Resonance disorders occur when there is an alteration to how air and sound move through your child’s mouth, nose and throat during speech production. These changes could be due to structural problems, neurogenic causes or occasional articulation errors; there are four different kinds of resonance disorders: hypernasality, hyponasality, cul de sac resonance and mixed resonance.
Hypernasality occurs when there is excess nasal cavity vibration during speech, making the speaker sound like they are speaking through their nose. This condition may result from microstomia, stenotic nares or cleft lip and palate conditions; or be caused by trauma such as whiplash or head impacts that cause neck injuries that cause hypernasality.
Hyponasality occurs when there is a reduced vibration of the nasal cavity during speech, making the sound seem muffled or muted. It may result from having an unusually small mouth opening, blocked pharynx passageways or conditions such as cerebral palsy or traumatic brain injury; bacteria infections may also lead to this effect.
Cul de sac resonance is the most severe type of resonance disorder, occurring when one or more cavities become blocked during speech production. This may be caused by microstomia (small mouth opening), an enlarged tympani bone, stenotic nasal passages or even concussion; other possible sources may include infection such as Strep throat.
Cul de sac resonance can be challenging to diagnose and treat due to multiple contributing factors. Therefore, it’s essential that an experienced speech-language pathologist be involved with treating your child’s symptoms of cul de sac resonance. If you suspect your child might have one, be sure to reach out to your local speech therapy clinic today for more information!
Recent research published in PLOS ONE examined correlations between auditory-perceptual ratings and nasalance scores from nasometer tests among people living with Velopharyngeal Impairment (VIP). While this particular study didn’t discover strong correlations, previous research has demonstrated a positive relationship between these measures.
