Nasal emission is a speech characteristic where air escapes audibly through the nose during the production of certain sounds. This escape is typically heard as a hiss, snort, or bubbling sound, indicating a failure to separate the nasal cavity from the oral cavity. The problem occurs when a speaker attempts to create the high air pressure in the mouth necessary for clear articulation of sounds like ‘p,’ ‘s,’ ‘t,’ ‘k,’ and ‘ch’. When the seal is incomplete, the built-up air pressure leaks out, distorting the intended sound and often making consonants weak or omitted.
The Role of the Velopharyngeal Valve
The separation between the oral and nasal cavities is managed by the velopharyngeal valve, a muscular mechanism composed of the soft palate (velum) and the pharyngeal walls. For most speech sounds, this valve must achieve a tight seal, known as velopharyngeal closure. The soft palate moves upward and backward, while the side and back walls of the throat move inward, effectively closing the passageway to the nose.
This closure is important for producing high-pressure consonants like plosives, fricatives, and affricates. When the valve closes completely, air pressure is directed solely into the mouth, allowing the speaker to form sounds like /s/ or /p/. If the seal is incomplete, the resulting leak causes air to escape through the nose, creating nasal emission.
A smaller opening creates greater resistance, often resulting in a loud, distracting sound described as a nasal rustle. Conversely, a large gap allows air to escape quietly, though the lack of oral air pressure still causes consonants to sound weak or distorted.
Distinguishing Nasal Emission From Hypernasality
Nasal emission and hypernasality are often confused because they can occur together, but they represent two distinct types of speech disorders. Nasal emission is an airflow issue defined by the audible escape of air through the nose, occurring only during the production of pressure-dependent consonants.
Hypernasality, conversely, is a resonance disorder that affects the quality of the voice. It is characterized by too much sound energy entering the nasal cavity during speech, making the speaker sound as if they are “talking through the nose.” This condition primarily affects voiced sounds, especially vowels, liquids, and glides, which do not require high oral air pressure.
Nasal emission is the sound of turbulent air friction, while hypernasality is a muffled or overly nasal quality to the sound itself. For example, a person with hypernasality will have a nasal-sounding ‘ah’ vowel, while a person with nasal emission will have an audible air leak when saying the sound ‘s’.
Common Underlying Conditions Leading to Air Leakage
The failure of the velopharyngeal valve that causes nasal emission is broadly classified as velopharyngeal dysfunction (VPD). VPD is categorized into two main types: Velopharyngeal Insufficiency (VPI) and Velopharyngeal Incompetence (VPC).
Velopharyngeal Insufficiency (VPI)
VPI is a structural problem where the physical structures of the soft palate and pharynx are not long or large enough to close the gap. This is most commonly seen in individuals with a history of cleft palate, a submucous cleft palate, or a congenitally short soft palate. Other causes include the removal of enlarged adenoids (post-adenoidectomy VPI), which may leave a gap where the soft palate previously sealed.
Velopharyngeal Incompetence (VPC)
VPC is a functional or neurological problem where the structures are physically adequate, but the muscles controlling them move poorly or are uncoordinated. This type is associated with conditions that affect neuromuscular control, such as cerebral palsy, traumatic brain injury, or certain genetic syndromes.
In some cases, abnormal speech habits or mislearning can lead to “phoneme-specific nasal emission.” Here, the air leak occurs only on certain sounds due to incorrect tongue placement, even when the valve mechanism is structurally and functionally sound.
Specialized Approaches to Correction
For generalized emission caused by structural problems (VPI) or significant movement impairment (VPC), surgical intervention is often the primary treatment. Surgical procedures, such as pharyngeal flap surgery or sphincter pharyngoplasty, are designed to physically narrow the opening in the throat, providing a better seal for the soft palate.
For individuals who cannot undergo surgery, prosthetic devices offer a non-surgical solution. Examples include a palatal lift appliance, which pushes the soft palate into a closed position, and a palatal obturator, used to cover a large opening or fistula.
Behavioral speech therapy is rarely effective for generalized nasal emission caused by a structural deficit. However, therapy is the correct intervention for phoneme-specific nasal emission or misarticulation. A Speech-Language Pathologist uses techniques like visual or auditory feedback to help the individual direct airflow correctly. Therapy is also necessary after surgery or prosthetic fitting to maximize the use of the improved physical mechanism.