What Causes Nasal Speech?

Nasal speech broadly refers to a person’s voice sounding like it has too much or too little air in the nose. Oftentimes, it’s challenging for listeners to tell the difference between these two characteristics, although technically they’re at opposite ends of a spectrum. To help understand what causes nasal speech, it helps to understand a few fundamentals.

What are resonance and airflow control?

Resonance refers to the enhancement of sound energy by a cavity or chamber. Why does this matter for nasal speech? Because when we make speech sounds like vowels (“a,” “e,” “i,” “o,” and “u” to name a few), the movement of our vocal folds creates sound waves. That energy moves through our speech tract and out of our mouth to reach the ears of listeners. One of the reasons we can recognize the voices of people we know is because we all have slightly differently shaped speech tracts. These different shapes cause sound wave energy to be enhanced in slightly different ways. Think about a performing theater—experts in sound engineering design the shapes of rooms to help promote ideal resonance, or energy enhancement.  

Airflow control refers to air from the lungs being shaped and valved by the articulators when we talk. For those without nasal speech, we don’t realize that we’re actually building up pressure in our mouth when we’re speaking. But, with very rapid timing, we’re sending air out of our lungs through our mouth and building pressure for different speech sounds. For example, when we make a /p/ sound, we’re putting our lips together to briefly stop the air behind them, then releasing the airflow to make the /p/. For /s/, we’re holding our tongue just behind our front teeth to create a narrow passageway for airflow to move through, and that constriction of air results in the /s/ sound.

What is normal resonance and airflow control for speech?

While the individual differences in the shape of our mouths and throats can create unique vocal resonance characteristics for us as speakers, there are a few general rules about resonance that are true for English speakers.

When we make vowels, or vowel-like sounds like “w,” “y”, and “l,” we expect our soft palate and the walls of our upper throat to seal our nose from our mouth. If these muscles work like they should, we’ve made the shape of our resonating chamber the shape of our mouth, so these sounds have oral resonance.

When we make nasal sounds, like “m,” “n,” and “ng,” we leave the passageway to our nose open. This makes the shape of resonating chamber larger, as it now includes our nasal cavity. We call the resulting change in how our resonance sounds “nasal resonance.”

When we make high pressure oral consonants, which in English are /p/, /b/, /t/, /d/, /k/, /g/, /f/, /v/, /s/, /z/, “sh,” “zh,” “ch,” “dz,” /k/, /g/, and voiced and voiceless “th,” we’re creating pressure build up and release to produce these sounds a certain way.

What types of nasal speech problems can occur?

Now that we know what type of resonance different sounds should have, we can understand what types of problems we can have with resonance, or what types of nasal speech can occur.

Hypernasal resonance occurs when sounds that should have only oral energy enhancement now have nasal resonance. The “hyper” part of the word basically means “too much.” So, sounds that can have hypernasal resonance are the vowels and vowel-like consonants.  We can then label this hypernasality as mild, moderate, or severe, and describe if it’s present all of the time or some of the time.

Hyponasal resonance occurs when the sounds that should have nasal energy enhancement do not have nasal resonance, or have less nasal resonance than they should. The “hypo” part of the word means “not enough.” Nasal sounds /m/, /n/, and “ng” can have hyponasal resonance. Just like hypernasality, hyponasality can be mild, moderate, or severe.

Nasal emission refers to the leakage of airflow through the nose when the speaker is trying to make one of the high pressure oral consonants. Additionally, when pressure build up is impaired, the speaker may have reduced oral power of these consonants.

What causes these types of nasal speech?

Velopharyngeal dysfunction causes hypernasal and hyponasal resonance. When hypernasality exists, it means that the muscle at the back of the roof of the mouth, or velum (also called the soft palate) isn’t making contact with the pharynx (or throat) to seal the nose from the mouth when it should. If hyponasality exists, it means there is either overclosure of the velopharyngeal port, or there is an obstruction in the nose.  There are three main causes of velopharyngeal dysfunction—structural problems, neurological problems, and mislearning.

Structural problems causing velopharyngeal dysfunction

A few different types of structural problems can create velopharyngeal dysfunction that results in problems with nasal speech.

Enlarged tonsils or adenoids can sometimes block the velopharyngeal port, which can result in hyponasality, or denasal speech. This can make a speaker sound congested, or like they have a cold. In these cases, an Ear Nose Throat doctor may recommend medication or surgery to remove all or part of the enlarged tissue. Typically, when this medical treatment is recommended, it’s because the speaker experiences other negative effects from the enlarged tonsils or adenoid tissue, like sleep apnea. In a very small number of cases, enlarged tonsils may prevent movement of the soft palate and result in mild hypernasality. However, careful evaluation by a speech-language pathologist and surgeon who specialize in nasal speech is needed to make sure that the tonsils are in fact the problem. In most cases of hypernasal speech, removal of adenoid tissue, which is often done at the same time as tonsil removal, results in worsening hypernasality.

Some children who do not have nasal speech may experience this as a side effect of adenoid removal. This occurs because the adenoid tissue is often involved in the closure of the velopharyngeal port during speaking in young children. When the adenoid tissue is removed, the dimensions of the throat are suddenly deeper, and children need to “recalibrate” how far they move their soft palate during speech. In most cases of hypernasality after adenoid removal, nasal speech resolves after a few months.

Speakers born with a cleft palate are also at risk for hypernasal speech. In cases of repaired cleft palate, when the soft palate isn’t long enough or doesn’t move well enough to seal the nose from the mouth, these speech problems are referred to as Velopharyngeal Insufficiency. While numbers vary, reports of around 20% of kids with a repaired cleft palate will have velopharyngeal insufficiency that requires an additional surgery for speech.

Some kids without a history of a cleft palate can have a condition that results in a structurally based nasal speech problem. One example of this is called a submucous cleft palate, and it means that the muscles of the soft palate didn’t develop correctly during the mother’s pregnancy. However, unlike a cleft palate, a submucous cleft palate exists under the skin of the roof of the mouth. This can make it hard to see by an untrained eye. Some submucous cleft palates never cause a problem for speech. Others impact speech as much as if the cleft had been overt, or wide open like a cleft palate. Others are asymptomatic, or don’t cause problems, until a child has their adenoid tissue removed, and then the mild differences in structure result in problems with nasal speech that were revealed when the adenoid surgery took place.

Adults can experience structural causes of nasal speech as well. First of all, adults can have residual problems with a cleft palate or submucous cleft palate. These problems may be due to incomplete treatment in childhood, or from gradually growing into a structural problem over time. Adults with a repaired cleft palate may have had a secondary speech surgery as a child, like a sphincter pharyngoplasty or pharyngeal flap. Sometimes these surgeries can result in velopharyngeal overclosure, or blockage of the space between the throat and the nose. If these past surgeries block off the nasal passages, hyponasality can occur.  Adults may also experience structurally caused nasal speech following oral cancer surgery, if resection removes a portion of the oral structures involved in sealing the nose from the mouth.

Neurological problems causing nasal speech

Nasal speech can also result from problems with controlling the muscles of the soft palate and walls of the throat with coordinated movement for speech. The two main types of speech diagnosis that result in neurological nasal speech are dysarthria and apraxia.

Dysarthria has many presentations depending upon what part of the neurological system is impacted. In dysarthria, speakers have reduced control and timing, range of motion, and strength of the articulators. This can impact the ability to seal the nose from the mouth and result in hypernasal resonance and nasal air emission. A few causes of dysarthria include motor neuron disease, stroke, or cerebral palsy.

Apraxia of speech is a disorder in which the speaker struggles with the ability to plan the movements needed for coordinated speech. Hallmark characteristics include inconsistent errors, errors when trying to make vowel sounds, intonation difficulty, and groping movements of the articulators when trying to make sounds. Speakers with apraxia can experience nasal speech because they are struggling with coordinating the movement of the palate and walls of the throat needed to achieve complete sealing of the nose from the mouth. There are two types of apraxia of speech—developmental apraxia of speech, which is diagnosed when a child begins speaking and demonstrates symptoms of apraxia, and acquired apraxia of speech, which results from brain injury such as a stroke. Developmental apraxia of speech can co-occur with cleft palate or submucous cleft palate, which can make differential diagnosis more challenging.

Mislearning and nasal speech

Occasionally, speakers may develop nasal speech as a result of mislearning the direction of airflow release when making certain sounds. In these cases, there is no underlying structural or neurological cause that’s led to the velopharyngeal mislearning, although some speakers may present with a variety of causes of nasal speech at the same time.

The most commonly encountered example of velopharyngeal mislearning is an error called a nasal fricative. A child who makes a nasal fricative send airflow through the nose as a habit, in place of orally directed airflow. This commonly occurs in a very rule-based and patterned way because the child substitutes the sound for other sounds. For example, a child may substitute a nasal fricative for all /s/ and /z/ sounds. Because /s/ and /z/ show up so often in the English language, in a conversation, this child may sound very nasal. However, when the speech-language pathologist has the child make sounds in an assessment, they can quickly detect the pattern of the nasal fricative.

Improving Nasal Speech

The treatment plan to improve nasal speech depends on the underlying cause of the problem. For structural causes, most often the solution will include surgery or management with an oral appliance. Treatment for neurological causes of nasal speech varies based on the presentation. For some types of dysarthria, increasing the overall breath support and effort used for speaking can help improve nasality. For apraxia, repetitive practice of speech movement and transitions between sounds can help improve coordination and result in improved resonance. For nasal fricatives, articulation therapy can help replace the habit of sending airflow out of the nose with correct productions. In all of these cases, having correct diagnosis information allows appropriate treatment planning. Speech-language pathologists have the necessary training and skill set to effectively evaluate and diagnose nasal speech. If you’re worried about nasal speech, we encourage you to learn more about Verboso’s services!