Health Resources

Unintelligible Speech

What causes it

Unintelligible speech can stem from undetected hearing loss or disorders affecting language, articulation, voice and resonance. It is crucial to detect and treat these issues early to achieve optimal speech outcomes.

Particularly, resonance problems can be easily overlooked. Public awareness is lacking regarding the possibility of addressing these issues. Resonance disorders include hypernasal and hyponasal speech, or a combination of both.

Hypernasality & Hyponasality can result in unintelligible speech

Imagine two glasses filled to different levels—they produce different sounds when tapped. Similarly, resonance issues can cause alter speech intelligibility by changing the space where sound vibrates during speech.

Hyponasal speech resembles the sound of speaking with a blocked nose, typically heard during a cold. Hypernasal speech sounds as if the individual is speaking through the nose, often accompanied by an abnormal air leak in non-nasal sounds.

Causes of hypernasality

Hypernasality is commonly associated with children with a cleft palate. However, it can also occur in individuals with poor oro-facial muscle tone, craniofacial disproportions or unnoticed defects in the hard palate leading to velopharyngeal insufficiency or incompetence (VPI). This condition arises from the soft palate's inability to seal off the nasal passage during the production of non-nasal sounds such as /s/, /z/, /k/, /g/.

Children with global developmental delay or subtle neurological weakness may struggle to close the velopharynx completely due to weak soft palate muscles.

VPI might also be a consequence of large tonsils or become apparent after adenoid surgery. Accurate diagnosis of VPI requires a formal examination, and speech therapy alone may not suffice for correction.

About the condition

Is your or your child's speech difficult to understand, as pointed out by teachers or peers?

It's a misconception that unintelligible speech is a sign of low intelligence or lack of environmental stimulation, often leading to the child being unfairly labelled as "slow".

Contrary to common belief, tongue length is usually not a determinant of speech clarity, except in severe cases of tongue-tie.

Diagnosis and Treatment Options

After a general ENT examination to rule out issues like hearing loss and problems with the mouth, tongue and voice, a detailed assessment is conducted. This involves passing a small flexible scope through the nose to observe the soft palate's movement during speech. Conducted alongside a speech therapist, this assessment determines the presence of a velopharyngeal gap and identifies any weaknesses or insufficiencies., and accurately identify the level, side and site of any weakness or insufficiency of the soft palate.

Voice Assessment

This comprehensive evaluation includes a voice history, visual imaging (e.g. laryngeal mirror, nasendoscopy, videostroboscopy), perceptual judgements of voice quality, acoustic measures such as pitch and intensity, and aerodynamic measures e.g., airflow rate and postural evaluations. The ENT surgeon / laryngologist collaborates with the speech therapist to gather and interpret all this data for a diagnosis.


Specialised clinics offer videostroboscopic voice assessments, providing a slow-motion view of the vocal folds to uncover abnormalities that may not be visible in standard examinations. This technique is particularly effective in identifying subtle issues like mild vocal cord swelling.

Voice Therapy

Voice therapy includes advice and exercises for correcting poor vocal habits, misuse, and techniques for voice projection and modulation.

VPI treatment

Many patients with VPI benefit from speech therapy alone, without requiring surgery. For some, surgical intervention may be necessary. Post-surgery, the patient typically stays one night in hospital and can resume eating and drinking. Continued speech therapy post-surgery is crucial to optimise speech outcomes.

Last updated on
Best viewed with Chrome 79.0, Edge 112.0, Firefox 61.0, Safari 11
National University Health System
  • National University Hospital
  • Ng Teng Fong General Hospital
  • Alexandra Hospital
  • Jurong Community Hospital
  • National University Polyclinics
  • Jurong Medical Centre
  • National University Cancer Institute, Singapore
  • National University Heart Centre, Singapore
  • National University Centre for Oral Health, Singapore
  • NUHS Diagnostics
  • NUHS Pharmacy
  • Yong Loo Lin School of Medicine
  • Faculty of Dentistry
  • Saw Swee Hock School of Public Health
Back to Top