Voice low tone to high tone ratio: A potential quantitative index for vowel [a:] and its nasalization

Guo She Lee, Ching Ping Wang, Cheryl C H Yang, Terry B J Kuo

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


Hypernasality is associated with various diseases and interferes with speech intelligibility. A recently developed quantitative index called voice low tone to high tone ratio (VLHR) was used to estimate nasalization. The voice spectrum is divided into low-frequency power (LFP) and high-frequency power (HFP) by a specific cutoff frequency (600 Hz). VLHR is defined as the division of LFP into HFP and is expressed in decibels. Voice signals of the sustained vowel [a :] and its nasalization in eight subjects with hypernasality were collected for analysis of nasalance and VLHR. The correlation of VLHR with nasalance scores was significant (r = 0.76, p < 0.01), and so was the correlation between VLHR and perceptual hypernasality scores (r = 0.80, p < 0.01). Simultaneous recordings of nasal airflow temperature with a thermistor and voice signals in another 8 healthy subjects showed a significant correlation between temperature rate of nasal airflow and VLHR (r = 0.76, p < 0.01), as well. We conclude that VLHR may become a potential quantitative index of hypernasal speech and can be applied in either basic or clinical studies.

Original languageEnglish
Article number1643415
Pages (from-to)1437-1439
Number of pages3
JournalIEEE Transactions on Biomedical Engineering
Issue number7
Publication statusPublished - Jul 2006
Externally publishedYes


  • Hypernasal speech
  • Hypernasality
  • VLHR
  • Voice spectrum

ASJC Scopus subject areas

  • Biomedical Engineering


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