The aim of this study was to further investigate one-third-octave analysis by (a) extending the application of the analysis to three vowels, /inverted a sign/, /inverted c sign/ and /u/, in addition to /i/ which has been investigated previously, and by (b) comparing the spectra of each vowel produced in oral and nasal consonant contexts for each speaker. The speakers included 20 individuals with hypernasality due to various etiologies and 20 control speakers. The speech materials were 18 Cantonese single words: nine were loaded with oral stops at syllable-initial and syllable-final positions and nine were loaded with nasal stops at syllable-initial and syllable-final positions. The results showed statistically significant differences between the experimental and control groups for the bands centered at 630, 800, and 2000 Hz for vowel /i/; at 3200 Hz for vowel /inverted a sign/; at 160, 1000, 2500, and 3200 Hz for vowel /inverted c sign/; and at 800 and 5000 Hz for vowel /u/. Most of the findings were in agreement with previous reports about nasalization of vowels. The study showed that individuals with normal resonance and hypernasality could be distinguished on the basis of their production of vowels /i/ and /inverted c sign/.

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