Spectral Evaluation of Hypernasality in Children with Repaired Cleft Palate

Objective: To identify the characteristics of the spectrum of hypernasality in relation to the formant amplitudes for the vowel ‘a’ (∂ in the International Phonetic Association alphabet chart of vowels) for children with repaired cleft palate and the relationship of hypernasality with other acoustic parameters.Patients and Methods: Fifty three children with repaired cleft palate were divided into 2 groups, based on perceptual speech rating: moderate to severe hypernasality (n = 33) and mild hypernasality (n = 20). The control group comprised 20 children without cleft palate. Sound segments ‘ka’ containing the vowel ‘a’ were recorded, digitised, and analysed to identify formant pattern, breathiness values, and amplitudes for one-third octave band frequency spectra using computer software.Results: Differences in frequency values obtained between the hypernasal groups and normal children for the fundamental frequency (F0) and formants F1 and F2 were not statistically significant. Significant differences in breathiness values were obtained for children with moderate to severe hypernasalality and those with mild hypernasality compared with normal children. Spectral analysis revealed an increase in amplitudes in frequency bands between F1 and F2 and spectral dips at 630 to 800 Hz band and at F2 with an additional Fn peak at 800 to 1000 Hz band in subjects with moderate to severe hypernasality.Conclusions: Formant amplitude measurement using one-third octave frequency band spectral analysis revealed characteristic features for the hypernasal vowel ‘a’ as an increase in amplitudes in some frequency bands and an additional spectral peak Fn between F1 and F2.