Temporal characteristics of nasalization in speakers with and without cleft palate

The purposes of the study were to compare the temporal characteristics of nasalization between speakers with cleft palate with or without cleft lip and normal adult speakers and to investigate the relationship between acoustic temporal measures and perceived nasality.

Fifteen speakers with cleft palate with or without cleft lip and 15 speakers without cleft palate aged 13 to 45 years participated in this study. Two listeners judged the degree of nasality in speakers with cleft palate with or without cleft lip. Two distinct acoustic energies derived from the mouth and nose were recorded simultaneously while speakers were producing the speech tasks /pimip/, /pamap/, and /pumup/. Absolute and proportional measures related to nasalization duration were obtained.

Speakers with cleft palate with or without cleft lip exhibited more extensive acoustic nasalization in the time domain than did speakers without cleft palate with or without cleft lip. Speakers without cleft palate with or without cleft lip showed larger nasalization-duration ratios in the high vowel contexts than in the low vowel context. Speakers with cleft palate with or without cleft lip did not exhibit distinct differences in nasalization-duration ratios among the vowel contexts. The acoustic measurements reflecting temporal patterns of oral-nasal acoustic impedance were related to the perception of hypernasality.

These results suggest that the speakers with cleft palate with or without cleft lip showed longer duration of acoustic nasalization than speakers without cleft palate with or without cleft lip. Temporal characteristics of acoustic nasalization grew longer as the degree of perceived hypernasality increased. The positive correlation between temporal measures of acoustic nasalization and degree of perceived nasality suggests that temporal measures of nasalization would provide supplementary diagnostic information in relation to the degree of hypernasality.