An acoustic study of the temporal characteristics of nasalization in children with and without cleft palate

Abstract

Objective: The purpose of this study was to measure the oral and nasal cavity acoustic energies to determine whether temporal patterns of nasalization differentiate children with and without cleft palate and the extent to which vowel context contributes to these temporal differences. Design: Nasal onset interval, nasal offset interval, and total nasalization duration measures were obtained from acoustic waveforms, spectrograms, and energy contours acquired using the Computerized Speech Lab (Kay Elemetrics, Lincoln Park, NJ). In addition to absolute temporal values, proportional durations of nasalization were measured to obtain information regarding the relative duration of nasalization. Participants: Fifteen children with cleft palate exhibiting mild hypernasality and 15 children without cleft palate participated in the study. Children in both groups were between 4 and 7 years of age. Results: Each of the three absolute measures was significantly different between the two groups of subjects and within the three vowel contexts. Children with cleft palate showed longer temporal characteristics than children without cleft palate in all three absolute measures. The three temporal variables of the high vowel contexts were generally longer than those of low vowel contexts. Regarding proportional measures, nasal offset interval ratio, and total nasalization ratio showed significant differences between the two groups. Conclusions: Nasalization, as reflected by acoustic signals, showed different timing characteristics between children with cleft palate and without cleft palate and across vowel contexts. This suggests that the duration of nasalization reflecting temporal patterns of the oral-nasal acoustic impedance may have an influence on the perception of hypernasality.