Nasalization Amplitude-Timing Characteristics of Speakers With and Without Cleft Palate

To examine the amplitude-temporal relationships of acoustic nasalization in speakers with a range of nasality and to determine the extent to which each domain independently predicts the speaker's perceived oral-nasal balance.

Rate-controlled speech samples, consisting of /izinizi/, /azanaza/, and /uzunuzu/, were recorded from 18 participants (14 with repaired cleft palate and 4 without cleft palate) using the Nasometer. The mean nasalance of the entire mid-vowel-nasal consonant-vowel (mid-VNV) sequence (amplitude-domain) and the duration of the nasalized segment of the mid-VNV sequence (temporal-domain) were obtained based on nasalance contours.

Strong linear and vowel-dependent relationships were observed between the 2 domains of nasalization (adjusted R² = 71.5%). Both the amplitude- and temporal-domain measures were found to reliably predict the speaker's perceived oral-nasal balance, with better overall model fit and higher classification accuracy rates observed in /izinizi/ and /uzunuzu/ than in /azanaza/. Despite poor specificity, the temporal-domain measure of /azanaza/ was found to have a strong correlation with the participants' Zoo passage nasalance scores (r_s = .897, p < .01), suggesting its potential utility as a severity indicator of perceived nasality.

With the use of relatively simple speech tasks and measurements representing the amplitude and temporal domains of nasalization, the present study provided practical guidelines for using the Nasometer in assessing patients with oral-nasal resonance imbalance. Findings suggest that both domain measures of nasalization should be examined across different vowel contexts, given that each domain may provide clinically relevant, yet different, information.