The relation of nasality and nasalance to nasal port area based on a computational model

Objective: The purpose of this study was to examine the relation of perceptual ratings of nasality by experienced listeners, measures of nasalance, and the size of the nasal port opening for three simulated English corner vowels, /i/, /u/, and /a/. Design: Samples were generated using a computational model that allowed for exact control of nasal port size and a direct measure of nasalance. Perceptual ratings were obtained using a paired-stimulus presentation. Participants: Five experienced listeners. Main Outcome Measures: Measures of nasalance and perceptual nasality ratings. Results: Differences in nasalance and perceptual ratings of nasality were noted among the three vowels, with values being greater for the high vowels /i/ and /u/ compared to the low vowel /a/. Listeners detected nasality for the high and low vowels simulated with nasal port areas of 0.01 and 0.15 cm², respectively. Correlations between ratings of nasality and nasalance were high for all three vowels. Conclusions: Results of the present study show a high correlation between ratings of nasality and measures of nasalance for nasal port areas ranging from 0 to 0.5 cm². The correlations were based on sustained vowel samples. The restricted speech sample limits generalization of the findings to clinical data; however, the results are a demonstration of the usefulness of modeling to understand the perceptual phenomena of nasality.