The effect of articulatory adjustment on reducing hypernasality

Purpose: With the goal of using articulatory adjustments to reduce hypernasality, this study utilized an articulatory synthesis model (Childers, 2000) to simulate the adjustment of articulatory configurations with an open velopharynx to achieve the same acoustic goal as normal speech simulated with a closed velopharynx. Method: To examine the effect of articulatory adjustment on perceived nasality, this study used an articulatory synthesis model (Childers, 2000) to synthesize 18 oral /i/ vowels, 18 nasal /i/ vowels, and 18 nasal /i/ vowels with computer-generated articulatory adjustments; these vowels were then presented to 7 listeners for perceptual ratings of nasality following the direct magnitude estimation method. Results: Comparisons of nasality ratings of nasal vowels showed a significant reduction of perceived nasality after articulatory adjustment. Moreover, the acoustic features associated with nasal resonances were attenuated and the oral formant structures changed by nasalization were restored after articulatory adjustment, which confirmed findings in Rong and Kuehn (2010). Conclusion: Appropriate articulatory adjustments are able to reduce the nasality of synthetic nasal /i/ vowels by compensating for the acoustic deviations caused by excessive velopharyngeal opening. Such compensatory interarticulator coordination may have an application in using articulatory adjustments to reduce hypernasality in clinical speech therapies.