Understanding the relationship between acoustics and articulation of nasal and oral vowels

• Published in: The Journal of the Acoustical Society of America Vol. 140; no. 4; p. 3219
• Main Authors: Barlaz, Marissa, Johnson, Sarah, Shosted, Ryan, Carignan, Christopher, Fu, Maojing, Liang, Zhi-Pei, Sutton, Brad
• Format: Journal Article
• Language: English
• Published: 01-10-2016
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4970150

While real-time magnetic resonance imaging (rt-MRI) provides high spatiotemporal resolution for speech research, the associated audio is noisy, presenting a challenge for research on the relationship between articulation and the acoustic signal and solving the articulatory inversion problem. Using state-of-the-art denoising methods, the current study denoised rt-MRI audio associated with nasal and oral French vowels produced by one speaker, and extracted F1-3 from the midpoints of each vowel for /a, o, e/ and their nasal counterparts. Oblique images were taken of the velopharyngeal port at 25 frames/second, and average pixel intensity (API) in the velopharyngeal region was taken from images corresponding to the vowel midpoint. General additive models showed a significant relationship between API and F1 for oral and nasal vowels. (Lower API indicates a wider velopharyngeal opening.) F1 of /ã/ was lower than /a/, while F1 was higher in the nasal /õ/ and /ẽ/ than their oral counterparts, all of which are expected effects of naso-pharyngeal coupling. These results show that the acoustic recordings produced during rt-MR imaging can be used to explore the relationship between articulation and acoustics, and can give insight into the articulatory effects of nasality, something difficult to understand through acoustics alone.