Comparison of native and non-native consonant articulation with real-time magnetic resonance imaging of the vocal tract

This study examines the effects of vocalic context and stress on consonantal articulation using real-time magnetic resonance imaging (rtMRI) of the vocal tract. A native speaker of English and an L2 English speaker of Mandarin produced eight repetitions of a set of vowel-consonant-vowel sequences in which the target consonants-voiceless stops and nasals-occurred before or after a stressed vowel.

 Images of the mid-sagittal plane of the vocal tract were acquired with a sampling rate of 8.1 ms, and were reconstructed using a variable density golden angle ordered spiral algorithm. Vocal tract variable time-series for each token were extracted from the images by taking the average pixel intensity for each frame in hand-labeled regions of interest. Analyses of variance were conducted on kinematic variables (movement range, velocity, and duration of consonantal closure and release movements) and relative timing of consonantal and vocalic gestural landmarks.

The results showed greater effects of stress and vocalic context on articulatory kinematics and timing for the native speaker compared to the non-native speaker. This study demonstrates that rtMRI can be used to assess fine-grained differences in articulation that are likely attributable to language background.