High speed MRI of laryngeal gestures during speech production

Abstract

Dynamic sequences of magnetic resonance images (MRI) of the vocal tract were obtained with a frame rate of 144 frames/second. Changes in vertical position and length of the vocal folds, both observable in the mid-sagittal plane, have been argued to play a role in consonant production in addition to their primary function in the control of vocal fundamental frequency (F0) [W. G. Ewan and R. Krones, J. Phonet. 2, 327–335 (1974); A. Lofqvist et al., Haskins Lab. Status Report Speech Res., SR-97/98, pp. 25–40, 1989], but temporal resolution of available techniques has hindered direct imaging of these articulations. A novel data acquisition sequence was used to circumvent the imaging time imposed by standard MRI (typically 100–500 ms). Images were constructed by having subjects rhythmically repeat short utterances 256 times using the same F0 contour. Sixty-four lines of MR data were sampled during each repetition, at 7 millisecond increments, yielding partial raw data sets for 64 time points. After all repetitions were completed, one frame per time point was constructed by combining raw data from the corresponding time point during every repetition. Preliminary results indicate vocal fold shortening and lowering only during voiced consonants and in production of lower F0.