Using partially separable functions to image spatiotemporal aspects of Arabic pharyngealization

Abstract

It has been challenging to estimate the temporal domain of pharyngealization in Arabic. Conventional MRI has limited assessment of dynamic pharyngeal shape during speech. In this study, fast spiral sequences, combined with partially separable functions, were used to achieve a relatively high spatiotemporal resolution (2.2 mm × 2.2 mm × 8.0 mm, at a frame rate of 86 fps) during dynamic speech imaging of a single midsagittal slice. One male speaker of Levantine Arabic produced pairs of words that differed minimally by one speech sound: pharyngeal fricative /ħ/ or non-pharnyngeal /b/. Each word was produced 23 times. The temporal extent of pharyngeal tissue displacement associated with /ħ/ was investigated. Sounds were segmented with reference to a simultaneous, noise-canceled acoustic recording. Spatiotemporal maps of differential pixel intensity (interpreted as tissue displacement) were generated for each segment preceding the pharyngeal / non-pharyngeal test segment. Average differential pixel intensity in the pharyngeal area was then sampled during these preceding segments. T-tests revealed significant differences (p < 0.01) up to two segments away from the pharyngeal / non-pharyngeal test segment. This technique should permit investigation of spatiotemporal aspects of pharyngealization across different varieties of Arabic, where distance and direction of pharyngealization are said to vary systematically.