Towards Automatic Determination of Critical Gestures for European Portuguese Sounds

Data-Driven Critical Tract Variable Determination for European Portuguese

“…Differently from the original application of the method to EMA [19] and subsequent extension to RT-MRI data by our team [24], for this work the considered variables are not landmarks placed over the vocal tract, but tract variables aligned with the Task Dynamics framework [27,37], that is, mostly based on the concepts of constrictions defined by their location and degree (distance). After preliminary work by the authors [25], which provided interesting results and has shown the applicability of the critical articulator method to this new set of variables, this work further extends this approach by also abandoning the landmark representation for the velum, identified as a limitation in our previous studies.…”

“…However, the tract data available from RT-MRI can potentiate the consideration of different tract variables moving beyond simple landmarks. In this regard, the authors have explored tract variables aligned with the Task Dynamics framework [25], adopting the concept of constrictions (except for the velum), and showed that these provided an alternative that was not only more compact (less variables involved), but also provided interesting critical articulator results with the benefit of having a more direct relation with existing Articulatory Phonology descriptions, supporting easier comparison with the literature. Nevertheless, the authors identified a few points deserving immediate attention to further assess and improve the tested approach: (1) enlarge the amount of data considered per speaker;…”

“…In previous work [25], the authors have shown that a change from the vocal tract representation based on landmarks (mimicking the work done for EMA [19]) to an approach more aligned with the Task Dynamics framework reduced the correlation between variable components (e.g., x and y coordinates of the landmark) and among tract variables. This potentially entails that the data provided by each component and variable is overall, more independent, and might offer added insight regarding what is critical.…”

“…Similarly to Silva et al [24,25], and considering the dynamic nature of nasal vowels [8,34,38,39], we wanted to have some additional information to assert if, for different timepoints, the determination of the critical articulators would highlight any relevant differences in behavior. Therefore, each nasal vowel was represented by three "pseudo-phones", focusing the starting, middle and final frame of the annotated interval and named, respectively, [vowel] start , [vowel] mid and [vowel], as in:ã start ,ã mid , andã.…”

“…To that effect, we normalized the articulator data, for each speaker, based on the variation ranges, for each variable component, computed over all selected data samples, and considered this gathered data as a new speaker following a similar analysis methodology. This is, naturally, a very simple normalization method, but considering the overall results obtained in previous work [25], it was deemed appropriate for this first assessment including three speakers.…”