Measuring laryngealization in running speech: interaction with contrastive tones in yalálag zapotec

The study of glottalization is usually based on methods whose limited reliability in the analysis of non sustained phonation is widely acknowledged. In this study we propose a method to measure the degree of glottalization which is robust to variation of fundamental frequency and which, applied to the electroglottographic signal, does not depend on changes in vocal tract resonances. The method, based on an original variant of recurrence analysis, is used to study the interaction between phonological glottalization of vowels and contrastive tones in Yalálag Zapotec. In this American Indian language, both modal and laryngeal vowels can occur with three different contrastive tones (low, high and falling). However, the rapid modulation of fundamental frequency needed for the production of contrastive tones is expected to be strongly limited by the presence of laryngealization. We study how speakers resolve the competition between the constraints on the articulation of these two features of Zapotec phonology. Through wavelet based functional mixed regression we could model the changes in the degree of glottalization over the duration of both modal and laryngealized vowels produced with the three different tones.