Analysis of Inter-Articulator Correlation in Acoustic-to-Articulatory Inversion Using Generalized Smoothness Criterion

The movements of the different speech articulators are known to be correlated to various degrees during speech production. In this paper, we investigate whether the inter-articulator correlation is preserved among the articulators estimated through acoustic-toarticulatory inversion using the generalized smoothness criterion (GSC). GSC estimates each articulator separately without explicitly using any correlation information between the articulators. Theoretical analysis of inter-articulator correlation in GSC reveals that the correlation between any two estimated articulators may not be identical to that between the corresponding measured articulatory trajectories; however, based on smoothness constraints provided by the real articulatory data, we found that, in practice, the correlation among articulators is approximately preserved in GSC based inversion. To validate the theoretical analysis on interarticulator correlation, we propose a modified version of GSC where correlations among articulators are explicitly imposed. We found that there is no significant benefit in inversion using such modified GSC, which further strengthens the conclusions drawn from the theoretical analysis of inter-articulator correlation.