Quantifying the time-varying relation between speech production and postural control at different levels of vocal effort
Robert A. Fuhrman, Adriano Vilela-Barbosa, Eric Vatikiotis‐Bateson · Canadian acoustics · 2016
Speech production affects the behavior of physiological systems beyond the vocal tract. In this study, we investigate how increasing the loudness of speech production (vocal effort) affects the coupling of kinematic motions the head, body, and speech acoustics, and the relation of these coupling patterns to postural control. We predicted that increasing vocal effort would result in stronger couplings and increasingly regular kinematic and acoustic signals, reflecting an entrainment effect related to the changes in respiratory patterning associated with producing speech at high levels of vocal effort. We also predicted that postural instability would accompany this effect, since the postural control system is biomechanically coupled to the speech system via the musculature of rib cage, which takes on a more active role in respiration in high vocal effort speech. Results from six talkers who produced spontaneous speech at multiple levels of vocal effort confirmed both of these hypotheses. Stronger within-talker coupling, and the diminished behavioral variability that accompanies it, is associated with weaker coupling between the individual feet—the interface of the body with the external environment. We demonstrate this using a combination of time-series analysis methods assessing signal fluctuations (detrended fluctuation analysis) and system dimensionality (principal component analysis (PCA), correlation map analysis (CMA)). In future work, we plan to include measures of respiration in this analysis.