Towards the computation of a variability index in orofacial muscle activity patterns during speech production using performance verification studies

Abstract

In previous work (Wohlert and Smith, 2002), it was determined that variability in children's speech production is reflected in upper lip muscle activity using electromyographic (EMG) data across repetitions of a phrase. Later studies (MacPherson and Smith, 2013) showed that a lip aperture variability index, which represents the difference in upper lip displacement and lower lip displacement, can also be used as a reliable variability measure from EMG data to determine the effects of multiple repetitions of the same utterance on speech motor production. This study is an extension of previous work and examines the orofacial muscle activity patterns (i.e., EMG data) during speech production in efforts to quantify EMG variability. This information can yield significant insights into how well the speech motor system is functioning in different groups of speakers (e.g., healthy young adults vs. healthy older adults). Initially for this study, kinematic measures of articulatory variability in healthy young adults and healthy older adults were verified using previously developed customized, interactive Matlab programming. The analysis provided the platform for studying the quantification of variability in EMG data. The results of these performance verification analyses are described in this paper.