Toward Acoustic-Based Normalization of Laryngeal EMG for Improved Interspeaker Consistency in Muscle-to-Acoustic Mapping.

Understanding how intrinsic laryngeal muscle activation relates to vocal output is essential for advancing experimental voice research. However, intrasubject variability remains a major challenge when comparing EMG recordings across sessions. To address this, a normalization framework based on acoustic targets was implemented to improve the consistency of EMG-acoustic relationships across sessions. Signals from the cricothyroid (CT), thyroarytenoid (TA), and lateral cricoarytenoid (LCA) muscles were collected across four sessions from a healthy adult performing a set of phonatory and non-phonatory vocal tasks. Muscle Activation Plots (MAPs) were generated to visualize the relationship between normalized EMG activity and acoustic outcomes, specifically fundamental frequency (f_o) and sound pressure level (SPL). Compared to traditional peak-based normalization, the proposed method reduced intrasubject variability and improved inter-session consistency in the EMG-f_o relationship, as reflected by an increase in ICC from 0.52 to 0.83 and a reduction in MAE from 84.87 Hz to 19.23 Hz. These findings represent a step toward more consistent intramuscular EMG normalization and improved interpretation of muscle-specific control strategies in human voice production.