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 (fo) 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-fo 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.