Noninvasive and Quantitative Measurement of Intrinsic Laryngeal Muscle Activity Using Surface Electromyography

Objective: Healthy functions of intrinsic laryngeal muscles (ILMs) are important for normal speech production. This work aims to measure ILM activities for accurate assessment of laryngeal function. Methods: A noninvasive method using two-channel surface electromyography (sEMG) was designed to extract activity signals of cricothyroid (CT) and lateral-cricoarytenoid (LCA) muscles. The extracted sEMG signals were verified by the clinical laryngeal electromyography (LEMG) signals and quantified by time-domain and frequency-domain features. The sEMG features were further compared with acoustic features (i.e., fundamental frequency ${F}0$ and closed quotient (CQ) of speech signals to investigate dynamic changes in muscle activity during speech control. Results: The extracted sEMG signals captured consistent features of muscle activity with the LEMG signals. The frequency-domain features of CT/LCA muscles had a significant positive correlation with ${F}0$ but not with CQ, indicating an increasing activation of CT/LCA muscles with voice pitch rising. Furthermore, CT muscle showed greater changes in the frequency-domain features than LCA muscle during pitch control. These outcomes were consistent with the effect of CT/LCA muscles on voice control reported in previous studies. Moreover, the frequency-domain features had a more stable pattern than the time-domain features across subjects, showing potential as reliable parameters for quantitative assessment of laryngeal muscle activity. Conclusion: The feasibility and reliability of the proposed method in the extraction and evaluation of dynamic muscle activity during phonation were verified. Significance: The proposed method is promising to develop into a practical technique for in vivo human research on neuromuscular control and clinical diagnosis of laryngeal disorders.