Normalization patterns of the surface electromyographic signal in the phonation evaluation

Area of Science:

• Laryngology
• Speech Science
• Biomedical Engineering

Background:

• Surface electromyography (sEMG) is valuable for voice evaluation.
• Standardization of sEMG signals from laryngeal extrinsic muscles is crucial for reliable clinical application.
• Identifying consistent phonatory tasks is key to normalizing electrical activity (EA) measurements.

Purpose of the Study:

• To compare different phonatory tasks for standardizing sEMG signals of laryngeal extrinsic muscles.
• To determine the optimal tasks for peak and mean electrical activity (EA) measurements.
• To establish parameters for consistent voice evaluation using laryngeal muscle EMG.

Main Methods:

• Evaluated electrical potentials of suprahyoid (SH) and infrahyoid (IH) muscles in 35 non-dysphonic subjects.
• Utilized rest, maximum voluntary sustained activity (MVSA), and vowel /ɛ/ and count emissions at usual/strong intensities.
• Normalized EA signals using root mean square (RMS) and identified tasks with minimal coefficient of variation.

Main Results:

• The peak of vowel /ɛ/ and 20-30 count emissions (usual intensity) showed the lowest coefficient of variation for EA in both SH and IH muscles.
• MVSA tasks were identified as a secondary option for normalization.
• Mean potentials varied across tasks, with specific values reported for IH and SH muscles.

Conclusions:

• The peak of vowel /ɛ/ and 20-30 count emissions (usual intensity) are recommended for sEMG signal normalization in SH and IH muscles.
• MVSA can be considered a secondary option for normalization.
• These findings support the use of sEMG in clinical voice assessment by providing standardization methods.