Normalization Patterns of the Surface Electromyographic Signal in the Phonation Evaluation

Abstract

The aim of the study was to compare the different parameters, regarding the peak and mean, at different phonatory tasks for standardization of electromyography signal of electrical activity (EA) of the laryngeal extrinsic muscles on voice evaluation. The electrical potentials of the suprahyoid (SH) and infrahyoid (IH) muscles of 35 voluntary nondysphonic subjects were evaluated using three evaluations of rest, two maneuvers to determine maximum voluntary sustained activity (MVSA), and usual and strong intensity of vowel /ɛ/ and 20-30 count emissions. The EA signal was converted using root mean square in microvolts and normalized by mean and peak of each task. The selected normalization task was that with minor coefficient of variation for all muscles. The tasks that provided minor coefficient of variation of EA in both muscle groups were the peak of vowel /ɛ/ (mean potentials equal to 43.31±2.97 for right IH, 36.27±2.76 for left IH, and 42.11±2.57 for SH) and the 20-30 count emissions (mean potentials equal to 31.30±308 for right IH, 30.56±2.76 for left IH, and 30.43±4.22 for SH), both in usual intensity and MVSA, as second option. The peak of vowel /ɛ/ and 20-30 count emissions is usual intensity, and the MVSA as second option should be considered for signal normalization in SH and IH muscles, and may provide conditions for using the surface electromyography in voice clinic.