Optimal signal bandwidth for the recording of surface EMG activity of facial, jaw, oral, and neck muscles

Abstract

Spontaneous pericranial electromyographic (EMG) activity is generally small and is contaminated by strong low-frequency artifacts. High-pass filtering should suppress artifacts but affect EMG signal power only minimally. In 24 subjects who performed a warned simple reaction time task, the optimal high-pass cut-off frequency was examined for nine different pericranial muscles. From four experimental conditions (visual and auditory reaction signals combined with hand and foot responses), 1-min EMG recordings were selected (bandwidth: 0.4-512 Hz) and divided into 60 1-s data segments. These segments were high-pass filtered, the -3-dB cut-off frequency varying from 5 to 90 Hz, and subjected to power spectral analysis. Optimal high-pass filter frequencies were determined for the mean power spectra based on visual estimation or comparison with a theoretical spectrum of the artifact-free EMG signal. The optimal frequencies for the different muscles varied between 15 and 25 Hz and were not influenced by stimulus or response modality. For all muscles, a low-pass filter frequency between 400 and 500 Hz was appropriate.

Physiological evidence of interpersonal dynamics in a cooperative production task

“…The 100 Hz high-pass filter served to filter out artifacts (e.g. from eye movements) [35,36] and the 500 Hz low-pass filter is an antialiasing filter. EMG signals have both positive and negative values, so the mean was substracted from each signal to give a centered signal before full-rectification.…”

Wireless Surface Electromyography and Skin Temperature Sensors for Biofeedback Treatment of Headache: Validation Study with Stationary Control Equipment (Preprint)

“…However, it is known that oversampling above this critical Nyquist rate does not significantly improve the signal quality [38], but will likely lead to higher cost and size of the sensor. The SEMG signals are usually bandpass filtered at 10-500 Hz [39], which we consequently chose to do for both setups. Furthermore, we observed that the notch filter, at 50 Hz, for the stationary equipment seemed to be saturated during recordings.…”

Motor Commands of Facial Expressions: The Bereitschaftspotential of Posed Smiles

“…Offline, EMG data were digitally bandpass-filtered from 20 Hz to 400 Hz [24] and rectified. Onset of EMG was automatically marked in each EMG-channel based on an amplitude threshold of 30 lV, and verified through visual inspection.…”