Reducing power line interference in digitised electromyogram recordings by spectrum interpolation

Abstract

Interference from power lines (50 or 60 Hz) is the largest source of extraneous noise in many bio-electric signals and is within the bandwidth of many such signals. In this study, two different methods were compared for their efficacy in removing 50 Hz noise added to surface electromyogram (EMG) signals free of power line interference. The first was a simple second-order recursive digital notch filter. The second was an approach called spectrum interpolation, in which it is assumed that the magnitude of the original 50 Hz component of the EMG signal can be approximated by interpolation of the amplitude spectrum of the signal. When the spectrum was based on records containing an integer number of cycles of 50 Hz interference, and the frequency resolution was finer than 1 Hz, spectrum interpolation performed similarly to, or significantly better than, the notch filter (p < 0.01). It was also possible to make spectrum interpolation more robust than the notch filter. The Pearson squared correlation coefficient r2 between clean signals and signals processed using the notch filter was reduced from 0.98 to 0.65 when the interference frequency was increased by 0.5 Hz, but r2 for spectrum interpolation at 0.2 Hz resolution was only reduced from 0.99 to 0.85 if spectral values between approximately 49.5 and 50.5 Hz were modified by interpolation.

Online Finger Gesture Recognition Using Surface Electromyography Signals

“…For the improvement of signal quality, the bandpass filter, spectrum interpolation technique [14] and wavelet analysis method were implemented and applied for the noise signal reduction.…”

ECG and PLI Artifacts Cancellation from Electromyogram

“…Two different methods were compared for their efficacy in removing 50 Hz noise. The first was a simple second-order recursive digital notch filter and the second method called spectrum interpolation, compared in [4]. Back propagation network, explains the concept of adaptive interference cancellation and efficiency of BPN to cancel the ECG interference in EMG signal is given in [5].…”

Effective Biopotential Signal Acquisition: Comparison of Different Shielded Drive Technologies

“…However, such filter banks would cause information loss of target signals since the frequency range largely overlaps for the biopotential signals and power line interference [35]. Hence, a number of improved filtering techniques have been proposed over the years to minimize interferences in biopotential recordings [36][37][38][39][40]. For instance, Tomasini et al used an adaptive power line interference filter to estimate the fundamental frequency and harmonics of power line interference, and the estimated interference was subtracted from the noise-affected biosignal [22].…”