SimEMG database- simultaneous recordings of noise-free and noise-contaminated ECG signals
SimEMG is a database that collects recordings of ECG signals with and without EMG noise simultaneously. It assumes that the potential on every point along the arm is constant when muscles are relaxed and that the EMG noise is generated locally in the hands. Then, the potential difference between electrodes placed on the hands will include the EMG noise, while the potential difference between electrodes placed on the shoulders distant from the noise source will render the reference signal without noise. The Ag/AgCl electrodes for recording the limb leads are placed in the standard manner. In contrast, the electrodes for recording the precordial leads measure the potential difference between arms with and without EMG noise. Since we have 6 precordial electrodes in standard 12-lead ECG device, we engaged one pair of electrodes to obtain the reference (noise-free) signal by placing the electrodes on the shoulders at the point of attachment of the deltoid muscle to the humerus (upper arm) and calculating their potential difference. We used the other two pairs of precordial electrodes (Ag/AgCl and orbital) to obtain signals contaminated by EMG noise by placing them on fingers and calculating the potential difference between fingers on the left and right arms. Therefore, we obtain 4 single-lead signals per one recording: one reference and three signals contaminated with noise (one from standard limb leads and two from the potential difference between fingers). EMG noise was introduced by activating hand muscles either by pressing the fingers of one hand against each other or by pressing the object that causes resistance. In order to obtain signals contaminated only with EMG noise, we applied signal processing: - Baseline wander is removed by applying a high-pass filter with the cutoff frequency of 1 Hz; - Power-line interference is removed by applying a notch filter with the cutoff frequency of 50 Hz; - High-frequency components are removed applying a low-pass filter with the cutoff frequency of 100 Hz. The SimEMG database contained 110 pairs of noise-free nad noise-contaminated single-lead recordings generated from 14 subjects (9 females and 5 males aged 40±13). The average SNR of the noise-contaminated signals is 8.53±5.5 dB. The sampling rate of signals is 500 Hz, while the amplitude resolution is 200 samples per mV. Names of recordings from SimEMG database are set in the following manner: patientNumber_patientRecordingNumber_ElectrodePosition.txt ElectrodePosition has 3 possible states: - lead I: noise-contaminated signal is collected with Ag/AgCl electrodes located on the wrist, - Ag-AgCl: noise-contaminated signal is collected with Ag/AgCl electrodes located on fingers, - ORB: Noise-contaminated signal is collected with orbital electrodes located on fingers.