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This database includes 12 half-hour ECG recordings and 3 half-hour recordings of noise typical in ambulatory ECG recordings. The noise recordings were made using physically active volunteers and standard ECG recorders, leads, and electrodes; the electrodes were placed on the limbs in positions in which the subjects’ ECGs were not visible. The three noise records were assembled from the recordings by selecting intervals that contained predominantly baseline wander (in record 'bw'), muscle (EMG) artifact (in record 'ma'), and electrode motion artifact (in record 'em'). Electrode motion artifact is generally considered the most troublesome, since it can mimic the appearance of ectopic beats and cannot be removed easily by simple filters, as can noise of other types.
The ECG recordings were created by the script nstdbgen- using two clean recordings (118 and 119) from the MIT-BIH Arrhythmia Database, to which calibrated amounts of noise from record 'em' were added using nst. (The process of making such records is now simpler; the simplified script nstdbgen can be used with current versions of the WFDB software package to recreate these records.) Noise was added beginning after the first 5 minutes of each record, during two-minute segments alternating with two-minute clean segments. The signal-to-noise ratios (SNRs) during the noisy segments of these records are:
|Record||SNR (dB)||Record||SNR (dB)|
Since the original ECG recordings are clean, the correct beat annotations are known even when the noise makes the recordings visually unreadable. The reference annotations for these records are simply copies of those for the original clean ECGs.