II. ECG Data Base :We have
collected ECG data from the laboratories at Boston’s Beth Israel Hospital (BIH)
and at Massachusetts Institute of Technology (MIT) have supported the research
in arrhythmia analysis and related subjects by creating a database. Types of
noises in ECG: Generally, the ECG signal is affected by different types of
noises that can be within the frequency band of ECG signal. The corruption of
ECG signal is due to following major noises.

 

a) Baseline
wander noise (0.1-0.5 Hz)

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b) Power line Interference
(50/60 Hz)

c) Electromyogram noise (100 Hz)

 

a) Baseline Wander noise

It is caused by variations in the
position of the heart with respect to the electrodes and changes in the
propagation medium between the heart and the electrodes. This causes sudden
changes in the amplitude of the ECG signal, as well as low frequency (0.1-0.5)
baseline shifts, as shown in Fig2. These changes can be reduced by window based
high pass filter with cut off frequency 0.5 Hz.

 

 

                                                            Fig2: ECG signal
with Baseline drift

 

b) Power line
Interference(60hz)

Power line
interference as shown in Fig3 is primarily caused due to inappropriate
grounding of the ECG equipment. It degrades the signal quality and affects the
tiny features, which can be critical for signal processing, monitoring and
clinical diagnosis as a whole. Actually, it is a narrow-band noise with
bandwidth not more than 1 Hz and the focus of 50 Hz or 60 Hz. This changes can
be reduced by window based stop band filter with cut off frequencies Fc1=59.5
Hz and fc2=60.5 Hz.

                                                            
Fig3: ECG signal with power line interference

c) Electromyography Noise
(EMG noise)

Electromyography
noise as shown in Fig4 is caused by the contraction of other muscles besides
the heart. The extent of the crosstalk depends on the amount of muscular
contraction and the quality of the probes. The frequency of this EMG noise is
in between 100-500 Hz. This can be reduced by using window based low pass
filter with cut off frequency (