Adding noise to an ECG signal I am doing a project on ECG arrythmia analysis using matlab.


I have designed notch filter for removing 50 Hz noise but don't know how to add a 50 Hz powerline interference noise to a clean ECG signal? 
Also, I want to check whether noise is reduced in the filtered signal. Will Power spectral density using modified welch periodogram indicate whether noise is filtered or not?
How can I compare which wavelet (e.g. db6) is best suited for ECG analysis?
1) Create a 50 Hz sinusoid and then simply add it to your ECG signal.  You can control the power of the 50 Hz noise by multiplying the sinusoid by some gain factor (can be less than or more than 1) before you add it to the ECG.

2) I'm not familiar with the Welch periodogram, but if it displays the power spectral density then it should do fine.  I would just do an FFT myself.