How to remove the background noise from a signal?

Hi. I have the following signal. I am mainly interested in getting the peaks of the red signal. So I want to remove the part (background noise whose data I have) within the blue box.

1. How can I do it?

2. If I want to remove the noise, can I simply subtract the original values in time domain? something like:

y = Signal (t) - Noise (t)

or I have to do it in freq domain?

Thanks

Answer 1

[Daniel M]

Seems like you have determined what you want your threshold to be.

You can set those values to zero (or whatever the mean of your signal is), pretty easily:

x; % this is your data
xpeaks = x; % duplicate 
thresh = 10; % or whatever it is
meanx = mean(x);
xpeaks(abs(x) <= threshold) = meanx;
% xpeaks will contain only the "peaks"

[Steven]

Thank you.

So it is not needed to take both of them to freq domain and then subtract them?

[Daniel M]

That's another approach, but it was unnecessary in this case.