Can someone suggest a filter to remove the noise from the signal shown in this image (with the sampling rate being 500)?
I'd try a modified median filter
% Take median filter. medianFilteredSignal = medfilt2(signal, [1,3]); % Find where signal is bad badElements = signal < 400 | signal > 900; % Replace bad elements with median filtered values. noiseFreeSignal = signal; % Initialize. noiseFreeSignal(badElements) = medianFilteredSignal(badElements); % Do the replacement
It is impossible to suggest a filter based on the information of the sample frequency only. We cannot know the nature of the noise and of the wanted signal. You could be interested in low or high frequencies or in a specific band. But the filter parameters must depend on these details. So please provide more information.