I would like to filter using a periodogram produced by spec.pgram() then pick the frequencies that I would like to filter out and then get the inverse back into the time domain. Any thoughts. Stephen -- Let's not spend our time and resources thinking about things that are so little or so large that all they really do for us is puff us up and make us feel like gods. We are mammals, and have not exhausted the annoying little problems of being mammals. -K. Mullis [[alternative HTML version deleted]]