Clicking noise from sound card

Hi,
it's the first time I post, I looked through the topics and couldn't find an answer. I have an Asus F3JM notebook with realtek HD soundcard. When the output jack is connected to external loudspekers (or headphones) I hear clicking static-like sounds, while the onboard speakers work fine. Has anyone had the same problem? May it be some software problem or is it just an impedance problem and there's no way to solve it? Thanks

I hear something too. Mine sounds more like what DJs would call 'scratching' but very short. It only happens from time to time and I don't know what the cause is either.