Speakers crackling when audio is played?

-I have a dell xps 17 and whenever i play audio through either my headphone or speakers i hear a slight crackle now and then, it has only started to do this recently. It is annoying the hell out of me because it is clearly a hardware problem, i have tried different headphones and using the speakers but still it comes. I even reinstalled my whole itunes. What can i do about this? Is it to with the sound card or the actual connection?If you have a laptop, than the problem is that the fan has too much dust on the bottom of your pc.I have no idea how you can fix it...but all i know is that your fan needs to be either cleaned or replaced.Hope I can help! (: