Theres a couple of things you can try.
!) Pull the jack out of card and make sure that there is no build up on the plug.
2) Where the wire goes in to the head set, gently wigle to see if there is a short. Also wiggle at jack end while plugged in of course.
3) if this is not the case, then make sure your wire is not run across electrical cords.
4) Try taking a pencil or pen, just something small, and wrap a few rounds of the cable around it and see if it changes
5) If it is a crackle sound then you might have a bust voice coil in the ear speaker
Static in headphones and microphones is caused by the unwrapping of the shield cable in side the coverd wire. It has either worked its way and is getting feed back through the ground side, or The voice coil of the speaker is doing the short, you can check the ohms of this with an ohm/ volt meter putting red on the tip of the plug, and black up on the longer part of the silver plug. Check documentation to see what the ohms of you speaker is and compare. The reading should be within 1 or 2 % of the actuall. Hope this helped.