If you are not using the foam covers, and pressing the ear buds tightly into your ears, you might be mashing the thin metal foil covering. This is a common occurence. Several people have suggested a remedy, that while it sounds silly, seems to work for many people. Take the foam cover off (if you have it on the ear bud), place the ear bud against your lips, with the metal (sound) side facing into your mouth, make a tight seal of your lips around the plastic cover, and then suck very hard. (Don't swallow the ear bud of course!). The will help pop the metal back out to it's normal position, and fix the crackling noise. It doesn't work all the time, but it has worked for a lot of people, and since it's totally free (and quick) it probably can't hurt to give it a try.