All Apple iPods come with a set of earphones. These earphones usually have a small up and down volume control attached to the wire, making them a little more useful than standard ear bud headphones. However, you may notice from time to time a slight crackling noise being emitted from the speakers in the earphones. There are a few troubleshooting methods for this issue, but it can also be due to excessive damage, in which case you need to just toss them and pick up a new pair.
Check the connection between your Apple iPod and the earphones. Make sure the cable is inserted completely into the headphones jack.
Feel the earphones to see if they are wet. Moisture in and around the headphones can cause it to crackle. This most commonly happens while you are working out or jogging and sweat gets into the earpiece.
Set the earphones aside to dry if they are wet. You may also want to wipe them dry with a clean cloth or towel to help speed up the drying process.
Lower the volume of your iPod. If the iPod volume is turned all the way up, the loudness can cause the earphones to crackle. If you do this for a long period of time, you can actually permanently damage the earphones--not to mention your ears.
Connect a different pair of headphones to the Apple iPod. If the new earphones don't crackle, you know your current earphones are damaged and no longer work properly. If the different earphones crackle as well, then there may be something wrong with your iPod. Taking the iPod in to the Apple store to get looked at may be necessary.