If you read our fantastic intro on "Care and Feeding of your Filament" then you remember that many materials used for FDM/FFF printing are hygroscopic, meaning they readily absorb moisture from the air. Some materials are more prone to this than others (Nylon...cough, cough... looking at you), but if you are getting excessive crackling and bubbling from your filament at normal extrusion temperatures this may be a sign that your filament has absorbed more water than it should. Fear not, your filament isn't totally ruined, it's possible to revive it to it's ideal extrusion state by drying it for 6-8 hours or so.
The key to proper drying is "LOW and SLOW." Please, do not just throw your spool in the oven and walk away for a few hours! Aside from being a great way to start a fire and release potentially noxious fumes into your house, most ovens don't run at low enough temperatures to properly dry filament. The temperature at which you dry filament at can vary a bit depending on material but when in doubt it's always better to use cooler temperatures for more time. I've found about 100 F (~38 C) It is possible to use something like a warming drawer or a food dehydrator given that it's large enough to hold your spool, but absent those items it's really easy to build a dryer using a container like a 5 gallon bucket or a large storage bin with some air holes poked in it. A 60-75w incandescent lightbulb or a mini-dehumidifier in an enclosure for about 6-8 hours should do the trick. If you do use an incandescent bulb be sure to keep the filament far enough away from it so that it doesn't melt.
Here's some links I've found online of how to make a filament dryer:
If you build one, let me know in the comments how it works for you.
Oh! And if you fancy yourself the more proactive type take a look at this sweet setup for keeping your filament dry when it's not in use: